Low-carbon retrofits in social housing: Energy efficiency, multidimensional energy poverty, and domestic comfort strategies in Southern Europe

Keywords: efficiency, multidimensional energy poverty, and domestic comfort strategies in southern Europe energy poverty, social housing, low carbon, retrofit, energy

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Introduction

Housing accounts for approximately 25% of all energy consumption in Europe [START_REF]The energy performance of buildings directive: Fact sheet[END_REF], and is therefore an important target for low-carbon transitions. In this field, social housing offers unique opportunities to address both energy efficiency and social inclusion, through potential economies of scale and the reduction of social and financial costs for residents [START_REF]UN-Habitat, Green building: interventions for social housing, United Nations Human Settlements Programme[END_REF]. However, a whole series of economic, technical, legislative, social and organizational barriers makes the social housing stock resistant to change [START_REF] Mccabe | The application of renewable energy to social housing: A systematic review[END_REF].

These barriers are salient in Spain and Portugal, due to the particular configurations of energy poverty drivers in the social housing stock and beyond. Firstly, much of the social housing stock is obsolete in energy terms, and the socio-economic profiles of the residents, with precarious households predominating, differ from those in northern European countries [START_REF] Scanlon | Social Housing in Europe[END_REF]. Secondly, the deep impacts of the 2008 socio-economic crisis have made large segments of the population more vulnerable to the important increase of gas and electricity prices [START_REF] Desvallées | The politics of domestic energy vulnerability in the Barcelona region, between deconfinement and reconfinement[END_REF]. Thirdly, mild winters have contributed to the invisibilisation of the problem, which has been largely overlooked by decision-makers until the end of the 2010 decade [START_REF]Republica portuguesa, Long-term national strategy to fight energy poverty 2021-2050[END_REF][START_REF]National strategy against energy poverty[END_REF]. In these Spanish and Portuguese contexts, retrofitting policies based on standardized user patterns have drawn criticism from architectural and engineering teams supporting pilot projects [START_REF] Escandón | On the assessment of the energy performance and environmental behaviour of social housing stock for the adjustment between simulated and measured data: The case of mild winters in the Mediterranean climate of southern Europe[END_REF][START_REF] Escandón | Field assessment of thermal comfort conditions and energy performance of social housing: The case of hot summers in the Mediterranean climate[END_REF][START_REF] Seabra | Low energy renovation of social housing: Recommendations on monitoring and renewable energies use[END_REF]. While limitations with regard to the energy savings achieved by upgrading buildings have been well documented as resulting from a rebound effect [START_REF] Scheer | Quantification of energy savings from Ireland's Home Energy Saving scheme: an ex post billing analysis[END_REF][START_REF] Rau | Changing energy cultures? Household energy use before and after a building energy efficiency retrofit[END_REF], these southern Europe assessments record the ubiquity of a "prebound effect" [START_REF] Sunikka-Blank | Introducing the prebound effect: the gap between performance and actual energy consumption[END_REF], whereby residents consume less energy than the projections of the standardised patterns, thus invalidating energy efficiency gains and reductions in CO2 emissions as well as the economic models relying on selling renewable energy to lowincome residents. This difference between theoretical models and a low actual consumption can be attributed in part to the overestimation of domestic consumptions in the calculation methodology used for the buildings energy performance certification [START_REF] Palma | Mapping the energy performance gap of dwelling stock at high-resolution scale: Implications for thermal comfort in Portuguese households[END_REF], and in part to the widespread nature of energy deprivation situations in southern Europe [START_REF] Liddell | Excess winter deaths in 30 European countries 1980-2013: a critical review of methods[END_REF]. These situations, known as energy poverty, occur when households living in energyinefficient homes are unable to afford adequate indoor thermal conditions. Conceptual developments about these conditions have widened the scope beyond an initial focus on thermal comfort to include a much broader range of daily services requiring energy, such as cooking or domestic hot water (DHW). These developments have conceptualised an inability to attain a socially and materially necessary level of such domestic energy services, emphasising the driving forces of energy deprivation and the multidimensional nature of these energy services [START_REF] Bouzarovski | A global perspective on domestic energy deprivation: Overcoming the energy poverty-fuel poverty binary[END_REF][START_REF] Bouzarovski | Multiple transformations: theorizing energy vulnerability as a socio-spatial phenomenon[END_REF][START_REF] Connon | Transcending the triad, political distrust, local cultural norms and reconceptualizing the drivers of domestic energy poverty in the UK[END_REF]. This paper takes this widened notion of energy poverty as a starting point to characterise registered social housing providers (RPs) in the southern European contexts of Spain and Portugal as stakeholders at the nexus between contradictory missions when conducting retrofits of the built estate. European, national and municipal expectations for RPs are set on energy efficiency gains, but this ambition is hindered by the socio-economic and material reality of a low-consumption social housing estate. This contradiction adds to the primary missions of RPs, which are to secure housing affordability and tackle social exclusion issues. We argue that RPs follow a sociotechnical approach to the built environment that considers energy poverty as a central and unchangeable plight for their tenants, a choice leading to widespread adoption of retrofitting policy designs aiming for passive thermal comfort. This paper also reflects these policy choices through a survey on the energy poverty situations experienced in broadly defined Portuguese and Spanish social housing, taking into account different forms of housing accommodating low-income households and including housing owned by private citizens whose inhabitants are facing severe energy poverty. The nature of these hidden domestic situations is receiving growing attention in southern Europe contexts, with a steady production of indicators showing the somewhat counter-intuitive prevalence of energy poverty in Spain and Portugal [START_REF] Healy | Housing, Fuel Poverty and Health: A Pan-European Analysis[END_REF][START_REF] Healy | Fuel poverty in Europe: a cross-country analysis using a new composite measurement[END_REF][START_REF] Thomson | Quantifying the prevalence of fuel poverty across the European Union[END_REF][START_REF] Liddell | Excess winter deaths in 30 European countries 1980-2013: a critical review of methods[END_REF][START_REF]OpenExp, European energy poverty index (EEPI)[END_REF], albeit with fewer empirical academic studies [START_REF] Gouveia | Mining households' energy data to disclose fuel poverty: Lessons for Southern Europe[END_REF][START_REF] Angel | Irregular Connections: Everyday Energy Politics in Catalonia[END_REF][START_REF] Desvallées | The politics of domestic energy vulnerability in the Barcelona region, between deconfinement and reconfinement[END_REF] than policy reports from civil society organisations [START_REF] Aca | Potencial de generación de empleo derivado de la rehabilitación energética de viviendas[END_REF][START_REF]ACA, 2ndo Estudio Pobreza energética en España: analisis de tendencias[END_REF][START_REF] Aca | vulnerabilidad y desigualidad energética[END_REF][START_REF] Tirado | Indicadores municipales de pobreza energética en la ciudad de Barcelona[END_REF]. We argue that bringing an empirical focus to Spanish and Portuguese energy poverty situations will contribute to a better understanding of the challenges and limits of RP policies.

We begin with a brief background on energy efficiency in the built environment and in social housing in Spain and Portugal. Then the methodology for empirical data collection on RPs and low-income households is described, followed by a results section divided into three main findings on RP policies, on the situations of energy poverty and on the limits of RP incursions into the domestic spaces of households. The paper concludes with some reflexions on the findings and their policy implications, followed by suggestions for future studies.

Understanding the context of energy poverty in the social housing estates

This section provides contextual elements on the energy efficiency, consumption profiles and energy poverty issues and policies in Spain and Portugal, before addressing the lessons from the pilot retrofitting projects with strong energy efficiency components that have been conducted in social housing estates.

Three challenges for social housing providers

Southern Europe contexts raise three significant challenges for energy efficiency retrofits. One of them is the socio-economic profile of social housing residents, a largely homogeneous population dominated by low-income and vulnerable households. This phenomenon is the result of the constant promotion of private ownership in national strategies, which has concentrated precarious households in social housing [START_REF] Pareja Eastway | La política de vivienda en España: lecciones aprendidas y retos de futuro[END_REF]. Social housing estates represent a small fraction of the total value of national housing, 5% in Portugal and 2,8% in Spain [START_REF]Affordable housing database -housing rented at a reduced/subsidised price[END_REF], and mostly accommodate low-income residents, whereas larger estates in northern European states accommodate other social groups [START_REF] Scanlon | Social Housing in Europe[END_REF]. While rent levels differ between the two contexts1 , in both cases these rents exclude utility costs, which are borne by the residents of social housing.

