I have wooden floors. I need to put insulation under the floor. It is easy to get access to as there is a garage/workshop underneath. I intend to do it myself (famous last words!). I would appreciate any opinions of what product to use to get the best insulation. The house was built in 1967, the floors are native timber.
nakiguy2,
Apr 21, 3:53am
Sheez pretty big job. !
whitehead.,
Apr 21, 4:00am
i would use the polestyren foam stuff that id used for fridges is great . if you use the blanket it works but you have to put strips of metal on to hold it in place and the rats and mice love nesting in it . one of my friends used the foam from an large fridge he cut it with a chain saw its also used in railway carrages
golfaholic2,
Apr 21, 5:54am
Half price batts from a demo yard . will be heaps cheaper and warmer than some poxy Expol ever will be
tweake,
Apr 21, 6:49am
depends on what wiring and plumbing etc is in there. electrical wires need to be wrapped as they react to polystyrene foam.
batts would be a pain as has little structure to it. very difficult to attach. polyester would be good. fairly easy to fit. fill it up the whole joist aera.
mm12345,
Apr 21, 7:19am
I've been looking at doing this with our early '60s house. The joists are close spaced - but not evenly spaced. The pre-cut grooves in expol etc will not work - it would need to be cut to size, and this means many hundreds of pieces, as well as the hassle dealing with PVC cables, working around plumbing etc. It would be a major PITA - a polyester batt system would be much better, perhaps also "Earthwool" which is good to handle. I'd also be cautious about benefits in a '60s house. I've completed a full re-clad which included installing insulation in all external walls, the cavity system now fully closed between sub-floor and roof space, except for correct venting / drainage of the cavity (any draughts around joinery with architraves effectively sealed off). I've added a layer of R3.8 blanket over the top of existing old batts. Most floors are carpeted with heavy duty underlay, Floors are ~20mm t&g rimu without gaps. Sub-floor is dry, and the wind doesn't blow through - only standard sub-floor vents. On a cold day, the basement area stays quite warm - so although I will install sub-floor insulation, I don't expect it to make a huge difference (like the wall and extra ceiling insulation did).
trade4us2,
Apr 21, 7:27am
Aluminium foil is now not recommended as several people have been electrocuted by touching foil that has been stapled into wiring. Polystyrene foam must not touch wiring as the wiring will dissolve over time.
tweake,
Apr 21, 7:31am
foil is not insulation anyway. there is the bubble type but its expensive for minor benefit and difficult to do a good install.
sooby,
Apr 21, 8:30am
I recently used Mammoth polyester - way easier than polystyrene!
Easy to cut & fit, no messy offcuts, AND higher R value. I highly recommend it, just my 2 cents
russ18,
Apr 21, 9:14pm
As a sparky I've been under a lot of houses, IMO the best for staying in place, not reacting with cables, not needing staples or nails etc is Novafloor plus it's very easily removed and refitted as needed by other tradesmen.
mm12345,
Apr 22, 12:36am
That looks pretty good. It's only R1.4 (some of the alternative are higher - but that's about the same as standard "Expol"). A problem that I'd have is that joist spacing (gap between) is about 375mm +/- 5mm or so) to install you need 25mm wider (400mm), they make it in 375mm (too small) and 435mm (would require trimming). It all looks so easy - but I have the feeling that it won't be - which is why I still haven't decided what to use. But I'd far rather be dealing with offcuts of polyester blanket than poystyrene.
golfaholic2,
Apr 22, 6:12am
I did a mix of R1.8 wall and R2.2 ceiling under my floors . the only areas that made any noticeable difference , and that was a HUGE difference , was areas with vinyl
naturalkiwi,
Apr 24, 6:31am
We had Insulpro blanket (polyester) installed under our floors. It's only R1.5, but has definitely made a difference. Very little mess too. Glad we did it.
russ18,
Apr 24, 6:41am
Installed some under my house, had to trim some, no problems.
k_billy,
Apr 25, 7:32am
I'm also thinking of installing underfloor insulation. I currently have silver foil, should I remove this and replace it with something else? Would I need to install a vapour barrier if I do remove the foil?
tweake,
Apr 25, 10:35am
remove the foil. it does next to nothing. the insulation will act as vapor barrier. if its dirt underneath lay the moisture barrier down.
lythande1,
Apr 25, 7:57pm
Why? Heat rises, cold air falls. So long as the rest of the house has insulation, you draw the curtains to keep warmth in, it's not necessary.
pooks3,
Apr 25, 8:36pm
I got told, if you walls and roof are done, it can act as a bit of a vacuum and suck the cold air up. We did walls and roof in our old house, it made a huge difference doing the floor, we had the black sheeting put on the ground to stop the moisture coming up, then we had Eco green put in, our current house has 2 levels, most of the living is upstairs, it's so nice walking on warm carpet, it is amazing how cold the floor can be without floor insulation,
mack77,
Apr 25, 8:43pm
Not precisely correct. Heat disperses evenly in all mediums except fluids (gases and liquids). In fluids the hot air or liquid rises to the top of the vessel it is contained in (e.g in a room with respect to gases).
golfaholic2,
Apr 25, 11:04pm
Someone needs to google "radiant heat loss"
trade4us2,
Apr 25, 11:51pm
Be very careful that the foil is not electrified by being stapled to wiring. The foil will make the house warmer.
k_billy,
Apr 26, 2:57am
I understand the whole electrification issue, what I'm not sure about is whether the existing foil is solely there for insulation or does it provide a vapour barrier too which I should reinstate if I put in better insulation?
tweake,
Apr 26, 5:34am
correction, hot AIR rises. heat goes from hot mass to cold mass in any direction. there is heat loss through the floor. also because your in contact with the floor you feel it a bit more as well.
bluecat1529,
Apr 26, 5:41am
Greenstuf underfloor. It is now all that we will use. Expol is as has been said a PITA. Earthwool too as it needs strapping to hold it in place. Greenstuf gets stapled up and it stays there and works. Quick and simple
tweake,
Apr 26, 5:44am
my understanding is that originally the foil was put in to reflect heat back and the sag was so moisture would collect on it and run down and drip off. reality is that it does both jobs badly.
the insulation will handle condensation ok as long as its not huge amounts and it gets to dry out during the rest of the day. if its really wet underneath put drainage in where required and barrier sheet on the ground.
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