I've just installed 100mm loft insulation between my existing 3x2 roof joists with the next step being to run a number of new 3x2 timbers across the existing roof joists therefore creating an area to fill with 170mm insulation. I'll probably fit the new timbers with the 3" side up to give more height. On top of this I would then like to lay a chipboard floor. A couple of questions........ This seems daft and I *may* regret asking but will anyway......If I was to compact 170mm roof insulation into a 75mm area (ie between existing joists and new chipboard floor) will any of its insulating properties be lost? Lastly, will general chipboard flooring be adequate for a loft or should I use the green treated chipboard?