The NEBB Professional – Summer 2013
Blower Doors and Thermography Provide
Effective Building Enclosure Testing
Colin Genge | CEO, Retrotec Energy Innovations Ltd.
The main points:
Blower Doors and Infrared Thermography
combine for effective measurement and location
of building air leaks.
Diagnostic procedures requiring Blower Doors,
smoke and Infrared Thermography will identify
performance problems.
HVAC balance must be addressed.
Audit procedures can effectively identify problems.
NEBB Procedural Standard for Building Enclosure
Testing provides clarity in training, certification
and audit procedures.
USACE pioneered quantitative large building
air leakage requirements with over 400 new
buildings tested to 0.25 CFM/sq ft.
Blower doors are used with smoke and thermography
to identify leaks in the air barrier. The effectiveness of
thermography is amplified when the building being
measured is under pressure, making leakage areas
easier to identify. Once leaks are identified and fixed,
the blower door is again used to measure the air
leakage to see if the building meets the air leakage
pass/fail criteria.
Reducing air leakage matters in your building because
higher leakage rates indicate increased energy costs
and indoor pollution. Air is driven through your building
whenever a temperature difference exists between
indoors and outdoors. The taller the building and the
greater the temperature difference, the more air is
pushed through your building. In cold weather, air
comes in from the street or garage level and then flows
upwards from one floor to the next. Building odors are
added in as the air moves up. In hot weather, the flow
is reversed.
Air is also driven through your building by wind. It enters
on the windward side and goes out the downwind side.
Higher floors receive a lot more wind than lower floors
because wind velocities increase with height and there
are fewer obstructions higher up. The pressure created
by this wind is enough to drive pollutants from upwind
units into downwind units. When upwind apartments
open their windows the flow through the building
Hallways are often pressurized with fans that blow
into the hallway while exhaust fans in the individual
units will add another layer of air movement. When
temperature differences are small and the wind is not
blowing, this mechanical ventilation is the dominant
air movement mechanism. When the temperature
difference and wind velocity increases, the air flow
patterns will be remarkably different and will often
overpower the mechanical ventilation.
Air leakage rates which contribute to the air flow
patterns in the building, are determined by subjecting
the building envelope to a constant pressure with
Figure 1: Large Building Enclosure Test with Retrotec calibrated fans