Passive Building Cooling

Natural ventilation collects prevailing winds and utilizes the tendency of hot air to rise, in order to cool a building. Creating a plan that aligns to capture prevailing winds and designing the building to take advantage of rising hot air to pull cooler air into the building is one of the most cost effective ways to reduce cooling loads in a building. The fundamental components of natural ventilation are an opening to allow outside air to enter and warmer air to exit a building. Operable windows, stack venting skylights and monitors, and fans are all components of a natural ventilation system.

Climate limits the effectiveness of ventilation systems. Firstly, because the exterior air must be cooler than the interior air. Thus, making it only possible to reduce the indoor temperature to around 3 degrees HIGHER than the outdoor temperature. This is still useful as so many of the buildings today have significant interior heat loads. It isn't uncommon for electronics heavy uses to require air conditioning even in cold winter months.

High mass construction uses the building equivalent of heat sinks in order to cool a space. Concrete, stone, or other massive and dense construction creates a potential to absorb heat. Some methods in use include Trombe Wall (usually used for heating, but equally effective at cooling), water containers, exposed concrete slabs. The effectiveness of this method can easily be experienced, on the next hot day, go lay down on a concrete floor that isn't directly in the sunlight, ahhh, cool! High mass systems can be used in concert with ventilation, particularly night ventilation, to cool in regions that reach temperatures s high as 110 degrees and are relatively dry, but are not very useful when the relative humidity exceeds 60%.

Everyone readily recognizes how nice it is to feel a spray of cool water on a hot day. But did you know that water can actually decrease the sensible temperature of the air? The principle is to allow water to evaporate at the top of a tower, either by using evaporative cooling pads or by spraying water.

Evaporation cools the incoming air, causing a downdraft of cool air that will bring down the temperature inside the building. The effectiveness of this method is restricted to hot dry climates.