Editing IPCC:AR6/WGIII/Chapter-9 (section)

== 9.7 Links to Adaptation ==

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Buildings are capital-intensive and long-lasting assets designed to perform under a wide range of climate conditions ( [[#Hallegatte--2009|Hallegatte 2009]] ; [[#Pyke--2012|Pyke et al. 2012]] ). Their long lifespan means that the building stock will be exposed to future climate ( [[#Hallegatte--2009|Hallegatte 2009]] ; [[#de%20Wilde--2012|de Wilde and Coley 2012]] ; [[#Wan--2012|Wan et al. 2012]] ) and, as such, adaptation measures will be necessary.

The impacts of climate change on buildings can affect building structures, building construction, building material properties, indoor climate and building energy use ( [[#Andrić--2019|Andrić et al. 2019]] ). Many of those impacts and their respective adaptation strategies interact with GHG mitigation in different ways.

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=== 9.7.1 Climate Change Impacts and Adaptation in Buildings ===

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A large body of literature on climate impacts on buildings focuses on the impacts of climate change on heating and cooling needs ( [[#de%20Wilde--2012|de Wilde and Coley 2012]] ; [[#Wan--2012|Wan et al. 2012]] ; [[#Andrić--2019|Andrić et al. 2019]] ). The associated impacts on energy consumption are expected to be higher in hot summer and warm winter climates, where cooling needs are more relevant ( [[#Li--2012|Li et al. 2012]] ; [[#Wan--2012|Wan et al. 2012]] ; [[#Andrić--2019|Andrić et al. 2019]] ). If not met, this higher demand for thermal comfort can impact health, sleep quality and work productivity, having disproportionate effects on vulnerable populations and exacerbating energy poverty ( [[#Biardeau--2020|Biardeau et al. 2020]] ; [[#Sun--2020|Sun et al. 2020]] ; [[#Falchetta--2021|Falchetta and Mistry 2021]] ) ( [[#9.8|Section 9.8]] ).

Increasing temperatures can lead to higher cooling needs and, therefore, energy consumption ( [[#Li--2012|Li et al. 2012]] ; [[#Schaeffer--2012|Schaeffer et al. 2012]] ; [[#Wan--2012|Wan et al. 2012]] ; [[#Clarke--2018|Clarke et al. 2018]] ; International Energy Agency 2018; [[#Andrić--2019|Andrić et al. 2019]] ). Higher temperatures increase the number of days/hours in which cooling is required and as outdoor temperatures increase, the cooling load to maintain the same indoor temperature will be higher ( [[#Andrić--2019|Andrić et al. 2019]] ). These two effects are often measured by cooling degree-days [[#footnote-001|1]] (CDD) and there is a vast literature on studies at the global ( [[#Isaac--2009|Isaac and van Vuuren 2009]] ; [[#Atalla--2018|Atalla et al. 2018]] ; [[#Clarke--2018|Clarke et al. 2018]] ; [[#Mistry--2019|Mistry 2019]] ; [[#Biardeau--2020|Biardeau et al. 2020]] ) and regional level ( [[#Zhou--2014|Zhou et al. 2014]] ; [[#Bezerra--2021|Bezerra et al. 2021]] ; [[#Falchetta--2021|Falchetta and Mistry 2021]] ). Other studies use statistical econometric analyses to capture the empirical relationship between climate variables and energy consumption ( [[#Auffhammer--2014|Auffhammer and Mansur 2014]] ; [[#van%20Ruijven--2019|van Ruijven et al. 2019]] ). A third effect is that higher summer temperatures can incentivise the purchase of space cooling equipment ( [[#Auffhammer--2014|Auffhammer 2014]] ; [[#De%20Cian--2019|De Cian et al. 2019]] ; [[#Biardeau--2020|Biardeau et al. 2020]] ), especially in developing countries ( [[#Pavanello--2021|Pavanello et al. 2021]] ).

