Underfloor Insulation

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weesinx

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Wannabe Geek

#87012 17-Jul-2011 22:05

Hi,
Can anyone help me?
We have a house built approx 40 years ago with solid chip board floor. Carpet in all rooms and good underlay.
Is it worth installing insulation/ I thinkthe thick chip board is pretty good and there will be no significant or noticable difference.
Does anyone know? It is going to cost just over $3000 with subsidy off. Novatherm has been recommended.
I live in middle of South Island. We get good frosts

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#494407 17-Jul-2011 22:18

Any insulation is better than none. Do you have a good thick layer in the roof. It should be at least 100mm thick. If it is not this thick add an additional layer. This is where you get the best return for your money.
If your house is wooden get airfoam installed in the external walls.
Once the ceiling and walls are insulated then you can consider underfloor insulation. This is the area where you get the lowest return for your investment.
Have you considered double glazing?

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NonprayingMantis

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#494410 17-Jul-2011 22:24

$3000 sounds a lot ($4500 before subsidy). how big is the floor area?

If it is fairly accessible then it is not too hard to do it yourself if you buy the stuff yourself.

mattwnz

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#494412 17-Jul-2011 22:30

NonprayingMantis: $3000 sounds a lot ($4500 before subsidy). how big is the floor area?

If it is fairly accessible then it is not too hard to do it yourself if you buy the stuff yourself.

Yes that sounds a lot! Polyester or wool with foil underneath can be a good option. A warning with installing polystyrene, don't let it come in contact with plastic pipes or wires.

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#494468 18-Jul-2011 08:34

Friends of ours purchased some of that Expol stuff and put it under the flooring, said its made a huge difference for them - their house is on stilts so a lot of air flow etc underneath.

Yet other friends down the road put it in the ceiling of their garage which is the floor of their bedroom, and havent noticed a difference at all - you'd think theyd notice it more than the others.....

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timmmay

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#494505 18-Jul-2011 10:22

I had underfloor insulation done in my really old house, that has floor boards, a thin underlay and carpet. My house is on piles, but there's not breeze under there. My insulation is about 4cm thick, stiff fabric that fits between the boards, though it falls down and needs to be put back in sometimes. I'd go with something that's permanently fastened if possible.

I think underfloor insulation helped a bit. Increasing my ceiling insulation from 10cm thick wool (though it was variable) by putting $1000 worth of pink batts on top made a bigger difference. Putting a ground sheet down made a big difference, it made the place drier and smell nicer. We had drainage problems though, so it was a bit damn under the house sometimes. The underfloor insulation also helped prevent smells coming through.

Foam in the walls helped as well, though again I don't know by how much. If they say all you need to do is a top coat over the holes they fill, don't believe them. It took a heap of work to sand them back, prime, and paint them, and they'll never be properly level. Knowing what I know now i'm not sure if i'd do it or not. Probably, I guess.

If you have downlights, they're the first thing you should replace, you get massive heat loss through them.

It's hard to work out how much insulation has helped.

weesinx

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Wannabe Geek

#494512 18-Jul-2011 10:31

Great replies thanks.

House has been all double glazed- retrofitted.

Ceiling was done years ago and added another good layer of high quality pink batts during this last year so it is as good as could expect in the ceiling.

Outside walls are concrete block and pink batts were inserted during original construction but of course a higher quality is put in these days. New batts have been put in in areas where we have done alterations.
So floor is the only area not really covered and I have pressure from my wife to look into it!!
The dearest quote was using R1.4 Polyester $24.36 s m x 179 = $4,360.44 and $47.75 to remove old foil that covered some of the area but I think was ineffectual and serves no purpose. So total $4,408.19 and that was under the old GST regime. I have been procrastinating because I am not sure we will get value for money and that is why I asked the original question Will it really make a difference when we have thick particle board ( was called chip board when originally put in)
I could probably install it but it is a job lying on my back and I am getting too old for all of that!!!!!
I do not want to put thaty insulfulf through the wall cavities as I hear it can do a lot of damage in stopping air flow in the cavity between the bricks and the walls. You would think I am an expert but I am just an amateur who knows a little!!!

