Tuesday, 31 January 2012

How much of your house do you heat?

We use about the same amount of energy to heat our houses now as we did 40 years ago, even though our houses are more energy efficient. In the '80s, only 9% of homes were mostly double glazed - now its 80%. In the '70s, only about a quarter of our homes had loft insulation and most of them had only 2" worth. Now three fifths have more than 100mm. Since 1970 heat loss from an average home has fallen from 376 Watts/C to 254 Watts/C - down by a third. However, we aren't using less energy. (This is per household - the number of households has gone up 39% in that time and the total energy used has gone up 40%) [1].


In fact space heating energy peaked in about 2004 and there has been a bit of a drop since, which is good news.

It seems that as our houses have become more efficient we have kept them warmer. That doesn't necessarily mean our rooms are warmer than they were before, only that we heat more of our house and for longer. This is very pleasant but often unnecessary. Do you use your bedrooms during the day? Maybe the children do, if you have any.

It's the central heating that makes us do it. Houses with central heating run on average about 3C warmer than those without (according to BRE models), and since practically everyone now has central heating we all do.

Central heating is supposed to be controllable - but is it? We have thermostatic radiator valves in every room. Many people do. In my Climate Friendly Homes surveys for Cambridge Carbon Footprint I have to ask people if they have TRVs and if they have them adjusted. These days most people say they have. One household told me that they adjust them during the day - when they go out of a room they turn the radiator off. I was amazed, because I never dreamed of doing that. But isn't it perfectly sensible? If you had an electric fire on in a room you wouldn't dream of leaving it on when you weren't in it. So why are radiators different? We just don't think about it - the radiators are effectively invisible.

If you do turn radiators off, you have to keep doors between rooms closed as well, otherwise there is no point - which is something I did as a matter of course as a child and am retraining myself to do again. But what do you do about the hallway? We have a loft conversion and the hall radiator effectively heats 2 staircases and 3 floors worth of hardly used corridor. We don't need to heat it at all, except that the main central heating thermostat is in the hall. If we don't keep that on the boiler will never switch off.

Some people would argue you hardly have to heat the house at all - only yourself. My neighbour has a heated pad he puts his feet on. You can get heated gloves and vests and other clothing too. You can insulate yourself with a slanket.

I'm looking out for better heating controls. Do let me know if you find some.

[1] Great Britain's Housing Energy Fact File  (DECC)

6 comments:

  1. modern heating systems can be run on a "manifold" system - it's used on underfloor systems in the UK but in France it's used on individual radiators as well - it means each radiator is supplied directly from a single point. Most central heating in the UK uses a circulating system - which means hot water is pumped around the home and although radiators can be turned off individually it means going from room to room to do it - with manifolds individual radiators can be turned on and off from a central point "by the flick of a switch" and (i think!) there are controllers which allow you to program individual circuits - It's oviously not something that can be changed readily in an existing system but would probably be worthwhile in a wholesale retrofit of heat pump boiler and system upgrade

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  2. I'm not absolutely convinced by this argument. Basically we live in old house which although its stone/lime built struggles to breathe and we do get damp issues. This has got progressively worse as we have improved its energy efficiency with double glazing etc. There's a couple of ways we have improved the situation more recently but we like air to circulate. In addition heating our house relies on thermal mass if you let one bit go cold surely it will take longer to heat up and use more energy? My solution has been to insulate more leave the heating off as much as possible ad use the wood-burner (using scrap wood). Thanks for looking at my site by the way.

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    1. If putting in double glazing has made your damp problem worse it must be because it has reduced the draughts. If you have a damp problem then your best solution is to identify the source and fix it. Alternatively, rather than blow a gale through the house to keep it dry, and have all your expensive heat going out with it, I would recommend you look at using a dehumidifier. They are surprisingly efficient as quite a lot of the energy they use finally gets dumped into the room as heat. (This article by my friend Ray explains more http://www.sciencedirect.com/science/article/pii/S0378778810002173)

      As for the thermal mass issue, it is a total fallacy that it takes more heat to warm up a house when you need it rather than keep it warm all the time - unless you have a heating system which is particularly inefficient when going at full blast. This does apply to heat pumps because they are less efficient when providing high temperatures but it does not usually apply to gas or wood heaters.

      Your solution of insulating but heating as little as possible does sound very reasonable as long as you keep sufficient ventilation to manage the damp.

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  3. Good point you shared here. Yes, heating devices can be costly. But, selecting the right heating oil additives to put in them can help one save resources and cost.

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  5. Would it be wiser if you just have your home have home heating installed?

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