Insulation of "Dormer" style bedroom

Hi,

I have read throught previous posts on insulation and while very helpful they don't answer my specifc query.

We moved into a new house 15 months or so ago. One of the bedrooms is a "dormer style" bedroom over the garage i.e. no attic over this room.

Since we moved in we have noticed that this room is almost impossible to heat and is atrocious at retaining heat. I don't give much credence to the fact that the garage is beneath for a couple reasons, one of which is our neighbours converted their garage and have the same problem.

As it is a dormer style room the the ceiling is sloped down to a stud partition which is about 4 ft high. There are no cupboards in this wall - just wasted space behind the partition wall.

Anyway, here's the interesting bit. I drilled exploratory holes on the walls and ceiling. And found that the the stud partition consisted of ordinary 15mm plasterboard backed by 15 mm standard OSB and nothing else - I can see the roof felt ! There was rockwool/fibreglass over ceiling but there is a good gap of ~ 4-5 inches between ceiling plasterboard and rockwool.

Naturally very p**sed off with this :mad:. As far as I am concerned this contravenes building regulations. What I would like to know is how are structures like this normally insulated and what action do you suggest I take. The builders are still on site but am not interested in getting this rectified from inside as its too inconvenient for us - I think its reasonable to expect them to remove roof tiles & felt and insulate from outside-in.

Thanks for your help
cybermate

Pretty often the gables are not insulated, or just very badly.The walls of rooms that are intended for living -as well as the ceilings- and the subfloor must adhere to the building regulations. Not the thickness of the insulation/wall is important but the U-value. You can find an U-value calculatur at the SEI home page, see [broken link removed]
You'll find there also some advice about insulation standards.

The technical guidance documents for Part L of the building regulations give standard details for the insulation of dormers (see the examples on page 32)

http://www.environ.ie/DOEI/DOEIPol.nsf/0/a137e0322d60e09780256f5d00504a79/$FILE/30183%20Build%20Regs%20L%202002.pdf

Also noticed that there is no insulation between the ceiling of garage and floor of bedroom. As far as I am aware this area should be insulated and not only that the slabs used should be fire retardent.

How can I tell if the proper fire retardent slabs are used? The thickness of the ceiling slab is standard 15mm. and grey centre although I think I can see a pink skim on bottom sufrace of slab and they have the "tin foil" on the other side.

thanks.
cybermate

we have a dormer and insultation is applied to the sloping roof - "stuck" in between the rafters, the floor of the void is also insulated, the back of the "knee" wall is not insulated but this isnt such an issue since the void itself is insulated from the roof.

The slab you are talking about are called "foil backed" - its a vapour barrier. We dont have insulation between the floors, (just on the floor of the void) if the dowstairs is used more then the heat seep up is not such an issue, just means less heating needed upstairs.

Hi Betsy,

thanx for the reply, I understand what you are saying. The problem that I have is that that there is no insulation in between the "sloping" rafters and there is no insulation on the back of the "knee wall" - I can see the roof felt through the exploratory holes that I drilled. They have some insulation above the sloped ceiling but did no continue this down behind the knee wall.

Our garage is still used as a garage, therefore I believe there should be insulation between the garage ceiling and the floor above to stop any draughts and downward heat loss.

If your garage has a plaster board ceiling -which it should have for firesafety reasons, no loadbering timber should be exposed in a garage -
then you might be able to glue a second layer of fire proof plasterboard ("red") equipped with a layer of insulation on it's back to the existing ceiling. The loadbearing of the old plaster board might not be good enough, so if you can still see/guess the screw heads then put additional screws along the existing rows of screw heads.The official distance from screw to screw is about 15cm. Then you can put up the new boards, but using here screws that are long enough in a safe and stable manner is difficult. The easier way is to use glue, it comes in 10-20 kg bags, depending on the manufacturer. Check the home pages of various plaster board manufacturers to see how it's done in detail.

thanks heinbloed,
sorry for being pedantic here, so you confirm that there should be insulation between garage ceiling and upper room floor? Also, am pretty sure there is no insulation in stud wall between garage and utility room. I would assume that any interface from garage to a living area should be insulated and fireproofed.

thanks

I'm not sure what the building regulations say about heat insulation, but I'm pretty sure a fire insulation is a must for a garage ceiling touching an inhabitated space.
Thinking about the thermal insulation - I would consider an unheated garage about as much an "energy sucker" as an uninsulated attic. It wouldn't cost much to do the job. And since the garage is not habitated you wouldn't have to stick to the min.height of inhabitated rooms: Put as much insulation under the ceiling as you can with out making the garage too low to use it.The boards come in various thickness, and EPS boards can be bought seperate, without the plaster board. So do two layers, one without the plaster board and one with "red" plaster board, both glued with the same material.
The fire proofing between the utility and the garage could have been done by the builder already by applying one layer of "red" plaster board to the garage side. So if there is no insulation in the wall/cavity you can get that blown in or do the same job again. As above - pun intended.
The insulation should be applied to the cold side of the wall/ceiling.

We had the same problem. Dormer bungalow, zero insulation upstairs. No one to enforce building regs (or anything else) in Ireland. Builder was ignorant chancer. The upstairs rooms are basically boxes which fit in the triangle formed by the roof. We were advised to insulate the sides and top of the "box" to keep heat in. This meant doing the attic floor (not sides) and the vertical "sides" of the box with rockwool, staples to the backside joists of the walls. It made an immense difference to heat retention. The rooms stay warm for hours in winter. We had to cut into the plasterboard either side of the dormer windows to get access but are putting tongue & groove over the access hole and window seats in so it doesn't matter.

Straightforward DIY project but do wear a mask, latex gloves & goggles if you use rockwool. Sheeps wool is better but dearer.

You might get an SEI grant these days to offset costs if a registered contractor does it.

Good luck...