New build extension too cold


Hi,
About 5 years ago we decided to put an extension on the side of the house but it has not been a success as it is always too cold in winter unless we spend a fortune on heating. It was built to current building regs, with large blocks of foam in the sub-floor, insulation in the walls, double glazed windows and two layers of insulation in the roof, but for some reason we are loosing a lot of heat. It is traditional build with brick outer, cinder block inner, dot and dab plaster board internal and a pitched roof on top.
I had been hoping for a really cosy set of rooms (living room and study) that would be built to need very little heating but it isn't and consequently we only use the rooms when we have to rather than as an extra integrated part of the house.
Does anybody have any ideas on what to do. My own suspicions are the french windows weren't installed as well as they could and leak air around the doors, also the dot and dab didn't include a solid line of goop top and bottom so that air is free to flow from attic to under the skirting boards.
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You say that the floor has "large blocks of foam in the sub-floor" so I assume you've a solid floor? If you haven't then certainly if you've got dot and dab plasterboard then cold air can move from attic to ground floor and chill the walls. If this is your feeling you could try expanding foam and drill holes along where the skirting board is and squirt the stuff inside to seal any gaps. Along the top of the wall you could do the same and then cover over with some nice coving.
The French doors .. are they double glazed? Try a match or a candle and slowly move it around all the joints in the doors (best on a windy day) and see if the flame flickers which will help locate any draughts. Be careful with the naked flame.
I presume you've checked that the builder did put two layers of insulation in the roof? Around the edges he will have left some ventilation gaps to help the free movement of air around the loft ... did he leave too big a gap and have you got too much of the ceiling un-insulated? It may be awkward to get right into the edge of the roof so try a stick with a mirror on the end or if you've got a mobile,camera or small digital video recorder try putting it on the end of the stick and try filming the edge of the roof/ceiling.
Ash
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Okay, much the same ideas as myself. A candle isn't required, as it is evident without it. I currently have clear tape around the door but that is not the most elegant solution. The insulation was put in by me and is double insulated as I said.
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You have to stop the draughts. Even a relatively low volume of air changing will undo the effect of lots of insulation.
Bon
snipped-for-privacy@martech-scot.freeserve.co.uk wrote:

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..
If I'm going to be drilling holes around the room any thoughts on how far between adjacent holes, it's going to be a lot of holes!
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If I'm going to be drilling holes around the room any thoughts on how far between adjacent holes, it's going to be a lot of holes!
If you're sure that you've got chilling of the walls by cold air from the attic (doubtful if you've got a solid floor as there wont be any means for the air to circulate) why not try drilling a hole somewhere not noticeable and see if you do feel a draught coming out of the hole ... if not there's no need to do the whole room/walls.
Are you sure that you've got a radiator that provides sufficient heat to heat the room? If your radiator isn't producing sufficient heat to heat the room then you may be under the misapprehension that the room is loosing heat because it's not getting warm.
The B&Q website have a nice little BTU calculator to see what size radiator you need. http://linkbee.com/F6HS
Have you thought about the exterior of the extension for heat loss? Is it on an exposed corner of the house? Can you try and break the wind down by some panel fencing, bushes or a garden shed? Presumably you extension will have 3 external walls which will all add to the heat loss in comparison to the other rooms in your house which will normally have 2 external walls and two internal walls.
Ash
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snipped-for-privacy@martech-scot.freeserve.co.uk wrote:

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Is the central heating correctly sized and tapped from the existing central heating at an appropriate point?
If the radiators are tapped off the end of the existing central heating run then you would need to balance all the radiators in the house to make the ones in the extension work correctly with the ones in the rest of the house.
There should not be much air down coming down the dot and dab as the ceiling boards should be close up to the wall and there should be loft insulation on the top.
Adam
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