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Estimate cooling needs and your passive cooling potential

Cooling loads come mostly from sun through windows and roofs, plus people and appliances. Before sizing any machine, check how much of the load shading, night ventilation and evaporative cooling could remove in your climate.

How

1. List glazing by orientation. East, west and south (north in the southern hemisphere) windows drive most solar gain.
2. Check your day to night temperature swing: natural night cooling works best with cool nights and regular breezes.
3. Look up your summer design wet-bulb temperature. In US guidance, areas with a 1% design wet-bulb below about 21 C (70 F) suit evaporative cooling well; up to about 23 C (74 F) can still work with reduced performance.
4. Decide which rooms truly need active cooling (often bedrooms only) to keep any air conditioner small.
5. If active cooling is needed, get a room-by-room cooling load from a designer before buying equipment.

Do these first

• design-1

Sources

1. Evaporative Cooling Systems. Pacific Northwest National Laboratory, Building America Solution Center, accessed 2026-11
2. Natural Ventilation and Cooling. U.S. Department of Energy, Building Science Education, accessed 2026-11
3. Landscaping for Shade. U.S. Department of Energy, Energy Saver, accessed 2026-11
4. Ductless Mini-Split Heat Pumps. Pacific Northwest National Laboratory, Building America Solution Center, accessed 2026-11

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