SUSTAINABILITY
INSULATION NOT A “MAGIC BULLET” SAYS CAMBRIDGE RESEARCH
A recently released 12-year study shows that energy-saving benefits from installing insulation are not permanent as BMJ finds out.
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nstalling insulation in a property does not automatically lead to huge energy savings. That’s according to research from the University of Cambridge which found that insulating the lofts and cavity walls of the UK homes in its study only reduced gas consumption for the first year or two, with all energy savings vanishing by the fourth year after a retrofit. The report suggested that insulation installation is often combined with other home renovations, such as adding an extension or conservatory which would lead to increased energy use. In fact, for households with conservatories, any gains in energy efficiency disappeared after the first year. The research found that, while insulation was vital for fighting fuel poverty, it was not a “magic bullet” for reducing energy use, and that it should come alongside advice to conserve energy and programmes to install heat pumps in homes.
The findings follow a 12-year study of 55,000 homes in England and Wales between 2005 and 2017.
Architect and technical director at insulation specialist Actis, Thomas Wiedmer, says that not taking a holistic approach to retrofitting a property could be another reason why the fuel savings weren’t as long-lasting as hoped, and that retrofit standards endorsing a whole house approach to energy efficiency - PAS 2030/2035 – were not even in place during the research data period.
“The standard champions a matrix approach in which each individual measure is examined in the context of the whole house. This is because one action might have unintended consequences elsewhere in the property. It is important to look at each case on an individual basis.
“One of the unintended consequences which could occur if not looking at the house in its entirety is the appearance of moisture or condensation.
“For example, while on the surface it may seem sensible to insulate all external walls to the best possible U-value, this could have unintended consequences elsewhere. Where the ceiling joists meet the walls, in some scenarios, can create a weak point called a thermal bridge. This might lead to moisture
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build-up and mould growth so it may, counterintuitively, be better to use less rather than more insulation.”
The report authors suggested that the disappearance of energy savings in the longer run could be explained by the energy performance gap, the rebound effect and/or by concurrent residential construction projects and renovations associated with increases in energy consumption.”
Wiedmer agrees: “There is growing understanding of as-built energy performance and the existence of the performance gap. We are playing out part in this education process, through one of our RIBA-approved CPDs - Addressing the performance gap with reflective insulation - which looks at why the performance gap exists, the effects of external factors on the fabric efficiency of a building, air tightness and thermal bridging.
“Construction detailing is one of the biggest issues causing the performance gap. Tying projects up with specific details used is important to close the gap between designed and expected performance.”
He explains that building with insulation which is effective on paper can still see huge heat losses of 20 to 30% if thermal bridging occurs, and that the only way to avoid such a scenario is for construction details to be thermally approved and followed through on site.
“Energy efficiency standards should always be based on reducing the need for energy first and in particular limiting the heat loss through thermal elements - that is through achieving excellent U-values, reducing thermal bridging
www.buildersmerchantsjournal.net February 2023
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