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

=== 9.6.1 Review of Literature Calculating Potentials for Different World Countries ===

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[[#9.4|Section 9.4]] provides an update on technological options and practices, which allow constructing and retrofitting individual buildings to produce very low emissions during their operation phase. Since AR5, the world has seen a growing number of such buildings in all populated continents, and a growing amount of literature calculates the mitigation potential for different countries if such technologies and practices penetrate at scale. Figure 9.15 synthesises the results of sixty-seven bottom-up studies, which rely on the bottom-up technology-reach approach and assess the potential of such technologies and practices, aggregated to stock of corresponding products and/or buildings at national level.

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'''Figure 9.15''' | Potential GHG emission reduction in buildings of different world countries grouped by region, as reported by sixty-seven bottom-up studies. Sources: North America: Canada ( [[#Trottier--2016|Trottier 2016]] ; [[#Radpour--2017|Radpour et al. 2017]] ; [[#Subramanyam--2017a|Subramanyam et al. 2017a]] ,b; [[#Zhang--2020a|Zhang et al. 2020a]] ), the Unites States of America ( [[#Gagnon--2016|Gagnon et al. 2016]] ; [[#Nadel--2016|Nadel 2016]] ; [[#Yeh--2016|Yeh et al. 2016]] ; [[#Wilson--2017|Wilson et al. 2017]] ; [[#Zhang--2020a|Zhang et al. 2020a]] ); Europe: Albania ( [[#Novikova--2020|Novikova et al. 2020]] , 2018c), Austria ( [[#Ploss--2017|Ploss et al. 2017]] ), Bulgaria, the Czech Republic, Hungary ( [[#Csoknyai--2016|Csoknyai et al. 2016]] ), France ( [[#Ostermeyer--2018b|Ostermeyer et al. 2018b]] ), the European Union ( [[#Duscha--2019|Duscha et al. 2019]] ; [[#Roscini--2020|Roscini et al. 2020]] ; [[#Brugger--2021|Brugger et al. 2021]] ), Germany ( [[#Markewitz--2015|Markewitz et al. 2015]] ; [[#Bürger--2019|Bürger et al. 2019]] ; [[#Ostermeyer--2019b|Ostermeyer et al. 2019b]] ), Greece ( [[#Mirasgedis--2017|Mirasgedis et al. 2017]] ), Italy ( [[#Calise--2021|Calise et al. 2021]] ; Filippi [[#Oberegger--2020|Oberegger et al. 2020]] ), Lithuania ( [[#Toleikyte--2018|Toleikyte et al. 2018]] ), Montenegro (Novikova et al. 2018c), Netherlands ( [[#Ostermeyer--2018c|Ostermeyer et al. 2018c]] ), Norway ( [[#Sandberg--2021|Sandberg et al. 2021]] ), Serbia ( [[#Novikova--2018a|Novikova et al. 2018a]] ), Switzerland ( [[#Iten--2017|Iten et al. 2017]] ; [[#Streicher--2017|Streicher et al. 2017]] ), Poland ( [[#Ostermeyer--2019a|Ostermeyer et al. 2019a]] ), the United Kingdom ( [[#Ostermeyer--2018a|Ostermeyer et al. 2018a]] ); Eurasia: Armenia, Georgia ( [[#Timilsina--2016|Timilsina et al. 2016]] ); the Russian Federation ( [[#Bashmakov--2017|Bashmakov 2017]] ; [[#Zhang--2020a|Zhang et al. 2020a]] ); Australia ( [[#Energetics--2016|Energetics 2016]] ; [[#Butler--2020|Butler et al. 2020]] ; [[#Zhang--2020a|Zhang et al. 2020a]] ), Japan ( [[#Momonoki--2017|Momonoki et al. 2017]] ; [[#Wakiyama--2017|Wakiyama and Kuramochi 2017]] ; Minami et al. 2019; [[#Zhang--2020a|Zhang et al. 2020a]] ; Sugyiama et al. 2020); Africa: Egypt (Makumbe et al. 2017; [[#Calise--2021|Calise et al. 2021]] ), Morocco ( [[#Merini--2020|Merini et al. 2020]] ), Nigeria ( [[#Dioha--2019|Dioha et al. 2019]] ; [[#Kwag--2019|Kwag et al. 2019]] ; [[#Onyenokporo--2019|Onyenokporo and Ochedi 2019]] ), Rwanda ( [[#Colenbrander--2019|Colenbrander et al. 2019]] ), South Africa ( [[#Department%20of%20Environmental%20Affairs--2014|Department of Environmental Affairs 2014]] ), Uganda ( [[#de%20la%20Rue%20du%20Can--2018|de la Rue du Can et al. 2018]] ), Algeria, Egypt, Libya, Morocco, Sudan, Tunisia (Krarti -2019); Middle East – Qatar ( [[#Krarti--2017|Krarti et al. 2017]] ; [[#Kamal--2019|Kamal et al. 2019]] ), Saudi Arabia ( [[#Alaidroos--2015|Alaidroos and Krarti 2015]] ; [[#Khan--2017|Khan et al. 2017]] ), Bahrain, Iraq, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi Arabia, State of Palestine, Syrian Arab Republic, United Arab Emirates, Yemen ( [[#Krarti--2019|Krarti 2019]] ); Eastern Asia – China ( [[#Tan--2018|Tan et al. 2018]] ; [[#Zhou--2018|Zhou et al. 2018]] ; [[#Xing--2021|Xing et al. 2021]] ; Zhang et al. 2020); Southern Asia: India ( [[#Yu--2018|Yu et al. 2018]] ; [[#de%20la%20Rue%20du%20Can--2019|de la Rue du Can et al. 2019]] ; Zhang et al. 2020); South-East Asia and Pacific: Indonesia ( [[#Kusumadewi--2015|Kusumadewi and Limmeechokchai 2015]] , 2017), Thailand ( [[#Kusumadewi--2015|Kusumadewi and Limmeechokchai 2015]] , 2017; [[#Chaichaloempreecha--2017|Chaichaloempreecha et al. 2017]] ), Vietnam ( [[#ADB--2017|ADB 2017]] ), respective countries from the Asia-Pacific Economic Cooperation (APEC) ( [[#Zhang--2020a|Zhang et al. 2020a]] ); Latin America and Caribbean: Brazil ( [[#de%20Melo--2015|de Melo and de Martino Jannuzzi 2015]] ; [[#González-Mahecha--2019|González-Mahecha et al. 2019]] ), Colombia ( [[#Prada-Hernández--2015|Prada-Hernández et al. 2015]] ), Mexico (Grande-acosta and Islas-samperio 2020; [[#Rosas-Flores--2020|Rosas-Flores and Rosas-Flores 2020]] ).

