Sunday, 15 July 2012

Beating the heat

Just because we live in a low energy house, it doesn't mean we can completely ignore the summer. In fact there are lots of things we can do to keep the house cool, now that it's going to get over 30 degrees centigrade oustide pretty much every day for the next two months. Some of these you may be able to try at home. Some of them rely on infrastructure such as high insulation, airtightness and good windows. Having a low energy house is one thing, but being a low energy person is another. Some try to tread lightly on the planet and make their carbon footprint small, but attempts are thwarted because they are surrounded by energy inefficiency. Others have all the low energy tools at their disposal, but they have so many of them, and use them so much that their energy consumption is even higher. The goal of low energy design is to make it both impossible and undesirable to consume energy copiously.

1. Shut the blinds in the morning. Tempting though it is to shut them at night and open them in the day time, as the sun starts getting higher and further south, we really don't want it's rays to reach into the house. After the summer solstice in June, the sun starts getting lower, so as summer builds up pace, the solar gain is also increasing. External blinds are more effective at keeping heat out.

2. Shut the windows when it gets hotter outside than it is inside. Also counterintuitive, but this will keep the heat out. There is an argument that opening the windows will get some breeze going through the house, and that breeze will take the heat away from us and cool us down. This is true if the breeze is blowing past us, but in terms of temperature, a breeze of hot air is going to heat up the house. If you have an air conditioner on, it will work much better with the windows shut, just like a heater works better with the windows shut, and a fridge works better with the door shut.

3. Open the windows when it gets cool in the evening, or early in the morning.This will let some of the heat out and let cool air in.

4. Use cold water. If you have to use hot water, use as little as you can, and turn it off as quickly as you can. Hot water is going to heat up the house, and the more airtight and well insulated you are, the more it will heat your thermal envelope. If you have a smart boiler, which I think we do but it's too smart to give itself away, a secondary effect of this is that using more hot water will encourage the boiler to make more hot water, in other words keeping its water at a higher temperature. This will mean that more heat leaks into the house.

5. Switch electrics off. They're all giving out heat too. Don't use them unless you have to. Switch them off as soon as you've finished.

6. Cook at night or early in the morning, especially if you're using an oven. If you boil a kettle it should just have as much water as you need in it. Any more means more heat in the house. I get really annoyed when I see a kettle or pan of water being kept on the boil with the cooker on low. Much better to boil the water when you need it, and switch off the heat and use it as soon as it's ready. If you don't use it as soon as it's ready it could be there putting out heat for half an hour, and in fact it often is.

7. Stop using ice. It may cool you down, but the fridge puts out a lot of heat to make it. Iced tea is probably the worst as it involves boiling water then adding ice. To be honest ice makes less of a difference than the things above, and a couple of lumps is not going to make a big difference to the heating effect of your fridge, but I'm with the Chinese that you should drink hot drinks when it's hot. Cold drinks just confuse your body. I grudgingly confess that ice improves gin and tonic.

8. There's a whole load of really obvious stuff like wearing light clothes and not doing much exercise, and slightly less obvious things like not eating so much, and eating food that will cool you down rather than heat you up. Cucumbers and bananas are good. Meat and potatoes are not. 

9. Also there's probably a lot of subliminal stuff that will make you feel cooler starting with the colours, patterns and textures you can see around you. Having an electric fan in the room, even if it's not switched on, may make a psychological difference. 

10. Use LEDs. The above are all about using or not using what you have. LEDs make sense for two reasons. First, they are more efficient so they add less heat to the thermal envelope. Second, while incandescent and fluorescent lights give of heat in their radiation, LEDs just radiate light, so you won't get hot standing under an LED. Also, LED light does not attract insects, in stark contrast to incandescent and fluorescent light, so there is less threat leaving windows open at night time. It's a good idea to get other low-energy appliances too.