Inexpensive Home Building

Cut through the jargon and nonsense of home building and house construction by starting from zero dollars and trying to figure best-value bang-for-your-buck when choosing construction methods or construction materials. My research might answer some of your questions and at other times perhaps you have the knowledge or experience to post the answers to my questions and thereby help others too. The goal is an affordable and sustainable home for all.

Saturday, March 31, 2007

Best Ways To Cool Your Home

The Best Cooling Is Not Heating in the First Place

Just like the best energy efficiency is conservation (not burning fuel), the best “cooling” is avoiding unnecessary heat in the first place. “Cool from inside” by turning off unnecessary electric devices, etc. (each one is an electric heater) but the big winner is “cooling from the outside” (stopping external heat sources):

Take your house out of the oven.

That big thermonuclear furnace in the sky, the Sun, will bake your house if you leave it in the solar oven so cut the direct connection between the Sun and your home with these light blockers:

  • Natural shade (landscaping): Deciduous (leaf-losing) trees southeast and southwest automatically adjust seasonally by shading in the summer but still allowing 50-80% of solar heat in winter. Hedges (or fences) east and west can block the low Sun at dawn and dusk. Vine-covered (or even bare) trellises also can shade walls. Substantial shading from the overhead midday summer Sun requires tree canopies to overhang the roof (less desirable if the roof is a rainwater catchment). Proper landscaping can save a quarter of your energy bill.
  • Structural shade; Fly roof / flying roof, shade cloth, fences, trellises, eaves, outbuildings/sheds: Some of these can be part of the main building and some can be part of landscaping but they do the same job as natural vegetation and can be any horizontal or even vertical structure (e.g. shade-cloth "fence" or "hedge") that prevents direct sunlight from hitting the home.
  • Reflective building exterior; cool roof, reflective house paint: For maximum reflectivity, use special materials suspended in paint to reflect light or suspended ceramic to reflect heat. At least use a white or light color. The simple difference between black and white can be 70 degrees F. Remember that even a small divergence from pure white can reduce reflectivity significantly: “Bone” is about 3/4 as reflective and “Almond” is about 1/2 as reflective.
  • Exterior window treatments; eaves, window awnings, window shutters: Properly sized eaves or awnings automatically will shade windows from the high summer sun yet allow the lower winter sun to enter the windows--but fixed overhangs are a compromise and seasonal adjustment is more effective. Homes in primarily hot zones should have minimal windows east and west unless they are fully shaded on the outside.
  • Interior window treatments; shutters, shades, blinds, drapes: These ideally use a reflective facing plus a thermal material (e.g. "solar shade" or "thermal shade") plus seal the window (caution: you need an escape valve or heated, expanded air can crack a window). Door-like interior shutters can have a gasket seal. Shades can mount in an edge-sealing frame or box, although even standard room-darkening shades are better than transluscent shades and any shade is better than nothing.
The Sun is on the south side in the northern hemisphere and north side in the southern hemisphere.

All these passive light barriers can make a big difference. Then add thermal barriers (conduction insulation, radiant barriers, caulk for air infiltration, etc.), especially if your area suffers from "heat island" effect, such as in the heat-trapping asphalt jungle of cities.

Remember, active cooling is always a last resort. Minimize or eliminate the need for active cooling by intelligent design.

Next: "Passive Cooling Solar Cooling: Use Heat To Cool."


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