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An On the wire story
Researchers have found that Britain’s home insulation schemes may be giving an overly optimistic picture of how much heat older properties actually retain, after a study of a typical 1930s semi-detached house showed that so-called thermal bridges can continue to leak significant amounts of warmth even after retrofit work.
The paper, published in the SCI journal Energy Science and Engineering, focused on the hidden weak points in a building’s fabric where walls, floors, roofs and windows meet, warning that these junctions can undermine the gains expected from insulation upgrades.
According to the University of Salford and Leeds Beckett University, a carefully designed whole-house retrofit cut the property’s overall heat transfer coefficient by as much as 63% when external wall insulation was used, and by 61% with internal wall insulation, compared with the original building. But the researchers said the figures commonly used to estimate heat loss are often too blunt to reflect what happens once homes have been improved in stages rather than through a comprehensive upgrade.
Their concern is significant because these assumptions feed directly into the models used to predict the effect of energy-efficiency measures across Britain’s housing stock, including Energy Performance Certificates and retrofit assessments. The study argues that when homes become better insulated, thermal bridges can make up a larger share of remaining heat loss, meaning that conventional methods may underestimate the benefits of joining measures together as part of a whole-house approach.
Dr Christopher Tsang, the study’s lead author from the University of Salford, said retrofitting has become increasingly important in the effort to meet climate targets, but added that more attention needs to be paid to how insulation connects across the building envelope. He said poorly dealt-with thermal bridges can also leave interior surfaces colder, raising the risk of condensation and mould, while a whole-house strategy could help reduce those problems as well as overall heat loss.
The research also takes issue with the simplified approach used under the Reduced Data Standard Assessment Procedure, or RdSAP, in which default thermal-bridge values are typically applied across a property rather than calculating losses at each junction. The authors acknowledge that bespoke modelling for every home would be costly and impractical, especially where the original construction is poorly documented, but they argue that a more representative database of thermal bridge values for common house types and PAS 2035-compliant retrofit scenarios would make performance forecasts more reliable.
References
Main reference: PBC Today [1]
• This On the wire article was created using Noahwire AI and reviewed by CIBSE Journal’s editorial team
