Editing IPCC:AR6/WGIII/TS (section)

=== TS.5.4 Buildings ===

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'''Global GHG emissions from buildings were 12 GtCO''' 2 '''-eq in 2019, equivalent to 21% of global GHG emissions. Of this, 57% (6.8 GtCO''' 2 '''-eq) were indirect emissions from off-site generation of electricity and heat, 24% (2.9 GtCO''' 2 '''-eq) were direct emissions produced on-site and 18% (2.2 GtCO''' 2 '''-eq) were embodied emissions from the production of cement and steel used in buildings (''' '''''high confidence''''' ''').''' Most building-sector emissions are CO 2 . Final energy demand from buildings reached 128 EJ globally in 2019 (around 31% of global final energy demand), and electricity demand from buildings was slightly above 43 EJ globally (around 18% of global electricity demand). Residential buildings consumed 70% (90 EJ) of the global final energy demand from buildings. Over the period 1990–2019, global CO 2 emissions from buildings increased by 50%, global final energy demand from buildings grew by 38%, and global final electricity demand increased by 161%. {9.3}

'''In most regions, historical improvements in efficiency have been approximately matched by growth in floor area per capita (''' '''''high confidence''''' ''').''' At the global level, building-specific drivers of GHG emissions include: (i) population growth, especially in developing countries; (ii) increasing floor area per capita, driven by the increasing size of dwellings while the size of households kept decreasing, especially in developed countries; (iii) the inefficiency of newly constructed buildings, especially in developing countries, and the low renovation rates and low ambition level in developed countries when existing buildings are renovated; (iv) the increase in use, number and size of appliances and equipment, especially information and communication technologies (ICT) and cooling, driven by income; and, (v) the continued reliance on carbon-intensive electricity and heat. These factors taken together are projected to continue driving increased GHG emissions in the building sector in the future. {9.3, 9.6, 9.9}

'''Building-sector GHG emissions were assessed using the Sufficiency, Efficiency, Renewable (SER) framework. Sufficiency measures tackle the causes of GHG emissions by limiting the demand for energy and materials over the lifecycle of buildings and appliances (''' '''''high confidence''''' ''').''' In [https://www.ipcc.ch/chapters/chapter-9 Chapter 9] of this report, ''sufficiency'' differs from ''efficiency'' : ''sufficiency'' is about long-term actions driven by non-technological solutions, which consume less energy in absolute terms; ''efficiency'' , in contrast is about continuous short-term marginal technological improvements. Sufficiency policies are a set of measures and daily practices that avoid demand for energy, materials, land and water while delivering human well-being-for-all within planetary boundaries. Use of the SER framework aims to reduce the cost of constructing and using buildings without reducing occupants’ well-being and comfort. {9.1, 9.4, 9.5, 9.9}

'''Sufficiency interventions do not consume energy during the use phase of buildings and do not require maintenance nor replacement over the lifetime of buildings.''' Density, compacity, bioclimatic design to optimise the use of nature-based solutions, multi-functionality of space through shared space and to allow for adjusting the size of buildings to the evolving needs of households, circular use of materials and repurposing unused existing buildings to avoid using virgin materials, optimisation of the use of buildings through lifestyle changes, use of the thermal mass of buildings to reduce thermal needs, and moving from ownership to usership of appliances, are among the sufficiency interventions implemented in leading municipalities ( ''high confidence'' ). At a global level, up to 17% of the mitigation potential in the buildings sector could be captured by 2050 through sufficiency interventions ( ''medium confidence'' ). (Figure TS.15) {9.2, 9.3, 9.4, 9.5, 9.9}

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'''Figure TS.''' '''15: Decompositions of changes in historical residential energy emissions 1990–2019, changes in emissions projected by baseline scenarios for 2020–2050, and differences between scenarios in 2050 using scenarios from three models: IEA, IMAGE, and RECC.''' RECC-LED data for '''(a)''' global, and '''(b)''' for nine world regions, include only space heating and cooling and water heating in residential buildings. Emissions are decomposed using the equation, which shows changes in driver variables of population, sufficiency (floor area per capita), efficiency (final energy per floor area), and renewables (GHG emissions per final energy). ‘Renewables’ is a summary term describing changes in GHG intensity of energy supply. Emission projections to 2050, and differences between scenarios in 2050, demonstrate mitigation potentials from the dimensions of the SER framework realised in each model scenario. In most regions, historical improvements in efficiency have been approximately matched by growth in floor area per capita. Implementing sufficiency measures that limit growth in floor area per capita, particularly in developed regions, reduces the dependence of climate mitigation on technological solutions. {Figure 9.5, Box 9.2}