The studies presented in Figure 9.15 rely on all, the combination, or either of the following mitigation strategies: the construction of new high energy-performance buildings taking the advantage of building design, forms, and passive construction methods; the thermal efficiency improvement of building envelopes of the existing stock; the installation of advanced HVAC systems, equipment and appliances; the exchange of lights, appliances, and office equipment, including ICT, water heating, and cooking with their efficient options; demand-side management, most often controlling comfort requirements and demand-side flexibility and digitalisation; as well as onsite production and use of renewable energy. Nearly all studies, which assess the technological potential assume such usage of space heating, cooling, water heating, and lighting that does not exceed health, living, and working standards, thus realising at least a part of the non-technological potential, as presented in Figure 9.14. The results presented in Figure 9.15 relate to measures applied within the boundaries of the building sector, including the reduction in direct and indirect emissions. The results exclude the impact of decarbonisation measures applied within the boundaries of the energy supply sector, that is, the decarbonisation of grid electricity and district heat.

The analysis of Figure 9.15 illustrates that there is a large body of literature attesting to mitigation potential in the countries of Europe and North America of up to 55–85% and in Asia-Pacific Developed of up to 45% in 2050, as compared to their sector baseline emissions, even though they sometimes decline. For developing countries, the literature estimates the potential of up to 40–80% in 2050, as compared to their sharply growing baselines. The interpretation of these estimates should be cautious because the studies rely on assumptions with uncertainties and feasibility constrains (see Sections 9.6.4, Figure 9.20 and Supplementary Material Table 9.SM.6).

The novelty since AR5 is emerging bottom-up literature, which attempts to account for potential at national and global level from applying the sufficiency approach (see Box 9.1 in [[#9.1|Section 9.1]] and decomposition analysis in [[#9.3.2|Section 9.3.2]] ). In spite of the reducing energy use per unit of floor area at an average rate of 1.3% per year, the growth of floor area at an average rate of 3% per year causes rising energy demand and GHG emissions because each new square meter must be served with thermal comfort and/or other amenities (International Energy Agency 2017; [[#Ellsworth-Krebs--2020|Ellsworth-Krebs 2020]] ). Nearly all studies reviewed in Figure 9.15 assume the further growth of floor area per capita until 2050, with many studies of developing countries targeting today per capita floor area as in Europe.

Table 9.4 reviews the bottom-up literature, which quantifies the potential from reorganisation of human activities, efficient design, planning, and use of building space, higher density of building and settlement inhabitancy, redefining and downsizing goods and equipment, limiting their use to health, living, and working standards, and their sharing, recognising the number of square meters and devices as a determinant of GHG emissions that could be impacted via policies and measures. Nearly all national or regional studies originate from Europe and North America recognising challenges, Developed Countries face toward decarbonisation. Thus, [[#Goldstein--2020|Goldstein et al. (2020)]] suggested prioritising the reduction in floor space of wealthier population and more efficient space planning because grid decarbonisation is not enough to meet the U.S. target by 2050 whereas affluent suburbs may have 15 times higher emission footprints than nearby neighbourhoods. [[#Cabrera%20Serrenho--2019|Cabrera Serrenho et al. (2019)]] argue that reducing the UK floor area is a low cost mitigation option given a low building replacement rate and unreasonably high retrofit costs of existing buildings. [[#Lorek--2019|Lorek and Spangenberg (2019)]] discusses the opportunity of reducing building emissions in Germany fitting better the structure of the dwelling stock to the declined average household size, as most dwellings have 3–4 rooms while most households have only one person.

