the foils doesn't have an insulation factor to it however when you consider the foundation open or closed, foil and depth of joist, the timber floor, underlay and carpet, I worked it out for my house and it was a overall rating of R1.32, I think to rent it out, it needed to be R1.30. If the house floor boards are T&G and there is a gap, say 1-2 mm (so you can see the tongue), then it is doing the job and drying out the house. Also you coul have a vapour barrier (DPC) intalled on the ground.
tweake,
Jul 5, 2:54pm
the under floor foil gets dusty and corrodes. then its heat reflectiveness goes to 9/10th of sweet stuff all. so overall its doing nothing on most homes. which is why they got rid of it, its an electrical hazard and it doesn't do much insulation wise.
golfaholic2,
Jul 6, 1:32pm
As I said , I struck some in the mid 2000's . From memory , it was Gib with poly adhered to the back . over the foil They may have been offloading last of the old stock
gabbysnana,
Jul 7, 7:41am
just to add, my previous home had an extension added in 2004, the gib was foilback, the plans were signed off by council. The house was built in 1986, all the gib was foilbacked and it had underfloor foil. In 2009 under some healthy homes scheme at the time, polyester was rammed up the underfloor covering the foil. The ground had 2 layers of black polythene . The weetbix floor had thick underlay and wool carpet but the floor was always freezing. It was also a metre above the ground. Now in a modern home on a concrete slab, the tiled floor is always freezing, can't win.
martin11,
Jul 7, 8:45am
Winstones have confirmed that they have not made Foil backed Gib since the early 90's and none was imported . It was done in the last years of its run as a special order only .
pauldw,
Jul 7, 8:57am
That's an improvement on your earlier statement that it was a 70's product.
martin11,
Jul 7, 9:27am
GIB lined with foil came out in 1972 but when Batts started to come on the market in 1977 the use of it declined because of the Batts better insulation rating . Definitely a 70's product but superceeded by a better item .
pauldw,
Jul 7, 10:04am
But until it finally disappeared developers were using it as a cheap way of ticking the box for the building consent. My relative still thinks her outside walls have insulation because that was the bs given to her at the time.
tweake,
Jul 7, 10:10am
just goes to show how long bad products can hang around for. it really illustrates how rotten the industry was.
tweake,
Jul 7, 10:12am
sounds like more to do with how the home is heated. insulation doesn't make heat.
trade4us2,
Jul 7, 11:13am
Half of my house is on a concrete slab. It's the middle of winter, and no heaters have been used for the last day (I intend working outside today). The concrete slab is 16.3 degrees and the wooden floor with no insulation under it is 15.9 degrees.
On Monday the temperature under the roof on my deck was over 30 degrees at 9am. I am tempted to blow heated air into the house in winter.
fresiaa,
Jul 19, 10:52pm
I'm looking at buying a house with metal foil underfloor insulation. I remember something on TV about getting electrocuted by it.
Should I be costing in replacing it with polystyrene sheeting or is it fine to leave the metal foils as it is?
nukhelenc,
Jul 19, 11:11pm
Just make your offer on the house on the condition its been removed and replaced with something fitted by a local insulation firm. Get it in writing maybe since your concerned, as the R value cant be good these days with that old stuff.
nzshooter01,
Jul 20, 7:47am
It was only a problem if whoever installed it had managed to put a staple or two thru a electrical cable at the time, Hence making the foil live
martin11,
Jul 20, 8:08am
It also cause problems if it was incorreclty installed . when it was originally laid over the tops of the joists under the flooring .
gabbysnana,
Jul 20, 8:30am
how else is it installed?
lythande1,
Jul 20, 8:59am
I bought a house with it. Didn't get electrocuted.
Better than flammable polystyrene.
oh_hunnihunni,
Jul 20, 10:12am
Most modern insulation is fire retardant.
wasgonna,
Jul 20, 10:15am
Yep, real good stuff. That's why it was banned as an insulation after about 5 years of use because of 5 electricians getting electrocuted and killed.
It's not even insulation, it's only a reflective.
trade4us2,
Jul 20, 10:36am
I think the foil should be removed. That should not be hard to do as long as the power to the house is shut off completely and the potential of the foil measured the whole time.
In 1990 the building code required the Gib board to have aluminium foil on the outside. And now we are not allowed to have foil anywhere. This is yet another example of the incompetence of the people writing the building code.
martin11,
Jul 20, 11:03am
It has been installed by stapling under the joist as a retro fit insulation Laid on top of the joists and sometimes people pull it tight (incorrect) That was a cause of problems if the foil was pulled tight over the top of the joists as the condensation went back into the flooring
The proper way was to lay it on top of the with a sag in between the joists to provide insulation . The really early stuff did not have holes in it to allow condensation to get out . It never did provide much insulation value .
tweake,
Jul 20, 12:30pm
its ok to leave as is. however as an insulation its not doing anything. most of it is now so old and dusty that it reflects little to no heat.
inho the best insulation for underfloor is polyester. polystyrene has a few major draw backs to it.
tweake,
Jul 20, 12:34pm
aluminum foil has vapor retarding issues. however these days you can get a myla coated version that is vapor permeable.
tweake,
Jul 20, 12:37pm
at least polystyrene works. foil gets dusty, corrodes and ceases to be effective. one of the reasons they banned it, its just pointless using it.
oh_hunnihunni,
Jul 20, 12:49pm
Actually, it is more about changing technology, better information and research, and updating of our systems.
The people writing codes do not have crystal balls.
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