Thursday, March 10, 2011

Simple summer comfort

In even the hottest climates it is possible to stay comfortable without depending on A/C and the electrical grid.
Heavy mass walls and night time ventilation can recharge the walls with "coolth" for the next day.
Heat build-up from fridge or incoming sun can be vented out passively by having a ceiling hatch to let warm air escape, this works best if you can allow cooler air to enter from the basement, thus creating a stack effect to drive the airflow.
I open a window on the shady side in the basement and let the air rise into the living space, to push the hottest air at ceiling level into the attic space, where it joins the airflow from the eaves, and pushes the hottest air out through a cupola at the highest point.
The cupola has a wind vane that only allows air to escape on the downwind side, where there is a lower air pressure.
Another method uses evaporation to induce cooling, but this does not work in moist conditions.
In Iraq in the old days people retired to the basement during the hot afternoon, but first they would spray the wall, let it evaporate thus cooling the air. This principle works well in hot weather when you wear a wet teeshirt under a ceiling fan!
I know, i lived in India in an apartment with lots of rebar in the ceiling that wicked the heat from the outside walls all around me, and even during a coool night outside, i would swelter inside.
And then the power goes off, you start to look for a place to sleep outside!
now i know why many roofs in hot places are flat, this makes a good sleeping place, and watertank, shower too!


During hot summer days the power usage peaks due to all the A/C usage.
In BC, Canada that means that we import dirty power from Alberta coalfired powerplants.
This means that if we reduce our A/C usage we immediately reduce greenhouse gas emissions.
So here are some strategies that are practical, cost effective and on top of that, provide peace of mind, with assured comfort, regardless of brownouts, blackouts, price rises!

To keep cool in summer, the first priority is to exclude direct sunlight, into the windows, and not with indoor blinds, because the heat is then already trapped inside, where the greenhouse effect will keep the heat in!
Instead, the blind has to be outside the glass, such as the traditional outhinging wooden shutter with horizontal blinds, excluding sun but bringing in breeze and soft light.
In hot climates it makes sense to have overhanging rooflines to shade openings, and a wraparound porch can provide shady sitting areas, that take full advantage of prevailing breeze. Don't forget to allow opposing openings on all sides to encourage the breeze throughout!
Traditional homesteads often were built under a big shade tree on the southwest corner, to keep the heat out..
If your house feels hot and stuffy at night, check if your floors feel warm, if so, then chances are your ceiling is radiating down, pumping heat into your livingspace. Then make sure that heat does not build up under the roof. Proper ventilation slots are needed under the eaves, all around, and outlets at the rooftop, taking care to have a low pressure downwind outlet, away from prevailing breezes, and an outlet at every peak... Turbine type exhausts are not very effective, a straight up and out pipe is better, a solar chimney with rotating wind deflector is more effective yet.
If your water comes from a deep well, or otherwise is cool enough, it can provide direct cooling in metal radiators on the ceiling to provide cool radiant exchange where ever desired, such as above the bed , and reduce humidity by condensation, which can be piped away to a drain.

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