Designing out Overheating

To be sustainable means it must endure.

“Approximately 80% of the design decisions that influence a building's energy performance are made in the early design phase” (Graphisoft EcoDesigner Star, 2014).

All new building should be designed to comply with UK climate projections and not only with current weather data, regarding overheating. Even if actions are taken to tackle concentration of greenhouse gases, climate change is going to increase temperature by 2 to 3°C by 2060 according to IPCC (Intergovernmental Panel on Climate Change) emission scenarios. If buildings are not smartly designed today this will have a considerable impact on thermal comfort and/or cooling consumption over their lifetimes.

It is difficult to make an existing building perform well, with respect to overheating, when it has been poorly designed, simply because finding cost effective refurbishment measures can be much more complicated than starting again with a new building. Therefore, it is necessary to build adaptable buildings, able to be modified easily in case of need.

Adaption can come from different solutions such as protecting the building against unplanned heat gains, ability to deal with unwanted heat once into the building or even free cooling solutions to counter an unexpected inside peak temperature.

The first step in the overheating battle is undeniably to protect the building against heat gains such as outside temperature rises, direct solar gains or internal heat gains. This can be achieved by a good building design including air-tightness, solar shading, using windows with a low g-value and by limiting internal heat from equipment and lighting.

The next step is to be able to deal with unplanned heat once inside the building. This can again be achieved with good design through use of thermal mass, natural ventilation strategy such as cross ventilation; solar towers with natural drafts and more.

Finally, the building must be able to cool down from inside high peak temperatures if the first two steps did not prevent overheating. Varying combinations of innovative envelope design, evaporative cooling, earth-coupled thermal mass and air movement with manual or automatic controlled action should be able to reduce air temperature. Active use of ‘coolth’ stored in thermal mass, could be an effective way to tackle overheating during the day.

The key to building sustainable buildings today, is to make sure that they are already designed for tomorrow’s weather in the early design stage.

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