What sort of underfloor insulation is recommended for a 1940s weather board house. I have been looking at R 1.8 polyester between the joists and plastic vapour barrier on the ground. Is this a good option?
bugalugs,
Jul 18, 10:25am
Where do you live? North or South?
trade4us2,
Jul 18, 10:39am
I think that's a good option. However I have put down carpet and underlay rather than underfloor insulation.
vanderbel,
Jul 18, 11:08am
Christchurch
tweake,
Jul 18, 10:54pm
carpet and underlay have next to no insulation value.
the big thing for underfloor is keeping it dry. drainage and vapor barrier on the dirt is very important.
mack77,
Jul 19, 1:07am
Yes, that is definitely a good option; the best option in my opinion. As "tweak" points out; carpet and underlay provide very little insulation.
pauldw,
Jul 19, 1:27am
There are a lot of sources other than you quoting an R value of 0.4 for carpet + underlay.
tweake,
Jul 19, 4:14am
it depends a lot. i have seen (once) extremely thick underlay which i'm sure would have insulation qualities, but thats rare. i've asked a couple local carpet guys and they have never seen it. look how thin normal underlay is compared to half decent insulation. i have seen specs for our normal underlay but i can't recall exact values.
don't forget there is a big difference between winterless north and south island weather.
macandrosie,
Jul 19, 4:39am
WE live in Southland & we layed polythene on the ground then installed expol. It definitely makes a difference in an older home, but then again older homes take some insulating & heating! We had the place completely re clad 20 years ago with palliside (plastic weather board), but also had put on builders paper & re batted all the walls. Have had ceiling batts all topped up too. Had installed HRV which has helped dry the place (120 yr old home). Still not really warm when it snows & you have days of frosts!
tweake,
Jul 19, 4:45am
just looking at this. i have only got 6" joists but even then i can fit R3.0 insulation in. thats a big difference to R0.4 for carpet. even cheaper R1.8 is still a big step up from R0.4
gabbysnana,
Jul 19, 5:59am
yes do it. Helps to have good carpet and thick underlay as well.
dinx,
Jul 19, 7:49am
Another tip is consider air movement in your area. If you are in a high wind area or have great airflow, then a rigid product like expol or novafloor is better suited. In most areas the polyester rolls are great but it was something that was mentioned to us when we were getting quotes. Our house is in high wind area but under house area is not (split level on bank at back of house so were good with 1.8 polyester rolls & barrier. Our ceiling space is however high wind lol.
I did note the tape used on the polythene was too thin and has lifted off in many places. DP knows this happens as from farming where they deal wih silage etc so he will be off to farm supplies shop at some stage to get some proper wide tape lol.
marte,
Jul 19, 11:26am
Haha, in my house in Ingill, theres no insulation and its around 2-5 deg C inside all the time at night. About 1/2 degree warmer than outside.
Ever seen olive oil freeze?
stevo2,
Jul 19, 7:24pm
Here's a hint. Use only 50mm polythene tape from a builders supply merchant. Its the same as we use under concrete floors. Make sure polythene is clean and dry. Sometimes it may not stick to well in the cold weather (or if it's damp) so put a metre or two down then go over it with a heat gun (or hair dryer). It will really make it stick down well.
golfaholic2,
Jul 19, 8:16pm
Half the secret to making builders tape stick , it to make sure it isn't stretched at all when its applied .
If I was insulating the under floor of a house in Chch , I'd head for a demo yard like Sopers , who sell large bags of recovered batts for $50 . $300 would probably do an average size home . some bags have more batts than others, so go for the thinner (wall) batts . Their stock (as is probably most demo yards) revolving , and most people want the ceiling batts . You could request they source wall batts maybe ? And no , I don't work for or have any affiliation with Sopers , it's just the devil I know
golfaholic2,
Jul 19, 8:20pm
I put mix of R1.8 and R2.2 under my floors , doing the vinyl area of a large open plan lounge kitchen dining room made a MASSIVE difference , night and day sorta thing . then I did the carpeted part , which is probably 60% , and noticed no difference at all . Double glazing offered what ? R0.25 ? I suggest R0.4 for carpet/underlay is being under valued by many . Ive always suggested doing the non carpeted areas first , and following on into the carpeted areas if needed
gabbysnana,
Jul 19, 8:57pm
I bought a property for my daughter, the house is on piles. Underneath with a 400m crwal space was littered with piles of dirt and rubbish. Although the house is fully insulated the floor was always freezing and there was this layer of cold air at foot level. Over christmas we got under the house removed the rubbish and levelled the dirt and put down the heaviest black polythene. Made sure all the joins and cuts were taped solid. They noticed a difference straight away and this winter being the worse ever they are toasty so covering the earth under the house works.
tweake,
Jul 19, 9:26pm
that sounds about right. because your walking on the floor you notice the difference very easily.
eljayv,
Jul 19, 9:32pm
There is underfloor insulation under our floor, unfortunately is is a blanket or sheeting type over everything and when a copper water pipe sprung a pinhole leak the water just collected and hung there. Had to cut it away to release water and repair pipe. I now want it all removed as I want to run some new wiring under there.
jonners2013,
Jul 19, 10:33pm
if it was holding the water like that, i assume it was the old style foil roll type. you're best ditching that and replacing with decent stuff.
golfaholic2,
Jul 19, 10:52pm
Was referring to the rooms heat retention . went from an hour , to overnight just by doing the non carpeted area . Doing the carpeted area didn't add any noticeable retention . tho logic says it must add some .
tweake,
Jul 20, 12:21am
probably polystyrene sheets, foil is open at the ends and drains out. good comment about holding water, would not be good to have the timber wet for a long period of time. probably better to put the insulation above any water pipes.
tweake,
Jul 20, 12:34am
point i was making before is thats its easy to "feel" a difference when its quite big, but also anything in contact is more noticeable. its highly subjective. i've had it where i've noticed a difference, then found i never turned it on so it was impossible for it to make a difference LOL. thats the trouble when your dealing with things like "i felt a difference". its hard to tell without measuring temps.
don't forget there is also the law of diminishing returns. double the insulation won't give double the effect.
sarahj1,
Aug 2, 3:21am
We have just done this (polythene vapour layer and polyester fill) under our 1920s Chch bungalow and it has made a huge difference. Warmer, drier - and we never thought our place was that damp before! One "drawback" to be aware of: All our polished floorboards are now drying out and separating, getting quite big gaps between them. Anyone have suggestions on filling them? Also, our painted wooden wall panelling is all splitting too( the paint is splitting as the wood dries out and shrinks I guess) so some repainting is needed. Still a warmer drier house is great. Wish we had done it years ago.
golfaholic2,
Aug 2, 4:01am
Point I was making , the uncarpeted areas being insulated was CHALK and CHEESE . the other areas made little to no difference . I again suggest anyone on a limited budget do the uncarpeted areas before any others . and move on from there
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