Whereas these studies suggest sufficiency as an important option for Developed Countries, global studies argue that it is also important for the developing world. This is because it provides the means to address inequality, poverty reduction and social inclusion, ensuring the provision of acceptable living standards for the entire global population given the planetary boundaries. As Figure 9.6 illustrates, the largest share of current construction occurs in developing countries, while these countries follow a similar demographic track of declining household sizes versus increasing dwelling areas. This trajectory translates into the importance of their awareness of the likely similar forthcoming challenges, and the need in early efficient planning of infrastructure and buildings with a focus on space usage and density.

Table 9.4 | Potential GHG emission reduction in the building sector offered by the introduction of sufficiency as a main or additional measure, as reported by bottom-up (or hybrid) literature.

{| class="wikitable"
|-
| Region

| Reference

| Scenario and its result

| Sufficiency for floor space

|-
| Globe

| Grubler et al.

(2018)

| The Low Energy Demand Scenario halves the final energy demand of buildings by 2050,

as compared the WEO Current Policy (International Energy Agency 2019c) by modelling

the changes in quantity, types, and energy intensity of services.

| The scenario assumed a reduction in the

residential and non-residential building floor

area to 29 and 11 m 2 cap –1 respectively.

|-
| Globe

| Millward-Hopkins

et al. (2020)

| With the changes in structural and technological intensity, the Decent Living Energy scenario achieved the decent living standard for all while reducing the final energy consumption of buildings by factor three, as compared to the WEO Current Policy Scenario (International Energy Agency 2019c).

| The scenario assumed a reduction in floor area

to 15 m 2 cap –1 across the world.

|-
| Globe

| Levesque et al.

(2019)

| Realising both the technological and sufficiency potential, the Low Demand Scenario

and the Very Low Demand Scenario calculated a reduction in global building energy

demand by 32% and 45% in 2050, as compared to the business-as-usual baseline.

| The Low Scenario limited the residential and

non-residential floor area to 70 and 23 m 2 cap –1 ;

the Very Low Scenario – to 45 and 15 m 2 cap –1 .

|-
| EU

| Bierwirth and

Thomas (2019b)

| For the EU residential sector, the authors calculated potential energy savings of 17%

and 29% from setting the per capita floor area limits.

| A reduction of the residential floor area to 30 m 2 cap –1 and 35 m 2 cap –1 , respectively.

|-
| EU

| Roscini et al.

(2020)

| With the help of technological and non-technological measures, the Responsible Policy

Scenario for the EU buildings allows achieving the emission reduction by 60% in 2030,

as compared to 2015.

| The scenario assumed 6% decrease in the

residential per capita floor area (to max.

44.8 m 2 cap –1 ).

|-
| Canada, UK,

France, Italy,

Japan, USA,

Germany

| Hertwich et al.

(2020)

| The potential reduction in GHG emissions from the production of building materials

is 56–58% in 2050, as compared to these baseline emissions. The reduction in heating

and cooling energy demand is 9–10% in 2050, as compared to its baseline.

| Via the efficient use of living space, the scenario

assumed its 20% reduction, as compared to its

baseline development.

|-
| UK

| Cabrera Serrenho

et al. (2019)

| The scenario found that the sufficiency measures allowed mitigating 30% of baseline

emissions of the English building sector in 2050, without other additional measures.

| The scenario assumed a 10% reduction in the

current floor area per capita by 2050.

|-
| USA

| Goldstein et al.

(2020)

| The scenario calculated 16% GHG mitigation potential in 2050, as compared to the baseline, on the top of two other scenarios assuming building retrofits and grid decarbonisation already delivering a 42% emission reduction.

| The scenario assumed a 10% reduction in

per capita floor area and higher penetration

of onsite renewable energy.

|-
| Switzerland

| Roca-Puigròs et al.

(2020)

| The Green Lifestyle scenario allows achieving 48% energy savings by 2050, as compared

to the baseline, due to sufficiency in the floor area among other measures.

| The scenario assumed a reduction in residential

floor area. from 47 to 41 m 2 cap –1 .

|-
| France

| [[#Negawatt--2017|Negawatt (2017)]]

| The Negawatt scenario assumes that sufficiency behaviour becomes a mainstream across all sectors. In 2050, the final energy savings are 21% and 28% for the residential and tertiary sectors respectively, as compared to their baselines.

| The scenario assumes a limit of the residential

floor at 42 m 2 cap –1 due to apartment sharing

and compact urban planning.

|-
| France

| Virage-Energie

Nord-Pas-de-

Calais. (2016)

| The authors assessed sufficiency opportunities across all sectors for the Nord-Pas-de-Calais

region of France. Depending on the level of implementation, sufficiency could reduce the

energy consumption of residential and tertiary buildings by 13–30% in 2050, as compared

to the baseline.

| The scenario assumed sharing spaces,

downsizing spaces and sharing equipment

from a ‘soft’ to ‘radical’ degree.

|}

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