The impacts of increased energy demand for cooling can have systemic repercussions ( [[#Ciscar--2014|Ciscar and Dowling 2014]] ; [[#Ralston%20Fonseca--2019|Ralston Fonseca et al. 2019]] ), which in turn can affect the provision of other energy services. Space cooling can be an important determinant of peak demand, especially in periods of extreme heat (International Energy Agency 2018). Warmer climates and higher frequency and intensity of heat waves can lead to higher loads ( [[#Dirks--2015|Dirks et al. 2015]] ; [[#Auffhammer--2017|Auffhammer et al. 2017]] ), increasing the risk of grid failure and supply interruptions.

Although heating demand in cold climate regions can be expected to decrease with climate change and, to a certain extent, outweigh the increase in cooling demand, the effects on total primary energy requirements are uncertain ( [[#Li--2012|Li et al. 2012]] ; [[#Wan--2012|Wan et al. 2012]] ). Studies have found that increases in buildings energy expenditures for cooling more than compensate the savings from lower heating demands in most regions ( [[#Clarke--2018|Clarke et al. 2018]] ). In addition, climate change may affect the economic feasibility of district heating systems ( [[#Andrić--2019|Andrić et al. 2019]] ).

In cold climates, a warming climate can potentially increase the risk of overheating in high-performance buildings with increased insulation and airtightness to reduce heat losses ( [[#Gupta--2012|Gupta and Gregg 2012]] ). In such situations, the need for active cooling technologies may arise, along with higher energy consumption and GHG emissions ( [[#Gupta--2015|Gupta et al. 2015]] ).

Changes in cloud formation can affect global solar irradiation and, therefore, the output of solar photovoltaic panels, possibly affecting on-site renewable energy production ( [[#Burnett--2014|Burnett et al. 2014]] ). The efficiency of solar photovoltaic panels and their electrical components decreases with higher temperatures ( [[#Bahaidarah--2013|Bahaidarah et al. 2013]] ; [[#Simioni--2019|Simioni and Schaeffer 2019]] ). However, studies have found that such effects can be relatively small ( [[#Totschnig--2017|Totschnig et al. 2017]] ), making solar PV a robust option to adapt to climate change ( [[#Shen--2016|Shen and Lior 2016]] ; [[#Santos--2021|Santos and Lucena 2021]] ) (see [[#9.4|Section 9.4]] ).

Climate change can also affect the performance, durability and safety of buildings and their elements (facades, structure, etc.) through changes in temperature, humidity, wind, and chloride and CO 2 concentrations ( [[#Bastidas-Arteaga--2010|Bastidas-Arteaga et al. 2010]] ; [[#Bauer--2018|Bauer et al. 2018]] ; [[#Rodríguez-Rosales--2021|Rodríguez-Rosales et al. 2021]] ; [[#Chen--2021|Chen et al. 2021]] ). Historical buildings and coastal areas tend to be more vulnerable to these changes ( [[#Huijbregts--2012|Huijbregts et al. 2012]] ; [[#Mosoarca--2019|Mosoarca et al. 2019]] ; [[#Cavalagli--2019|Cavalagli et al. 2019]] ; [[#Rodríguez-Rosales--2021|Rodríguez-Rosales et al. 2021]] ).

Temperature variations affect the building envelope, for example, with cracks and detachment of coatings ( [[#Bauer--2016|Bauer et al. 2016]] , 2018). Higher humidity (caused by wind-driven rain, snow or floods) hastens deterioration of bio-based materials such as wood and bamboo ( [[#Brambilla--2020|Brambilla and Gasparri 2020]] ), also deteriorating indoor air quality and users health ( [[#Huijbregts--2012|Huijbregts et al. 2012]] ; [[#Grynning--2017|Grynning et al. 2017]] ; [[#Lee--2020|Lee et al. 2020]] ).

Climate change can accelerate the degradation of reinforced concrete structures due to the increase of chloride ingress ( [[#Bastidas-Arteaga--2010|Bastidas-Arteaga et al. 2010]] ) and the concentration of CO 2 , which increase the corrosion of the embedded steel ( [[#Stewart--2012|Stewart et al. 2012]] ; [[#Peng--2016|Peng and Stewart 2016]] ; [[#Chen--2021|Chen et al. 2021]] ). Corrosion rates are higher in places with higher humidity and humidity fluctuations ( [[#Guo--2019|Guo et al. 2019]] ), and degradation could be faster with combined effects of higher temperatures and more frequent and intense precipitations ( [[#Bastidas-Arteaga--2010|Bastidas-Arteaga et al. 2010]] ; [[#Chen--2021|Chen et al. 2021]] ).

