My son and his partner moved to a Victorian house around 18 months ago. The loft insulation is poor. Very tatty 100mm at most, so they signed up for the Great British Insulation Scheme via their energy provider. A few emails and questionnaire later and nothing heard since last Christmas. I'm thinking it's time to DIY.
Their boiler is situated on the end wall of the loft space and the loft hatch is about 2/3rds towards the front of the house. There's a boarded walkway to aid access but headroom is limited and I don't want to raise the boards by c200mm as it will mean access will be a crawl.
So the question is, would using 100mm PIR insulation board with a thermal conductivity valve of 0.022 W/mK under the boards, provide the same insulation value equivalent to 200mm of conventional mineral roll with a value of 0.044 W/mK? The rest of the loft would have 270/300mm of mineral roll.
Anyone had the same issue?
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I live in an Edwardian terrace, you probably don't want PIR insulation - it's not breathable (especially if foil faced) so you can end up with condensation issues. You might get away with it if it is only under your walkway & there is an adequate gap for ventilation, what size are the joists?
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I haven't carried out a "survey" yet, but I'm guessing 4" so no ventilation gap.
Last edited by: ChrisM on Thu 9 Oct 25 at 19:34
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Have you got somebody who will service the boiler? There have been stories of main stream organisations who will not touch loft installations unless easy access with full protection, walkway with guard rails and staircase access. Crawl access is not likely to be permitted.
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Yes we have the engineer we've used for 15 years and he serviced it last year, but I take your point. That's the reason I want to keep access as easy as possible. When you get to the boiler there's a large boarded area with good lighting. Bit of a pain if you get there and realise you're forgotten your screwdriver.
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Loft Insulation - Heidfirst
