Insulation under loft boarding

[mikebakke]

Grateful for any advice:

I am going to lay some mdf boards I have in my loft. Based on reading so far I'm either going to re-route wiring whch is over the joists or cross-lay 3x1 first.

There is very thick fibreglass insulation laid throughout which stands well proud of the joists. My question is whether it is acceptable to compress the insulation and just lay the new boarding on top or does this reduce the effectiveness?

Thanks

 

[JohnD]

Insulation works by thickness, so if you squash it you will reduce its effectiveness. Also it is preferred to leave an air gap to prevent condensation. The air gap and the flooring will also reduce heat loss a little.

If you have the chance to use thicker counterbattens this will help give you more room, as well as a more rigid floor. 2"x2" would probably be no more expensive.

 

[mikebakke]

Thanks, I suspected that may be the answer. I've had another brief look up there (don't want to spend real time there till I have a mask and gloves) and it's actually 2 layers of 4-4.5in fibreglass. The joists appear about 4 inches so I will have a look at relative costs for the 3x1 and 2x2.