Under floor insulation

[harrisonness]

Hi

I was looking for some advice/other peoples experience with under floor insulation.

We have a single-storey 1950s cavity brick home with floor boards throughout and a large void underneath that causes the floor boards to get rather chilly under foot in winter with the cold air swirling around.

Are there any options for us to put something under the boards to take the chill off?

Thanks

Gary

[Barry_White]

You could fit fibreglass or polyester batts between the joists and staple foil under the joists to hold them up.

[harrisonness]

Would that present any problems running electrical wires in the future?

And would it be a problem covering all the ones that are there now?

Thanks

Gary

[jackiew]

I believe that with bulk insulation you will have to leave a space round electrical fittings .... and wiring

AS 3999-1992 : Thermal insulation of dwellings - Bulk insulation - Installation requirementsClause 2.6 (apparently) also sets out the requirements for bulk thermal insulation near electrical wiring and equipment. ( wonders of google ).

http://www.standards.com.au/catalogue/script/Details.asp?DocN=stds000006192 but it isn't free ....


I'm looking at putting in concertina foil insulation under my floors. This staples to the timber ( sides of timber / not bottoms ).

I suspect whatever is put in is going to have to be adjusted if you have any alterations done to your underfloor wiring. Which is one of the things that is delaying me as I know I want some extra power points put in and I'm psyching myself up to dealing with an electrician.

I've also seen some insulated foil board materials which you fix with special fixings to the underside of the floor joists ... this looks easier than bulk insulation.

[Sturdee]

Gary,

My workshop is built in under my house and I placed insulation bats between the joists and nailed against the joists masonite and in the other part ceiling panels. It was mainly done for soundproofing but has the added advantage of improving the heating in the house.

Jackiew point about the wiring is valid. I have the advantage of knowing what wiring is covered and where (and my friendly electrician :D :D knows also).

Thus it would be wise to make a wiring plan and take photos from underneath for future reference and add all the extra points now before you close it up.


Peter.

[harrisonness]

Jackiew:

Are you able to point me in the direction of a concertina foil insulation or foil board manaufacturer? I know I could 'google' it - I was just wondering if any one had a product that they would recommend (from experience)

Do these products have good 'R' ratings?

Thanks

Gary

PS Thanks to everyone for their prompt responses. :)

[jackiew]

the two products are on display in the timber advisory centre in nunawading ....

http://www.concertinafoilbatts.com/
I've had email correspondence with them and they were very helpful

I've got a sample of the foil board ( you can pick them up from the timber advisory service ) ... but I can't find the link with a quick google search .. so I'll let you know the details later this evening

[Barry_White]

Well insulation does derate the cable by a percentage but normally you would only have power and lighting running under the floor and it would have minimal effect. If you had the cables for your stove or items drawing high currents it may cause the to overheat slightly.

As far as running new cables you could suspend them under the joists with either a batten nailed to the joists or in conduit fixed to each joist or run them along the bearers.

[jackiew]

the link for the insulation board

http://www.foilboard.com.au

[Snoopy]

I have seen insulation that is basically like bubble-wrap plastic sandwiched between two layers of foil. It has a very good R rating, is fire resistant and vermin proof. I would have used it myself on our last place but it was a little on the expensive side - but well worth a look and seems a very good Aussie made product.

When I lived in the USA our house had floor boards and a "crawl space" underneath. They had used normal insulating batts, but instead of foil they had held them in place with pieces of high tensile wire (about 2.5mm diameter)cut just longer than the distance between the floor joists. They had just pushed the wire up into the space between the joists after the batts were put in to hold them in place. I have to say it worked just fine. The house was well insulated, the wiring still accessable and the wire and batts were easy to remove and replace if needed.

[Theva]

Gary,

One of the best references on this topic for timber framed construction is found at the following site:http://www.timber.org.au/ThermPerf/R-valuesfortimberframedbuildingelements.htm


A few key facts on insulation level of timber floors from their tables:

1) typical R value for timber floor on joists with open access is 0.7. If you have carpet & underlay, it R value increases to1.0.

2) If the subfloor area is enclosed, the R values increase to 1.5 and 1.8 respectively.

3) R values can be further increased by adding wall bats (R1.5 bats).

Minimum requirement is R 1. Best way to improve insulation is:

a) make sure that there are no drafts coming in from the subfloor then enclose the subfloor area (leaving 6000sq mm per liner meter for ventilation).

b) Next step is to add wall bats under floorboards if really required.

Electrical wiring on joists / bearers should be 50mm below the floorboards by regulation; so bats (if one really wants to put up with the hassle) can stay just above the wiring.

Concertina foils cost around $8 per sq m, Aircell (bubble warp type thing, some bunnies got them) costs $8.50. Both are more suitable for roofing applications. It is more to do with the way heat is transferred, conduction, convection vs radiation.

Every beast to its own devices.

Hope this is of some use.

Regards,

Theva

[Eastie]

If it were me I'd steer well clear of batt insulation in under-floor applications. They are a nest for rodents and possums, get in the way of any future electrical wiring, unless strung up properly will sag and last but not least they hinder termite inspections.
In the past couple of weeks I've had my floor up and was considering the options. The advice that I got from all builders/energy efficiency raters I've spoken to confirms their concerns on these issues. If you do put anything down use foil.

[Theva]

Agreed.

In my own place, We have nothing.

Regards,

Theva

[harrisonness]

Just wanted to give a big thanks to everyone for responding to my thread. Lots of great info.

Gary