Energy Matters Forums

[Nige]

Hello everyone,

A new one for those of you who like to think outside of the box.

As there are so many roof insulation bats floating around at give away prices has anyone used similar to insulate under the house??
Considering the house we are in is on stumps I was thinking a bit of insulation under the floor would negate a reasonable amount of thermal transfer as I know this is widely done in north america canada etc.
Just look on e-bay I have seen them as low as $10 each.

At current prices I could do the entire underside of the house for under $150-200 and a few days labour crawling around with all the beasties & creepy crawlies under the house.
Have any of you done similar? any pitfalls to my scheme I should consider? The Polistyrene underfloor bats are priced in the ridiculous range per sq mtr so why waste the coin. Lets be honest it's not like they are fire retardent...

Cheers

Nige

[Gordon-Loomberah]

I've thought about batts under the floor, but I think it would be too much of an incentive for new warmer housing for the rats to move into. We hear them running around the steel joists and bearers all the time, every time we catch one, (and feed it to the chooks), its seems another one comes out of the bush and takes up residence in the boxes of stuff under there.
I'm thinking about stapling some air cell insulation thats left over from the walls under 1 room as a test one of these days... but the ugg boots do a pretty good job on frosty nights

[470rigby]

all the beasties & creepy crawlies under the house.

What about all the beastie & creepy crawlie habitat that your underfloor batts will provide?

[Nige]

I will merely charge rent or just let the cats loose every now and then.

I am more thinking big bin bags and cans of expanding foam? or plastic sheeting to cover it up, or possibly shade cloth to keep it in place. ahhh so many options to play with, so much stuff in the garage I can use to shore up insulation depending on it's location.
No matter what you put in a certain amount of wildlife will inhabit the space that is a given it's more about managing it accordingly.
Anyway I have three cats who will enjoy me giving them access under the house as everywhere I go they are there following me. The local vermin will be taken care of accordingly by them.

Oh and rats love peanut butter so make sure you give your ratsac a liberal coating to make sure it's all consumed. But the food in with the chooks will bring in the rats.

[sandystone]

IN colder or mixed climates it is a really worthwhile thing to do, especially if there are gaps between the floorboards, especially too if there are no walls to stop cold winds flowing under the house.
Under the just revamped office space, I have put 4 mm cement sheeting underneath. The sheeting is relatively low cost.
Under another part of the house, I used reclaimed corrugated iron instead, which was free. both options are pretty solid against rats and most other critters.
To support the batts while installing, I used some old string stretched between clouts nailed to the side of the joists.
The difference has been noticeable, and the results justified the squeeze in the narrow space.

Soon I intend to insulate under the tiled bathroom floor, as I think the heat retained in the tiled floor (on 25mm thick cement sheeting) from the shower water would help with drying the floor quickly.

[Nige]

I was thinking about the less accessable regions under the house... A toy shop fixed that, some long plastic tubes 2.7mtrs long i think they are for children to run with while catching air to make them inflate?? Sounds like a wonderful way to tucker them out so they sleep more
Anyway a can of expanding foam a couple of tie wraps should fix the problem or I could use the plastic bags from bakers delight that they put loaves of bread in to make supports for between eves.
it's just form work in a slightly different manner.
If nothing else it's keeping me amused.

[PeterC]

A few years ago I did this in Canberra. We have a suspended timber floor and deliberate ventilation under the floor to minimise damp. At the time the recommendation of a local insulation supplier was to use 'wall batts' R1.5 from memory. These look like normal fibreglass roof insulation except that they are slightly stiffened. This helps to not have them immediately flop out onto your face as you install. They also sold me a roll of mesh stuff to staple gun to the joists to hold the batts in place. It was a horrible job with dust mask on, and lots of laying on my back and bruising my knees and elbows. I have done the half of the house that has bare floor boards with some rugs but ran out of energy for the other half with fitted carpets and less working space. It contributed along with lots of other retrofitting to getting a 6 star rating on our house that would otherwise have perhaps rated 1-2 at most.

[Nige]

The reason for using the roof insulation was just cost and quantity. If you have a warehouse full of the stuff it's costing coin to keep it there..
I am thinking strips of shade cloth and a staple gun as the more cost efficent way of doing this.
But most definately not looking forward to doing this one.

[PeterC]

The reason for using the roof insulation was just cost and quantity. If you have a warehouse full of the stuff it's costing coin to keep it there..
I am thinking strips of shade cloth and a staple gun as the more cost efficent way of doing this.
But most definately not looking forward to doing this one.

I'm sure that would work just fine. Perhaps just slightly more fiddly if the batts are more floppy but certainly a good idea if you can get them cheaply.

[lad]

There has been a study at the local University looking at flooring and building types and their effect on thermal property of the building.

Suspended timber floors with insulation are better than not (no brainer). What you are looking to stop is air flow primarily and secondarily thermal transfer.

Interestingly (and this does not help anyone with suspended timber floors) a concrete floor on the ground will assume the ground temperature (lets say 15 degrees). Now in winter when it is say zero outside, then the floor is assisting in keeping the house warm and in summer when it is say 35 degrees it is assisting in keeping the house cooler.

When the outside temperature and house temperature are graphed, the suspended timber floor closely follows the outside temperature, insulating slightly widens the gap between inside and out but a concrete floor on ground makes for a considerable difference and greater thermal stability.

Of course roof and wall insulation are required in this picture.

I changed my plans and now have a concrete floor.