Retrofit insulation in sloping ceiling

[ed518]

Hi all. We've just bought a house with a loft conversion that's a few decades old, and predictably it's a bit cold. From the crawl space the stud walls look fairly well insulated. From the crawl space (looking above the stud walls) I can also see into the open ends of the sloping ceilings (i.e. the gap between the roof felt and the plasterboard) and there's only about an inch of loosely fitting fiberglass wool insulation in here that's probably pretty much useless.

I thought I could pull out the fiberglass and shove in 50mm of Kingspan/ Celotex, which would leave a similar sized air gap above it. It would have to be a fairly loose fit to let me shove it in from the crawlspace. Does anyone have a view on whether this is a good idea, or would I just be creating any issues with ventilation, etc? Thanks.

 

[Ian H]

I’m doing my porch roof now and the cold air comes in between the small gaps in the celotex, they really need foaming.

Would it be a massive job to pull of the plasterboard so you could insulate between and under the rafters? Would make a very nice warm room.

 

[ed518]

Thanks Ian. In the longer term we're planning to renovate the loft conversion, and we'll stick insulation in properly at that point as you suggest. I was just wondering if I could do something in the short term to make it a bit warmer, especially as the kids are up there.

 

[Leofric]

I thought I could pull out the fiberglass and shove in 50mm of Kingspan/ Celotex, which would leave a similar sized air gap above it. It would have to be a fairly loose fit to let me shove it in from the crawlspace.

50mm air gap over the insulation is ok if it is ventilated but 'loose' fit insulation between the rafters is no good.