Insulation For Attic.

[TomBrown]

I know this has been discussed before and on other forums also, but after reading loads of information I still can't decide if I would be better to install M-PE Metalized Polyethylene (double sided aluminium foil PE foam, 10mm thick) or the Stay Cool 75mm Premium fiberglass blanket encased in aluminium foil, or something else.

The house has the usual Monier CPAC tile system, but there is no insulation on the underside of the roof tiles or on the attic floor / ceiling. Obviously as an existing build I am limited in what I can do without spending too much. My thinking is that installing insulation onto the attic floor is my best option and should reduce the air-con usage too.

On paper the M-PE foam sheets seems to offer the best results (R=20), but I've not actually found anyone who has said it works just as good or better than the other solutions. On the flip side, although on paper the fiberglass encased in aluminium foil (R=11) doesn't seem to preform as well as the M-PE, most people seem to opt for the fiberglass solution.

Anyone got some experience with the above solutions or other recommendations?

I know there is the PU spray foam, but two quotes from ARC and the other company in Naklua were quite high compared to other solutions.

Thanks,

Tom.

Edited January 8, 2009 by TomBrown

[Rimmer]

SNIP

I know there is the PU spray foam, but two quotes from ARC and the other company in Naklua were quite high compared to other solutions.

Thanks,

Tom.

Foam holds the heat in the house at night when the walls leach out the accumilated heat from the day time sun. If badly installed it can also lift tiles and you get lots of leaks in your roof. Bin there done that with the largest foam squirter company in Thailand.

Important to vent the roof space whatever insulation you decide on.

Edited January 8, 2009 by Rimmer

[donne]

Good that you have done your homework.

I will recommend PU spray foam if you live in the bloody hot area without shade and/or strong sunlight.

OR- fiberglass blanket 75 mm. thk with alu. foil on both side in case your attic has ventilation. It works well for blanket insulation if you also help the heat pocket to ventilate out.

There are 2 main methods to stop heat transmission to house that I wrote above - 1. spray to rafter, block the heat and reflect out or 2. let them in but not to ceiling and ventilate it out.

Hope this can help.

[TomBrown]

I wasn't going to choose PU Foam spray from a spraying company as it'll cost too much. Good point about it lifting the roof tiles though if not done correctly.

The insulation would be on the attic floor, not the roof tiles. I can't help but think that the screws pointing up through the attic floor and the metal clamps on the cables that hold the suspended ceiling will rip open the aluminium and expose the encased fiberglass. At Home Pro I noticed there are spray cans of Polyurethane Expanding Foam and was thinking that I could use one to cover these possible sharp edges before the fiberglass was installed. Of course if I went with the PU Foam sheets from Home Pro, this wouldn't be a problem, but I would like the best possible insulation option too. What do you think?

Also, can I use the spray can of Polyurethane Expanding Foam to close the small gaps between the walls and the suspended ceiling at the attic side?

Thanks,

Tom.

[yabaaaa]

Also be careful not to cover halogen light fittings with insulation they get very hot

[TomBrown]

Also be careful not to cover halogen light fittings with insulation they get very hot

Yeah I knew about that one, about three inches from the light? thanks.

Looks like I'll be going for the Stay Cool foil wrapped installation after all, but wonder if its easy enough to cut down to size and seal it up using aluminium tape as the lengths don't match where the lights protrude in the attic floor.

[dsfbrit]

Also be careful not to cover halogen light fittings with insulation they get very hot

but wonder if its easy enough to cut down to size and seal it up using aluminium tape as the lengths don't match where the lights protrude in the attic floor.

Its easy to cut. I didn't use tape as I thought it may come adrift and let insects/rats etc... get inside. I cut it, folded over the foil and stapled it. I expect I will be told that was a really bad idea. I have only covered 4 Sq/Metres over the smaller bedroom at the moment to see how well it works, lasts etc... Its been so cold at night recently though, I am not sure if this 'test' is going to be very useful.

edit:

Yes it does rip really easily if it gets snagged up. Unless you can 'pull' it into position it can be quite difficult to line up neatly, especially behind the struts sticking down that hold the ceiling in place. Getting it nicely fitted into a far corner was quite time consuming as well in my roof space. Why not try a small area first and see how you go? If my test does not work out I will just leave the bit I fitted and try something else.

Edited January 14, 2009 by dsfbrit