Hope the hive can help with this one

Loft

I am about to re-insulate the loft, part of it is boarded with 100mm rock wool underneath it. I will lift the boards and put Kingspan on the joists, what is the optimum thickness for this?

Floor

I have a suspended floor with a very spacious crawl space underneath, however the hatch is smaller than the width between the joists, so cutting kingspan to pass down the hole with be laborious and difficult to piece together. Anyone insulated a floor in similar circumstances? What is the best material, amounts and application method. Was thinking I would just shove some cheap rockwool in-between as it would be better than nothing.

Ta

When we did ours we put 100mm between the joists and 50mm over the joists. Can’t remember what went under the floor, 200mm rock wool?

Lots of good knowledge over on Navitron

Can you cut a bigger hatch? IIRC my dad just added another plank width to the existing hole in his floor when he found he was a bit broader than previous owners…

From experience lifting the floor boards is by far the quickest/easiest way to do a floor with little/no crawl space. I did the first one without lifting boards, took best part of 20hrs, second room I did by lifting the boards – 10hrs, and way less swearing to boot!