Right. We have a house. The loft is partly boarded with degraded rock
wool as joist level insulation ranging from 10cm to 2cm in places.
It is pouring heat out the roof. Within the next 6 years we have plans
to convert the loft to create another bedroom. Thinking long term I
can't quite figure out whether I'm best to:
1 - Kingspan/Cemotex between rafters (leaving a 50mm clearance off the
sarking for ventilation) but saving the drylining for another day.
2 - Kingspan/Cemotex between the joists as it'll all be floored
eventually and reinsulate the water tank is it will get a lot colder in
the loft above the ceiling! My thoughts were to simply cut to width,
insert between joists and leave it at that after reaffixing the existing
3 - Rockwool it all for a pittance now, only to rip it all out within a
My preference is for option 1 or 2 but would welcome the thoughts of the
learned souls on here as googling the subject provides a dazzling array
of ways to go about it.
On Mon, 25 Mar 2013 14:18:50 +0000, Bob Minchin wrote:
That it well worth looking into but the conditions attached might not be
meetable by the OP.
Even so glass wool is cheap (are the power company subsidies still
about?) and as others have said what is planned, what happens and when
are completely different things.
The gap alone would not be enough without also ensuring there are ridge
and soffit vents. Depending on the type of conversion you ultimately
plan, you may find it easier to opt for reroofing with a breather
membrane in place of the existing sarking. That would allow full fill
insulation on the inside which may also give more headroom.
Note also that 50mm of PIR foam between the rafters will not by itself
meet building regs for a habitable room - you would need a second layer
of it under the rafters.
I would probably be less keen on this given you plans.
There would be no requirement to remove it later, and also its worth
noting that it would add extra fire resistance to the existing ceiling.
You may in fact find installing rockwool (or similar) to be a
requirement when you convert the loft. (it also adds a bit of noise
insulation as well)
I'd suggest 3 for now. It's dirt cheap and we all know only too well
that plans for the future often remain just that. Plan for now unless
it *prevents* the future plans.
P.S. I have trouble following my own advice.
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