A second challenge is the low energy efficiency of existing buildings. In Spain and Portugal, 70% of the housing stock was built before the first regulations were issued to establish limitations on energy demand in buildings in Spain [START_REF]RD 2429/1979, por el que se aprueba la norma básica de edificación NBE-CT-79, sobre condiciones térmicas en los edificios[END_REF] and in Portugal [START_REF] Rccte | Aprova o Regulamento das Características de Comportamento Térmico dos Edifícios, Decreto-Lei n. o 40/90[END_REF]. Much of this stock, therefore, is not equipped with thermal insulation [START_REF] Gangolells | Energy mapping of existing building stock in Spain[END_REF][START_REF] Gouveia | Residential Sector Energy Consumption at the Spotlight: From Data to Knowledge[END_REF], central heating or space cooling, with biomass and electricity providing the majority of final energy [START_REF] Horta | Energy poverty in Portugal: Combining vulnerability mapping with household interviews[END_REF]. These issues are particularly salient in social housing estates, where most large projects were built from the 1940s to the 1980s, with no district heating2 and little incentive for retrofits until the 2010 decade when national priorities shifted from new constructions to retrofitting buildings [START_REF] Eresee | Estrategia a largo plazo para la rehabilitación energética en el sector de la edificación en España[END_REF][START_REF] Eresee | Actualización de la Estrategia a largo plazo para la rehabilitación energética en el sector de la edificación en España, Ministerio de fomento, secretaría de estado de infraestructuras, transporte y viviendas[END_REF]. Social housing estates combine these energy characteristics with pathologies specific to the massive use of concrete as the primary construction material [START_REF] Gómez | Principales problemas de patología en las construcciones de estructura de hormigón[END_REF][START_REF] Curado | Conforto Térmico e Eficiência Energética nos Edifícios de Habitação Social Reabilitados[END_REF], as shown in Figure 1, a photo taken in the Lagarteiro neighbourhood of Porto. Built between 1973 and 1979 to relocate households from the dilapidated city centre, this ensemble of social housing blocks has reached the highest levels of socio-economic deprivation indicators in the Porto agglomeration [START_REF] Monteiro | Atlas da saúde e da doença, vulnerabilidades climáticas e socioeconómicas na Grande Área Metropolitana do Porto e Concelho do Porto, Climate, health and environment research group[END_REF]. The concrete walls are in direct contact with the exterior and exposed to wind and rain, allowing humidity to penetrate the walls and causing pathologies aggravated by the appearance of thermal bridges between panels and the building's structure. The windows have no insulation and their frames are degraded, as are the laundry rooms protected by the red bricks on the right of the photograph. This second efficiency challenge is exacerbated by the discrepancies between energy certification procedures modelled on northern European contexts and real consumption profiles in the Iberian peninsula. Numerous studies demonstrate that certificates are built upon full occupation schedules and full climatization projections that are disconnected from local contexts [START_REF] Castaño-Rosa | Cooling Degree Models and Future Energy Demand in the Residential Sector. A Seven-Country Case Study[END_REF]: deviations up to 90% between real and simulated consumption have been measured in Portugal, strengthening the argument of a "performance gap" distorting energy efficiency gains expectations in the design of retrofitting policies [START_REF] Magalhães | Characterization of thermal performance and nominal heating gap of the residential building stock using the EPBD-derived databases: The case of Portugal mainland[END_REF][START_REF] Magalhães | Predicting and characterizing indoor temperatures in residential buildings: Results from a monitoring campaign in Northern Portugal[END_REF]. These observations do not contradict the widespread low efficiency levels of Portuguese and Spanish residential buildings. Rather, they point to the challenges of designing retrofitting policies in contexts where consumption profiles deviate substantially from certification standards, with low final energy consumption figures compared to the EU average 3 . They reflect specific structures in the domestic sector energy consumption, where electricity is the dominant domestic fuel, and where heating takes a lower share of energy consumption than in EU averages (See Annex 1) [START_REF]INE, Resultados preliminares do inquérito ao consumo de energia no sector doméstico 2020[END_REF][START_REF] Spahousec | Análisis del consumo energético del sector residencial en España, Instituto para la diversificación y el ahorro de energía (IDAE)[END_REF]. Furthermore, when compared with southern European countries, Spain and Portugal exhibit similar low levels of air conditioning, which can be justified by lower incomes, cultural habits and larger use of alternative passive measures [START_REF] Castaño-Rosa | Cooling Degree Models and Future Energy Demand in the Residential Sector. A Seven-Country Case Study[END_REF].

Thirdly, the combination of poverty, low efficiency standards and low consumption practices create the conditions for pervasive and difficult to measure energy poverty situations, which represent an additional challenge for social housing providers. The prevalence of this problem in Spain and Portugal has already been documented in various policy reports based on Europe-wide surveys on income and living conditions [START_REF] Aca | Potencial de generación de empleo derivado de la rehabilitación energética de viviendas[END_REF][START_REF]ACA, 2ndo Estudio Pobreza energética en España: analisis de tendencias[END_REF][START_REF] Aca | vulnerabilidad y desigualidad energética[END_REF][START_REF] Kyprianou | Energy poverty policies and measures in 5 EU countries: A comparative study[END_REF][START_REF] Aca | Pobreza energética en España, hacia un sistema de indicadores y una estrategia de actuación estatales[END_REF][START_REF] Antepara | Improving Energy Poverty Measurement in Southern European Regions through Equivalization of Modeled Energy Costs[END_REF], and the correlation between thermal discomfort and socio-economic conditions has been made with in situ measurements in case studies [START_REF] Terés-Zubiaga | Field assessment of thermal behaviour of social housing apartments in Bilbao, Northern Spain[END_REF][START_REF] Alonso | Methodological proposal for monitoring energy refurbishment. Indoor environmental quality in two case studies of social housing in Madrid, Spain[END_REF][START_REF] Miguel-Bellod | The relationship between poverty and indoor temperatures in winter: Determinants of cold homes in social housing contexts from the 40s-80s in Northern Spain[END_REF]. Nationwide surveys have shown how the margins of tolerance in low-income households regarding thermal comfort are higher, with heating and cooling systems either absent or unused, and households where it is "usual to forgo comfort and live in energy poverty conditions" [START_REF] Sendra | Energy intervention in the residential sector in the south of Spain: Current challenges[END_REF][START_REF] Escandón | On the assessment of the energy performance and environmental behaviour of social housing stock for the adjustment between simulated and measured data: The case of mild winters in the Mediterranean climate of southern Europe[END_REF], to the point that modelled energy costs appear as better indicators of energy poverty than actual bills [START_REF] Antepara | Improving Energy Poverty Measurement in Southern European Regions through Equivalization of Modeled Energy Costs[END_REF]. In these contexts, the distinction between cultural and socioeconomic explanations are somewhat blurred, with policy reports describing as "cultural habits" practices such as ventilating and changing clothes to adapt to temperature changes [START_REF] Horta | Energy poverty in Portugal: Combining vulnerability mapping with household interviews[END_REF][START_REF] Cardoso | The energy/comfort nexus: towards adaptative approaches in Europe, Social green Interreg Europe[END_REF], when these practices could also be described as the product of deeply entrenched energy poverty.

Design of retrofitting policies in Iberian social estates and lessons from pilot projects

In spite of these challenges, RPs have the potential to achieve large-scale results because their housing stocks are typically co-located in large building complexes, known as "polígonos" in Spain and "bairros sociais" in Portugal, and managed by a small number of stakeholders. Because of this potential, national and local government players have targeted social housing sites to achieve decarbonisation targets through efficiency measures. European legislation acts as a strong incentive, from the EPBD setting minimum energy efficiency requirements for major residential retrofitting projects and translated into the Spanish [START_REF] Cte | [END_REF] and Portuguese codes [START_REF] Rccte | Aprova o Regulamento das Características de Comportamento Térmico dos Edifícios (RCCTE), Decreto-Lei n. o 80[END_REF], to implementation of the nZEB norm for social housing [START_REF]Directive 2010/31/CE, sur l'efficacité énergétique des bâtiments[END_REF]. The shift in national priorities towards retrofitting buildings in the 2020s also encompasses social housing. Portuguese governments have devised a national renovation strategy [START_REF]Governo de Portugal, Long-term strategy to retrofit Portuguese buildings (ELPRE)[END_REF] based on a series of national funds and financial schemes to retrofit municipally-owned residential buildings, in coordination with the Norte 2020 European Regional Operational Program (ROP) 4 . In Spain, social housing was included in the long-term strategy for energy retrofits in the housing sector [START_REF] Eresee | Estrategia a largo plazo para la rehabilitación energética en el sector de la edificación en España[END_REF][START_REF] Eresee | Actualización de la Estrategia a largo plazo para la rehabilitación energética en el sector de la edificación en España, Ministerio de fomento, secretaría de estado de infraestructuras, transporte y viviendas[END_REF] with ambitious targets [START_REF] Castellazzi | Synthesis Report on the assessment of Member States' building renovation strategies[END_REF]. This policy shift also mirrors the emergence of energy poverty as a new public problem [START_REF] Desvallées | Problematizing, politicizing and reducing energy vulnerabilities, between a right to energy and a control of the practices of the poor in Porto and Barcelona[END_REF]. Both countries have elaborated national strategies of energy poverty mitigation, providing national definitions for vulnerable consumers and targeting both energy prices and energy retrofits, with interventions in social housing appearing as an important item in the Portuguese policy5 [START_REF]Republica portuguesa, Long-term national strategy to fight energy poverty 2021-2050[END_REF][START_REF]National strategy against energy poverty[END_REF].

These incentives have brought an increase in the production of policy reports and academic literature documenting the results of a decade of pilot projects with strong energy efficiency components conducted in social housing estates in Spain and Portugal. These assessments are unanimous in documenting the prevalence of a "prebound effect", which is the opposite of the "rebound effect" whereby energy efficiency improvements increase energy consumption. The prebound effect causes households to consume less energy than in the theoretical models predicting the outcomes of retrofitting projects [START_REF] Sunikka-Blank | Introducing the prebound effect: the gap between performance and actual energy consumption[END_REF]. These studies observe households in social housing who are living in thermal discomfort "100% of the time in winter", both in Spain [START_REF] Escandón | On the assessment of the energy performance and environmental behaviour of social housing stock for the adjustment between simulated and measured data: The case of mild winters in the Mediterranean climate of southern Europe[END_REF] and in northern Portugal [START_REF] Seabra | Low energy renovation of social housing: Recommendations on monitoring and renewable energies use[END_REF]. The specificity of Spain and Portugal has been further highlighted by a comparative assessment of energy retrofits conducted in social housing estates at the European scale as part of an EU Interreg programme [START_REF] Nordregio | Social green -regional policies towards greening the social housing sector. Integrated self-assessment report, Social green Interreg Europe[END_REF]. Energy consumption in these case studies was very low, with social housing providers struggling to adapt the energy-efficiency goals of the EPBD directive to the "socio-climatic reality" of their social housing estates [START_REF] Escandón | Field assessment of thermal comfort conditions and energy performance of social housing: The case of hot summers in the Mediterranean climate[END_REF][START_REF] Cardoso | The energy/comfort nexus: towards adaptative approaches in Europe, Social green Interreg Europe[END_REF].

