Keep Cool this Summer (without the expense of an air conditioning unit)

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When I first moved down to the South Coast of England from Glasgow, the first few summers came as a massive shock to me. It wasn’t so much that the days themselves were much hotter (and that the hot weather lasted a lot longer than up in Scotland), it was the fact that where I live doesn’t seem to have any natural cooling in the evenings.

I’m a good 40 minutes drive from the coast (so effectively pretty far inland) from where I live. Why should this make a difference? Well, we all know about sea breezes (although in the evening it’s technically a land breeze) coming in in the evening to cool things down. This is caused by the fact that the sea cools down slower than the land in the evening for the same reason that it heats up slower during the day – it has a higher specific heat capacity. I won’t go into the physics of it all, but specific heat capacity basically means the amount of heat that is required to be input for a change in temperature to take effect. As the land is cooling faster than the sea, the air pressure over the land is higher than that of the sea, and as nature likes balance, the air runs from the higher to lower pressure area, resulting in a nice evening breeze wafting through your windows at night.

So, back to my issue. Even with my bedroom windows open in the evening, the room (and house) remained hot and stuffy throughout the night, even when it was reasonably chilly outside, all because there was no air movement going on.

Fortunately my background in physics (which I studied from high school all the way through to when I left University) kicked in, along with some of the physical sides of geography, which I’d also studied.

We all know that heat rises, and so the first thing I did was to open the hatch to the loft (or attic as some might call it) which meant that all the heat that was trapped in the top floor had a means of getting up and out into the dead space then on through the roof. But that didn’t seem to be enough.

I think most of us have known the futility of having a fan in the bedroom that does little else but blow hot air at you. Having given this some thought, and on one of the hottest nights I’d experienced without the benefit of real air conditioning, I decided to give something cheap and simple a go.

1. Freezer bag (the ziplock kind) filled with water and thrown into the freezer to, well, freeze.
2. At evening time place frozen water (still in bag) in a roasting tray that you’d put in the oven, with about an inch of water in the bottom on window sill.
3. Place fan in front of this in such a way that the tray of water and ice is directly behind the fan and that the fan will be drawing it’s air across the water and ice.

This is basically how air conditioning works (except using pipes filled with coolant). As the water evaporates it cools the room and when the fan is running it is blowing cooler air out than the air surrounding it. The only downside of this is that it won’t work very well when the humidity is high, and in some cases may make you feel more uncomfortable, but fortunately that doesn’t seem to be an issue where I live as it doesn’t get that humid.

Another tip is, if the house will be empty during the day then leave curtains drawn and windows closed. Most homes have double glazing, and while they’re great at keeping heat in during the winter, they’re just as good at making your home a greenhouse in the summer. With the curtains drawn you’re reducing the amount of radiant heat (sunlight) coming into your house, and with the windows closed you’re cutting out some of the convective heat (the air outside warming the air inside) as double glazing works just as well in reverse in this situation.

This won’t stop daytime heating completely, but it will make a noticeable difference. Then, come evening time and when the outside temperature starts to drop off, open your windows both downstairs and upstairs. As the warm air in the house escapes through your windows upstairs (and loft hatch or skylight if you’re really posh), the cooler outside air will be drawn into the house from the downstairs windows, and eventually you should find that the house starts to cool down nicely. Of course, it’s pretty much common sense that you need to keep your doors open to facilitate the movement of air around the house.

Hopefully I’ve shed some light on how to keep cool in the evenings. Any comments or other tips are greatly appreciated!

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