drop ceiling / insulation in garage?

[ColJack]

My parents house has an integral garage with a room above it ( used to be my room )
I'm pretty sure there is no insulation in the ceiling of it, from when we added some sockets..
the room above is not heated and was always fairly chilly..

could I put some 2x6's at right angles under the existing ceiling and infill with rockwool?

 

[noseall]

Full fill with rockwool plus a 25mm under-draw with foil backed foam board insulation will achieve regs and give a vapour barrier.

For belt and braces seal all the joins on the foil back foam board and use 12.5mm foil back plasterboards.

Snug as a bug.

 

[jono_h]

150mm of rockwool may not make a load of difference though. I had 170mm of rockwool and 50mm of celotex in my garage roof and the ensuite above was still chilly. I put another 70mm of celotex in this winter and it has been better.

 

[brig001]

We have a room like this and found that most of the heat loss was from air coming into the void past joist ends and from unsealed pipes and cables going into the void from the garage. If yours is the same, insulating underneath won't help much. If you are going to fit a new ceiling, you could remove the old one and fix any problems you find, then add insulation and new ceiling.
HTH,
Brian.