Windcatchers as an Alternative to HVAC Systems
qanat [29]
What is a windcatcher?
A windcatcher (also known as a windtower) is an architectural feature which cools a building by harnessing the wind. This feature is relevant to North Texas because indoor climate control is a major consumer of energy in the region and a substantial expense to home owners [10]. By using this passive form of cooling, the building consumes less energy to maintain a desirable temperature.
How do windcatchers work?
Traditional windcatchers take the form of a tower attached to the structure with one or more openings at the top and bottom[12]. Windcatchers may be used in a variety of configurations. In the single tower design the opening at the top of the tower is facing the prevailing wind (typically, adjustable ports at the top of the tower allow for the opening to face the wind regardless of direction). The wind is directed downward and into the tower. At this point, the air is constricted and, following Bernoulli's principle, moves faster and compresses [11]. As this fast moving air is released into the structure it expands and cools (in accordance with the Joule–Thomson effect) [11].
To achieve further cooling, a qanat can be incorporated into the design. The air moving through the tower is redirected horizontally through the qanat and over a pool of water. The shaft, being subterranean, has a lower temperature than the surface and cools the air current through conduction as well as through evaporative cooling as it passes over the surface of the water. At this point, the air is channeled into the building. As the cool air entering the structure warms and raises, it is vented through openings in the upper portions of the building [12].
Air flow using a windcatcher. [30]
The convection current created by this rising warm air can be further potentiated by the inclusion of another tower at the opposite end of the building (the multiple tower design). This tower acts to expel exhaust (hot air) from the house [1]. This tower’s port is opened to face counter the prevailing wind. This creates a pressure differential that increases the flow of air through the building, providing additional ventilation [13].
Windcatchers. [31]
Examples of windcatchers in the past:
Windcatchers have been used for thousands of years in hot climates and are particularly common in Egypt and Iran. However, they have also been employed more recently in western architecture [9]. For example, Zion National Park Visitor Center in Utah and the Kensington Cricket Ground in Australia utilize the windcatcher concept in a modern interpretation. These iterations of the windcatcher demonstrate the concept’s adaptability to modern architecture [9].
How do windcatchers reduce energy consumption in North Texas?
In contrast to windcatchers, the most common way of cooling a residential building in North Texas is the use of an HVAC system. HVAC systems consume 50% of the energy used by buildings and 20% of total energy usage in the United States [10]. The incorporation of windcatchers into residential buildings represents a serious opportunity to cut energy usage and consequently greenhouse gas emissions. Further, because windcatchers reduce energy consumption, they lower the homeowner’s energy bill. In hot climates, such as North Texas, where energy cost associated with air conditioning can be quite high, the windcatcher presents a financially attractive option.
Windcatchers have been used for thousands of years in hot climates and are particularly common in Egypt and Iran. However, they have also been employed more recently in western architecture [9]. For example, Zion National Park Visitor Center in Utah and the Kensington Cricket Ground in Australia utilize the windcatcher concept in a modern interpretation. These iterations of the windcatcher demonstrate the concept’s adaptability to modern architecture [9].
How do windcatchers reduce energy consumption in North Texas?
In contrast to windcatchers, the most common way of cooling a residential building in North Texas is the use of an HVAC system. HVAC systems consume 50% of the energy used by buildings and 20% of total energy usage in the United States [10]. The incorporation of windcatchers into residential buildings represents a serious opportunity to cut energy usage and consequently greenhouse gas emissions. Further, because windcatchers reduce energy consumption, they lower the homeowner’s energy bill. In hot climates, such as North Texas, where energy cost associated with air conditioning can be quite high, the windcatcher presents a financially attractive option.