Loft Insulation

ifti

Hi,

i will be carrying out some loft insulation in a few days but just had one question, i want to know if its ok for me to compress 150/170mm loft roll insulation into 100mm spaces becuase we have planks of wood on top, which we will lift and put back.

i would like to know if it will be just as effective or shall i stick to 100mm rolls.

Thanks on advance

Mr_Warren_2

Failing this, a compressed 170mm will be more efficient than an uncompressed 100mm and better than nothing.

ifti

how about compressed 150mm

fas3robinj

I just had my loft done. Did it through the Gas company (Altantic). It only cost £190, and thats for a 4 bed detached house.

It took the guy 90 minutes, and there was very little mess or disruption. They blow loose stuff into the space.

I don't think it's worth the effort to do it yourself anymore. It would have cost me at least £190 if I had bought rolls of stuff from the local DIY store anyway.

Mr_Warren_2

Good point for the blown stuff. It will entrap air (air is the best form of insulation) and fit snuggly in the given space.

Grumps

Good point about screwing additional timbers as opposed to nailing them. If adopting this method then it is also adviseable to 'crown' them first. 'Straight' timber is very much a misnomer. Look along the length and see which way it bends, and mark it accordingly.

If the additional timbers span load bearing walls, then the Crown needs to be on top, in order to pull any sag out of the underlying joists. Alternatively, if the additional timbers are centred on a load bearing structure, then the Crown needs to be on the underside so as to 'lift' the unsupported areas.

Another alternative would be to use wood composite 'I' beams, although I have only ever seen them on U.S. Discovery Channel programes. They have the advantage of strength whilst being light in weight.

One question that intrigues me, and to which I have yet to find an answer is, "What is the thermal value of wood." In the context that, with the current recommendation for insulation being 11 inches, and with ceiling joists normally being 75mm. 20mm chipboard or ply, above 75mm of insulation will have a thermal characteristic of a certain value. How does that value correlate to a specific depth of fibrous insulation?