Foil insulation in dormer space behind rooms

batman1

Hi,

I have a dormer house and the upstairs can get too cold in the winter and too hot in the summer. I plan to double the insulation in the space which lies behind the walls in the ustairs bedroom. The floor part will be done with fibre insulation but this would not be an option for behind the walls.

I have been told that the easiest way to increase the insulation in the area behind the upstairs room walls would be to staple foil type insulation over the existing fibreglass which is packed between the studs.

Access to the area is a squeeze so the foil would be easiest to work with in the space.

I am wondering if anyone else has done a similar job and what type of foil was use. I have been quoted 190 euro for 15m2 rolls of 'Alumiflex' insulation from by local builder supplies. Are there any alternative products and can they be ordered online?

cnocbui

I have my doubts as to the effectiveness of foil. I recently came across a product I had high hopes for. basically it is like a heavy duty bubble wrap with reflective foil on both sides. When I looked up the specs I was rather disappointed in it's R value - 0.14.



http://www.air-cell.com.au/pages/retroshield.htm

That being said, If I were in your position with scarcely any room, I think I would be looking at a product like this, rather than just foil. The stuff is called Retroshield made by Air-Cell, now part of the Kingspan group. They also have a product called insulbreak 80 that is 8mm thick with an R value of 0.25

Foil on it's own has basically no insulating properties of it's own, it just reflects radiant heat. http://www.articlesbase.com/construction-articles/what-is-foil-insulation-r-value-2272495.html

dathi

hi guys the most important page on that website is the certification page and when you click it it is empty so it has no iag. certs if its not certified you shouldn't use it you could fix kingspan/xtherm to the studs in the walls

gsxr1

cut the fiberglass inso inbetween the studs. It will stay there if you do it right. use 4" nail tapped into the sides of the studs , it acts as hooks that grip the fiberglass, and/or a line or two of string to hold it in
Be sure to leave the eaves open with fresh air from the soffet outside. Its an important part of the vent system in your home and damp
could be a problem if blocked

tinofapples

gsxr1 wrote: »

cut the fiberglass inso inbetween the studs. It will stay there if you do it right. use 4" nail tapped into the sides of the studs , it acts as hooks that grip the fiberglass, and/or a line or two of string to hold it in
Be sure to leave the eaves open with fresh air from the soffet outside. Its an important part of the vent system in your home and damp
could be a problem if blocked

It does lead to draughts in wintry windy weather though, I too have a dormer house and have been thinking about increasing the insulation in the "crawl space" and blocking off any open areas. Not a great idea then ?

gsxr1

tinofapples wrote: »

It does lead to draughts in wintry windy weather though, I too have a dormer house and have been thinking about increasing the insulation in the "crawl space" and blocking off any open areas. Not a great idea then ?

there should be a free space the whole way up to the ridge of your roof. From the eves behind the inso. 50mm at least. The draft should be able to travel from one side of the roof to the other. This prevent damp and condensation.

.
you could put a vapour barrier on one side of the stud to prevent the draft entering your room.


you can certainly increase the level of insulation, but keep ventilation spaces working.

Sparkpea

if you block off the vent space you will get damp and mould problems down the line as said. the idea with the insulation is to keep the heat in the room rather than the cold out imo,so you would expect the crawl spaces to be cool. maybe worth draft proofing the door into the crawl space.

RKQ

If you block the ventilation to your roof you will get Dry rot in the roof timbers! :eek:
50mm air gap between underside of roof felt and top of insulation is a minimum requirement of the Building Regulations.

IMO foil bubble wrap type insulation requires 50mm air space to both side to act effectively. Check Retroshield IAB cert, if it has one.

yop

Have the exact same issue, was going to get the foil insulation.
Was looking at this or similar
http://www.ecoquilt.ie/Usage.html

Pricey though!