To adapt retrofitting policies to these contexts, pilot project evaluations establish a set of lessons for RPs. First, they recommend "passive" instead of "active" strategies, with "passive" solutions including "envelope treatment, thermal control, solar gain protection and night-time natural ventilation" [START_REF] Escandón | Evaluating the environmental adaptability of a nearly zero energy retrofitting strategy designed for Dutch housing stock to a Mediterranean climate[END_REF][START_REF] Suárez | Impact of Climate Change: Environmental Assessment of Passive Solutions in a Single-Family Home in Southern Spain[END_REF] and "active" solutions describing renewable energy-producing installations such as solar thermal and solar PV [START_REF] Seabra | Low energy renovation of social housing: Recommendations on monitoring and renewable energies use[END_REF][START_REF] Ceiia | Policy recommendations on greening the social housing sector, Social green Interreg Europe[END_REF]. They also advocate the monitoring of actual consumption, before and after retrofits, and the inclusion of this monitoring into financial incentive schemes [START_REF] Weber | EU policy, neighbourhood results: towards efficient & impactful green building projects in Europe, Social green Interreg Europe[END_REF], in order to analyse patterns of consumption and habits [START_REF] Escandón | Field assessment of thermal comfort conditions and energy performance of social housing: The case of hot summers in the Mediterranean climate[END_REF]. Thirdly, they recommend working and engaging with residents to understand their patterns of consumption [START_REF] Mccabe | The application of renewable energy to social housing: A systematic review[END_REF], before advocating changes in energy efficiency standards for retrofits in southern European social housing [START_REF] Escandón | Field assessment of thermal comfort conditions and energy performance of social housing: The case of hot summers in the Mediterranean climate[END_REF].

We investigated how Spanish and Portuguese RPs respond to these many challenges when implementing energy-efficiency retrofits. Low consumption levels in social housing can jeopardise the implementation of energy-saving measures: upfront costs are high as residents are seldom creditworthy, and there is little return on investments in either insulation or renewable energy equipment. Given the absence of economic incentives, this paper is interested in the pull exerted by other motivations for RPs, and how they balance against metric-based expectations on energy efficiency set by local, national and European authorities, both in the management of pilot projects and in the translation of their inputs into measures adapted to the bulk of the social housing estate.

programme [START_REF]Reabilitar para arrendar -Habitação accessível, Instituto Da Habitação e Da Reabilitaãi Urbana[END_REF] and financial schemes for retrofitting projects [START_REF] Iffru | Resolução do conselho de ministros n°52-A/2015, que estabelece o quadro de funcionamento do Instrumento Financeiro para a Reabilitação e Revitalização Urbanas[END_REF][START_REF] Iffru | Resolução do Conselho de Ministros n. o 84-O/2016, que autoriza o lançamento dos procedimentos financeiros para a reabilitação urbana[END_REF]. A new generation of housing policies was adopted in a 2018 legislative package to establish retrofits as a national imperative [START_REF] Ngph | Resolução n°50-1/2018 Para uma nova geração de políticas de habitação, Sentido estratégico (NGPH), objetivos e instrumentos de atuação[END_REF]. The PRBS, the PROHABITA and the IFFRU combine national funds with European funds from the Portugal 2020 scheme [START_REF]ROP, Regional Operational Program Norte 2020[END_REF]

Methodology

To understand the agency and capacity of RPs in addressing the prebound effect in southern European social housing, two urban case studies were chosen, in Spain [ES] and Portugal [PT]. Porto [PT] and Barcelona [ES] have similar local climates, with hot summers and mild winters, and a large and ageing social housing estate under similar management. In the Metropolitan Area of Porto and the Metropolitan Area of Barcelona, most social housing is managed by local authorities, with a municipal social landlord in each case. There is also a national landlord in Portugal and a regional social housing agency in Catalonia, the latter coordinating its strategies with the municipal landlords through a consortium. There are currently 30 000 units under this scheme in Barcelona (1% of total housing in the metropolitan area) and 17 500 units in Porto (14%). In Barcelona, this public housing deficit has motivated municipal schemes aimed at capturing vacant privately-owned apartments in order to rent them at subsidised prices.

Local authorities in both contexts received strong incentives to tackle energy poverty during the 2010 decade. Reinforcing the shift from new constructions to retrofits at the national scale, the regional and municipal authorities in the metropolitan areas have set energy efficiency targets for social housing. In the Porto region [PT], the commission in charge of coordinating local development has played an influential role in securing funding for social housing retrofits from the European ROP fund [START_REF] Nordregio | Social green -regional policies towards greening the social housing sector. Integrated self-assessment report, Social green Interreg Europe[END_REF], while municipal authorities have adopted ambitious renewable energy targets for the social housing estate in the Porto Action Plan for energy efficiency [START_REF] Adeporto | Plano de acção para a energia sustentável da cidade do Porto, Porto energy agency[END_REF]. In the Barcelona region [ES], regional and municipal plans for an energy transition [START_REF] Icaen | Bases para constituir el Pacto Nacional para la transición energética de Cataluña, Instituto Catalan de energia[END_REF][START_REF] Icaen | Pla de l'Energia i Canvi Climàtic de Catalunya 2012-2020 (PECAC)[END_REF][START_REF]Plan clima 2018-2030[END_REF] have pointed to social housing as a potential target for energy retrofits, installing PV panels and promoting local production and consumption. Moreover, energy poverty became a public issue for the Barcelona local authorities at the end of the 2010 decade, thanks to a strong social movement and a politicized municipal government [START_REF] Desvallées | The politics of domestic energy vulnerability in the Barcelona region, between deconfinement and reconfinement[END_REF]. The Barcelona Climate Plan for 2030 places the fight against energy poverty as a central objective, an imperative that translates into the creation of a new municipal utility company [START_REF] Rodriguez | Barcelona Energía: public energy company, Energy Cities Webinar[END_REF] and local offices staffed by social workers responsible for helping households in energy poverty situations [START_REF]Plan clima 2018-2030[END_REF].

In both case studies, two methodological approaches were applied in parallel. One was based on 13 semi-directive interviews with RPs and low-carbon policymakers between January 2015 and June 2018. The interviewees were five RPs (RP1 to RP5), five architects and project managers charged with designing and evaluating retrofit projects (AR1 to AR5), two heads of missions in local NGOs conducting retrofits in social housing and the head of the Barcelona energy agency. The institutions were selected according to a preliminary survey of organizations having delivered notable retrofit schemes or completed other significant energy-related retrofits in their housing stock and among tenants. The interviews were conducted in person and audio-recorded. The audio recordings were transcribed, and quotes from the interviews were anonymised.

The second approach aimed to shed light on the socio-climatic realities underlying RP retrofitting strategies by gathering quantitative and qualitative information on low-income residents in Porto and Barcelona. Contact with interview partners was established through two NGOs. In Porto, the partner NGO provided food to low-income households and shared the individual datasheets for the 246 households they supported, comprising income and energy bills for January and February 2015. In Barcelona, the partner NGO was created to implement a pilot scheme designed to expand social housing into the private rental sector 6 . For 100 of these households, individual datasheets comprising income and energy bills covering the years 2015-2016 were collected, along with the energy certificates for each apartment, and a questionnaire on thermal discomfort was applied. Further data were collected through qualitative interviews with ten Spanish households and eight households in Porto, using an open interview guide supplemented by the individual NGO protocols for eliciting socio-demographic data. The interviews were conducted during the spring of 2015 in Porto and the spring of 2016 in Barcelona. All interviews were transcribed and analysed with a qualitative data analysis software. The socio-economic profiles giving further characteristics of the households in the survey are shown in Table 1.

Table 1 -socio-economic profile of surveyed households

Composition of households

Monthly household income compared to the national at-risk of poverty thresholds for single households [ This approach covers three types of social housing, all built before the adoption and application of national energy efficiency norms for residential buildings. Half of the quantitative information gathered in Porto corresponds to households living in collective buildings managed by RPs, while the other half corresponds to de facto social housing.

According to the NGO's social workers, most of these households live in Porto's "ilhas", small degraded urban ensembles built in the 19 th century to accommodate factory workers that are rented at well below Porto's market prices [START_REF] Vásquez | Ilhas" do Porto, levantamento e Caracterização, Domus Social[END_REF]. In Barcelona, a third type of social housing is concerned, consisting of refurbished privately-owned apartments that are managed as part of the Catalan registered social housing estate, hence rented to lowincome households at a subsidised rate. Their construction periods range from the 1940s to the 1980s and energy efficiency standards are low 7 .

RP strategies and the challenges of energy poverty in social housing

On the following pages, the three main results of the paper will be described, linking RP strategies for implementing energy efficiency measures in registered social housing with the energy poverty situations observed in low-income households in broadly defined Portuguese and Spanish social housing.

Passive comfort as a new retrofitting strategy for RPs

All of the RPs expressed normative aims of providing thermal comfort for social housing residents. They recognised that it is their responsibility to ensure that vulnerable people are protected from extreme summer and winter temperatures. RP1 summarized this approach as follows: "we decided that, if nothing else, we would bring thermal comfort to these families". This choice, formulated here as a compromise due to the prevalence of energy poverty situations, is the result of a learning process common to both Spanish and Portuguese RPs.

This responsibility is recent, as thermal comfort and the management of energy poverty was not part of RP missions until 2010. As stated by RP1 in Portugal: "retrofitting has largely been empirical, the experience was new, in the early 2000s we mostly painted façades, and energy questions only appeared at the end of that decade". This statement on energy poverty is mirrored by RP5 in Catalonia: "we were receiving a lot of complaints, people saying that they were paying too much for energy, our technicians finding illegal connexions to the grid, but it took [the pilot retrofit project] for us to really understand the depth of the problem".

These energy poverty situations came to light through the use of metrics during the implementation of pilot projects designed to increase energy efficiency and meet European, national and municipal imperatives. Situations previously hidden in the domestic space, known to but not tackled by RPs, became visible, as temperature, hygrometry and CO2 concentration levels were measured over monthly and yearly periods. As stated by a Catalan architect in 2016 (AR1): "when we started the retrofit project five years ago and started talking about energy poverty, the social housing provider did not understand what we were talking about. First, we monitored thermal comfort, with spectacular results.

