Calculate actual room heat loss

srichards

srichards

Suspended / Banned
Messages
10,968
Name
Suz
Edit My Images
Yes
I have a stubbornly cold room. I've bunged up draughts but when the outside temperature gets close to freezing then the temperature will drop in the room down to 17c even with the heating on 24/7. It can be brought up a bit with another oil filled radiator but I'd like to work out whether it's just the radiator in there being too small (likely) or whether there is also more heat loss than there should be and a possible case of missing insulation. The outside walls in the extension seem noticeably cold and there is a sudden chill when you step from the old side into the new extension area.

The radiator for the room is too small as the previous owners nearly doubled the size of the room but kept the same radiator. It's a double panel sort with a single convector in the middle. 690 x 600mm so piddly.

Half the room is in the existing house and half is in an extension. There's no radiator in the space directly below but there is in the other bedroom that is totally in the extension. That's nice and warm and has a small radiator. The dining room which is all extension is also reasonably warm and that has a large radiator.

Is there a way of calculating the actual heat loss in a room from the output of a radiator, room temperature and outside temperature? I want to check the theoretical losses against what is actually disappearing.
 
Last edited:
You want to use an infrared camera to check where heat is being lost on the outside of the house and from the inside check where the cold is coming in from the outside. You can compare it to the rest of the house and see where the most heat is escaping.
 
There's quite a few calculators on line, ( not sure its exactly what you're looking for) it'll give you the heat requirements for the room, some are very in depth and require what the walls are made of, type of insulation etc... Here's a more basic one...
http://www.plumbnation.co.uk/heating-calculator.php
 
Last edited:
Checking the plumbing site that radiator should be 1200w which actually should be reasonable which is why I wonder whether the heat losses are a lot more than the actual calculated ones...
 
What kind of house is it? lack of insulation might be a cause.
 
Detached. But it afflicts just one room which is half in and half out of the extension. Rest of the house and rooms are warm even when this one is much colder.

I also wonder if wind chill is a factor more in this room.
 
Is the extension on a concrete base?
 
exorcism??? just a thought:D:D
 
Does it have large windows?
 
Just one window. Most of the exterior is wall. 2 external walls and 2 internal. The radiator sits right under the window.
 
You say extension - does it have a flat roof? They tend to leak heat dreadfully. You also haven't said the size of the room.

One other thing to check is if any of the walls are single skin if it's single story. At my old home, which was a bungalow, the front wall of the main bedroom was single skin rather than cavity and it got very cold overnight, not helped by the radiators being mounted to it so the heat went through the blocks and out into the street.
 
Last edited:
I had the problem Mark described in a bathroom that was 3 exterior stone single skin walls. It was a tiny room but even with a relatively large rad it was still freezing. Problem solved by skinning the walls with 2x2 frame and heat reflecting plasterboard. The gaps between the the frame was filled with 2" expanded polystyrene sheets/boards. I replaced the rad and pipework with a smaller but more efficient rad and the difference was utterly staggering.

If wind cooling on the wall is the problem then bolstering the insulation would make a massive difference.

I never place rads under windows either. One easy solution to insulating a window is a thick curtain and having a rad under the window means the heat often goes under the curtain.
 
Last edited:
Extension is two storey and has a pitched roof. Insulation seems ok as it seems to have the same as the rest of the loft area.

I'm assuming the front and side walls are cavity. I have the plans that were approved somewhere. Fairly certain it was cavity wall all round as it was built in about 1999.

I've ordered an IR thermometer so I am going to run that round all inside the room to see if there are any obvious cold patches.
 
vixmix said:
I had the problem Mark described in a bathroom that was 3 exterior stone single skin walls. It was a tiny room but even with a relatively large rad it was still freezing. Problem solved by skinning the walls with 2x2 frame and heat reflecting plasterboard. The gaps between the the frame was filled with 2" expanded polystyrene sheets/boards. I replaced the rad and pipework with a smaller but more efficient rad and the difference was utterly staggering.

If wind cooling on the wall is the problem then bolstering the insulation would make a massive difference.

I never place rads under windows either. One easy solution to insulating a window is a thick curtain and having a rad under the window means the heat often goes under the curtain.
Click to expand...

I was thinking battening the extension part within that room was next after just making the radiator bigger and checking for obvious issues.

I have the radiator under the window but I deliberately make sure the curtains are tucked behind so the heat has to go into the room. They're quite thick and have blackout stuff on them too.
 
What size is this room?
 
16 feet by 11 feet narrowing to 9 feet or so wide in the extension. I think that's about it. Measuring laser doodad gone walkies or I'd be more precise.
 
That radiator will never heat that room up
 
First calculator I found on google suggested 1550 watts of radiator for that room, admittedly with some assumptions (e.g. that it is a ground floor room with a heated room above) on my part and averaging of the room width. You might want a bigger radiator. They are pretty easy to fit, I loathe plumbing and am pretty hopeless at it, so if I can do it anyone can.

I internally battened and insulated the single skin wall at the old house but you shouldn't need to do that if your walls are cavity - you should be able to work this out just by looking at how thick they are around the window, cavity walls will be about 10" to a foot (for youngsters, that's 25cm to 30cm), single skin half that, the width of the window ledge usually gives it away.
 
It's definitely cavity. I checked the width of the window sills :thumbs:

The heatloss calculator you found sounds about right. Radiator is supposedly a decent output and observations do concur with it being just too small once outside temperature drops below 3c or so. It's a first floor room and the rooms below are heated but more due to ambient heat than direct heat as the radiators in those rooms aren't anywhere under this one.
 
Well.... I stuck a load of insulation in the extension roof as I noticed some berk had removed it from where the old bit and new bits join. I also stuck in some of the jumbo space blanket across the rafters so there is about 300mm near of insulation. It is slightly better... but when the wind is blowing on the wall it is still hard to heat even with using the electric radiator as a top up. I think over night heat loss is less and it doesn't feel quite as siberian as it did but it is obviously chillier when the wind is blowing the wrong way.

What is the best thing to use to stick to the inside of a wall to increase insulation but not cause a fire hazard? Polystyrene sheets seem to be popular but I thought those were an absolute no-no as polystyrene ceiling tiles were lethal. The front wall seems to be colder than it should be for some reason so just making it 'feel' warmer I think would help massively. I was considering bubble wrap as a cheap idea but I don't know whether it is fire retardant or just a fire hazard.
 
Dry lining might help but would lose you a few inches of space in the room. If you weren't so far away, I would offer my services with my FLIR camera which would show exactly where any cold spots on the wall are and also shows up any damp problems even if they don't manifest themselves in other ways.
 
Thanks. I've got a laser thermometer and that is quite good at showing me where the cold bits are. The section around the join between the old house and the new extension bit seems to be where the cold spots are. I've spent many a happy hour wafting it around :) There are two air vents in the room which vent into the cavity. I've blocked those up already. They cannot be helping either.

Cavity wall insulation designed for properties that are pelted with horizontal rain is another possible solution but unless it is free or under a couple of hundred quid I won't be doing it as I don't think it will pay back or not cause other problems.
 
You must log in or register to reply here.
Back
Top