Insulating a dormer wall

[gbrown100]

I have a 1960's house which is chalet style, the upper floor is in the roof and has dormers for all bedrooms at the front and back. I recently had the front dormer flat roof replaced and found no insulation in the roof space, this was remedied by the roofers and I have pushed insulation through the roof at the back to insulate that.

That got me thinking, I have drilled a hole in the wall of our bedroom and found that there is no insulation there, just a 4-5 inch gap and then I can see some sort of bitumen layer on the outer side of the stud. My question is how should I insulate this? (it is both cold and noisy) I am not sure whether there should be a ventilation gap left there or not. I tried calling a few insulation companies to ask their advice and they all told me that they didn't do dormers, just cavity wall and loft.

Any help appreciated!

Thanks

Graham

 

[Deluks]

Is the wall plasterboard? If so, it'll all have to come out!

There are companies that can 'blow in' loose fibres who might be worth checking out.

 

[gbrown100]

Hi,

The internal walls are plasterboard, we haven't decorated yet so I figured that now would be a good time to insulate!

I am assuming that I can just fill this gap with an insulation such as that solid stuff you can get and then just re-plasterboard the wall. Is that the case?

Also, where the dormer ends I have a sloping ceiling following the contour of the roof. I suspect this is not lagged either, do I need to leave an airgap there? I do not have any soffit vents so I am assuming ventilation happens differently in my house.

Thanks

Graham

 

[Deluks]

If in doubt, leave a gap, 50mm.

You could rip out the PB, put insulation in the walls: rockwool is great for sound insulation, but not as effective as rigid (kingspan/celotex etc.) at the same thickness.
With this in mind you can get insulation backed plasterboard in different thicknesses. So rockwool cavity slabs between the studs, then overboard with the insulation board for the best of both worlds. You will lose between 30 and 50mm of space internally though, depending on what thickness you use.

 

[gbrown100]

Unfortunately there is a window in the way so losing that much would bury the window sill.

I'll have a look round to see what products I can find that'll do the job. After drilling the hole I do get a draught from it, not sure if this is because there is ventilation or that it is just a crap dormer lol.

 

[Deluks]

Unfortunately there is a window in the way so losing that much would bury the window sill.

I'll have a look round to see what products I can find that'll do the job. After drilling the hole I do get a draught from it, not sure if this is because there is ventilation or that it is just a rubbish dormer lol.

You can build the window sill out and use wider plasterboard for the side and top, so the whole window will look slightly set back into the wall. Remember we are only talking about 30mm here.

If you don't want to lose any roomspace then junk the rockwool idea and just use rigid insulation cut to fit between the studs, then overboard with foil backed plasterboard.

 

[Deetum]

Hi

Could you tell me what you ended up doing re the dormer insulation please? I have exactly the same scenario and I am concerned re potential condensation problems.

Any help would be greatly appreciated - can't find answers anywhere!!

Thanks

Dee

Unfortunately there is a window in the way so losing that much would bury the window sill.

I'll have a look round to see what products I can find that'll do the job. After drilling the hole I do get a draught from it, not sure if this is because there is ventilation or that it is just a rubbish dormer lol.

You can build the window sill out and use wider plasterboard for the side and top, so the whole window will look slightly set back into the wall. Remember we are only talking about 30mm here.

If you don't want to lose any roomspace then junk the rockwool idea and just use rigid insulation cut to fit between the studs, then overboard with foil backed plasterboard.