Summerhouse insulation

3 Nov 2016
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United Kingdom
Hi All,

Would greatly value any input here. Helping out my Dad on the refurbishment of an existing outhouse, which he wants to turn into a summerhouse-type structure, but one that can be used all year round.

The problem I have is that we've removed the existing cladding and replaced with breather membrane and 15mm shiplap externally. On the inside, I think I've made a mistake by insulating directly in-between the 2"x2" frame with 50mm PIR board and foil tape, leaving no air gap. Was planning on battening inside leaving gap behind plasterboard for cables but suspect plasterboard could be susceptible to condensation/mould in winter months.

Given that it's only going to be used very occasionally, will it suffer from condensation? Windows and doors will be double-glazed and roof and floor both have 100mm PIR insulation. I can potentially take out all the PIR boards but I've already cut them to size so there'll be a lot of wastage.

Essentially what I'm asking is; should I rip out the insulation boards I've spent a while installing and insulate between the battens internally, leaving a 50mm air gap behind the membrane/cladding.

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