Under floor insulation

[geraldthehamster]

I've posted a couple of times before with speculation on how to
insulate under my suspended timber ground floor. Now I've finally
taken up half the floorboards in the room I'm starting on (the rest
will follow tomorrow). I have 4 x 2 joists crossing the room,
supported mid way by a block dwarf wall. There's about 8 inches under
the bottom of the joists, above concrete.

I'd planned to suspend space blanket between the joists, on netting,
but it's looking a lot simpler to fix sheets of 50mm Celotex under the
joists. I have a few air bricks on the two external walls, which are
level with the adjacent joists and will need ducting to the underfloor
space ( which I could do with a bit of Celotex crafting).

It seems to be that the masonry in the void will still be vented, and
the joists are unlikely to suffer damp from below, due to the foil on
the Celotex, nor condensation from moist air above, due to being on
the warm side of the insulation.

Can anyone think of anything wrong with this plan?

There is a small prize for the first person to say "notifiable work".


Cheers
Richard

 

[Deluks]

Sounds like a plan. As long as the air can circulate beneath the joists it'll be fine.

 

[mointainwalker]

I reckon it will cost you 3-4 times more with Celotex for 20% less insulation effect ( 50 mm Celotex = U 0.5 vs 100 mm fibre wool = U 0.4 ) plus lots of carving if joists not absolutely regular.