Editing IPCC:AR6/WGIII/Chapter-4 (section)

==== 4.2.5.7 Efficient Buildings, Cooler in Summer, Warmer in Winter, Towards Net Zero Energy ====

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Most accelerated mitigation pathway scenarios include significant increase in building energy efficiency. Countries in cold regions, in particular, often focus more on building sector GHG emissions mitigation measures such as improving building envelopes and home appliances, and electrifying space heating and water heating.

For example, scenarios for Japan project continued electrification of residential and commercial buildings to 65% and 79% respectively by 2050 to reach 70–90% CO 2 reduction from 2013 levels ( [[#Kato--2019|Kato and Kurosawa 2019]] ). Similarly, a mitigation pathway for China compatible with 1.5°C would require 58% to 70% electrification of buildings according to ( [[#Jiang--2018|Jiang et al. 2018]] ; [[#China%20National%20Renewable%20Energy%20Centre--2019|China National Renewable Energy Centre 2019]] E; nergy Transitions Commission and Rocky Mountain Institute 2019). For the EU-28 to reach net carbon neutrality, complete substitution of fossil fuels with electricity (up to 65% share), district heating, and direct use of solar and ambient heat are projected to be needed for buildings, along with increased use of solar thermal and heat pumps for heating ( [[#Duscha--2019|Duscha et al. 2019]] ). In the UK and Canada, improved insulation to reduce energy demand and efficient building appliances and heating systems are important building strategies needed to reduce emissions to zero by 2050 ( [[#Vaillancourt--2017|Vaillancourt et al. 2017]] ; [[#Chilvers--2017|Chilvers et al. 2017]] ; [[#Roberts--2018a|Roberts et al. 2018a]] ). In Ireland, achieving 80–95% emissions reduction below 1990 levels by 2050 also requires changes in building energy technology and efficiency, including improving building envelopes, fuel switching for residential buildings, and replacing service-sector coal use with gas and renewables according to ( [[#Chiodi--2013|Chiodi et al. 2013]] ). In South Africa, improving industry and building energy efficiency is also considered a key part of mitigation strategies (Altieri et al. 2016; [[#Ouedraogo--2017|Ouedraogo 2017]] ).

In addition, an increasing number of countries have set up net zero energy building targets (Table 4.8) ( [[#Höhne--2020|Höhne et al. 2020]] ). Twenty-seven countries have developed roadmap documents for NZEBs, mostly in developed countries in Europe, North America, and Asia-Pacific, focusing on energy efficiency and improved insulation and design, renewable and smart technologies ( [[#Mata--2020|Mata et al. 2020]] ). The EU, Japan and the USA (the latter for public buildings only) have set targets for shifting new buildings to 100% near-zero energy buildings by 2030, with earlier targets for public buildings. Scotland has a similar target for 2050 ( [[#Höhne--2020|Höhne et al. 2020]] ). Technologies identified as needed for achieving near-zero energy buildings vary by region, but include energy-efficient envelope components, natural ventilation, passive cooling and heating, high performance building systems, air heat recovery, smart and information and communication technologies, and changing future heating and cooling supply fuel mixes towards solar, geothermal, and biomass ( [[#Mata--2020|Mata et al. 2020]] ). Sub-national regions in Spain, USA, Germany, and Mexico have set local commitments to achieving net zero carbon new buildings by 2050, with California having the most ambitious aspirational target of zero net energy buildings for all new buildings by 2030 ( [[#Höhne--2020|Höhne et al. 2020]] ). The EU is also targeting the retrofitting of 3% of existing public buildings to zero-energy, with emphasis on greater thermal insulation of building envelopes ( [[#Höhne--2020|Höhne et al. 2020]] ; [[#Mata--2020|Mata et al. 2020]] ). China’s roadmaps have emphasised insulation of building envelope, heat recovery systems in combination with renewable energy, including solar, shallow geothermal, and air source heat pumps ( [[#Mata--2020|Mata et al. 2020]] ).

'''Table 4.8 | Targets by countries, regions, cities and businesses on decarbonising the b''' '''uilding sector.'''

{| class="wikitable"
|-
!
! Countries

! Sub-national Regions

! Cities

! Businesses

|-
| Shift to 100% (near-)zero energy buildings for new buildings

| 3

| 6

| &gt;28

| &gt;44

|-
| Fully decarbonise the building sector

| 1

| 6

| &gt;28

| &gt;44

|-
| Phase out fossil fuels (for example, gas) for residential heating

| 1

| –

| &gt;3

|
|-
| Increase the rate of zero-energy renovations

| 1 (public buildings)

|
|}

Source: [[#Höhne--2020|Höhne et al. (2020)]] , supplementary information. [https://newclimate.org/ambitiousactions https://newclimate.org/am bitiousactions] .

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