Housing Specification Blog

Zero-carbon drive leads to overheated homes

December 17, 2012 Alexandra Blakeman Housing Design

It might not seem likely at this time of year, but as we progress towards zero-carbon by 2016, our homes run the risk of overheating.

Older housing stock is less energy efficient, with poorer insulation systems – which means there’s a greater chance of heat loss.

Zero-carbon homes will be well insulated and built with  high standards of airtightness. Together with double glazed windows  and communal heating pipework, it’s hardly surprising that there’s a growing concern.

The NHBC Foundation has released a report which investigates the causes and risks of overheating your home.

Understanding Overheating: Where to Start points out that it isn’t just our homes that are changing. Our weather is too. Climate change will deliver more extreme weather systems over the coming years. With hotter, drier summers and milder, wetter winters expected, our homes need to adapt to the anticipated changes.

The report says that most people feel warm at 25°c and hot at 30°c. A stuffy house isn’t only created by cranking up the central heating system. A lack of air movement contributes significantly towards overheating.

Short, intense bursts of ventilation will provide the answer. This is known as ‘purge ventilation’ – not just opening a single window every now and then.

Velux CarbonLight home in Rothwell

This method of ventilation is difficult to achieve. Opening French windows or external doors will get the air moving, but it’s unlikely that they will be open long enough to have a significant, ‘purging’ effect.

Keith Riddle, Managing Director at VELUX said: “New homes that resemble hermetically sealed boxes could become the norm as developers strive to meet increasingly strict energy efficiency standards.

The NHBC’s research will, we hope, mean that many developers will now pause for breath and consider adequate ventilation as a viable means to building affordable zero carbon homes that are also healthy places to leave.”

To circulate large amounts of air throughout the home, a mechanical ventilation device will be installed. Occupants must be briefed on the importance of activating the system.

Solar Shading might also be used to reduce a property’s heat gain. The NHBC report suggests that external louvres provide good shading without blocking the view, whilst shutters provide the most protection in buildings unoccupied during the day.

Keith continued: “Our own CarbonLight Homes in Kettering use stack and purge ventilation to great effect to reduce overheating and carbon emissions. Scientific monitoring of their French equivalent has revealed marked improvements in the health of one of the family members, who before living in the home, had always suffered from chronic symptoms of asthma.”

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