A warning from a concerned Building Control Officer
One of our technical team had a call from a concerned Building Control Officer who had just returned from a site inspection. Here’s the story…
During the site visit the Officer inspected a brick and block cavity wall. On plan the target U-value was 0.27 W/m2K – achieved using 50mm Kingspan Kooltherm K8 Cavity Board in a 100mm cavity with dense block inner, brick and plasterboard on dabs. What was actually constructed used a different insulation board with an inferior thermal performance (a worse lambda value) which achieved a U-value of just 0.29 W/m2K.
Clearly the client had been short-changed on the thermal performance, and it left the Building Control Officer with no option but to state that the wall had not been built to the designed specification.
What was most worrying is that the builder insisted that the insulation installed was the same as that specified. It clearly wasn’t as it didn’t carry the correct branding, but this can be a problem when a brand name like ‘Kingspan’ is used generically to cover or describe any rigid insulation board – a bit like ‘Hoover’ or ‘Sellotape’ is used to describe vacuum cleaners and, in the words of Blue Peter, ‘sticky-backed plastic’.
The advice given was that confirmed U-value calculations need to be gained for whatever was constructed and installed – either from the product brochures or from a bespoke calculation carried out according to the BBA/TIMSA Scheme for Calculation Competency Part 1 — U value and condensation Risk.
The moral of the story is that not all insulation is the same – it may look similar, but the performance can be very different.
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