timmmay

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#494520 18-Jul-2011 10:36

Foil stops draughts. I think sure, go for it, it won't hurt and it may make a significant difference. If you have 3 degree air, then a little wood and carpet, having insulation under that should make a decent difference, and $3K isn't that much compared to what a house is worth.

jonb

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#494567 18-Jul-2011 11:09

It sounds like you've already got very good insulation compared to most NZ homes, you're right: the more insulation the better, but you're starting to reach the point where you get diminsihing retruns on your investment. Try and work out what the payback period would be, if its ten years or so it might be better to just put on a room heater on the coldest days of the year? Or solar heating, a wet back boiler or a ground-based heat pump system to reduce your energy bill?

openmedia

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#494583 18-Jul-2011 11:23

timmmay: I had underfloor insulation done in my really old house, that has floor boards, a thin underlay and carpet. My house is on piles, but there's not breeze under there. My insulation is about 4cm thick, stiff fabric that fits between the boards, though it falls down and needs to be put back in sometimes. I'd go with something that's permanently fastened if possible.

I think underfloor insulation helped a bit. Increasing my ceiling insulation from 10cm thick wool (though it was variable) by putting $1000 worth of pink batts on top made a bigger difference. Putting a ground sheet down made a big difference, it made the place drier and smell nicer. We had drainage problems though, so it was a bit damn under the house sometimes. The underfloor insulation also helped prevent smells coming through.

Foam in the walls helped as well, though again I don't know by how much. If they say all you need to do is a top coat over the holes they fill, don't believe them. It took a heap of work to sand them back, prime, and paint them, and they'll never be properly level. Knowing what I know now i'm not sure if i'd do it or not. Probably, I guess.

If you have downlights, they're the first thing you should replace, you get massive heat loss through them.

It's hard to work out how much insulation has helped.

I'm also looking at underfloor insulation. Who did you use for the install or did you do it yourself.

I'm looking at Expol or Greenstuff to go into the beams, plus a ground sheet as we are on clay and it can get a bit damp.

Steve

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Jaxson

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#494586 18-Jul-2011 11:25

timmmay: If they say all you need to do is a top coat over the holes they fill, don't believe them.

I'd always wondered about this, and would have preferred to have them inject this from inside to maintain the weather tightness of the house.

timmmay

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#494587 18-Jul-2011 11:26

I can't remember who I used, but it was partially funded by some government or health board fund due to medical conditions (minor ones). This is before the current insulation subsidies were introduced.

Expol sounds like a good plan to me. The polystyrene works well, and the foil prevents draughts.

timmmay

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#494588 18-Jul-2011 11:27

Jaxson:
timmmay: If they say all you need to do is a top coat over the holes they fill, don't believe them.
I'd always wondered about this, and would have preferred to have them inject this from inside to maintain the weather tightness of the house.

That's what they told me, but then later claimed they never said it. They fill the holes, and prime them, but were a bit rough. You really need to sand, seal, prime, and paint, and that may mean painting the whole house.

It turns out I need to replace all my weatherboards in the next 5 years, so not big problem. I don't know if i'll leave the foam in or take it out and put in pink batts. If it looks like it's filling the space then i'll probably leave it in and just fill gaps with batts. It'll be interesting to see how well they did with their filling.

eXDee

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#494591 18-Jul-2011 11:32

I think we were looking at a quote of $19 something per square metre incl installation minus the subsidy for what i believe is polyester (its something recycled anyway).
Want to double check this though.

tchart

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#494602 18-Jul-2011 11:49

Have a read of this thread;

http://www.geekzone.co.nz/forums.asp?forumid=48&topicid=76553

That was my saga. Almost got ripped off by the first company that cold called me.

The insulation has made a difference. The house is still cold first thing in the morning but retains a lot more heat than before.

Handle9

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#494619 18-Jul-2011 12:11

If you are doing it yourself I would not recommend polystyrene. The reason for this is that everysheet has to be cut individually. It's really time consuming and if you only have crawling access under the house then it's a real PITA.

When I used expol in my old house I had the wife underneath the house measuring (because of course every joist was a different width) and fitting while I was cutting and dragging it in to her. It was good for a whole lot of negative brownie points....

I'd use blanket polyester if I did it again - much easier to fit and generally a higher R rating as there are no gaps nlike polystyrene.

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