Residents only turned up the heat when the temperature dropped to 14°C, and there were apartments with 9°C during the whole winter. And yet, for 70% of the households, the percentage of energy expenditure in their income was more than twice the national average". This observation echoes the discourse of all five RPs following pilot projects, summarised by RP5 as: "we had an idea of what was fuel poverty [sic and pronounced as such in English], we knew about the context… but when we saw it, it was frightening… and we learned that in the UK they had been working on it for years".

Along with measuring thermal discomfort, the pilot projects highlighted the underuse of domestic hot water (DHW), thus invalidating energy efficiency gains to be achieved by equipping social housing buildings with renewable energy equipment. For the Barcelona RP2 : "in 2009, we were planning and building new social housing apartments with energyproducing installations: solar thermal and PV panels and even a district heating and cooling network 8 . We wanted to create comfort at a cheaper price for our users. But when the first installations were completed, the residents had very little use for them and we had lots of issues with their maintenance. The obvious fact was that this kind of energy efficiency was not suited to their needs". The same conclusions were drawn from the failure of the Porto [PT] energy efficiency action plan to attract private investors. None of the 50 000m 2 of solar thermal panels planned for 2020 [START_REF] Adeporto | Plano de acção para a energia sustentável da cidade do Porto, Porto energy agency[END_REF] have been financed by the initial public-private financing scheme due to the lack of investment returns. The exception is the installation of solar thermal panels for DWH on a social housing block that was entirely financed by public funds, for which maintenance remains a liability as stated by RP1: "in this case, we do not have to expect returns on investments and tenants will not have to pay for DHW, but problems will arise when we have to repair the pipes, the heaters, the tanks: we are no specialists and have few financial resources for this".

Faced with the reality of the lack of investment returns, there is little financial incentive for RPs to invest in low-carbon retrofitting activities, either for the RPs themselves because utility bills are paid by residents, or for residents who consume little energy for their domestic daily activities. The same observation can be made for CO2 emissions reduction targets. For RPs charged with achieving climate change mitigation targets under European, national and municipal policies, this impasse is summarised by the Portuguese partner of the EU-funded Social Green project [START_REF] Ceiia | Policy recommendations on greening the social housing sector, Social green Interreg Europe[END_REF], AR4: "energy retrofits only translate into a theoretical reduction in consumption, and in these conditions, choosing energy consumption reduction as a criterion for evaluating projects and expecting returns on investments for energy-producing installations is ill-advised".

Instead, the retrofitting strategies devised by the Porto and Barcelona RPs are based on a redefinition of the priorities to focus instead on measures that have no maintenance costs for the large bulk of the built estate. The term used to describe these measures is "passive", which encompasses the thermal control, ventilation and insulation interventions on the built envelopes that have grown into a new internal policy for RPs. The chosen indicators have also been adapted to shift the imperatives from reducing consumption to achieving internal temperature targets in the social housing apartments without operating heating or cooling systems. As stated by RP5 in Catalonia: "we chose to secure an internal temperature of 17°C or 18°C to avoid respiratory problems, because we have accepted that they will never turn on their heating systems, regardless of how efficient we choose them". This focus on domestic temperatures is theorised by a chief architect in Porto (AR2) as follows: "what is important is to calculate and mitigate passive discomfort: how buildings behave when they are not heated or cooled". This is translated as follows by the corresponding RP1: "if we manage to raise winter temperatures from 14°C to 16°C in the retrofitted buildings, this will already be a success as residents will have more comfort". For RP3 in Catalonia, this choice amounts to a profound "paradigm shift" in RP goals and practices, as the conclusions reached by pilot projects are deemed to be applicable to the majority of the social housing estate. We summarised this change in the following table ,  distinguishing between what RPs see as an "efficiency" paradigm and a "comfort" paradigm and the implications in terms of objectives and technologies. However, this shift still accommodates energy-producing equipment when additional funds are available, in the form of European funding schemes or public-private partnerships made possible by the inclusion of private real-estate operations in the retrofitting projects 9 .

Table 2 -Efficiency and comfort paradigms in RPs' retrofitting strategies

Efficiency paradigm Comfort paradigm

Objectives

Reach emission reductions objectives measured in CO2

Secure a minimum temperature in winter and a maximum temperature in summer with little or no use of heating or cooling systems Technologies All systems producing energy for social housing tenants: solar thermal and photovoltaic panels as well as heating and cooling systems Install or improve existing insulation and ventilation of built envelopes, reduce thermal bridges

The multidimensional presence of energy poverty in social housing

The RPs' choice of a passive approach follows the recommendations given in the literature and project analyses accompanying the Spanish and Portuguese pilot projects. However, other suggestions made in this literature regarding monitoring and understanding consumption practices, in line with a wider understanding of energy poverty than thermal comfort alone [START_REF] Bouzarovski | A global perspective on domestic energy deprivation: Overcoming the energy poverty-fuel poverty binary[END_REF], are not as closely followed. The results of the surveys on low-income households in Porto and Barcelona reiterate the scientific evidence that energy deprivation situations are multidimensional, adding empirical observations on an under-studied southern European context, but their main contribution is to explore the discrepancies between these conditions and RP policies. Three main findings can be drawn from this research, lead in coherence with the literature striving to measure energy poverty in different contexts of the EU though three main methods of measurement [START_REF] Epov | Methodology guidebook, The EU Energy poverty observatory[END_REF].

First, the results of a direct measurement method have shed light on the discrepancies between the level of energy services and a set standard. Indeed, the households surveyed have low consumption levels when compared to national averages. In Barcelona where the partner NGO gave us access to monthly electricity bills over two years, the annual consumption per household was 2100kWh/year, well under the 3 490kWh/year national average measured by the 2011 survey on Spanish residential sector consumption [START_REF] Idae | Consumos del Sector Residencial en España Resumen de Información Básica[END_REF]. Furthermore, the results emphasise the discrepancy between actual energy consumption of the households surveyed including all end uses (92kWh/m 2 /year) and the theoretical levels established by the building's energy certificates if the households were only to attain WHO standards of thermal comfort and DHW use (182kWh/m 2 /year), omitting other end uses such as washing machines and refrigerators.

Second, a consensual approach based on self-reported assessments has shown that these low consumption figures are the result of austere domestic practices. Indeed, domestic temperatures in the homes are constantly controlled, with a focus on areas where heat is deemed more important, such as children's rooms. As stated by RES1: "All my life I have been careful with bills. I have a small electric heater and that's all. If it is very cold, I turn it on, and I move it around to save on the bills, I put it in my son's room before he goes to bed, and then in my room for an hour". This monitoring is not limited to electricity use, as in the experience of RES2 "we installed a butane heater, but only in the kid's room, or in the living room when he's with us". This behaviour is mirrored by the results of secondary indicators covering thermal comfort: in Barcelona, where a survey was designed to answer the research questions, households declared feeling too hot or too cold in higher percentages than the mean national values measured in the 2016 EU-SILC [START_REF]EU-SILC, At-risk-of-poverty threshold -EU-SILC survey 2015-2016[END_REF]. 40% feel uncomfortably cold during the winter (well over the 10% national mean) and 40% uncomfortably hot in the summer (also over the 20% mean). This discomfort could be enhanced by the impacts of climate change on this Mediterranean city, as only 20 out of the 40 households equipped with air conditioning declared not turning it on during the warmer months.

This meticulous monitoring goes well beyond heating needs to encompass water heating, lighting and cooking needs, which are not taken into account by the passive strategy adopted by RPs. For these needs, energy vectors are often described as having an influence on how appliances are used: domestic electricity in Spain and Portugal is more expensive than natural gas, and as such is more rationed. RES2 described her fear of using the electric boiler for DHW: "to wash the dishes, I try to use as little hot water as possible, when I give my children a bath, I use the water several times, including for me. Before the crisis, when we were living in an apartment connected to the gas network, where we would each have our own bath, but now with an income of 300€, it has become very difficult". For RES5 in Porto: "I needed a dehumidifier to absorb humidity, but I couldn't install one, because it consumes a lot of electricity, it's easy for them [RPs] to advise us residents to compensate for damp homes, but it costs 100€ upfront plus the electricity it uses". Cooking practices are also closely monitored, as stated by RES3 "I am afraid because of the oven. There is no gas network in this apartment, and as I use the oven to bake cakes that I sell, every time I receive a bill, I get scared. Even 60€, it seizes us by the throat". A strategy adopted by households interviewed is to rely on gas bottles, which allow them to keep track of the expenses, as for RES4: "a bottle of butane costs 14€ and it lasts a month, I can cook large pots of soup, whereas the last electricity bills have scared me. The only problem is to buy them at the petrol station and bring them up to the apartment, door-to-door salesmen sell them for 18€". In all the households interviewed, this constant monitoring has a strong gendered component, as women appear to bear the responsibility of keeping track of domestic expenses and negotiating between family needs. This result echoes wider surveys on day-to-day coping strategies in households experiencing energy poverty in Catalonia [START_REF] Gonzalez Pijuan | Desigualdad de género y pobreza energética: Un factor de riesgo olvidado, Asociación catalana de ingenería sin fronteras[END_REF].

A third dimension of energy poverty can be approached through an expenditure method, confronting the surveys' results with absolute and relative thresholds. In Porto and Barcelona, we measured three primary indicators, the high share of energy expenditure in income (2M), the low absolute energy expenditure designed to identify households dangerously underconsuming energy (M/2) and the arrears on utility bills due to financial difficulties 10 . These indicators draw a portrait of a low-income population heavily affected by rising energy prices, with the majority of households positive on at least one indicator of energy poverty. The 2M indicator represented in Figure 2 reaches 57% in the Barcelona case study and 71% in the Porto households. Both figures are well above the national 10 The 2M indicator is the proportion of households whose share of energy expenditure to income is twice the national median share. This median share has been measured for Spain by the Spanish NGO ACA, estimating the mean share as 4,9% of energy expenditure to income [START_REF] Aca | Pobreza energética en España, hacia un sistema de indicadores y una estrategia de actuación estatales[END_REF]. This methodology was replicated by Desvallées [START_REF] Desvallées | Problematizing, politicizing and reducing energy vulnerabilities, between a right to energy and a control of the practices of the poor in Porto and Barcelona[END_REF] for the Portuguese income/expenditure survey [START_REF]Microdados del Inquérito aos orçamentos familiares[END_REF] and resulted in a similar figure: the Portuguese median threshold is also 4.9% of energy expenditure to income. The M/2 is the low absolute energy expenditure indicator, presenting the share of households whose absolute energy expenditure is below half the national median expenditure. Similary, this indicator has been measured for Spain by the NGO ACA and replicated by Desvallées in Portugal. In both countries, the national median expenditure for domestic energy is 48€ per month and per household setting the threshold for energy poverty under 24€ per month and per household.

means, already placing Spain and Portugal at the top of European comparisons on this indicator [START_REF] Epov | Indicators & Data -low absolute energy expenditure (M/2) and high share of energy expenditure in income (2M)[END_REF].

