Air pressure q50 test
The q50-value over one hour is used to describe the air leakage (or air infiltration rate) of a building envelope at a pressure difference of 50 Pascals (Pa). This standard is related to the rate that air infiltrates the whole envelope of a building when doors and windows are closed thus the volume is calculated to include everything within the envelope or the air tightness line.
This is measured through a q50 pressure test which is carried out by closing and sealing doors and windows and installing a door blower to create a pressure differential of 50 Pa (equivalent to a 5 mm water column) between the inside and outside, to measure the air leakage. The standard (or q50) and the UK building regulations requires a test result which is less than 5m3 of air per hour per m2 of floor area @ 50 Pascals expressed as < 5m3/hm2@50pa. Note that the volume of the building is based on the total volume within the building envelope as opposed to the sum of the volume of all internal rooms as is used for the Passivhaus standard.
[edit] Related articles on Designing Buildings
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- Airtightness of energy efficient buildings.
- Draughts in buildings.
- Energy audit.
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