Overheating risks in eco homes
An article was recently featured in the Daily Mail concerning overheating risks in eco homes.
Summer overheating can be a potential problem in all modern buildings because of our preference for much more glazing than in former times. Passivhaus is better at addressing this than any other method because it takes account of solar gain and shading as standard within its calculation methodology, and alerts the designer to any potential overheating, enabling it to be eliminated at design stage. For maximum performance the glazing and shading specification should be fine-tuned on each façade of a Passivhaus building. Any problems with a specific project might be site-specific or could be due to incorrect use of the shading.
It is a requirement for Passivhaus certification that temperatures exceeding 25°C cannot occur in a building for more than 10% of the occupied year. In the light of climate change predictions, UK designers are recommended to achieve a maximum figure of 0-5% overheating frequency or less (using current day data.)
Large glazed areas require shading devices to help prevent risks of overheating from solar gains in summer. River Studio. Photo Credit: Sjolander da Cruz Architects
In a properly designed building, the use of conventional cross ventilation and night purge ventilation should be sufficient to remove any heat build-up during the day. Mechanical options include using the Heat Recovery Ventilation system in by-pass mode with or without additional ground or brine loop pre-cooling options.
Part of the Trust’s activities include delivering educational events such as Masterclasses and Tutorials, as well as research with leading Practioners and experts in UK Passivhaus construction. We currently have a research group exploring occupant comfort via post occupancy evaluation and potential overheating risks form part of this investigation.
11th May 2015
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