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Air Flow and Control in Green Building |
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Air Flow in Green Building |
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Air flow occurs only when there is a difference between pressures. Air will flow from a region of high pressure to one of low pressure--the bigger the difference, the faster the flow. The negative and positive pressure differences of air in homes control its flow. Ventilation is controlled air flow--the purposeful introduction of fresh air to the conditioned space in order to ensure acceptable indoor air quality, control condensation, and reduce stuffiness and odors. Infiltration is uncontrolled air leaking into the house, allowing too much air from outside in cold or hot weather and too little air in milder, warm weather when we need a breeze. Exfiltration is uncontrolled air leaking out of the house. Common air leaks in buildings can take three forms: Orifice Air Flow: Air flow where the air entry point and exit point are in a linear pathway; such as a crack between a window frame and the window opening.Diffuse Air Flow: The passage of air through porous building materials such as fiberglass or uncoated concrete blocks. Channel Air Flow: Air passing through openings in the building envelope where the air entry and exit points are not in a linear pathway. This often gives the air adequate time to cool below its dew point and deposit moisture in the building envelope. Channel flow is typically found at the interface of dissimilar materials and is probably the most common and serious of all air leaks. Air movement carries with it humidity, heat, pollutants, and sound. Controlling airflow across the enclosure, between zones, and from the distribution system to hollow partitions is necessary to build a high-performance, green home. Control of air movement is essential to build an energy-efficient, healthy, comfortable, and sustainable home. Air flow is also one of the most important methods of heat transfer so the control of air flow is an important control of temperature in green homes. Airflow also affects the oxygen supply & the spread of smoke and other toxic gases in a fire. More information about air flow and green
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