Cold room above garage

adamleucine

After some advice please (see picture also)

I have an integral garage with a bedroom above. The roof of the house is kind of split level (not sure of the professional name for it) and the bedroom has a dormer window.

The bedroom (my daughters) is so cold overnight and when the heating is off (gets down to 10 degrees often) and the 4th bedroom (used as an office) is similarly cold at the back of the house.

Above the garage door is a vented soffit. I was wondering (or if this would be a bit far fetched) if the cold air would be gusting through the ceiling/floor void and making both rooms cold? The floors of both rooms are noticeable cold under foot. 

I am looking into having the garage ceiling over boarded with insulated plasterboard and having the bedroom above redecorated but wanted to sort out the cold first.

Any advice welcome. 

Mutton_Geoff

You'd be better off pulling the garage ceiling down and filling the void with insulation than overboarding. You should be able to get at least 100mm in the void vs 25/50 overboarding. If the void is vented, overboarding will be a waste of money.

Robin9

Mine is similar and we did what Mutton has suggested - a dramatic improvement

Browntoa

As above , putting insulation in cured this for me at my old house 

grumbler

Mutton_Geoff said:

You'd be better off pulling the garage ceiling down and filling the void with insulation than overboarding. You should be able to get at least 100mm in the void

It can be beam&block for fire safety, i.e. less than 100mm and concrete beams with high thermal conductivity.

adamleucine

Mutton_Geoff said:

You'd be better off pulling the garage ceiling down and filling the void with insulation than overboarding. You should be able to get at least 100mm in the void vs 25/50 overboarding. If the void is vented, overboarding will be a waste of money.

Thanks! I will look into this. 

Jeepers_Creepers

That's pretty conclusive then :-)  

Over-boarding the garage ceiling would only help to keep the garage warm - not really a consideration.

If you do tackle that ceiling-to-floor space, it's important to still allow the soffit vents to do their job, and that's to keep that sticky-out front section of your house - which is an eaves void - well ventilated. So I'd focus only on the area that's the underside of the actual bedroom above, and pack insulation tightly up against the bedroom floor. It'll need something to hold it in place, and the best would probably be rigid insulation, cut snugly, and then given a bead of polyurthane glue along all four edges before pushing it up tightly into place - the glue will 'foam' and seal it off, and also hold it securely in place.

I'd also look at the floor of that bedroom - any gaps between the skirtings and floorboards? These are notorious for letting through draughts - seal with caulk or frame sealant, cheap flexible stuff. Is the floor chipboard sheets? If so, they should be pretty draught-free, but look for gaps between each joint, and run a thin trickle of Poly (eg Gorilla) glue along these too (after a quick scrape and hoovering clean) - again this'll expand and seal off any remaining gaps.

That low front eaves wall in the bedroom - is there a hatch in it? If so, have a gander in there and see if the backs of the p'board have been insulated. If they haven't, the walls will be freezing. Similar approach - cut insulation to fit snugly between the studs, a bead of Gorilla, and press them in tight against the p'board. Have a foam gun handy for these jobs too - any awkward shapes/missed gaps - fill 'em.

And can you get access to the roof section overhead from the bedroom/office? If so, check them too - stuff with normal loft insulation, whilst avoiding the very front and back corners so as not to impeded air-flow.

If you can afford to lose 5mm height from the floor (ie won't interfere with doors, etc) then if you do lift the floor coverings as part of this job, you could lay something like this fibreboard underlay first, tight-and-sealed against the shirtings, and sealed against each other https://www.wickes.co.uk/Wickes-Wood-Fibre-Laminate+Wood-Flooring-Underlay---10-03m2-Pack/p/215589 I think it should be ok with the carpet replaced - along with its normal underlay - but is it primarily designed for timber/laminate floors. It will add another useful level of insulation, and seal of any remaining draughts - it's great stuff. In fact, if you just wanted the simplest solution to your cold floor without the agro of removing garage ceilings, that's what I would go for.

(When I fitted new T&G floorboards in our hallway - over a large ventilated foundation void below - I laid these sheets over the joists first, sealing them tight against the walls and eachother. Then laid the boards on top. Although only a minimal thickness, my hallway is draught-free and the boards pleasant to walk on barefoot. Fitting it over the flooring will work just as well. Ok, you can do a LOT better than this, but all I'm saying is, for the LEAST hassle and disruption, it will make a significant difference. (I think, tho', that the stuff was 8mm thick when I used it - 5mm seems very thin). (If you can lose 10mm, fit two layers at right-angles to eachother... But you'll need a neat beading across the door threshold.)