On 19/10/2019 20:21, Andrew wrote:
On 19/10/2019 19:46, polygonum_on_google wrote:
On Saturday, 19 October 2019 16:00:54 UTC+1, Another JohnÂ* wrote:
As the nippy evenings and cold nights become more frequent again, I'm
once again thinking about insulating the garage ceiling.

- The garage is roughly 6m by 4m, and our bedroom is above it.

-Â* The bedrooom often feels rather cooler than the main house
(admittedly it's a big room, therefore "airy").

- Yes. I know that bedrooms are supposed to be cooler than the rest of
the house, but I'd rather achieve that by turning down the radiators.

- I keep thinking about sticking (say) 50mm Celotex boards to the
ceiling [of the garage], using mastic of some kind.

- Would it be _worth_ adding more insulation? When built, 25 years ago,
as an extension to our semi, the joists above the garage were packed
with insulation before theÂ* plasterboard was fixed.Â* We also have a
roller door fitted, therefore pretty good insulation at that end.

- The whole house is very well insulated in the roof, and also with
cavity wall insulation.

Any comments would be welcome, to help me with this decision!

Cheers
John

I certainly wouldn't stick insulation up with anything.

I think my first action would be to check the bedroom with an infrared
thermometer and, with great care, a candle. Looking for cold spots and
draughts.

If, after investigation, you still consider it appropriate to add
insulation to the garage ceiling, don't leave it bare. Cover it with
plsterboard (or whatever is approved) and fix with the sufficient screws.



Pull the garage ceiling down and make sure there are no gaps where the
joists are built into the walls. Seal with firestop mastic if so, then
in place of the fibreglass or whatever they used 25 years ago,
cut 4 inch thick celotex so that it fits *tightly* up against
the bedroom floor and use tile battens to provide extra support.
infill remaining space with whatever fibreglass you pulled out
then add another layer of celotex over the joists (ie.on the
underside), and fit new 15mm fireline plasterboard.

Something else just occurred to me. Does this extension have
the same roof line as the original house or did the planners
insist on a 'set back' ?. That being the case are the
bedroom windows dormer-type windows ?. This style of construction
is notoriously leaky where heat is concerned. 25 years ago
the builder probably didn't put any insulation in the dormer
cheeks, and quite possibly little of none above the
ceiling. Retrofitting this is not going to be easy.