Why is this important?
High-performing envelopes (the parts of a building that separate the indoors from the outdoors, including exterior walls, foundations, roof, windows, etc.) are the most effective way to reduce the thermal needs of buildings. Compared to other solutions, the selection of envelope structure and materials is particularly important given the long lifetime of buildings and the cost of construction.
What is the role of building envelopes in clean energy transitions?
Efficient building design, integrating high-performing envelopes, is the most effective way to reduce the thermal needs of buildings and ensure occupants’ thermal comfort. Compared to other solutions in buildings, the selection of envelope structure and materials is particularly important, given the long lifetime of buildings and the associated cost of the envelope.
Where do we need to go?
More than 110 countries lacked mandatory building energy codes or standards in 2022, meaning that over 2.4 billion square meters of floor space were built without meeting any energy-related performance requirements. To be in step with the Net Zero Emissions by 2050 Scenario, all countries need to establish zero-carbon-ready building energy codes for residential and non-residential buildings by 2030 at the latest. Being in step also requires 20% of existing building floor area to be renovated to this level by 2030.
Stronger efficiency is the first and best policy to bring down energy bills
Countries across Europe and Asia progressively tighten energy performance standards in building regulations
Countries and regions making notable progress to advance on building envelopes include:
- The European Union adopted a new revision of the Energy Performance of Buildings Directive (EPBD) in 2023 (pending trilogue approval) that stipulates higher Minimum Energy Performance Standards for existing buildings, timelines to achieve them, and earlier deadlines for buildings to become zero-emissions: for all new public buildings from 2026, and for all new buildings from 2028.
- The European Union’s REPowerEU initiative, one of a wide range of measures for clean energy transition, promotes energy-efficient building retrofits to support rapid reduction of dependence on Russian fossil fuels.
- Türkiye, Japan, China, India and Australia updated their buildings regulations, adding more stringent energy efficiency requirements.
- The United Kingdom Department for Energy Security and Net Zero (DESNZ) announced GBP 1.8 billion in 2023 to upgrade the energy efficiency of homes and public buildings through the Social Housing Decarbonisation Fund, Home Upgrade Grant and Public Sector Decarbonisation Scheme.
Improvements in building envelope performance have helped reduce space heating intensities by 7% since 2015, but more needs to be done, especially in warmer (and warming) regions
Good building design, integrating high-performing envelopes, is the most effective way to reduce the thermal needs of buildings and ensure occupants’ thermal comfort. Compared to other solutions in buildings, the selection of envelope structure and materials is particularly important, given the long lifetime of buildings and the associated cost of the envelope.
Since 2015, more widespread and stringent building codes, as well as increased retrofit rates, have helped decrease space heating intensity by 7% on average globally. Efficiency gains have decreased global space heating service demand by about 4% in advanced economies since 2010, but were not sufficient to offset floor area growth in emerging and developing economies.
Global space cooling service demand has increased across the world by more than two-thirds since 2010, driven by increased floor area, growth in equipment ownership, and rising temperatures, but also because cooling-oriented envelope solutions are often neglected during building design.
Building envelope performance improvements are critical to getting on track with the majority of the NZE Scenario milestones in heating and cooling intensity (energy use per total m2). To align with the NZE Scenario, the final energy intensity of space heating and cooling needs to fall considerably, by at least 35% and 25% respectively in 2030 compared to today. Progress in space cooling efficiency from improved envelope performance and air-conditioning equipment is particularly needed due to growing demand.
Although all countries need to implement mandatory building energy codes within this decade to align with NZE Scenario milestones, many have yet to make them an explicit policy priority.
Building floor space has expanded by more than 15% since 2015, while energy use per m2 has improved only 6%
Constructed floor space worldwide has increased by about 70% since 2000, to reach around 260 billion m2 in 2022, of which nearly 80% is residential. At the same time, however, average energy use per m2 has declined by only around 20%, meaning advances in energy efficiency have only partially offset floor area growth.
In addition to the lack of building energy codes in certain countries, the average retrofit rate of the building stock is currently around 1% per year, with retrofits generally delivering average energy intensity reductions of less than 15%. To get on track with the NZE Scenario, retrofit rates must jump to at least 2.5% by 2030, and retrofits need to be deep – or extensive – retrofits. All new buildings and retrofits are zero-carbon-ready by 2030 in the NZE Scenario.2
2 This means that a zero‐carbon‐ready building will become a zero-carbon building by 2050, without any further changes to the building or its equipment, thanks to decarbonisation of the power grid.
Material innovation and adaptive building envelope systems are increasing buildings’ resilience and reducing insulation space constraints
Building envelope solutions are well known, such as energy-efficient insulation and fenestration. But innovation is also taking place in building envelope materials and components, for instance to reduce the thickness of insulation, resulting in a product five times more efficient than traditional insulation. Use of super insulating materials, such as vacuum insulation panels and silica aerogel, can offer additional economic benefits by creating additional usable space and hence increasing the financial value of the building. This solution is particularly interesting for areas that previously would have remained uninsulated due to insufficient space.
Ongoing research is taking place in the area of supercool and smart materials, which can stay several degrees cooler than ambient temperature even in direct sunlight, thereby reduce cooling needs inside the building, with particularly promising results in hot and dry climates.
Adaptive building envelope systems, including control and automation technology, are on the rise. Among the building envelope technologies that enhance the envelope’s function through solar energy gains, “climate-adaptative building shells” offer the opportunity to activate buildings against climate change. The façade's adaptation to climate conditions creates changes in the building's energy balance through convection flow, radiation and energy storage.
Building renovation often occurs over a long period and requires multiple skills, such as selecting the most cost-effective measures to implement and dealing with complex bureaucracy. Renovations on a multi-building scale can be coordinated at the local level, facilitating co-operation among multiple stakeholders and speeding up the renovation process while reducing costs (for example, for renting scaffolding and buying materials). The IEA Energy in Buildings and Communities Technology Collaboration Programme (EBC TCP) is working to highlight opportunities for district-scale renovations.
One notable development in business models for building renovation is the expansion of the Energiesprong programme, now active in five countries in Europe, through which renovation or new build is financed by future energy cost savings plus the budget for planned maintenance and repairs over the coming 30 years. This makes use of new technologies such as prefabricated facades, insulated rooftops with solar panels, and efficient heating, ventilation and air conditioning installations.
Coverage by mandatory building energy codes is expanding, but not quickly enough and without the adequate stringency to meet Net Zero Scenario milestones