The low absolute energy expenditure indicator (M/2) is above the national average by a smaller margin than the 2M indicator. This gap can be traced to different expressions of energy poverty in the households surveyed, as shown in Figure 3, a Venn Diagram representing the overlap between the indicators. 2M and M/2 appear as complementary, distinguishing households with a high share of expenses from households with low consumption. For the thirty-three Spanish households and the one Portuguese household validating both indicators, the available income is low enough for even limited gas and electricity bills to weigh heavily in the domestic budget.

ANAP (PT) Portugal

Surveys National averages

Following this expenditure method, the survey was also designed to identify arrears on utility bills due to financial difficulties. This indicator is more prevalent for low-income households than in the mean national values, as shown in Figure 2. Half of the Barcelona households experienced bill arrears in the past 12 months, well above the national mean, and 10% of Porto households experienced bill arrears in the two months covered by the data provided by the partner NGO. When repeated, these arrears can lead to electricity and gas cut-offs, again with a high prevalence measured in Barcelona with 27 respondents having experienced one or more cut-offs in the twelve months preceding the survey.

Following cut-off operations, and being unable to pay for accumulated debts and reconnection fees, households can turn to illegal connections to the electricity network. These frauds are difficult to approach through surveys, but they are recurrent in RPs interviews, who deal with them on a case-by-case basis when technicians encounter them during interventions, as stated by RP4 in Porto: "our response is to declare these situations [to the utility companies] when we encounter them, but as there are now several utilities, we don't know who to contact", because no protocols were established to deal with contracts with energy utilities in the liberalised market from 2006 onwards. This observation highlights the status of energy retail as external to the scope of RPs, only becoming visible during crises such as the regularisation operation conducted in the Porto neighbourhood of Lagarteiro in October 2013. Technicians from the utility company Energias de Portugal (EDP) entered this large district with a police escort and identified several dozen electricity frauds, before distributing fines and suspending illegal connections, prompting a fatalistic response from the RP1: "there is a lot of fraud, then the utility intervenes and regularises the situations, but they always find new ways, for example setting up illegal connections from equipment in common areas. When one of them does it, others follow, and it is a very harrowing task for us to intervene in situations where fraud is the general rule".

In the light of these energy poverty situations, the strategy adopted by RPs to focus on thermal comfort appears limited, as it only addresses the thermal component of a problem that concerns not only other daily needs but also causes conflicts with energy utilities. Interviews with RPs help to shed light on the complexities of extending their scope of action and their normative aims beyond thermal comfort.

The challenges of RPs incursions into domestic energy consumption

RPs in Porto and Barcelona are aware of the prevalence of bill arrears and low consumption practices, but we argue that they do not respond to these energy poverty situations with a structured approach beyond passive thermal envelopes, and choose to develop discrete programs illustrating the limits of their technical and legal competences and of their financial means.

First, interviewed RPs recognize the limitations of available financial and technical resources to streamline the process of monitoring everyday practices and turn the results into meaningful interventions in domestic spaces, as summarised by RP5: "we do not know how to gather and interpret the data on users' consumption [from the pilot projects], there are data privacy concerns, and we need tools to do that and time and money that we don't have…". This technical challenge is also illustrated by the close monitoring of a retrofitting project in Porto advertised as "the best social housing complex in Portugal" [START_REF] Ferreira | Custo ótimo de ciclo de vida na requalificação urbana da urbanização de vila d'Este[END_REF], where a university-led research team did not manage to take into account the real consumption of the households, instead highlighting theoretical consumption reductions that are quite unconnected with the experiences of the households [START_REF] Cardoso | The energy/comfort nexus: towards adaptative approaches in Europe, Social green Interreg Europe[END_REF]. The same observations are raised by the reports drawn by the EU Interreg program designed to develop regional energy efficiency policies in the social housing sector, recognizing the "key challenge" in the "lack of monitoring" of households consumptions across a range of European social housing case studies including the Porto social housing estate [START_REF] Ceiia | Policy recommendations on greening the social housing sector, Social green Interreg Europe[END_REF]. Beyond the metrics for temperature and kilowatt hours gathered during pilot retrofitting projects, energy patterns in social housing therefore remain a "black box" [START_REF] Bouzarovski | Conceptualizing energy vulnerability: Why home matters[END_REF]. Without precise knowledge of user practices, policies designed by RPs lack comprehensiveness and focus only on structural interventions for passive envelope retrofits.

Secondly, when aiming beyond advice on everyday behaviour, the authority of RPs in domestic energy consumption is faced with legal barriers in the regulatory framework of the energy sector. Along with retrofitting the envelope of a social building and the installation of solar PV, the pilot project merged groups of four individual 4kW meters into collective 10kW meters, for which the provider established a contract with the utility company, thus saving the monthly 30€ fixed connection charge corresponding to the subtraction of 6kW. Small individual meters were installed in each apartment by the RP to measure individual consumption and charge the households along with other rental costs. "We provide one more service", states RP5, "we already rent the apartments with the utility costs, this would be another service that we provide". However, this experiment was limited to one retrofitted building in the Catalan countryside: energy retail is not within the competencies of Spanish social housing providers, and the merging of smart meters was dependent on negotiations with local energy distributors, a scheme described by RP5 as "not illegal, not legal either, provided that there are no complaints from the Spanish government". This exception was made by a historic local energy distributor who agreed to sign a contract with the RP, but it could not be replicated for the majority of the social housing estate in more densely populated areas where larger energy distributors rejected the scheme. "Users were very happy, recalls RP5, but not the companies, and starting conflicts with utilities is highly problematic, even for public institutions like ours".

Thirdly, adding to the absence of leverage on energy retail, RPs lack financial means to conduct large-scale interventions in domestic interiors other than for EU-funded projects. As stated by RP5, "the pilot had a 90% investment from the EU [for solar thermal and PV installations] and we could invest 20 000€ for each of the twenty apartments, which is a very large sum. Now we have to retrofit 2500 apartments, and our choice to focus on envelope efficiency allows us to invest only 9000€ per apartment, which it is still a high level of investment for us". Because of this, interventions in homes are secondary for RPs, and take the form of low-cost pilot projects designed to cut down electricity and gas bills by promoting careful monitoring of everyday consumption practices 11 . They are part of a larger dynamic targeting individual households and aiming to help them afford energy bills through low-cost tools and protocols, as implemented by the Barcelona municipality on 40 000 low-income households in both private and social housing. This piecemeal approach contributes to blurring of individual and collective responsibilities, individualizing energy poverty by reframing it as a problem of household consumption, and serving the interests of RPs and local authorities neither willing nor able to bear the cost of more expansive schemes [START_REF] Desvallées | The politics of domestic energy vulnerability in the Barcelona region, between deconfinement and reconfinement[END_REF].

Discussion, policy implications and future research steps

By cross-analysing the conclusions obtained from the surveys on RPs and on consumption practices in low-income households, this study investigated the manifestations of energy poverty and how they are perceived and treated by social housing providers. The results show that RPs respond to the ubiquity of low-consumption practices in the social housing estates of Porto and Barcelona with a focus on passive measures designed to provide thermal comfort without heating and cooling appliances, thus placing energy poverty at the core of their retrofitting strategies for social housing. However, as these conditions exceed thermal needs [START_REF] Bouzarovski | A global perspective on domestic energy deprivation: Overcoming the energy poverty-fuel poverty binary[END_REF], energy-poor households also keep a close track of their cooking, lighting and DHW use, while still struggling to afford gas and especially electricity bills, leading to frequent cut-offs and frauds. The avoidance by RPs of the multidimensional expression of energy poverty can be traced to the limitations of their budgets and technical and legal competences, which restrict their capacity to understand and act in indoor domestic spaces. However, our results suggest three possible directions for policymakers.

First, energy poverty situations appear as a central characteristic for tenants living in social housing in Porto and Barcelona, shaping the design of RP retrofitting policies. However, the nature of these situations is still little understood by RPs beyond their assessment of low-consumption practices, leading to flawed interventions aiming for closer monitoring of household habits that are unlikely to mitigate energy poverty. In line with the literature [START_REF] Escandón | On the assessment of the energy performance and environmental behaviour of social housing stock for the adjustment between simulated and measured data: The case of mild winters in the Mediterranean climate of southern Europe[END_REF], we argue that RP policies would benefit from in situ assessments of user consumption profiles including, but not limited to, thermal comfort, and covering monthly expenses as well as perceptions regarding the fulfilment of social needs. Such assessments would help to shed light on the differences between practices stemming from cultural traits and practices that are themselves the result of economic deprivation. They could establish a foundation for the definition of new, context-based indicators of energy poverty situations to anchor the design and evaluation of retrofitting policies in real user profiles.

Secondly, these indicators could be established as criteria for applying to European and national funds, in the design of which RPs have a role to play as "process innovators", as conceptualised by Cauvain and Karvonen, whereby retrofit processes involve engagement with policies and financial instruments [START_REF] Cauvain | Social housing providers as unlikely low-carbon innovators[END_REF]. Portugal's Region Norte stakeholders have already demonstrated their capacity to align funding opportunities for retrofitting social housing, combining energy efficiency upgrades with urban development measures into place-based financing schemes [START_REF] Weber | EU policy, neighbourhood results: towards efficient & impactful green building projects in Europe, Social green Interreg Europe[END_REF]. The project implementation process could be improved further by adapting the regulatory frameworks to allow flexibility in the design of EU-funding criteria and promote structural changes in standards, in order to acknowledge specific southern European contexts, characterized by both inefficiency and lower-thanstandard energy consumption practices, where recouping energy costs in social housing retrofits is near-unachievable.

