"Gelf" wrote in message
...
We had a builder construct an extension about 3 years ago, comprising
2 single bedrooms over an existing garage.
The floors of the bedrooms sit on 5" joists with fibreglass insulation
between the joists. The ceiling in the garage comprises of pink
(fireproof?) plasterboard.
The problem is that the front bedroom is very cold in winter and also
soundproofing between the bedroom and garage is very poor.
The back bedroom is not so bad because it is half over the kitchen.
The garage isn't actually used as a garage, more a small workspace/
store.
I suspect the builders have skimped fairly seriously on the fibreglass
and I'm wondering what the best way to improve matters is.
I'm thinking along the lines of
(a) taking off the plasterboard and adding more fibreglass,
(b) removing the fibreglass and putting 75mm Kingspan between the
joists
(c) leaving the ceiling as is and fixing sheets of 40 or 50mm Kingspan
below it
Not sure how (b) and (c) fit in with building regs even if the garage
will never see a car!

Best to remove ceiling and the fibre glass and install rigid Rockwool bats
4" thick. These are superior in sound and heat insulation. Cut them
slightly wider than the joists to give a tight fit. Available from Wickes.
Then put 25mm of Kingspan under the joists. This will eliminate cold bridge
to the room above and increase thermal insulation even further. Then add
plasterboard over. Use prefinished Fermcell which meets the fire regs and
can be DIYed easily enough. http://www.fermacell.co.uk

Important: make sure there are NO air leaks between the garage and the room
above by ensuring the Fermacell is well fitted. Any cables running through,
seal with silicon sealing.

If you feels rich, replace the garage doors with sealed and insulated doors.
This has great benefits all around.



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