Insulating My Loft Now, With A Conversion In Mind Later...?

[jagillham]

I want to up our insulation in the loft before winter kicks in this year, but I am planning on converting it some point next year.

Currently the roof is the tiles, and some kind of backing underneath (feels like a tar sheet?). This is all complete, apart from one tear which is about 10cm square. There is a small amount of rockwool between the joists too.

As we are planning on doing a loft conversion at some point not too far away, my plan was to insulate between the rafters now with Kingspan or something similar. The whole idea being that it would be suitable (ie building control acceptable) for next year to save taking anything back out.

Can anybody offer any advise as to how much thickness would be required, and if any ventilation gap would be required?

Thanks

James

 

[freddiemercurystwin]

Its not as simple as just adding some insulation. How do you know the rafters won't need to be beefed up, structural walls added beneath purlins. Continuous ridge ventilation needs to be installed. How will Building Control know what size insulation you've installed? Etc etc ......

That said typically you'd be looking at about 90mm between your rafters if they're deep enough and a continuous layer of 40mm odd beneath. A 50mm ventilation gap will be required between the insulation and the membrane.

 

[stuartturbo]

ignoring the structural side etc as feddy said

STG required (medway gravsham swale)
In the rafters
50mm ventillated gap
90mm Celotex phenolic insulation (I fitted 100mm)
multifoil layer web dynamics
50mm batten
12.5mm plasterboard with skim
this gives 0.18W/M2K
Continuous ridge ventilation
If you beef up the rafters with 50mmx50mm then fix with 50mm C16, 12 gauge screws at 400mm centre with structural glue

 

[freddiemercurystwin]

multifoil layer web dynamics

Why did you do this? Instead of 50mm of Celotex or whatever?

 

[stuartturbo]

Thats what the build reg spec'd in my case that is the dead storage to the front.
the dormer had spec'd 50mm in the wall then the insulated plaster board. ( i have since used 100mm and some foil as had load left over and std board, They have signed this stage off