Thirdly, acknowledging this reality could serve as an incentive for redefining the missions of social housing providers in Spain and Portugal, and challenging the limits of their legal competences in the energy retailing sector. There have been successful experiments of social housing institutions taking on a role in energy retail for their vulnerable tenants, at once reducing households energy bills and protecting them from cut-offs. Such incursions into retail, with possible synergies with the nascent municipally-led local energy companies like the Energía Barcelona [START_REF] Rodriguez | Barcelona Energía: public energy company, Energy Cities Webinar[END_REF] could lead to new missions for RPs, ensuring that social housing tenants can continue to have access to affordable energy in the context of both climate change and rising energy prices.

Further research could follow these directions, by further monitoring the evolution of energy consumption in the social housing estates and by comparing Spanish and Portuguese RPs energy poverty mitigation strategies with their European counterparts. We argue that these future lines of investigation will be more concerned with summer cooling issues, in the context of climate change projections predicting temperature increases that exceed peoples' -and social landlords? -capacity to take adaptive actions [START_REF] Castaño-Rosa | Cooling Degree Models and Future Energy Demand in the Residential Sector. A Seven-Country Case Study[END_REF].

Conclusion

This study investigated the retrofitting strategies initiated by Spanish and Portuguese registered social housing providers (RPs) in Barcelona and Porto. The contribution of the paper is threefold. First, we traced the challenge faced by RPs charged with energy efficiency imperatives that appear largely unachievable in the context of widespread energy poverty situations. Pilot retrofit projects have demonstrated that upfront costs cannot be compensated by energy-saving measures, and have prompted RPs to implement new strategies targeting thermal comfort achieved through passive measures such as insulation and ventilation and limiting energy-producing equipment to well-funded stand-alone pilot projects. Secondly, we compared this strategy with the reality of energy poverty situations in a broadly defined social housing estate, showing that these situations extend well beyond thermal needs because they encompass cooking, lighting and DHW needs as well, which leads to frequent crises involving energy cut-offs and electricity frauds. This portrait also sheds light on the careful monitoring by low-income households of their own domestic practices, which is unacknowledged by RPs in their interventions beyond the implementation of passive thermal measures. The third result of the study is to have plotted the technical, financial and legal limitations encountered by RPs when designing schemes that, beyond building envelopes, target domestic spaces and the practices that take place within them. We therefore argue that the widespread nature of energy poverty situations justifiably calls into question the expectations regarding the success of retrofitting projects conducted in social housing in southern European contexts. We further argue that it points to a need to redefine the missions and competences of Spanish and Portuguese RPs, to move from awareness of the diversity of energy poverty to the adoption of new roles in the provision of energy in social housing estates.

-

Figure 1 -

 1 Figure 1 -a social housing block in the Lagarteiro neighbourhood, before retrofitting

Figure 2 -Figure 3 -

 23 Figure 2 -Values for energy poverty indicators: local surveys and national Portuguese and Spanish averages

  Presence and role of universities in interventions -Content of training on energy practices -Number and identity of local government departments involved -Technologies mobilized -Tools to measure the success of projects -Presence of an energy transition objective towards a low-carbon model Specific issues in Catalonia regarding Law 24/2015 -Application of the protocol framing Law 24/2015 -Changes in the treatment of cases of non-payment after the adoption of Law 24/2015 -Changing relationships with energy providers -Training administered to social assistance services (number of participants, content of training, reception of messages). General view of energy deprivation -Personal views on the concept of energy poverty and its evolution -Evolution of the meaning and relevance of the concept over time -Political support for bill payment or energy assessments LINES OF QUESTIONING -VULNERABLE HOUSEHOLDS Broad Introductory Questions: Major Events Leading to Habitat 3 Housing -Family composition -Occupational history of working household members -Residential history (what housing the household has lived in and what work they have done on it) -Current household income Energy bill payments -Average bill amount (current and past) -Perception of the evolution of the price of electricity, natural gas and butane -Weight of energy budget in household income -Description of energy payment arrears, if any -Interactions with energy suppliers in case of unpaid bills Description of the dwelling -Type of heating, cooling, water heating and cooking facilities -Sunlight in the dwelling -Insulation of the dwelling -Change in heating/hot water/electricity needs from previous housing Home energy deprivation -Feeling of deprivation of heat/hot water/gas or electricity for cooking/lighting -Practices to reduce consumption Association support in Catalonia -Knowledge of the Alliance against Energy Poverty and PAH networks -Knowledge of law 24/2015

The Spanish social housing estate is covered by the "Official protection of housing" scheme, whereby subsidies are defined at the national scale and based on a Family Income Indicator. In Portugal, local authorities may adopt their own regulations according to social realities.

The diffusion of district heating is recent and limited in Spain[START_REF] Paredes-Sánchez | Analysis of District Heating and Cooling Energy Systems in Spain[END_REF] and absent in Portugal, where its potential has been deemed null by central administration services[START_REF] Dgeg | Assessment of District Heating and Cooling Potential in Portugal[END_REF].

The final energy consumption averages 324 kgoe/capita in Spain and 254 kgoe/capita in Portugal, well under the EU average of 558 kgoe/capita[START_REF] Kyprianou | Energy poverty policies and measures in 5 EU countries: A comparative study[END_REF].

Portugal has five national funds for social housing: a social housing rehabilitation programme[START_REF] Prbs | Programa de Reabilitação Urbana de Bairros Sociais[END_REF], the PROHABITA (national financing program for access to housing[START_REF] Prohabita | Decreto-lei n°54-2007 de 12 de março: apoio para a reabiltação dos bairros sociais[END_REF], a special rehousing programme[START_REF] Per | 163/93, de 7 de Maio, Diário Da República[END_REF] and two funds for larger rehabilitation ambitions, the Reabilitar para arrendar or "retrofit to lend"

In the Portuguese "long term national strategy to fight energy poverty" , social housing estates appears as one of the seven areas of intervention in the "energy efficiency" priority, with housing policies receiving 1,2 billion euros from the National Resiliency Program dedicated to "rebuild" the country after the economic and sanitary crises[START_REF]Republica portuguesa, Long-term national strategy to fight energy poverty 2021-2050[END_REF].

With funds from the Barcelona City Council and support from the Catalan entity federating social welfare NGOs, vacant and deteriorated apartments are refurbished and rented to low-income households that the social housing estate cannot accommodate. Under this scheme, private owners renounce rental payments in exchange for up-front payments for retrofits over a period corresponding to the repayment of the cost of the repair work.

Under the CTE code[START_REF] Cte | [END_REF], an apartment in Barcelona's climatic zone should consume

80kWh/m 2 /year. Based on the energy certificates calculating theoretical energy consumption based on the buildings characteristics and equipments, only 10 of the 100 apartments comply with this standard and most have theoretical consumptions ranging from 100 to 270kWh/m 2 /year, which do not correspond to real energy consumption. .

This pilot project was part of the 22@ neighbourhood, a showcase for municipal involvement in energy efficiency in the 2000s[START_REF] Maassen | Municipal Engineers and the Solar Guerrillas[END_REF]. This vast urban renewal project included the construction of a 53-apartment block dedicated to social housing.

This is for example the case in Porto, where the retrofitting of the Rainha D Leonor social neighbourhood in 2019 included the sale on the private market of one third of the retrofitted apartments.

For example, a scheme to tackle energy poverty in social housing led by RP1 in Porto was entrusted to the municipal energy agency, resulting in minor investments in 400 homes such as low-energy lightbulbs and a leaflet giving a set of consumption guidelines that showed little awareness of the socio-economic and material conditions of the households, in line with the little attention given to real benefits for users: low-income households are advised to buy highly efficient domestic energy appliances, are expected to spend time choosing a suitable energy deal in the liberalised market and are given recommendations on the use of irons, microwaves, ovens and refrigerators[START_REF] Adeporto | Vamos economizar! Guia de boas práticas na utilização de energia e água[END_REF].


Dr Alexandre Challine
email: alexandre.challine@aphp.fr

Bertrand Dousset
email: bertrand.dousset@aphp.fr

Nicola De'angelis
email: nic.deagelis@yahoo.it

Jérémie Lefèvre
email: jeremie.lefevre@aphp.fr

Yann Parc
email: parc@aphp.fr

Sandrine Katsahian
email: sandrine.katsahian@aphp.fr

Andrea Lazzati
email: andrea.lazzati@chicreteil.fr

De'angelis N

Lefèvre Jh

MD Challine Alexandre

Angelis De'

MD Nicola

MD,PHD Katsahian Sandrine

Impact of coronavirus disease 2019 (COVID-19) lockdown on in-hospital mortality and surgical activity in elective digestive resections: A nationwide cohort analysis

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

The outbreak of COVID-19 infection has led to the reorganization of hospital care in several countries.

