Air conditioning as we know it today, based on the refrigeration cycle, is a bit more than 100 years old. Prior to modern air conditioning, did humans spend hundreds of thousands of years being miserable? No, they used other methods to keep their cool, and these methods work just as well today. In some climates, a no-refrigeration approach may be all that’s needed. In more demanding situations, the methods below can reduce the size and expense of either air conditioners or heat pumps, and reduce the amount of energy they use. Start at the design stage to build effective cooling into the structure of the home. Then add active strategies for cooling with little or no energy use or refrigeration.

Keep It Tight

High performance homes already include two basic features that reduce the need for cooling, such as high levels of insulation and very tight construction. This keeps the inside in and the outside out.

Select Windows Carefully

If you are building where you expect cooling to be a significant issue, it’s best to choose windows that help reduce overheating. That may mean a low solar heat gain coefficient. Also, carefully consider window placement to optimize lighting, while reducing glazing – especially on the east and west facades.

Make It Massive

Thermal mass absorbs heat when the temperature is high and releases heat when the temperature drops. This can be used as a heating or cooling strategy. High mass buildings have been used for thousands of years around the world to keep people comfortable by reducing daily temperature swings. The principle applies to homes, including those using mass materials such as concrete, gypcrete, masonry, soil blocks, and even tanks of water

Throw Some Shade

Provide even more protection from overheating by shading the windows. Deciduous vegetation is nature’s way of providing summer shade and winter sun. For some exposed western windows, properly placed evergreen trees will prevent excessive late afternoon heating, which can occur even in winter. Moveable exterior shading can intercept the sun before it penetrates the glazing. You can deploy the shading during the times of year when it’s needed and stow it away when you want to take advantage of the sun’s heat.


Ventilate, Naturally

Buildings can promote ventilation by embracing the forces of nature. Carefully placed operable windows capture prevailing winds and create cross ventilation. Tall spaces drive the stack effect when openings high in the building allow warmer, lighter air to rise and escape while being replaced by cooler air from lower window openings.

Mix It Up

Simple ceiling fans will supplement the air flow of natural forces. Ceiling fans also mix the air in a room to better distribute comfort. They can be a big help in homes that don’t have a forced air heating system. In summer, ceiling fans can be set to blow air down to improve occupant comfort by washing air over peoples’ bodies to enhance their natural cooling ability. In winter, you can reverse the setting so the fan blows upward to break up the pool of warm air that accumulates near the ceiling and force it down into the living area. This is most useful with high ceilings.

Flush at Night

In many climates, it’s much cooler at night than during the day. Take advantage of natural cooling by flushing the house with cool night air. In some cases, simply opening windows for natural ventilation may do the trick. To boost cooling power, add a large fan to drive cool air through the building. This has been common in the past with a large axial ceiling fan, sometimes called an attic fan. Adding an exhaust window fan in a second story window can effectively pull warmer air out of a home, while pulling in cooler air from an open window on the ground floor. If there’s a forced air system with a fresh air duct, you could run that system at night. There are also some dedicated night flush cooling ventilation systems that pull in outside air and push it into the living space.

Consider Energy-Efficient Cooling

Evaporative cooling is used in hot, dry climates to cool and humidify. It improves on simple air flow by using fans to drive a continuous stream of outside air through a wet pad into the living area, without recirculating the air. The blowers in these systems use much less electricity than a refrigerant- based air conditioner and even less than a heat pump.

While you most often see rather basic, inexpensive, window mounted evaporative coolers, there are more sophisticated products that operate independently or tie into a ducted air delivery system for improved distribution throughout the house.

Combining Approaches

All buildings should start with the basic structural cooling measures first mentioned, such as good insulation, air sealing, landscape shading, and thermal mass where appropriate. These are effective in all buildings, everywhere. Additional cooling can be achieved by applying one or more of the more active approaches. Moveable, exterior shading is always effective where direct sunlight hits the building, especially east and west sides. In many climates, natural ventilation using night flushing and cross ventilation is a good next step. Adding a mechanical boost to natural air flow with fans increases the cooling capacity, especially at night. Evaporative cooling comes next, but works well only in some climates. And energy-efficient heat pumps are always available as a last resort.

A good example of combining these approaches can be seen in traditional courtyards. This design innovation was introduced thousands of years ago in hot parts of the world. Properly oriented courtyards provide shade, promote natural air flow, and absorb heat in the thermal mass of surrounding walls. The addition of moving water or a fountain adds the benefit of evaporative cooling. A courtyard creates a comfortable refuge when a home is overheated and improves the comfort of surrounding spaces as well.

While all these cooling measures are tried and true,  integrating them into a building design requires careful thought. An energy model is a valuable tool that will inform natural home cooling design. Employing several of these low-tech cooling strategies will keep building occupants comfortable while eliminating the need for or reducing the size of refrigeration-based equipment and the energy they use. It’s a great way to collaborate with nature and enjoy the comfort.