I want to insulate some of my underfloor area this weekend, but my local Bunnings doesn't stock underfloor specific Earthwool and it will take 2 weeks to get it in.
What is stopping me using the wall batts instead, they are R2.5 vs the 2.1 underfloor batts at about the same (or slightly lower) cost.
I'm looking for something easier to install - the panels require a lot of cutting to fit as the joists are not all 450 centres.
Also it is a smallish crawl space - I'm thinking batts will be easier, if slightly fiddly with the strapping to hold it.
They cut very easily with a hand saw
Will the wall insulation be ok exposed to elements? I know it's under the house but moisture etc could make them wear fast. Polystyrene is the go but I had a mate install under house insulation and he said it barely made a difference
Under the house is very dry and minimal draughts- about as good as you would find - it's just damn cold here in New England - It will have to make a difference as you can feel the cold in the floors and there are lots of small gaps in the BIR's that let lots of cold air in - as well as insulating, this should stop cold air infiltration.
The Expol polystyrene that Bunnings has is only R 1.4, I'll be wanting 2.0 - 2.5
heat rises, cool air sinks. insulating under the floor does nothing in regards to temperature. you're on the right path with blocking the gaps.
insulating under the floor does nothing in regards to temperature.
Not entirely correct. Cool air drafting under the floorboards may certainly affect the ambient temperature of the room directly above.
Insulation reduces heat loss from the floor; if the cool air against the floorboards above is warmer than the cool air below the floor (sub zero in my case) then heat must be lost from the room.
Physics
I'd use foil lined polystyrene panels