The world is currently undergoing the largest wave of urban growth in human history. More than half of the global population is now concentrated in urban areas, and by 2060 two thirds of the expected population of 10 billion will live in cities. To accommodate this tremendous growth, we expect to add 230 billion m2 of new floor area doubling the global building stock, by 2060.
However, the built sector is already responsible for nearly 40% of annual global GHG emissions and this massive urbanization will seriously threaten our mission to achieve carbon neutrality by 2050. To be on track to achieving a net-zero carbon building stock by 2050, the IEA estimates that direct building CO2 emissions would need to decrease by 50% and indirect building sector emissions should go through a reduction of 60% in power generation emissions by 2030. These efforts would need to see building sector emissions fall by around 6% per year from 2020 to 2030.
In 2019 CO2 emissions from the operation of buildings have increased to their highest level yet at around 10 GtCO2, or 28% of total global CO2 emissions. With the inclusion of emissions from the buildings construction industry, this share increases to 38% of total global CO2 emissions. This makes the built sector the largest contributor to climate change, followed by the Industry with 32% and Transportation with 23% of total emissions (overall cities are considered to be responsible for almost 70% of total GHG’s emissions)
Building related emissions can be divided into three main categories: Operational Direct (i.e. emissions from heating system), Operational Indirect (i.e. power generation for electricity and commercial heat) and Embodied Carbon (emissions connected to materials and construction). Indirect emissions account for the largest share of energy-related CO2 emissions in the buildings sector, representing around 68% of total buildings-related emissions from energy consumption in 2018. Embodied carbon emissions, connected to the 6.13 billion square meters of buildings constructed every year, amount to approximately 3729 million metric tons CO2 or 28% of the total building related. By the year 2050, accounting for all the new construction in that 30 year span, embodied carbon emissions and operational carbon emissions will be roughly equivalent.
In addition to the unprecedented growth in the global building sector, nearly two-thirds of the building area that exists today will still exist in 2050. Therefore, any transition to low-carbon/carbon neutral built environment must address both new construction and existing buildings.
Compared to demolition and new construction, by simply repairing, refurbishing and retrofitting existing structures, renovations can offer more cost-effective, less resource-intensive and lower emissions-creating solutions to improving the building stock. This is particularly interesting for OECD countries to note, where 65% of the projected building stock required by 2060 already exists, and is in need of 50% to 70% energy intensity improvements.
As of today, annual building renovations affect only 0.5-1% of the building stock signaling a slow pace of change for the building sector. Similarly, energy intensity (final energy use per m2) has been decreasing continuously by only 0.5% to 1% per year since 2010, while the average annual floor area growth has remained around 2.5% in the same period. To get on track with the Sustainable Development Scenario (SDS), annual drops in energy intensity per m2 globally need to be at least 2.5%.
To achieve these results by 2030 we need to implement more stringent building energy codes and deep energy renovations, to reduce energy demand, and improve buildings energy efficiency through more advanced heating and cooling technologies as well as much faster adoption of innovative digital technologies and energy management systems (a 2017 report by the International Energy Agency found that innovative digital solutions, such as smart lighting and smart thermostats, could lower a building’s total energy use by 10% between 2017 and 2040).
According to the 2020 Global Status Report for Buildings and Construction, by the IEA, the largest share of final energy consumption is connected to space heating and cooling and water heating (with space cooling experiencing a fast growth as living conditions keep improving in the world’s south). These are also the major causes of emissions since fossil fuel-based and conventional electric equipment, such as electric resistance heaters and water heaters, continue to dominate the global buildings market, accounting for around 80% of heating equipment sales in buildings globally.
To be in line with the Sustainable Development Scenario (SDS), the share of clean energy technologies such as heat pumps, solar thermal heating, low-carbon district energy systems and biomass boilers, as well as hydrogen boilers and fuel cells, needs to exceed 50% of new heating equipment sales by 2030. The combined effects of efficiency improvements, fuel-shifting and power sector decarbonisation would reduce buildings’ heating-related emissions 30% by 2030.
While improvements in energy efficiency and growth in renewable energy generating capacity is having an impact, it has not been nearly enough to amply offset the increase in emissions from new construction. Only by eliminating CO2 emissions from new building operations will we begin to significantly reduce building sector emissions before they are locked-in for the foreseeable future.
To make sure that new constructions will support the decarbonization of buildings we need to develop and implement mandatory codes to strengthen performance requirements and integrate renewable energy into new building designs to achieve net-zero emissions or net-zero energy.
An example of such design codes is the ZERO Code, a national and international building energy standard for new building design and construction, developed by Architecture 2030, that integrates cost-effective energy efficiency standards with on-site and/or off-site renewable energy resulting in zero-net-carbon (ZNC) buildings.