"Another John" wrote in message
...
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.

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

Trivial to measure the temperature and see if it actually is cooler.

- 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?

Normally not in your situation.

When built, 25 years ago, as an extension to our
semi, the joists above the garage were packed
with insulation before the plasterboard was fixed.

So unlikely you are losing much heat that way
unless its very leaky due to drafts in the garage.

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!