Have you insulated your house, yet some of the rooms are still cold? Draught proofing may be the answer. Two clients I saw in recently both had this complaint and the solution was the same for both.

The complaint; a room that has been insulated is still cold. In one case the problem was immediately apparent – an unused open fireplace. The chimney was doing exactly what it was designed to do, which is draw the air from the room (actually it works the other way round with cold outside air dropping down the chimney into the room).

Fixing the problem was easy, simply block the chimney top and bottom and no more draught. It is important to seal the top as well as the bottom to stop rainwater getting in.

The other case was less obvious. It was a 1980s-built house that the clients had been at some pains to insulate to minimise their CO² emissions. Cavity wall insulation, loft insulation, solar thermal on the roof, draught proofing and a new wood burning stove had all be added in the past couple of years. But it seemed that no matter what they did, they could not keep heat in the lounge. When the wood burning stove was going the room was toasty warm, but the temperature would drop alarmingly over-night.

Eventually the problem was traced to a vent installed by the wood burning stove installers a couple of metres away from the stove and hidden under a book case. The "vent" was actually a length of 100mm drain pipe cut into the wall and covered with a louvered grill. The effect of a 100mm hole in the wall is fairly obvious, but less so when you can’t actually see the hole. In this case the solution was less obvious but still doable – replace the “vent” with a sealed ventilation system.

In 2005 NASA carried out some test on its various buildings and found that 50% of the heat lost from a building could be attributed to gaps in insulation amounting to 5% of the surface area. In their report they likened the gaps in insulation to a pin prick in a balloon – the temperature difference inside to outside means that heat escapes more quickly through a small hole than it does through a big hole, but ultimately the same amount of heat escapes.

In the typical UK house draughts will account for at least 10% of the total heat loss. If there is an unused open fireplace that figure will rise to over 50%. There are all the obvious places to seal – gaps around sash windows and under doors, floor to wall joints, ceiling to wall joints, gaps between floor boards – but the real culprits tend to be penetrations. Where pipes and cables are brought through walls or floors there is often a gap around the pipe or cable that can be simply sealed with mastic.

I often get asked if it is possible to do too much draught-proofing and end up with a stuffy house. I guess the answer is yes, but you would need to have a lot of time on your hands to get that far. It is something I have never seen and feel no need to worry about.

Photo by iAreef

About the author: Tim Pullen is eco-editor for Homebuilding & Renovating magazine, author of Simply Sustainable Homes and founder of sustainable property consultancy WeatherWorks.

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