Passive Cooling Techniques

Passive cooling is a way of designing a building that focuses on improving indoor heat to a comfortable level with little or no energy consumption. This is often done through non-mechanical conditioning solutions that involve preventing heat from entering the building or by removing heat from the building. To be effective, passive cooling, which is the least expensive means of cooling a building as it helps to reduce the cost of air conditioning, needs to cool the building and the people in it.

Solar heat gain prevention
The prevention of heat entering a building is known as solar heat gain prevention, which refers to the increase in temperature in a building from the sun. Almost half of all heat gain in a home is generated through windows that are unshaded. External passive cooling techniques to help keep out the heat include shading east or west facing windows hit by direct sunlight through the use of sun screens, awnings, roll-up shades, or creating a trellis with vines for shading. Internal techniques include applying window tint or installing blinds, shutters or drapes.

Creating a living wall, also known as a vertical garden, can reduce heat gain -- as is painting exterior walls a light color. Light colors help to reflect the sun and prevent buildings from absorbing as much heat, thereby keeping the inside cooler. Likewise, a reflective roof made of a highly reflective type of paint, sheet covering, tiles or shingles stay cooler as it reflects more sunlight and absorbs less heat than a standard roof. Proper insulation, which provides resistance to heat flow, also helps with heat gain prevention and thereby helping to create a comfortable space. The higher the insulation's R-value, which is the capacity of an insulating material such as fiberglass or mineral wool to resist heat flow, the more effective the material is at reducing heat transfer. It's important to insulate from the roof down to the building's foundation.

Another solution to heat gain prevention is to install windows with passive and solar control low-e coatings. This minimizes the amount of ultraviolet and infrared light that passes through glass. Moveable reflectors reduce heat gain in the summer. A curved reflector acts as a shade and reflects sunlight to prevent heat from reaching the skylight and heating a space. However, it does so while still allowing daylight to enter.

Natural cooling methods
The removal of interior heat is known as natural cooling. One way to maximize heat loss is by creating a thermal chimney. This is achieved in a home by opening the lowest windows on the side of the home where the breeze is coming from and leaving interior doors and upstairs windows on the opposite side of the house open. This works much like a chimney in that the warm interior air is draw upwards and out the upper windows.
Installing inexpensive roof vents in the attic, such as a solar powered attic vent fan, reduces the amount of accumulated heat which radiates down into a home. Moreover, roof vents help remove moisture from the attic during winter.

A continuous ventilation system known as a metal ridge vents or shingle-over vents can be installed from end to end on the roof to remove excess heat and allows condensation to escape. Not only does this method allow energy efficiency, but it prolongs the life of your roof by preventing roof rot and mildew damage. Furthermore, the use of energy efficient ceiling fans help to circulate warm air evenly in rooms and thereby creating cooler air.

Do you think passive cooling should be mandatory in all buildings in warm climates?