Heating, Ventilating & Plumbing
Home
Menu
Understanding overheating in Green Deal homes
Published:  17 July, 2013

Industry figures have issued insulation advice following the recent warning about overheating in Green Deal homes.

Industry figures have issued insulation advice following the recent report warning about overheating in Green Deal homes.

The report, by professor Chris Goodier of Loughborough University’s department of civil and building engineering, drew widespread attention to the potential risk of overheating in homes insulated under the Green Deal scheme. Goodier warned that these homes could face dangerous temperatures during the summer months, which could ultimately lead to an increase in heat-related fatalities.

Responding to these concerns, the Department of Energy & Climate Change (DECC) is now referring to previously published guidelines (pages 22-27 of its document The National Adaptation Programme: Making the country resilient to a changing climate) to ensure installers are aware of the factors which may contribute to such scenarios.

Insulation firm Actis has welcomed DECC’s acknowledgement of the issue and outlined how overheating can occur.

"At night, a highly insulated building will retain a lot of the heat built up through solar gain during the day,” explained Actis UK’s technical manager David Curtis (pictured). “Masonry walls act as a thermal store, releasing heat into the building at night – similar to storage heaters. Therefore when external nighttime temperature declines, insulation prevents a similar decline internally, which means internal temperatures remain close to daytime temperatures. A topping-up process occurs the next day when the sun rises again.”

Curtis suggested that certain types of insulation can combat this problem. "While some forms of insulation retain the heat for longer when outside temperatures cool at night, others are designed specifically to keep a house both warm in winter and cool in the blistering heat,” he said. “Reflective insulation technology and wood-fibre insulation, which can be used in roofs and in timber-framed walls, are two such examples.”

Overheating is not the only risk of an airtight home. John Kelly of ventilation products manufacturer Airflow Developments has also emphasised the importance of ventilation to avoid mould and associated health risks.

“Increased levels of airtightness will have a significant impact on the existing means of ventilation and how effectively they expel air from the indoor environment,” said Kelly. “Take, for example, the kitchen or bathroom areas; both spaces often have high levels of moisture in the air from everyday activities such as cooking and showering. If this moisture is left to dissipate without the aid of mechanical ventilation, it can often result in damp growing on the walls or ceilings. If the volume of insulation is increased, this issue becomes even more concentrated, risking the health of the building occupants.

“In many instances extractor fans are already in place, but often they are only set to come on when the light is switched on, which means it may not be sufficient to rid the air of the excess moisture generated within an exceptionally airtight building. Under the Green Deal, installers have a massive opportunity to either install or upgrade ventilation methods in both domestic and commercial buildings.”

Kelly proposed there are certain types of ventilation which can be installed to remove excess moisture while maintaining an energy-efficient ethos.

“De-centralised mechanical ventilation differs from a standard extractor fan in that it delivers continuous background extract ventilation to a property. Because of the continuous running of the fan, it’s important to look for a product that operates as low wattage as possible. Under the 2010 Building Regulations, for a continuous running fan, a specific fan power of 0.7 w/l/sec is required, but some fans – including those from Airflow – offer rates that are significantly lower than this."

He concluded: “Ventilation is an issue that won’t be vanishing from the day-to-day lives of installers…By recognising this in the early stages and making sure it is factored in to all upgrade plans in the initial stages, the industry can prevent future problems which may present far more serious consequences that are costly to rectify.”