Air changes per hour
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Air changes per hour is a measure of how many times the air within a defined space (normally a room or house) is replaced.
The actual percentage of an enclosure's air which is exchanged in a period depends on the airflow efficiency of the enclosure and the methods used to ventilate it. The actual amount of air changed in a well mixed ventilation scenario will be 63.2% after 1 hour and 1 ACH. [1] In order to achieve equilibrium pressure, the amount of air leaving the space and entering the space must be the same.
ACH equation in Imperial units
Where:
- N = number of air changes per hour
- Q = Volumetric flow rate of air in cubic feet per minute (cfm)
- Vol = Space volume L × W × H, in cubic feet
Air change rate [edit]
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This table does not cite any references or sources. (February 2013) |
| Commercial kitchens & Toilets | 15–30 |
| Classrooms | 3–4 |
| Laboratories | 6–12 |
| Smoking rooms | 10–15 |
| Warehousing | 1–2 |
| Basement Parking | 15–30 |
The Passive House standard requires a 0.6 ACH.[2]
References [edit]
- ^ Bearg, David W. (1993). Indoor Air Quality and HVAC Systems. CRC Press. p. 64. ISBN 0-87371-574-8.
- ^ "International Passive House Association - Guidelines" (in english). Retrieved 23 March 2013.
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