'''The potential associated with sufficiency measures, as well as the replacement of appliances, equipment and lights by efficient ones, is below zero cost (''' '''''high confidence''''' ''').''' The construction of high-performance buildings is expected to become a business-as-usual technology by 2050 with costs below USD20 tCO ''2'' ''–1'' in developed countries and below USD100 tCO ''2'' ''–1'' in developing countries ( ''medium confidence'' ). For existing buildings, there have been many examples of deep retrofits where additional costs per CO ''2'' abated are not significantly higher than those of shallow retrofits. However, for the whole building stock they tend to be in cost intervals of USD–200 tCO ''2'' ''–1'' and &gt;USD200 tCO ''2'' ''–1'' ( ''medium confidence'' ). Literature emphasises the critical role of the 2020–2030 decade in accelerating the learning of know-how and skills to reduce the costs and remove feasibility constraints for achieving high-efficiency buildings at scale and set the sector on the pathway to realise its full potential ( ''high confidence'' ). {9.3, 9.6, 9.9} .

'''The development, since AR5, of integrated approaches to the construction and retrofit of buildings has led to increasing the number of zero-energy or zero-carbon buildings in almost all climate zones.''' The complementarity and interdependency of measures leads to cost reductions, while optimising the mitigation potential achieved and avoiding the lock-in-effect ( ''medium confidence'' ). {9.6, 9.9}

'''The decarbonisation of buildings is constrained by multiple barriers and obstacles as well as limited finance flows (''' '''''high confidence''''' '''). The lack of institutional capacity, especially in developing countries, and appropriate governance structures slow down the decarbonisation of the global building stock (''' '''''medium confidence''''' ''').''' The building sector is highly heterogenous with many different building types, sizes, and operational uses. The sub-segment representing rented property faces principal/agent problems where the tenant benefits from the decarbonisation’s investment made by the landlord. The organisational context and the governance structure could trigger or hinder the decarbonisation of buildings. Global investment in the decarbonisation of buildings was estimated at USD164 billion in 2020. However, this is not enough by far to close the investment gap ( ''high confidence'' ). {9.9}

'''Policy packages could grasp the full mitigation potential of the global building stock. Building energy codes represent the main regulatory instrument to reduce emissions from both new and existing buildings (''' '''''high confidence''''' ''').''' The most advanced building energy codes include requirements on each of the three pillars of the SER framework in the ''use'' and ''construction'' phase of buildings. Building energy codes have proven to be effective if compulsory and combined with other regulatory instruments such as minimum energy performance standard for appliances and equipment, if the performance level is set at the level of the best available technologies in the market ( ''high confidence'' ). Market-based instruments such as carbon taxes with recycling of the revenues and personal or building carbon allowances could also contribute to fostering the decarbonisation of the building sector ( ''medium confidence'' ). {9.9}

'''Adapting buildings to future climate while ensuring well-being for all requires action. Expected heatwaves will inevitably increase cooling needs to limit the health impacts of climate change (''' '''''medium confidence''''' ''').''' Global warming will impact cooling and heating needs but also the performance, durability and safety of buildings, especially historical and coastal ones, through changes in temperature, humidity, atmospheric concentrations of CO 2 and chloride, and sea level rise. Adaptation measures to cope with climate change may increase the demand for energy and materials leading to an increase in GHG emissions if not mitigated. Sufficiency measures which anticipate climate change, and include natural ventilation, white walls, and nature-based solutions (e.g., green roofs) will decrease the demand for cooling. Shared cooled spaces with highly efficient cooling solutions are among the mitigation strategies which can limit the effect of the expected heatwaves on people’s health. {9.7, 9.8}

'''Well-designed and effectively implemented mitigation actions in the buildings sector have significant potential to help achieve the SDGs (''' '''''high confidence''''' ''').''' As shown in Figure TS.16, the impacts of mitigation actions in the building sector go far beyond the goal of climate action (SDG 13) and contribute to meeting 15 other SDGs. Mitigation actions in the building sector bring health gains through improved indoor air quality and thermal comfort, and have positive significant macro- and micro-economic effects, such as increased productivity of labour, job creation, reduced poverty, especially energy poverty, and improved energy security ( ''high confidence'' ). (Figure TS.29) {9.8}

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'''Figure TS.''' '''16 |''' '''Contribution of building-sector mitigation policies to meeting Sustainable Development Goals.''' {Figure 9.18}

'''The COVID-19 pandemic emphasised the importance of buildings for human well-being and highlighted the inequalities in access for all to suitable, healthy buildings, which provide natural daylight and clean air to their occupants (''' '''''medium confidence''''' ''').''' Recent WHO health recommendations have also emphasise indoor air quality, preventive maintenance of centralised mechanical heating, ventilation, and cooling systems. There are opportunities for repurposing existing non-residential buildings, no longer in use due to the expected spread of teleworking triggered by the health crisis and enabled by digitalisation. (Box TS.14) {9.1}

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