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- 19 May 2018
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Hello -
Am in the process of upgrading the insulation in an old loft room.
Rafters are just 100mm deep, so will need to use a combo to achieve 0.18 u value
The headroom is reasonably low so would rather not build up the rafters for deeper PIR if possible.
Was thinking about 75mm of PIR (allowing 25mm droop gat for the breather membrane) with YBS superquilt or similar over the top, counterbattened.
Am no expert on the thermal dynamics - but wouldnt the counterbattening of the superquilt compress it and thus make is subject to thermal bridging?
Have also seen a vid when the quilt goes first as it were (i.e. between the rafters, under the PIR board)
So rather than the below, the quilt would go under the breather membrane, with the PIR on top?
Any advice on how best to achieve required u-values without dropping the cieling height would be more welcome!
NB (Rafters are spaced 400mm)
Cheers
Am in the process of upgrading the insulation in an old loft room.
Rafters are just 100mm deep, so will need to use a combo to achieve 0.18 u value
The headroom is reasonably low so would rather not build up the rafters for deeper PIR if possible.
Was thinking about 75mm of PIR (allowing 25mm droop gat for the breather membrane) with YBS superquilt or similar over the top, counterbattened.
Am no expert on the thermal dynamics - but wouldnt the counterbattening of the superquilt compress it and thus make is subject to thermal bridging?
Have also seen a vid when the quilt goes first as it were (i.e. between the rafters, under the PIR board)
So rather than the below, the quilt would go under the breather membrane, with the PIR on top?
Any advice on how best to achieve required u-values without dropping the cieling height would be more welcome!
NB (Rafters are spaced 400mm)
Cheers