Underfloor Insulation

[gobbledegeek]

I have two downstairs rooms with traditional floorboards, nailed\screwed to joists. The boards are not tongue and groove and have about a 3mm gap between them. The boards are varnished and no carpets/rugs fitted. Both rooms are difficult to keep warm despite double-glazing and cavity wall insulation and I think I'm losing heat through the floor. I'd like to insulate the space beneath the floor which is about 300mm deep.
It would be difficult to take up all the boards due to the time involved, and possible damage in doing so. Does anyone know if I could just take up a few boards and use loose-fill polystyrene balls by using a blower to blow them under the floor? Where could I get this equipment?

[gobbledegeek]

Mmmm, never thought about fire risk. However, you can get fire retardant beads, see http://www.expanded-polystyrene.co.uk/expanded -polystyrene-bead.htm
I already have this type of insulation in my cavity walls.
I really just need to know if there would be any problems with using this in a floor cavity (my air vents are above floor level so there shouldn't be a problem there).

[Clanad]

You don't say what's in the space beneath the floor. If it's earth then I would say this is a good opportunity to do the job right and cover the floor with a layer of roofing felt, and lay 1/4 inch construction grade plywood over this for a sound, draft proof subfloor, onto which you can then lay carpet or other acceptable flooring. Fact is, with 1/8 inch gaps in the flooring boards, it's a wonder you don't have an infestation of bugs and such coming up. Additionally, since heat rises, I doubt you are losing heat down through the floor. Obviously, depending on how weather tight the subfloor space is, you coud be getting drafts, which the suggested fix above would eliminate... Best of luck!

[gobbledegeek]

Clanad, I have a traditional timber floor (house is 100+ years old). The boards sit on 100mm joists and there is a further 200mm empty space below the joists with just earth as the base.
Have never had insect infestation. I don't feel any draughts coming up through the gaps but the rooms do not keep as warm as other rooms that are carpeted.
Your solution would work but, as I mentioned previously, I really want to avoid taking up all the boards in three separate rooms. It's fairly decent old wood and I'd be worried about damaging them.