Best insulation to use?

[tommyl18]

Hi i have a ceiling in a garage to insulate, board and skim there are rooms above it.

The garage is aprox 5m x 5m and already boarded and skimmed. I have 2 options but not sure which will be best for cost and for thermal properties.

1, lower ceiling with timber, apply 4 inch rockwool insulation, board and skim
(lowering of the ceiling will not be an issue because it is already a high ceiling)

2, Fix 25mm thermalbacked plasterboard over existing ceiling and skim .

thanks

 

[RF Lighting]

The thicker the better. Why not use both products?

 

[r896neo]

4 inches of rockwool and 25mm of kingspan are not equivalent.

The rockwool is better if you have the space as its cheaper and will help sound insulation if that matters?

Otherwise if you want to make it easier screwing 62.5mm insulated plasterboard direct throught the lot to exisiting joists will be very quick. You will probably have to put a coat of bonding on the ceiling before final skimming though as it may pull into all sorts of bumps and dips.