Climate proofing of buildings against excessive heat

Several approaches can be used to climate-proof of buildings against excessively high temperatures. Such options relate to building design (including the use of IT technologies to optimise thermal comfort) and building envelopes (roof, ceilings, external walls, doors, windows – including solar control glasses that reduce the solar radiation entering the dwelling - and foundations).

Building design solutions include traditional features commonly found in regions with warm climates, such as:

• Building aspect ratio: The ratio between interior space and the external surface of the building, which optimizes internal heat dispersion while minimizing solar heat absorption.
• Architectonical elements: Features like awnings, overhangs, window shades, porticoes, white or lightly coloured external walls and roofs to reflect heat.
• Solar orientation: Positioning the building to minimise the daily exposure to direct sunlight.

Hi-tech solutions can also play a very important role. These include sensors that monitor thermal conditions, enabling precise adjustments of air conditioning and ventilation, as well as the real time orientation of shading panels based on insulation conditions. Sensors and digital thermal regulation devices can be integrated with demand side management measures, helping to reduce the impact of cooling demand on peak loads during periods of electrical system stress (see also the adaptation option on changes in individual behaviour in the energy sector). A famous example of a building in which a complete package of state-of-the-art solutions has been applied is The Edge office building in Amsterdam, completed in 2014. Its envelope includes dynamic windows, automatic shades and displacement ventilation. With 28,000 sensors monitoring movement, lighting levels, humidity and temperature, the building can immediately adjust to energy needs, such as automatically switching off heating, air conditioning and lighting in unused areas. Moreover, employees can use an app to adjust temperature and lighting levels in their work space. Additionally, cooling and heating is optimized by heat transfers between the building and an aquifer beneath it.

The technical features of the building envelope are crucial for its ability to control indoor temperatures. The materials used in the envelope and their mass play a key role in how quickly temperature differences between indoors and outdoors are compensated. For example, traditional thick-walled buildings in the Mediterranean require far less air conditioning than modern structures. Alternatively, using materials with high thermal resistance can help minimize the heat entering the building. This option is particularly interesting for retrofitting existing building with insulation layers that compensate the poor thermal properties of the original building materials.

Also, the use of mechanical or natural ventilation, or storing cold in materials with high thermal mass like tiles or stones, reduces the need of air-conditioning. Cold storage can be coupled with a heat pump (possibly based on a geothermal system, exploiting the differential between underground and surface temperatures) to increase the flexibility in the deployment of cold air. Adjusting indoor humidity can have a strong impact on perceived temperatures and ultimately on thermal comfort of the occupants of a building.

Roofsare also important heat exchange surfaces, and their design (e.g. white roofs, green roofs) can help reducing significantly the energy needs of a building. For instance, the presence of trees increases air flow, reduces the impact of solar radiation and also helps counteract the urban heat island effect. When implementing measures to cope with extreme heat, it is in fact important to consider the impact of building materials and building styles on the microclimate of urban areas. Urban heat mitigation research promotes the use of reflective surfaces to counteract the negative effects of extreme heat. Surface reflectance is a key parameter for understanding, modeling and modifying the urban surface energy balance, to cool cities, and improve outdoor thermal comfort (Fox et al., 2018). Solutions for reducing the urban heat island effect, while improving  indoor conditions through the building envelope, can be approached in two ways: increasing solar reflection and enhancing evaporation and transpiration. Solar reflectance (albedo) of building exteriors and urban paving can help mitigate the heat island effect. This can be achieved by using cold colour coatings and reflective coatings such as retro-reflective materials. Additionally, increasing evaporation and transpiration can be facilitated by green surfaces and trees, like vertical greeneries, green facades and green roofs.

Additional information about the use of green infrastructure to improve the liveability of cities under climate change can be found in the Climate-ADAPT adaptation option urban green and blue infrastructure.

Specific attention should given to historical buildings, as many of the measures described may not be applicable due to existing laws and regulations aimed at preserving the original materials and construction techniques used. Different specific interventions need to be identified, planned and implemented, carefully taking into consideration the characteristics of historical buildings and their cultural meaning. It is highly recommended to consult with experts in historical preservation and building engineering to develop a tailored cooling plan for specific buildings. However, climate proofing solutions that preserve the historical significance of buildings while maintaining their architectural and cultural value are already available. Some examples are provided by the RIBuild project.

The Energy Performance of Buildings Directive (EPBD) allows Member States to adapt minimum energy performance requirements for both residential (art 5.2), and non-residential buildings (art. 9.6a).