Insulation over exisitng 19mm T&G chipboard flooring?
RodP
posted on 24-02-06
You did not say how high the space under the floor is.
Can you get in there and install the insulation blanket from underneath, without taking up the existing floor? Miserable job but maybe your handy dad would like to spend a few hours laying on his back.
Neil
posted on 25-02-06
RodP, I've never had the floor up as yet so I can't comment as to how much space there is beneath it. One thing I know for certain though is that my old man won't be crawling under it for me! :oD
I'm expecting there to be around 18-24" clearance looking at the position of the airgates from the outside but I guess I won't know for sure until I take up the first board. Taking up just a few boards to get underneath to do the insulation does make sense but won't I have to take all the boards up anyway to fit the vapour and draught barrier afterwards? I was under the impression it went over the joists but still under the floorboards?
Neil
posted on 26-02-06
Been google'ing and found this:
Condensation
A vapour barrier is not normally required for most ground floor constructions. However, a vapour barrier should be installed between the insulation and a chipboard floor, especially if there is a risk of excessive moisture from the floor slab drying out.
Think I've just answered my own question. It's a pity the whole floor's got to come up but if a jobs worth doing............ :o)
Tony
posted on 26-02-06
Technically the vapour barrier should go on the warm side of the insulation and as the chipboard itself has some insulating properties then polyethene should be laid over the flooring! Or it's surface could be painted with oil based paint.
So you could cut out panels and get down there but it is horrid work and easier faster and better to take up the floor.
The polyethene could be missed out as a vapour barrier but I wouldn't and as an air tightness barrier it is absolutely crucial. There is little point in insulating if there are draughts which is why our building regulations are so silly as we can have all the draughts we like so long as we have put in the right ammount of insulation!
Neil
posted on 27-02-06
Tony, thanks for all your help and advice mate. I'm hoping to do the spare room in a few weeks time. If that goes well then i'll do the rest of the ground floor in stages.
Just looking at my options regds flooring. If possible i'd prefer to save the current flooring but if it's glued (like I think it is) then I don't think that will be possible. :o(
Will get my old man down for a look when he gets back from holiday anyway and then start to buy the bits and pieces.
Thanks again.
RodP
posted on 27-02-06
Dont want to belabour the point but I really dont like throwing away material which is still capable of doing a job. Leave the floor in place and work from underneath.
Technical points:- A vapour barrier is installed on the warm side of insulation because thats where the most moisture is, in the form of water vapour in the warm air. While polyethelene film is usually used, any material with a permeability low enough to meet code requirments, or to meet practical needs where meeting codes is not an issue, will do the job.
We are simply trying to prevent warm moist air from meeting a cold surface, within the wall or floor structure, where it will condense causing mould growth, structural degredation and insulation reduction. The latter serves to compound the problem.
In the floor under discussion (think of it as a wall laid flat) the current flooring can easily be made into an effective vapour barrier for all practical purposes.
Secondly an air barrier is usually placed on the outside of a wall system to prevent air entering the wall (floor) structure and showing up as a draft inside. The driver for this movement is pressure differences caused by wind etc. Again the material is not the important thing, the effectivness is. Sheets of steel are effective and can be welded, however, in the floor in question a building paper or sheets of rigid insulation, attached to the underside of the joist, are just as good as long as they are properly sealed at the joints and perimeter. Draft excluding foam in cans is excellent for this sealing work, if rigid insulation is used. Both would also serve to hold up the fiberglass insulation between the joist.
Probably bored the vapour out of everybody, if you've read this far I hope it helped.
