Cool Evenings and Air Conditioning

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There is the idea that the way to fight against heat is to add air conditioning to every single building. This would be true, if we were in Dubai and the temperature never went below 20°c at night, but in Europe it very often does. This means that a mosquito net is more interesting than air conditioning, and far cheaper.

Air conditioning is great when you deal with heat for weeks or months, without the opportunity to get rid of that heat at night. In Europe, nights are usually cool enough to lower the temperature inside buildings. As I write this I have the balcony door opened fully, trying to vent residual heat from this Minergie building.

With air conditioning, you’re using energy to cool the building. With cold outside air you can use naturally cooled air to cool the building instead. Instead of investing in air conditioning, well placed mosquito nets allow you to open windows when the air cools, and keep them open overnight.

The heat that had accumulated during the day can then vent and the building becomes pleasant once again. With minergie opening windows at the right temperature between outside and inside helps. A draft is created, and the temperature drops until the windows close, or the air conditioning is turned off.

With mosquito nets and open windows, at night, you get the same benefit with a much lower energy expenditure, if any.

As I write this I finally had a real opportunity to attempt to cool this building. I’ve managed to remove 2°c from several rooms, mainly using open windows, but also the pressure difference with the storm earlier, and a fan, just to stir the air further.

If you can dump the heat, every night, using nature, rather than machines, then you have a sustainable way to make heatwaves more liveable. Getting rid of heat is one of the challenges, but for liveability the key is to get airflow.

During the hottest part of a heatwave fans provide that “breeze” but in the evening open windows, with mosquito nets achieve the same as air conditioning, without the hot exhaust, noise, or energy requirements.

Tomorrow I will begin my night cooling experiments in full. In Rome, and mountain huts I’m happy with an open window, without mosquito nets, but at home I prefer to keep mosquitoes and spiders out.

In a normal building I’d ventilate all day long, but in a minergie building ventilating all night, to avoid capturing heat makes more sense.