In a house designed for passive cooling, your home interiors are kept naturally fresh, cool, and comfortable on hot summer days, but with little to no energy use. Passive cooling is a home design strategy that works by removing heat from a home through natural ventilation, and also preventing heat from entering the home in the first place through heat-gain prevention. This approach is called “passive” because it can require no special technological or mechanical devices, just smart design and quality home construction.
Natural ventilation is achieved through three strategies: cross ventilation, convection through stack effect, and Venturi effect. By utilizing a combination of these different passive strategies, a home can be cooled on both breezy and non-breezy days. In order to set up these effects within a home, windows are positioned low to the floor on the cool side of the building and high windows are positioned on the high-wall side of the building. Stack effect, for example, helps to cool the home on a non-breezy day. In this strategy, a natural vacuum is generated throughout the home when hot air rises and exhausts through the high windows and fresh, cool air enters through the low windows. The air pressure differences due to hot and cold variations inside the building and outside the home create a natural cross breeze. This air movement encourages evaporation of moisture on our skin and gives the sense of cooling. AKA, free air conditioning! Prevailing wind directions are also taken into effect to further pressurize the home, promoting a jet-like Venturi effect, which increases air flow rate within the home.
A high-performance building envelope is the second component in passive cooling design and is used to prevent interior heat gain during the hotter months. This is done by constructing walls, roofs, and floors that are very well-sealed and insulated. A high-performance building envelope not only prevents summer heat from entering the home, but also prevents heat loss in the colder months. This helps promote energy-efficiency within the building during all seasons.