Is reflective foil wrap worth it for walls?

I asked my builder to quote me on wrapping the external walls with reflective foil. They came back with a quote of $2750. Is this good value? How long do you think it would take to get my money back?

Foil wrap cost about 70-140 per roll. Usually two rolls per house on average. The more expensive product ie ($140 roll) is usually thicker.

I still cant understand why its not compolsury where you are. It is sooooo cheapppppp!!!!!! and IMHO does so much as a vapour barrier, and as basic insulation.

The price you have been quoted is more in line to as what i would expect if you wanted sarking to be installed on you roof.

I thought it was expensive. I really want it but at this price the builder can forget it.

RFL ranges from $2-5 per square metre.

It is the most cost-effective method of radiant heat control. Its stops >99% of direct solar heat entering the building. It's main benefit is in summer (heat predominantly escapes by conduction/convection during winter). The shiny side should face an air gap.

It has som additional benefit in retaining winter warmth. The sheet also forms an air barrier within the cavity. Air movement in the cavity will reduce the effectiveness of installed batts (imagine wind chill blowing through your woolen layers). The foil also reduces radiant heat loss during winter. Don't expect foil to address the winter losses by itself. You will still need batts.

If you are trying to skimp on the foil then the best place is first in the roof extended right to the gutter to protect the eaves. The next is on the west then east walls where local angled hot sun beats on the walls.

I am not sure why the builder is charging so much. Labour is relatively easy - a nail gun and some battens and the house will be wrapped in a morning.

Is this sisalation you are talking about or something else?

Yes. Sisalation is just a brand of reflective foil.

The roof is getting done as part of BASIX (NSW energy rating system).

My plan is to ask the site supervisor if I can pay one of his tradies to install foil that I'll purchase for the east and west walls. Fingers crossed.

That sounds very expensive for sarking.

I just got a quote today for supply and install of sarking to all external walls $370 (123m2) and for concertina reflective foil $875, which together will give me R2.2 on my walls.

I got the following price in my Tender of 02-03-09 from Coral for a appr. 300m2 house:

Reflective Building Membrane (RBM) to all external walls including garage to suit BC of Australia (has just become compulsary) - $810

RBM (medium duty) under entire roof + 1 ventilator - $ 2,803

R1.5 glasswool insulation batts to West side wall - $286

cheers

Reflective foil inside an outside wall cavity adds about an additional R1 to the wall insulation value. Best to get foil that is reflective on both sides.

Make sure the foil has an air gap to both sides (OK to touch the frame since this is only a small percentage for the wall area).

Despite all the literature going around, it is a nonsense to assign R values to foil. It blocks radiant heat, not conducted heat. Therefore, it does little to stop heat getting out of the house during a winter night but far more effective than batts at stopping summer solar radiation coming in.

The extra shiny side\ adds a neglible amount to the effect. The first layer stops 99% of solar radiation. The second layer stops 99% of what's left e.g. 99% of 1%. The difference is imperceptible. But as you mention, the shiny side MUST face the air gap.



I wouldn't bother with a ventilator. They don't work.

http://forums.envirotalk.com.au/Whirlyb ... t8445.html

could this also be used on the sides of a shed? company called air-cell makes it dont they?

-Nathan

Yes. They are better for keeping heat out (via the foil surface) then warmth in (via the foam). The air cell foam is not very thick and only offers around R 1.0. A standard batt would be at least double that depending on thickness.

My brother insulated all his external walls with fat batts and he's house is very cool in summer compared to mine. When I build again, I'll definately insulate the external walls with fat batts.

mm i might be sufficient to reflect the heat away from my shed ease of install aswell no need for big batts

-Nathan

The other thing sisalation does, it allows any build up of condensation within the wall cavity to run down the material it self and into the damp course (small amount of plastic that is attached through bricks to the weep holes) thus allowing the water to get out, so as you don't have mould/mildew and dry rott issues (lack of ventilation, stagnent moist air/

Why don't you just go and purchase yourself and install, see breakdown of DIY cost:

Bunnings sell:
Sisalation/Builders paper/Trade wrap (whatever you want to call it)
Medium duty 1350mm x 60m(will do up to 2650mm hugh wall with 50mm overlap) $85
Light duty 1350mm x 60m $96

now worse case scenario:

Buy 3x rolls of whcih ever one say for example 3x $85 = $255.00
Staple gun/staples $20

2x people with no experience should knock this over in 2-3 hours max

All you do is start at the bottom at any corner, staple it to the corner stud and walk it to the end of the wall, while one peron hold it tight, you work your way down eah stud and staple it off, if the window s are in just paper over them and cut them out with a stanley knife after, and then just repeat the same again for the top

So really if you couldn;t do it yourself for under $300 bucks i'd be suprised, and save yourself a small fortune and get all the benefits sisalation has to offer.

cheers Ben

DIY! You may buy the materials and have it fix with a relative or a friend if you can.

Or ask for quote from another supplier and compare.

I agree with the previous posters - DIY.
I went and bought 2 rolls of sisalation and a couple of boxes of sisalation clips - these things:


We took down two hammers, a ladder and a knife and it took me and a mate just under three hours to wrap a 35 sq house.

I think the rolls of paper were about $120 each, and the clips $30 per box.

We built a double brick house and have reflective wrap between the 2 layers. We also have thick batts in the ceiling. It was a council requirement here due to new zoning regs. We noted that the wall insulation did make a difference both in cooling terms even when the house was still being built. ( last summer) The house was cooler that our rental even before it was at lock up This house is far larger and quite open plan compared to the rental we were in. This house seems to warm up quicker and stays warm for longer after heating has been turned off during winter. Hopefully it will also stay cooler in the coming summer.