Loft insulation: Rigid boards over joists & rockwool

[Daddy]

Hi all,

A common requirement - I'd like to beef up my loft insulation whilst keeping a boarded area for storage. I've already got a good layer of 200mm rockwool which fully fills the gaps between the joists but the rooms below are still getting too cold. My plan is to keep the rockwool and over-board the joists with 100mm Kingspan TP10 or similar and then lay some chipboard as a storage surface. My thinking is:

1. The rockwool is new and I don't want to loose it.
2. From experience, cutting boards to fit *tightly* between joists is fiddly and time consuming (it's quite a large area)
3. Overboarding will eliminate cold bridging through the joists.

I just wanted to know if anyone can see any disadvantages ? I'm most concerned about loss of efficiency and/or condensation problems.

Any thoughts ?

Many thanks !

 

[fogster74]

Hi Daddy,

We're thinking of doing exactly that too - there's a good parallel post going on - the OP was originally thinking of raising his ceiling joist height, but someone done exactly what you're suggesting:

//www.diynot.com/forums/floors-stairs-lofts/increasing-joist-height.337430/

You can see what one of the people replying has done here:
//www.diynot.com/network/jabuzzard/albums/13868/51401

It may be worth posting there and closing this thread?

Steve