In France, on March 12 th 2020, the government imposed national restrictions to elective surgery. Several guidelines were rapidly published to help surgeons to adapt their practice to the pandemic context.(1-

7)

The first reason for postponing elective surgery was optimizing manpower and healthcare resources to favour COVID-19 patients' treatment, impacting the overall activity. The COVIDsurg collaborative study estimated a worldwide decrease in elective surgery of about 70%, representing more than 28 million people during 3 months of disruption with a major effect on benign disease surgery. [START_REF] Collaborative | Elective surgery cancellations due to the COVID-19 pandemic: global predictive modelling to inform surgical recovery plans[END_REF] The same trend has been estimated in France, in 14 academic hospitals, with a reduction of 50% of elective colorectal surgeries during the lockdown period. [START_REF] Collard | COVID-19 heath crisis: less colorectal resections and yet no more peritonitis or bowel obstruction as a collateral effect?[END_REF] Nevertheless, it has been suggested that these estimations could be biased because of a possible transfer of oncological patients from hospitals massively impacted by COVID-19 (especially public and academic hospitals) to institutions less involved in COVID-19 management (in particular, private institutions). [START_REF] Collard | COVID-19 heath crisis: less colorectal resections and yet no more peritonitis or bowel obstruction as a collateral effect?[END_REF] The second reason for this strategy was the prevention of hospital-acquired COVID-19 infection for surgical candidates and the prevention of postoperative complications in COVID-19-positive patients. [START_REF] Fiore | COVID-19 epidemic: Proposed alternatives in the management of digestive cancers: A French intergroup clinical point of view (SNFGE, FFCD, GERCOR, UNICANCER, SFCD, SFED, SFRO, SFR)[END_REF][START_REF] Collaborative | Global guidance for surgical care during the COVID-19 pandemic[END_REF][START_REF] Wexner | COVID-19: Impact on Colorectal Surgery[END_REF] In fact, a study by Aminian et al. reported an uncommonly high mortality rate after four frequent procedures during the COVID-19 pandemic: cholecystectomy, hernia repair, gastric bypass, and hysterectomy. [START_REF] Aminian | COVID-19 Outbreak and Surgical Practice: Unexpected Fatality in Perioperative Period[END_REF] These findings were confirmed by the work of the COVIDsurg collaborative that reported a 30-day mortality rate of 24% in over 1100 COVID-19 patients after elective surgery. [START_REF] Nepogodiev | Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study[END_REF] Mortality was strongly associated with postoperative pulmonary complications, especially in elderly men (age >70 years).

The bias of data mostly reported from high-volume hospitals (not representative of the entire healthcare system) could be amended by information on a larger scale. Nationwide solid data on the decrease of elective surgery during the lockdown period are lacking. [START_REF] Maspero | Major cancer surgery during the coronavirus pandemic: experience from a tertiary referral center and COVID-19 hub in Northern Italy[END_REF][START_REF] Farid | Decrease in surgical activity in the COVID-19 pandemic: an economic crisis[END_REF][START_REF] Pirracchio | The response of US hospitals to elective surgical cases in the COVID-19 pandemic[END_REF] The objective of the present study was to assess the impact of lockdown on postoperative mortality and on surgical activity in elective digestive surgery on a national scale using administrative data covering the entire healthcare system in France.

Methods

Study design

This is an analytical observational study comparing surgical activity during the COVID-19 pandemic lockdown with the surgical activity of a historical control group from the corresponding period of 2019.

Data were collected from a National Health Database (the Programme de Médicalisation des Systèmes d'Informations, PMSI), which is a mandatory billing tool for all hospital stays in France, either for public or private institutions. [START_REF] Domin | Le Programme de médicalisation des systèmes d'information (PMSI): De l'indicateur de comptabilité hospitalière au mode de tarification (1982-2012)[END_REF] The purpose of this database is to establish the financial budget of hospitals based on the number of patients admitted and the type of procedures performed. Information in the database includes patient and hospital identifier, length of stay, date of admission and discharge, any diagnosis reported according to the international classification of diseases, 10 th version (ICD-10), and any surgical procedure coded according to specific procedural classification (the Classification Commune des Actes Médicaux, CCAM), which is used in France to classify any surgical, endoscopic or radiological act. [START_REF] Bousquet | Evaluation of the CCAM Hierarchy and Semi Structured Code for Retrieving Relevant Procedures in a Hospital Case Mix Database[END_REF] The validity of this database has been tested by cross-referencing with other cohort databases. [START_REF] Quantin | Qualité des données périnatales issues du PMSI : comparaison avec l'état civil et l'enquête nationale périnatale 2010[END_REF][START_REF] Quantin | Estimation of National Colorectal-Cancer Incidence Using Claims Databases[END_REF][START_REF] Pierron | Évaluation de la qualité métrologique des données du programme de médicalisation du système d'information (PMSI) en périnatalité : étude pilote réalisée dans 3 CHU[END_REF] Access to the database was requested from and granted by the National Commission on Informatics and Liberty (CNIL). As the identifier is anonymous, patient consent was not required.

Population

All adult patients operated on for elective digestive resections, as defined by Appendix 1, were included. These comprised oesophageal, gastric, colic, rectal, pancreatic, and hepatic resections. Patients with multiple resections (more than 2 procedures) and patients undergoing emergency surgery (defined by a hospital admission after an emergency department visit) were excluded.

All data from January 1 st 2019 to June 30 th 2020 were extracted from the database. Two groups were created: the lockdown group defined by hospital admissions between March 17 th 2020 and May 11 th 2020, corresponding to the lockdown period in France, and the control group selected as hospital admissions occurring between March 19 th , 2019 and May 13 th, 2019 (i.e., corresponding to the same calendar days, from the 2 nd day of the 12 th week of the year, to the 1 st day of the 20 th week of the year).

Covariates

Patient characteristics and demographics extracted from the database included: age, gender, hospital, and region. The ICD-10 codes of previous hospital stays in the past 3 years were used in order to calculate the comorbidity index according to the Charlson Comorbidity Index (CCI) defined in Appendix 2, and neoadjuvant chemotherapy or radiotherapy (codes Z511 and Z510). [START_REF] Charlson | The Charlson Comorbidity Index Can Be Used Prospectively to Identify Patients Who Will Incur High Future Costs[END_REF][START_REF] Charlson | A new method of classifying prognostic comorbidity in longitudinal studies: development and validation[END_REF] Nutritional status (E43, E44, E46) and obesity (E66) were also recorded.

Data on the type of surgical resection were collected. Different groups of surgery were created in order to match patients: esophagectomy; total and partial gastrectomy; right, transversal, left and total colectomy; low anterior rectal resection, rectal resection associated with colo-anal anastomosis, total colo-protectomy with ileo-anal anastomosis, abdomino-perineal resection and prolapsus surgery; minor or major (≥3 segments) hepatectomy; pancreatic head or other pancreatic resections.

The volume of resection per week per centre was categorized using the quartiles of surgical activity.

The COVID-19 infection status was defined according to the ICD-10 th codes, and classified as symptomatic (U0710, U0711, U0714, and U0715) or asymptomatic (U0712 and U0713) defined in the appendix 3. A high viral spreading zone was defined as a rate over 0.1 of outpatients for COVID-19 at emergency departments in a region or as a rate over 0.8 of intensive care unit hospitalization for COVID-19 in a region on 4 th May, 2020 (governmental announcement defining the type of zone).

Outcomes

The primary outcome was the in-hospital postoperative mortality, which is defined as death occurring during the hospital stay for surgery, irrespective of the time between the surgery and the event.

The secondary outcomes were the change in the number of hospital admissions for digestive surgery and in the postoperative morbidity rate. The decrease in surgical activity was calculated by reporting the difference between 2020 and 2019. In the assessment of postoperative morbidity, we included the following complications: surgical site infection; bleeding; thromboembolic disease; pulmonary complication; and renal failure. The ICD-10 codes used to identify any selected complication are reported in Appendix 3.

Statistical analysis

Description of data was performed with absolute values and percentage for categorical variables and mean and standard deviation for continuous variables. Univariate analysis was realized with a univariate general linear model. A propensity score was calculated on the probability of being operated on in 2020 using the age, gender, CCI, [START_REF] Charlson | The Charlson Comorbidity Index Can Be Used Prospectively to Identify Patients Who Will Incur High Future Costs[END_REF][START_REF] Charlson | A new method of classifying prognostic comorbidity in longitudinal studies: development and validation[END_REF] nutritional status, cancer status, neoadjuvant chemotherapy or radiotherapy, and hospital volume. A matching between the lockdown and control groups was performed using the nearest neighbour for propensity score and the exact method for surgical procedure and region, in order to perfectly match on the same procedure in the same region where the surgery was performed. A multivariate analysis for in-hospital mortality was conducted on this matched population including the group (lockdown and control) and type of COVID-19 infection (none, asymptomatic, symptomatic) in a general linear model. The same type of analysis was performed using morbidity as dependent variable. Odds ratio (OR) and 95% confidence intervals (CI) were estimated.

Statistical analyses were performed with R software. The R-package Matchit was used to perform the group matching. [START_REF] Core | R: A language and environment for statistical computing[END_REF][START_REF] Ho | MatchIt : Nonparametric Preprocessing for Parametric Causal Inference[END_REF]

Results

Characteristics of the study population

The overall population included 15,217 patients, 5,892 in the lockdown group and 9,325 in the control group. Patients' characteristics are summarized in Table 1. The mean age was 65±15 years, with 54% being male patients. In the lockdown group, there were more severe patients as the CCI was higher (control=2.2 ± 2.7 vs. lockdown=2.3 ± 2.5, p<0.0001), with a higher prevalence of resection for cancer (control= 5791, 62% vs. lockdown=4445, 75%; p<0.0001). Moreover, neoadjuvant chemotherapy or radiotherapy were more common among patients in the lockdown group (control=1,504, 16% vs. lockdown=1,064, 18%; p=0.002). In total, 574/5892 (8.7%) surgical patients were diagnosed COVID-19 positive in 2020, and 61 (1.0%) were classified as symptomatic. The characteristics according type of COVID-19 infection is reported in the appendix 4. Patients with infection were more severe patients as the CCI was higher, with a higher rate of malnutrition. The most common symptom of COVID-19 infection was respiratory symptoms (n= 56/61, 92%). Table 2 reports the decrease in activity by type of surgery. Hepatic resections were the most impacted by the lockdown with a significant decrease of 44% (p=0.02). The decrease was more important in a high viral propagation zone (high viral spreading zone: 44%, low viral spreading zone: 32%, p<0.001).

Decrease in surgical activity

The decrease of "high" volume center (> more than 4 resections by week) was more important than the decrease of activity of lower volume center (p=0.001).

