Internal insulation of Cold bedroom above garage

[jda19780]

Hi
We have a very cold dormer bedroom above a garage and i want to insulate it better internally. It is already plasterboard that has been skimmed and I was wondering if something like celotex could be simply bonded to the existing plastered wall. I dont want to remove the existing plasterboard to cram insulation between the studs and then reboard and plaster.
Would bonding or screwing the celotex to the wall improve the insulation significantly to justify the cost of the celotex or similar? As the room is not large I would only be using something around 25mm thick.
Many thanks for any advice.
jda19780


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[jeds]

Use thermal laminate. Kingspan k17 or k18, or equivalent. Obviously thicker the better but any thickness will help.

PS. Given the work to fix and finish an additional layer it wouldn't be that much more to remove plasterboard and do the job properly.

 

[theprinceofdarkness]

Is the underfloor area insulated and draught proofed?
Frank

 

[jda19780]

Thanks for your reply Frank. The garage ceiling is insulated and I have sealed all round the edges. I am going to change the laminate flooring in the bedroom and carpet it with a decent underlay so that should help the floor further. Its the walls that get really cold which in turn affects the room. The dormer was constructed 35 yrs ago and I cannot remember the amount (if any) insulation was placed in the dormer cheeks and front. Presumably it was. I just don't know if I added the Kingspan/celotex if will make that much difference.

 

[noseall]

There is also the issue of carrying out the work robustly so that you don't leave vulnerable condensation spots.

My guess is if you are going to do it you may as well do it right. Half hearted jobs of this nature usually end up yielding disappointing results..

 

[JohnD]

if you are ending up with new plasterboard surfaces in the room, what is the objection to pulling off the old plasterboard?

If you are taking up the laminate flooring, consider pulling up the whole floor and packing it with mineral wool insulation. Floors don't lose much, but often have cold draughts round the edges.

 

[jda19780]

Thanks to all for your inputs. The majority seem to think the best course of action is to take off the old plasterboard and 'do it properly'
If I were to do this:-
1. what would be the best kind of insulation to put between what I guess will be 4x2 studs?
2. What kind of plasterboard would be best to put back - ordinary or some with insulation attached?
3. Could I achieve an acceptable finish without having it skimmed ie using a feathered edge board?
Thanks again

 

[messimagician]

How much of an area do you have to cover with insulation ?
The best insulation you can buy without losing too much room is Aerogel, it is rather expensive though. This stuff is better than Celotex, Kingspan and you only need half the thickness.

40mm of Aerogel will better latest building requirements for wall insulation where as Celotex you would normally require 75mm

 

[jda19780]

The area would be probably be about 18m2. So are you suggesting that the aeroflex could overlay the existing skimmed walls and be an effective alternative to stripping out the existing plasterboard?
Thanks for your response.

 

[JohnD]

see if you can find a price for aerogel

 

[jeds]

see if you can find a price for aerogel

Try NASA. They have some, apparently.

 

[JohnD]

I would rip off old plasterboard, pack with mineral wool quilt (treated with ecose), moisture barrier, reboard with plain or insulating plasterboard depending on what thickness of insulation was already achieved.

The foam slabs are better insulators, but more difficult to pack tightly between timbers so there are no air gaps for cold spots and draughts.