Energy Audit – Blower Door, Thermographic or PFT Testing?

The blower door, thermographic scan and PFT air infiltration are the three main tests that are commonly used in professional energy audits. These help an auditor identify where in your home energy efficiency can be improved, particularly when it comes to air leak. What is the difference between these tests and which one is best?

If you don’t know what an energy audit is you can read the following article first: What is a Home Energy Audit?


The importance of airtightness in a home

An airtight home is much more efficient when it comes to maintaining a comfortable temperature in your house than what one that hasn’t been optimized yet is. There is a lot of money to be saved.

There are several other reasons why you should make sure that your home is not leaking air as well:

  • Eliminating annoying air drafts.
  • Reducing the chances of moisture and condensation.
  • Stopping outside pollution from entering the home.

These test are also used to verify that energy code requirements are met.

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The Blower Door Test

The blower door test is the most common test in an energy audit. It is an excellent test in helping to determine how airtight a house is.

Blower door audit

How a blower door test works

When all windows and doors are closed a powerful fan (mounted to a door) is switched home and either pressurized or depressurizes your house. What this means is that there is a pressure difference between the air inside your house and the air on the outside.

By the laws of physics, air starts flowing in to or out from the building (depending on whether the fan pressurized or depressurized the interior). An auditor can now easily detect air leaks by using smoke pencils (incense sticks).


Calibrated vs. uncalibrated blower doors

Make sure to ask the auditor if he/she will use a calibrated or uncalibrated blower door. We highly recommend going with an auditor that uses one that is calibrated.

While uncalibrated blower doors can detect air-leaks, an uncalibrated blower door is also capable of provide quantifiable data of how air is seeping out, which means the effectiveness of a sealing job also can be determined.

You should make sure that the auditor uses a blower door that is calibrated. This is a crucial and if not satisfied, choose another auditor.


Perfluorcarbon Tracer Gas (PFT) Test

The perfluorcarbon tracer gas test is another way to determine airtightness in a building. While a blower door test is measuring airtightness at the time of testing. However, this may not give a true picture on how the situation is under different weather variables such as wind velocities, temperatures and pressures.


How a perfluorcarbon tracer gas test works

An emitter is placed in a room or area of your house that is to be inspected for air leaks. This emitter starts to send out odorless, colorless and completely safe perfluorcarbon tracer gas. A receiver measures the concentration of the gas, which is data that can be used to determine air tightness.


Thermographic Scans

Thermographic images are very good at detecting energy losses in buildings by looking at differences in surface temperatures. It is an excellent way of determining whether or not a building should upgrade insulation.


How thermographic imaging works

A thermographic camera can be used to make thermograms, images where the infrared spectrum of light is measured. This information says something about how warm or cold a surface is. By looking at the differences, we can easily determine thermal defects, which fixed or improved.


Exterior or interior scans

Thermal imaging can be taken from both the exterior and interior of a building. Whether or not the energy auditor chooses exterior or interior is often a result of weather.

Also keep in mind that interior scans more easily pinpoint exactly where the leaks are. This is due to heat transferring through the walls is not always in a straight line. Interior thermal images are in most cases the best way.

Not all auditor companies are willing to do a thermographic scan. We recommend choosing an auditor that does these types of tests.

There are things you can do to test for air leaks without have to hiring a professional energy auditor. Read our How To Detect and Seal Air Leaks at Home to find out more.

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Comments - 2


This is a really good analysis, the termographic cameras are perfect for this

June 26, 2012 10:50 am Reply

Elion Technologies

Elion technologies carry out Thermography on your installations in a fast and cost-effective way to locate faults on your equipment with no disruption to the running of your business.

February 13, 2015 10:20 am Reply

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