Insulating the floor

[Slider]

Has anyone had any experience in insulating floorboards on a stumped house? I find that the floor gets mighty cold in winter and was wondering if others find this, and what can be done about it.

The subfloor access is okayish, (a little squeezy). The floorboards are Tassie Oak.

I was thinking maybe using sheets of ply and nailing/screwing them to the bottom of the floor joists. Possibly including some insulation between the ply & the floorboards. dunno.

Any clues?

[ED T]

The plywood alone won't do much. The gap between ply and the underside of the floor is too large, and you will get air circulation in the gap, and therefore heat transfer.

You need stagnant air in that gap, and that means a glass or fireproofed wool matting. tack it up and seal it any way you like, depending on whether you are concerned about rodents and insects taking up residence 30mm under your feet.

ET

[ozplanit]

My folks too have the same issue about the cold floorboards.

Has anyone ever come across the polystyrene boards that can be fixed underneath?? Mum recently visted rellies in NZ and they have them installed and have supposedly made a huge difference. Also a friend in Ireland is a building inspector and says that they are used heaps over there. (walls mainly)

I am wondering if anyone has seen/used them and has opinions good or bad??

ET can you let me know what you decided on doing and how good it works?

cheers

Dean

[Theva]

Dean,

They have some thing similar for walls (EPS), normally installed outside on top of hardiflex and the likes then some fibreglass mesh / render type thing to finish it off.

Polystyrene does produce some nasty stuff when set on fire; NOT recommended for indoor applications; also possibly the reason why it is not available / promoted for underfloor applications.


Regards,

Theva

[ozwinner]

Has anyone ever come across the polystyrene boards that can be fixed underneath??
http://www.foilboard.com.au/fboard/index.htm


Try here.
Al

[ED T]

I lightly stapled pink (glass) bats the the floor and joists, then thoroughly stapled fly wire across the joists to seal the whole space. Not good looking, but worked well.

Doing it again, I would bead a stack of "liquid nails" to the underside of the floor, let it skin up a bit, then push the bats up into place. Think they would stick.

Would not dream of using foamed polystyrene under a floor. It is an excellent insulator, but extremely inflammable and releases nasty stuff when burning. I think a fire could flash across the whole floor of a house in minutes, before you felt heat through the timber floor.

ET

[ozwinner]

I think you will find that any product for use in building will be fire rated..


Al

[soundman]

For fitting any insu;ation bats to walls or underneath floors or roof sheet spray glue is wonderfull.

spray the wall (or whatever) spray the bat let it go off a bit & stick it up. Sheet up over ar your convienience.

sure beats the hek out of a whole pile of other fuddly methods.

the current poly bats would probably be ok just glued to the floor boards in some situations.

but slats or straps over ...... would be better.

cheers

you used to be able to get a fibregalss board at one stage about 25mm thick.

[rsser]

One printed pub from Sustainable Energy Vic reckons that insulating your floor only saves about 5% of your energy costs (Insulating Your Home ). Though the subjective comfort factor might put it at higher than that :).

Check out this option...

http://www.concertinafoilbatts.com/

which suggests perforated concertina foil batts to allow the floor to breathe. They can easily be stapled under or between the joists. An R2.2 is claimed for them. Tim Renouf is well worth a chat to.

I also found this to be a useful site, esp. the case studies of housing in different states - the climate obviously determining the balance of effort in keeping heat in or out:

http://www.greenhouse.gov.au/yourhome/technical/fs16a.htm

Good luck,

Ern

[jackiew]

bunnings in nunawading had foilboard for sale but it was on a rack high up so I couldn't check if it was the same stuff as i've seen at the timber advisory centre. from memory it was about $21 for a sheet the size of a standard plasterboard sheet.

[Theva]

You can get foilback plasterboard from most manufacturers / suppliers in all sizes; they may have to order it in. Cost an extra $7 (app) per sq m.

Regards,

Theva