What Does Air Permeability Test Mean In Construction
What Does Air Permeability Test Mean In Construction
Air permeability testing is a method used to measure the rate of airflow through a material or building structure. It is used to help product development, including for automotive filters and performance clothing, as well as to increase the energy efficiency of buildings.
The air permeability test measures the air leakage rate per hour per square metre of envelope area at a test reference pressure differential across the building.
Air tightness testing is a practice used to measure the amount of air that escapes through gaps or building fabrics of dwellings. It determines the amount of air leakage in cubic metres per square metre of internal surface area of the building m3.
Air tightness testing is required for all new builds both domestic and non-domestic, in addition to the requirements detailed in Part L of building regulations sections 1A and 1B. Blower door testing equipment is installed to pressurise the dwelling and measure air leakage rates.
How Does An Air Permeability Test Work?
An air tightness test is used to measure the air leakage in a building. The test involves using a fan to pressurise the building, and then measuring the pressure difference between the inside and outside of the building.
The fan will typically depressurise the house to a pressure of at least -60Pa. An anemometer will read the internal pressure, external pressure and the strength that the fan has to work at to create the pressure difference. This will help to calculate the air leakage.
Air Permeability Test Standards
To assess the resistance of textiles to the flow of air, industry standards like ASTM D737 and DIN 53887 are followed. The former applies to woven and knitted fabrics, whereas the latter is used for nonwoven textiles.
These standards specify the methodology for measuring air permeability using an Air Permeability Tester, which subjects the sample fabric to a constant, preset air pressure to gauge its air permeability. The results of this test are expressed in SI units as cm^3/s/cm^2 and in inch-pound units as ft^3/min/ft^2, rounded to three significant figures.
By complying with these standards and conducting the test using the recommended equipment, fabric manufacturers can determine the air permeability of their products, aiding in product development and quality control.
Air Permeability Test Procedure
The procedure for an air permeability test involves measuring the rate of airflow through a known area of material by applying a known pressure differential across the material.
This is usually expressed in terms of air velocity (mm/sec), but can also be direct instrument readings of volume of air permeated per second.
Air permeability tests are generally conducted for no longer than one day, although for larger sites long term testing may be recommended.
The Frazier test method is commonly used to measure the air permeability of nonwoven fabrics, in accordance with standard test methods such as ASTM D737 and DIN 53887.
Air permeability tests can be conducted using a James Heal AirPro tester, following any of the above test methods. Factors that influence the air permeability of a material include its density and structure.