Higher frequency and intensity of hurricanes, storm surges and coastal and non-coastal flooding can escalate economic losses to civil infrastructure, especially when associated with population growth and urbanisation in hazardous areas ( [[#Bjarnadottir--2011|Bjarnadottir et al. 2011]] ; [[#Li--2016|Li et al. 2016]] ; [[#Lee--2017|Lee and Ellingwood 2017]] ). Climate change should increase the risk and exposure to damage from flood ( [[#de%20Ruig--2019|de Ruig et al. 2019]] ), sea level rise ( [[#Bosello--2014|Bosello and De Cian 2014]] ; [[#Zanetti--2016|Zanetti et al. 2016]] ; [[#Bove--2020|Bove et al. 2020]] ) and more frequent wildfires ( [[#Barkhordarian--2018|Barkhordarian et al. 2018]] ; [[#Craig--2020|Craig et al. 2020]] ).

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=== 9.7.2 Links Between Mitigation and Adaptation in Buildings ===

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Adaptation options interacts with mitigation efforts because measures to cope with climate change impacts can increase energy and material consumption, which may lead to higher GHG emissions ( [[#Kalvelage--2014|Kalvelage et al. 2014]] ; [[#Davide--2019|Davide et al. 2019]] ; [[#Sharifi--2020|Sharifi 2020]] ). Energy consumption is required to adapt to climate change. Mitigation measures, in turn, influence the degree of vulnerability of buildings to future climate and, thus, the adaptation required.

Studies have assessed the increases in energy demand to meet indoor thermal comfort under future climate ( [[#de%20Wilde--2012|de Wilde and Coley 2012]] ; [[#Li--2012|Li et al. 2012]] ; [[#Clarke--2018|Clarke et al. 2018]] ; [[#Andrić--2019|Andrić et al. 2019]] ). Higher cooling needs may induce increases in energy demand ( [[#Wan--2012|Wan et al. 2012]] ; [[#Li--2012|Li et al. 2012]] ), which could lead to higher emissions, when electricity is fossil-based (International Energy Agency 2018; [[#Biardeau--2020|Biardeau et al. 2020]] ), and generate higher loads and stress on power systems ( [[#Dirks--2015|Dirks et al. 2015]] ; [[#Auffhammer--2017|Auffhammer et al. 2017]] ). In this regard, increasing energy efficiency of space cooling appliances and adopting dynamic cooling setpoint temperatures, can reduce the energy needs for cooling and limit additional emissions and pressures on power systems ( [[#Davide--2019|Davide et al. 2019]] ; [[#Bienvenido-Huertas--2020|Bienvenido-Huertas et al. 2020]] ; [[#Bezerra--2021|Bezerra et al. 2021]] ) ( [[#9.4|Section 9.4]] , Figure 9.11 and Supplementary Material Tables 9.SM.1 to 9.SM.3). This can also be achieved with on-site renewable energy production, especially solar PV for which there can be a timely correlation between power supply and cooling demand, improving load matching ( [[#Salom--2014|Salom et al. 2014]] ; [[#Grove-Smith--2018|Grove-Smith et al. 2018]] ).

Mitigation alternatives through passive approaches may increase resilience to climate change impacts on thermal comfort and reduce active cooling needs ( [[#Wan--2012|Wan et al. 2012]] ; [[#van%20Hooff--2016|van Hooff et al. 2016]] ; [[#Andrić--2019|Andrić et al. 2019]] ; [[#González%20Mahecha--2020|González Mahecha et al. 2020]] ; [[#Rosse%20Caldas--2020|Rosse Caldas et al. 2020]] ). Combining passive measures can help counteracting climate change driven increases in energy consumption for achieving thermal comfort ( [[#Huang--2016|Huang and Hwang 2016]] ).

