Insulation between rafters

[RyanAirelle]

Hi

I am in the process of converting my loft and wanted to know which is the best insulating material to use based on what is available out there?

Also, would it be best to use plasterboard with insulation or can I opt for standard PB if I insulate the rafters?

Any suggestions would be appreciated.

Ryan

 

[freddiemercurystwin]

You'll need something like 110mm Celotex or Kingspan rigid insulation between the rafters and a continuous 25mm layer beneath, then use foil backed plasterboard. Can't be more specific as it depends on sizes of rafters and spacing of rafters, whether you have a breathable membrane, felt or nothing under the tiles, information you've not included.

Something like this:

Untitled

• freddiemercurystwin
• 8 Jun 2010
• 20

 

[RyanAirelle]

Thanks for the information. Aware of issues concerning the 50mm gap between the roof and insulation (condensation). Not aware of the membrane and if its breathable so will work on the basis that it isnt.

Cheers

 

[RyanAirelle]

Freddy,

Back to this issue. My rafters are at 450 centres and the membrane is breathable.

As the rafter is only 85mm deep, my intention was to purchase a 140mm celotex board and notch out around each rafter so I end up with a complete wall of insulation. The breathable membrane allows me to leave a 25mm gap rather than 50mm.

If I can notch out the edges of the insulation board this will save on making up the rafter and over laying on the under side.

Do you think that this is wise?

 

[freddiemercurystwin]

If you feel it is practicable to do so then there is nothing wrong with your proposal.