Insulating Roof

[chuckalicious]

Ok, quick question.

I have a slate roof. The attic has been converted and the walls follow the angle of the roof, meaning there is a 9-10 inch gap between the wall and the wood of the roof. The roofline has eaves on this side.

Untitled

• chuckalicious
• 21 Oct 2011
• 1

The image above should hopefully help.

Access is only as far as I can stick my arm down the gap.

My question is, can I put insulation down the gap so that the internal attic room stays warmer? The roof is unfelted so there's a hell of gale blows through the attic (which is a good thing I know).

My concern is that because it is a very old roof, inevitably some water will get in but if I block that bit all up with insulation it won't be able to dry out due to lack of airflow, increasing the risk of rot.

Is that assumption correct? Is so, is there anything I can do to improve this situation?

 

[freddiemercurystwin]

Yes the sloping ceilings should be insulated leaving an air gap beneath the tiles. If your roof finish is allowing water to enter it has failed and needs replacing/fixing. Felt/underlay is only ever intended as a back-up should a tile slip or crack not as fundamental part of keeping the inside dry.

 

[chuckalicious]

It's over 100 years old - I know it needs replaced, but is holding up well enough until I can get the £5k together to get it done!

Because I don't have much access, I was wondering if I could use the foil backed foam and slide it down between each rafter - do you think that would be better than trying to stuff glass wool down such a restricted space and get it to lie flat?

 

[freddiemercurystwin]

I think either methods would be a royal pain in the backside chances are your 100 year old roof the rafters are gonna be about as straight/regimented as a banana and shoving pre-cut strips of rigid insulation down the gaps (PITA factor aside) is gonna leave all sorts of gaps and voids. So I would say rockwool will be the way to go you will just need to faff about with something like a pole hook as best you can, you only need to maintain a 50mm gap and you say you have a fair old gap so may not be too bad. Shove in a couple of layers if you can as its cheap as chips and a poorer insulator than the rigid.

 

[chuckalicious]

Thanks. I'll need to go up and take a proper look again and see how much access I do have. I did look at the pricing of the boards and good god could it end up being expensive - rock wool may be the way to go.

Thanks.

 

[catlad]

You can get the attic insulated properly when you get the roof done.

 

[chuckalicious]

Nice idea but that may be a few years down the line.