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

Bump TTT etc!

Hi,

You need to look up the Thermal Value for each item, Google it!

SSM

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Measure twice, cut once!

300mm loft roll is equal to 130mm of celotex or kingspan. I would therefore put 100mm loft roll between the ceiling joists and then put 100mm kingspan over the joists, with loft boards over the top. The kingspan 8 foot by 4 foot sheets would need to be cut to get them into the loft, ideally three rips lengthways or less, then build a frame around them so that they cannot move and board over the top.