Studies raise the concern that measures aimed at building envelope may increase the risk of overheating in a warming climate ( [[#Dodoo--2016|Dodoo and Gustavsson 2016]] ; [[#Fosas--2018|Fosas et al. 2018]] ) ( [[#9.4|Section 9.4]] ). If this is the case, there may be a conflict between mitigation through energy efficiency building regulations and climate change adaptation ( [[#Fosas--2018|Fosas et al. 2018]] ). However, while overheating may occur as a result of poor insulation design, better insulation may actually reduce overheating when properly projected and the overheating risk can be overcome by clever designs ( [[#Fosas--2018|Fosas et al. 2018]] ).

Strengthening building structures to increase resilience and reduce exposure to the risk of extreme events, such as draughts, torrential floods, hurricanes and storms, can be partially achieved by improving building standards and retrofitting existing buildings ( [[#Bjarnadottir--2011|Bjarnadottir et al. 2011]] ). However, future climate is not yet considered in parameters of existing building energy codes ( [[#Steenbergen--2012|Steenbergen et al. 2012]] ). While enhancing structural resilience would lead to GHG emissions ( [[#Liu--2018|Liu and Cui 2018]] ), so would disaster recovery and rebuilding. This adaptation-mitigation trade-off needs to be further assessed.

Since adaptation of the existing building stock may be more expensive and require building retrofit, climate change must be considered in the design of new buildings to ensure performance robustness in both current and future climates, which can have implications for construction costs ( [[#Hallegatte--2009|Hallegatte 2009]] ; [[#Pyke--2012|Pyke et al. 2012]] ; [[#de%20Wilde--2012|de Wilde and Coley 2012]] ; [[#de%20Rubeis--2020|de Rubeis et al. 2020]] ; [[#Picard--2020|Picard et al. 2020]] ) and emissions ( [[#Liu--2018|Liu and Cui 2018]] ). Building energy codes and regulations are usually based on cost-effectiveness and historical climate data, which can lead to the poor design of thermal comfort in future climate ( [[#Hallegatte--2009|Hallegatte 2009]] ; [[#Pyke--2012|Pyke et al. 2012]] ; [[#de%20Wilde--2012|de Wilde and Coley 2012]] ) and non-efficient active adaptive measures based on mechanical air conditioning ( [[#De%20Cian--2019|De Cian et al. 2019]] ) ( [[#9.4|Section 9.4]] , Figure 9.11 and Supplementary Material Tables 9.SM.1 to 9.SM.3). However, uncertainty about future climate change creates difficulties for projecting parameters for the design of new buildings ( [[#Hallegatte--2009|Hallegatte 2009]] ; [[#de%20Wilde--2012|de Wilde and Coley 2012]] ). This can be especially relevant for social housing programs ( [[#Rubio-Bellido--2017|Rubio-Bellido et al. 2017]] ; [[#Triana--2018|Triana et al. 2018]] ; [[#González%20Mahecha--2020|González Mahecha et al. 2020]] ) in developing countries.

The impacts on buildings can lead to higher maintenance needs and the consequent embodied environmental impacts related to materials production, transportation and end-of-life, which account for a relevant share of GHG emissions in buildings lifecycle ( [[#Rasmussen--2018|Rasmussen et al. 2018]] ). Climate change induced biodegradation is especially important for bio-based materials such as wood and bamboo ( [[#Brambilla--2020|Brambilla and Gasparri 2020]] ) which are important options for reducing emissions imbued in buildings’ construction materials ( [[#Peñaloza--2016|Peñaloza et al. 2016]] ; [[#Churkina--2020|Churkina et al. 2020]] ; [[#Rosse%20Caldas--2020|Rosse Caldas et al. 2020]] ).

Although there can potentially be conflicts between climate change mitigation and adaptation, these can be dealt with proper planning, actions, and policies. The challenge is to develop multifunctional solutions, technologies and materials that can mitigate GHG emissions while improving buildings adaptive capacity. Solutions and technologies should reduce not only buildings’ operational emissions, but also embodied emissions from manufacturing and processing of building materials ( [[#Röck--2020|Röck et al. 2020]] ). For instance, some building materials, such as bio-concrete, can reduce lifecycle emissions of buildings and bring benefits in terms of building thermal comfort in tropical and subtropical climates. Also, energy efficiency, sufficiency and on-site renewable energy production can help to increase building resilience to climate change impacts and reduce pressure on the energy system.

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