I am currently staying in a retrofitted hotel. Given the weather I am taking full advantage of the treble glazing, A2A heat pumps and EWI but can anyone identify the mistakes made with the EWI?
(There are at least two.)
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It stops near the top of the window, but should go the top of the wall, rafters and/or meet the roof insulation
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It Could have come further across the window frame, nearer the glass
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Looks like there is a gap where it meets the sill
Right on all 3 counts.
Rather than stopping below the soffit insulation is often fitted to it but as you say it should continue to overlap loft insulation or abut warm roof insulation, giving a contiguous insulation jacket.
The outer edge of the EWI does protrude enough to meet the mid to inner line of the frame but is then tapered to meet the frame/wall interface. All that does is marginally reduce the amount of light. The frame is always the part of the window with highest U value so any overlap with the insulation is to be encouraged.
The gap at the cill is more understandable. As any seal between render and cill cannot be guaranteed to remain waterproof it may be decided to leave a drainage channel.
Who has the skills to specify that correctly and the experience to do those works correctly? I was talking with a senior local authority manager that a contractors job is to fulfill the specification and not to suggest other approaches
Normally that is the case. A contractor has to fulfil the contract (it’s in the name) as specified. In cases where the contractor is more experienced or qualified than the client then there ought to be a proper discussion on what to do for the best. Unfortunately such conversations are very rare. The main reasons seem to be trust and project creep.
This should be changing with PAS2030 & PAS2035, particularly in public sector work where those standards are mandated. For now, at least, they are only advised for private sector work but any job involving a government grant will require them to qualify.