Mortality during the lockdown period

The in-hospital mortality was 2.5% (n=233/9325) in the historical control group and 3.0% (n=174/5892) in the lockdown group (p=0.1). After matching, 5823 patients were included in each group. The characteristics of patients after matching are presented in Appendix 4. There was no significant difference between groups in the variables included in the propensity score, region, and type of surgery.

The multivariate analysis on in-hospital mortality is reported in Table 3. There was no difference in mortality before and after adjustment on COVID-19 infection between the two groups (OR: 1.05 [95%CI: 0.83-1.34], p=0.669). An asymptomatic COVID-19 infection was a risk factor for a twofold increased mortality (OR=2.00, 1.27-3.05, p=0.002), whereas a symptomatic COVID-19 infection was associated with a tenfold increased mortality (OR=10.51, 5.35-19.31, p<0.001).

Postoperative complications

Table 3 reports postoperative complications. In the univariate analysis on the matched groups, overall morbidity and other postoperative complications were not different between the control and lockdown groups. In the multivariate analysis, the lockdown group was not associated with higher overall morbidity (OR: 0.95 [95%CI: 0.87-1.03], p=0.227).

The overall morbidity was higher in the asymptomatic group compared to the COVID-19-free group (No infection= 27% vs. Asymptomatic=47%, p<0.001) and even higher in the symptomatic group (No infection= 27% vs. Symptomatic=80%, p<0.001). The rates of pulmonary complications, surgical site infection, and thromboembolic disease were higher for COVID-19-infected patients compared to COVID-19-free patients.

Discussion

In this nationwide data analysis, the overall postoperative mortality after elective digestive surgery during the COVID-19 pandemic lockdown was comparable to the mortality rate observed during the same period in 2019. However, COVID-19 infection, either symptomatic or asymptomatic, was a strong independent risk factor of postoperative mortality and morbidity. We observed a reduction of more than 3400 procedures (37%) in gastrointestinal surgical resections during the lockdown.

During the most acute phase of the pandemic, several national and international guidelines indicated that nonurgent surgery had to be postponed in order to allocate more resources to COVID-19 patients' care. [START_REF] Tuech | Our challenge is to adapt the organization of our system to the six stages of the epidemic to go beyond the COVID-19 crisis: Surgical organization beyond the COVID-19 crisis[END_REF][START_REF] Tuech | Strategy for the practice of digestive and oncological surgery during the Covid-19 epidemic[END_REF][START_REF] Collaborative | Global guidance for surgical care during the COVID-19 pandemic[END_REF][START_REF] Diaz | Elective surgery in the time of COVID-19[END_REF] Elective surgery decreased more markedly in regions where the viral surge was In our study, despite the important reduction in elective surgery during the lockdown period, the percentage of patients operated on for cancer increased. In fact, all guidelines published in that context recommended to postpone nonurgent elective surgery, primarily delaying surgery for benign conditions. This could explain why in 2020 patients were older and presented with more severe comorbidities. [START_REF] Collaborative | Elective surgery cancellations due to the COVID-19 pandemic: global predictive modelling to inform surgical recovery plans[END_REF][START_REF] Collaborative | Global guidance for surgical care during the COVID-19 pandemic[END_REF] In the present study, the comparison between groups showed a greater proportion of patients who had a higher Charlson Comorbidity Index and received neoadjuvant treatment during the lockdown period.

For the overall population, we did not observe any significant difference in postoperative mortality between the lockdown period and the corresponding period in 2019, before and after matching. The only increase was observed in the COVID-19-infected population, as already reported by several authors. Effectively, we reported a twofold increased mortality for asymptomatic COVID-19 infection, whereas a symptomatic COVID-19 infection was associated with a tenfold increased mortality. Doglietto et al. analysed 41 surgical patients with positive results at the COVID-19 screening and showed results similar to ours in symptomatic COVID-19 patients. [START_REF] Doglietto | Factors Associated With Surgical Mortality and Complications Among Patients With and Without Coronavirus Disease 2019 (COVID-19) in Italy[END_REF] The COVIDSurg collaborative study also reported a mortality rate of 24% for patients undergoing surgery with an active COVID-19 infection. [START_REF] Nepogodiev | Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study[END_REF] The observed increase in mortality rate in the COVID-19-positive patients supports the need for systematic screening prior to elective surgery and we think that, whenever possible, elective surgery for cancer in COVID-19-free patients should not be delayed in order to limit a potential increased risk of over staging. This fact is supported by a recent study showing a low risk of postoperative mortality for patients operated on for oncologic elective surgery with a COVID-19-free surgical pathway. [START_REF] Glasbey | Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study[END_REF] In light of these results, we think that surgery for benign disease or for early cancer should be postponed after a positive screening. On the other hand, for locally advanced cancer, in case of symptomatic COVID-19 infection, the surgery should be delayed because of a high risk of post-operative death. In case of asymptomatic COVID-19 infection, the decision should be discussed in multidisciplinary staff included anaesthesiologist, oncologist and surgeon.

The analysis of postoperative morbidity showed increased risks of several complications after COVID-19 infection in patients operated on in 2020 such as: thromboembolic disease, surgical site infection and pulmonary complications. This finding is consistent with other studies.(8, 30) Doglietto et al. also reported 10% of thrombotic complications and 60% of pulmonary complications for COVID-19 patients group (n=41). [START_REF] Doglietto | Factors Associated With Surgical Mortality and Complications Among Patients With and Without Coronavirus Disease 2019 (COVID-19) in Italy[END_REF] This study has some limitations. First, the real impact of COVID-19 infection on postoperative mortality and morbidity should be interpreted with caution. Data on systematic screening in each institution and delay of reverse transcription polymerase chain reaction prior to surgery were not available. Hence, undiagnosed asymptomatic patients could have been assigned to the COVID-free group. This ascertainment bias has already been suggested for the aforementioned study of the COVIDSurg collaborative, and could also be argued in our analysis. [START_REF] Myles | Mitigating the risks of surgery during the COVID-19 pandemic[END_REF] Moreover, the mortality of COVID-19 patients could be associated to a more severe patient status, not permitting to postpone surgery. We tried to limit this bias by excluding patients operated in an emergency setting, and adjusting for neoadjuvant treatment and surgery for cancer in the statistical analysis. We think that the strong association between mortality and COVID-19 status could not be only attributed to a selection bias.

Secondly, the PMSI database does not allow accurate screening of the cause of death because of unavailable information.

The main strength of this study is the data source. As the PMSI database is mandatory for all hospitals and clinics, it gives a pragmatic and comprehensive picture of the surgical activity on a national scale, allowing a true assessment of in-hospital mortality.

Conclusion

Despite a considerable reduction in the surgical activity for elective digestive resections during the lockdown period, mortality remained stable on a nationwide scale in COVID-free patients. In contrast an asymptomatic COVID-19 infection was a risk factor for a twofold increased mortality, whereas a symptomatic COVID-19 infection was associated with a tenfold increased mortality. These findings support that systematic SARS-CoV-2 screening should be advocated prior to elective GI surgery and that all efforts should be made to maintain elective surgical resection for cancer during the second wave of the pandemic viral infection in COVID-free patients.

Legend

Figure 1

 1 Figure 1 compares the overall surgical activity during 2019 and 2020. The overall activity decreased by

  higher, probably due to restrictions to favour COVID-19 patients' treatment. As reported in other countries, reduction of activity was motivated by reallocation of anaesthesiologists, nursing staff and mechanical ventilators in medical-COVID-19 units or ICU-COVID-19 units. (27, 28) Soreide et al. furthermore described operating theatres and surgical intensive care units converted to rescue additional ICU units for severe COVID patients requiring mechanical ventilation.(29) Those facts contributed to a higher decrease in surgical activity, especially in high viral spreading zones.

Figure 1 .

 1 Figure 1. Overall digestive elective resections according years per weeks

Figure 1 .

 1 Figure 1. Overall digestive elective resections according years per weeks

Table 3 .

 3 Impact of the Lockdown on mortality and morbidity compared to control group on the matched population and adjusted on the COVID-19 infection

			No death N = 11337	Death N = 309	OR (univariable)	OR (multivariable)
	Group	Control	5684 (50) 139 (45)
		Lockdown	5653 (50) 170 (55) 1.23 (0.98-1.54, p=0.074) 1.05 (0.83-1.34, p=0.669)
	COVID-19 infection	No infection	10805 (95) 271 (88)
		Asymptomatic	484 (4)	25 (8)	2.06 (1.32-3.07, p=0.001) 2.00 (1.27-3.05, p=0.002)
		Symptomatic	48 (1)	13 (4) 10.80 (5.56-19.58, p<0.001) 10.51 (5.35-19.31, p<0.001)

Data are reported as nb (%) unless otherwise specified.

Table 4 .

 4 Univariate analysis of mortality and morbidity for 2020 patients according to COVID-19 infection statusData are reported as nb (%) unless otherwise specified.

	Outcomes	No infection (n=5318)	Asymptomatic (n=513)	Symptomatic (n=61)	p-value (no infection vs asymptomatic)	p-value (no infection vs symptomatic)
	Mortality	136 (2.6)	25 (4.9)	13 (21.3)	< 0.001	< 0.001
	Overall morbidity	1459 (27.4)	240 (46.8)	49 (80.3)	< 0.001	< 0.001
	Bleeding	343 (6.4)	44 (8.6)	6 (9.8)	0.08	0.42
	Surgical site infection	744 (14.0)	127 (24.8)	19 (31.1)	< 0.001	< 0.001
	Thromboembol ic disease	172 (3.2)	28 (5.5)	7 (11.5)	0.01	0.001
	Pulmonary infection	155 (2.9)	62 (12.1)	38 (62.3)	< 0.001	< 0.001
	Pulmonary insufficiency	305 (5.7)	88 (17.2)	24 (39.3)	< 0.001	< 0.001
	Overall
	pulmonary	395 (7.4)	116 (22.6)	40 (65.6)	< 0.001	< 0.001
	complications
	Renal insufficiency	327 (6.1)	60 (11.7)	13 (21.3)	< 0.001	< 0.001

Acknowledgements:

No Funding for research or publication No conflict of interest