Passive cooling strategies are based on...
1) shading strategies,
2) natural ventilation,
3) heat gains control and...
4) home design.
Ventilation and Breezes
In hot climates, whenever possible, buildings should be designed to benefit from breezes.
Breezes are found almost everywhere, even if for short periods of the day or the night. Breezes can bring fresh air into your house for free, and will cut your cooling requirements.
- Involves: cooling breezes, shade, heat gains control and home design;
- Goal: cool the house naturally;
- The opposite of cooling a building with air conditioners.
It's obvious, but often neglected: eliminate the solar heat loads to which homes are subject and most of their internal heat sources - baths, lighting, ovens, laundry, appliances - and cooling needs will be reduced accordingly.
Issues such as the house's floor plan are key for cross ventilation and fresh air circulation. The size and the shape of house, or the size and location of the windows in each side of the house, or overhangs and roofing are also critical in cooling strategies.
Trees and shrubs, but also pergolas, overhangs, awnings and other shading devices are key elements of passive cooling.
Some passive cooling strategies rely on low-thermal mass materials, that is, lightweight materials (like wood) able to release solar heat gains quickly, instead of storing them. It may advantageous in home cooling strategies.
But high thermal mass floors and walls can also be used in passive cooling strategies - in climates with cool nights and night breezes.
High thermal mass (concrete, bricks, tiles...) walls and floors can capture and store solar heat gains during the hotter periods of the day, allowing lower temperatures during those periods.
But this strategy involves another step: instead of letting the heat escape slowly into the house as temperatures fall (as it happens in heating strategies) the heat should be pulled out of the house by using breezes or fans, as shown in the image below (see, for details: Thermal Mass Principles).
That's a very general principal, valid for specific types of hot climates.
See also: Thermal Mass for Low-energy buildings
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