March 2017
Inspection Toolbox to include Blower Door?
Visual inspection is a mixture of subjective judgment based on information gathered from our five senses including
our gut feel and weight of experience. In other words, our judgment is limited.
Objective measures also have their limitations. The tools available include moisture meters, simulations, thermal
imaging cameras, Blower Door testing, materials and biological analysis. They are each limited. Thermal imaging can
only show temperature not moisture, and moisture meters don’t consider temperature.
Blower Door testing can show overall leakage rates related either to the internal air volume of the building, or the
surface area of the building. It doesn’t measure mould, wet, dry, decay, structural integrity, material composition or
age. It does give an objective number of air changes per hour at 50 pa pressure difference. What you do with that
number becomes subjective.
• It does give an indicator of thermal performance (subjective).
• It does give some indication of wetting and drying capacity of the structure though we would argue the
reason for wet structure could easily be due to lack of airtightness (subjective).
• It can give an indication of indoor air quality (other measurements also required).
• It will be an indicator of flanking sound pathways for acoustics.
So, what use is a Blower Door test of airtightness and its measurement? Firstly, the principle of draft stopping is
simple. Drafty buildings are uncomfortable. Draft stopping is the same as airtightness, just at a different point on the
continuum because ‘The more controlled [comfortable] the environment, the more liveable it becomes.’ Secondly,
drafty buildings cost more to run and are by default less durable.
So, why wouldn’t a Blower Door test for airtightness be part of the inspection toolbox? We would suggest it is
an important consideration, especially for newer buildings. An objective measure of existing buildings against
internationally recognized standards provides another weapon in understanding and predicting performance.
For more information, please visit www.blower-door.co.nz or call 0800 776 254.