Cold bedroom above porch

[chameleon001]

Hi,

Our house has one bedroom which is always colder than the others. It is the only one with 2 external walls but is also above an unheated porch and unheated downstairs toilet.

Do you think the cold bedroom could be due to the cold rooms below? If so what would be the best way to fix. There’s plenty of head height so would be no issues with me taking the ceilings down, checking for cracks/ voids in brickwork and replacing with insulated PB. Would people tend to use 100mm insulated board fixed directly to the joists, foam/ seal any small gaps then skim it? Any issues with needing building regs for this?

Im going to add a radiator to downstairs loo at some point but don’t really want to waste energy heating the porch.

Thanks

 

[John D v2.0]

Cold bedroom is due to the heat input lower than the heat loss.
Heat loss is due to insulated surface area and draught proofing. Heat input is radiator size.

 

[John D v2.0]

Sorry posted too soon
You need to work out which surfaces are losing the most heat a are cheapest to insulate.
Draught proof definitely first, then loft insulation, then floor if removable, then walls.

 

[chameleon001]

Hi,

Yes the room is just a bit of a minefield, has the loft hatch, on 2 external walls and cold rooms below.

I have a radiator which should be of sufficient size for the room. I have insulated the loft hatch with celotex and draft excluder around the seal. Loft insulation has been upped to 270mm. The walls I don't want to touch as recently decorated so next is the floor/ ceilings below.

 

[John D v2.0]

Sounds good. The only bit I'm not convinced is you say the radiator should be enough for the room. How did you decide that? As seemingly it isn't, either that or there's a problem with the circulation.

 

[chameleon001]

Hi,

Used a load of online rad btu calculators (which all came out different) so took an average. The room warms up when rad on but cools quickly but room colder than others when no heating on which makes me feel it’s the cold rooms below causing the issue?

 

[JohnD]

Do you think the cold bedroom could be due to the cold rooms below?

yes of course, and the external walls and the ceiling.

Start by taking the floor up and packing mineral wool between the joists and especially round the edges and between the last joist and the wall. As well as insulating, this will muffle cold draughts. Get a can of expanding foam and fill any gaps you see while you are working. Hoover out all dirt and dust and wipe the gap with a damp sponge, since foam will not stick to dirt. I use the pink fire grade foam now, the cost is not significant and one day it may prevent or delay a fire spreading. Do the ceiling too, and draughtstrip windows.

It's quite possible that cold air currents in the floor are the biggest problem, but mineral wool will fix them.

The external walls will be harder, but you can clad them with a bonded insulating foam backed plasterboard. The foam has about twice the insulating power of the same thickness of mineral wool, but it considerably more expensive and needs more effort and skill to fit neatly, so mineral wool is fine in a ceiling or floor.

 

[^woody^]

The principle is always to insulate the heated room to keep heat in, and not insulate the cold room to keep cold out.

 

[chameleon001]

Ok great, it would be easier for me to take down the porch ceiling and work from under the room than to rip up the new carpet etc. Do I need to fill the entire depth of the void with rockwool, also do I need to be mindful of contact with any electrical cables?

Certainly agree to insulate the warm room, but I guess in this case the cold room is adjacent to the warm one, you can insulate from either side and get the same result?

 

[John D v2.0]

The principle is always to insulate the heated room to keep heat in, and not insulate the cold room to keep cold out.

Can I have some of whatever you're drinking?

 

[JohnD]

Do I need to fill the entire depth of the void with rockwool, also do I need to be mindful of contact with any electrical cables?

you don't need to fill the void, but I would. Mineral wool is cheap enough and it will ensure no flow of cold air under the floor. Usually cold air enters through defects in the walls, and blows out under the skirting where there is a gap, so pack the edges of the room with extra care. It will also pass through holes for pipes (and downlights, if you are unfortunate to have any).

Mineral wool (unlike polystyrene) will not damage cables BUT they should either be underneath, or on top of the insulation, not buried in it, so that any heat can escape. It's easier to see that they are open to the air if they are on the side you are working (usually the top, if you have taken the floor up). Keep them away from anything hot such as radiator pipes.

If you have taken the ceiling down, you can staple garden netting to the joists as you go to prevent the quilt from falling out.

Lighting cables are very lightly loaded and unlikely to get warm, but immersion heaters, and especially electric showers, may be carrying a big enough load for long enough to warm up.