What is a blower door testing and how does it work?
Please find below the answer to some common questions about the blower door testing:
Blower door testing , also known as Air Leakage Testing or Air Tightness Testing, is the process of measuring the amount of conditioned (heated or cooled) air leaking from a building through uncontrolled ventilation. A fan is installed into the external envelope of the building and supplies air into, or extracts air out of, the property creating a pressure difference. In simple terms, the amount of air going into, or out of the property when the building is subject to a pressure differential is the amount of air leakage. The result can be described as the air permeability. The process is known as Air Leakage Testing . More about Air Leakage Basic in the manufacturer’s knowledge base.
How does a blower door system work based on the power law equation?
The fan motor and blades push air out of the building with the fan sensor located where the air is being pulled into the fan [more on this below]. Channel A reads the hose pressure [with the reference outside], while Channel B measures the pressure at the fan sensor and just upstream of the sensor, converting this pressure difference to flow.
NOTE: The relationship between the pressure difference inside to outside the building and the air flow resulting from the pressure difference can be expressed by a power law equation:
Q = CΔpn
Q is the flow (cubic feet per minute), C is a constant, P is pressure, and n is the exponent of the power law equation.
The exponent can vary between 0.5 and 1.0, with essentially big holes in the building making an exponent of 0.5 the best fit (curved line) and very tiny holes making the exponent of 1 the best fit (a straight line). The cool thing about this power law equation is that it is just about the relationship between pressure and flow. Yes, other factors such as temperature and air density have impact, but they are easy to correct for and don’t fundamentally affect the pressure/flow relationship.
Who is authorized to perform an Airtightness Test?
The testing organization or the individual shall hold the following accreditation or equivalent at a minimum:
- Being ATTMA Registered Air Tightness Testers.
- Holding UKAS (or national equivalent) accreditation specifically for building air leakage testing in line with BS EN ISO/IEC17025:2005 (ISO 17025)
- Having an active registration with a nationally recognized competent person scheme (CPS).
How to become ATTMA Registered Airtightness Tester?
Salimus Consultancy DMCC is the only ATTMA Airtightness Training Partner in the Middle East, and one of the few companies in the Middle East to be certified by ATTMA to carry out Blower Door Test for Envelope Tightness Verification. We are providing ATTMA Air Tightness Testing training courses. You can view the schedule and contact us to sign up for the next steam.
Can blower door test be carried out with a duct pressure tester?
Yes, it can be carried out for homes and spaces in the range of 3 to 5 ACH50. While testing the multi-family units (in the range of 3 to 5 ACH50), we can literally leave the fan in the panel as you move it from floor to floor and unit to unit, assuming that the unit entry doors are the same size. The real change between the blower door and the duct tester / blaster is the shroud. TEC’s duct blaster is famously called as a mini-blower door.
Based on article Deep Dive into Blower Door Testing where Peter Yost interviews Collin Olson from The Energy Conservatory and learns about the blower door equation exponent, depressurization vs. pressurization, using sound to assess air leakage.