Cavity Wall Slabs / Standard Loft insulation / Other options

[DIYNotIan]

Hi all

I'm looking to board a small area of my loft. The rest of the loft will be insulated to 300mm. But if I board onto the existing joists in the small area, there will only be space for 100mm insulation beneath the boards.

As luck might have it, I've got some spare Knauf RS60 (density 60kg m/3) cavity wall slabs which are 100mm thick.

What I wondered was whether the RS60 is a better insulator than standard loft rolls, and of so by how much? Or to be more specific, how would 300mm of standard loft roll perform compared to 100mm of the RS60.

I would also be interested to hear about any alternatives there might be - other forms of thinner insulation which would be just as effective as 300mm loft roll.

Many thanks

Max

 

[freddiemercurystwin]

Your insulation isn't much better than normal loft roll insulation.

There are thousands of threads on this in the Floors section of the Forum, Fit some your 100mm Knauf between the exiting ceiling joists then add 100mm joists perpendicular to the ceiling joists with another layer of your insulation between. Then board on top.

You can get PIR rigid insulation (for eg Celotex or Kingspan), 60mm of Celotex is roughly equal to 100mm of loft insulation.