Overheating Risks In Eco Homes

The Passivhaus Trust has responded to a recent article featured in the Daily Mail concerning overheating risks in eco homes.
The Trust is keen to stress that 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.)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.