Testing your home for leaks

A long time customer recently purchased a home. The customer replaced a defective thermostat with a newer version that displayed interior humidity. The heat pump system in their home was a better than average two speed system.

As a point of reference, this is not an old home but one built with the past 10 years or so in Timbercreek.

We received a follow-up call a few weeks later reporting that the new thermostat was registering above 70% relative humidity. We told them that we expected 50% even though it had been raining daily.


After checking that the equipment was operating within expected limits, I recommended that the customer call a colleague who performs our duct testing in new construction.

Mark Kennedy

Mark Kennedy

Mark Kennedy with Home Energy Conservation scheduled an appointment with our customer to perform a ‘whole house blower door test’ and allowed me to tag along and watch. Before the technology was available that Mark is able to carry with him on the job, we would have had to crawl through the attic spaces looking for visible signs of damage or errors in construction, usually with inconclusive results. Now when we suspect building and/or duct leakage Mark is the first call we make.


Preparation for Blower Door Test

Mark affixed a calibrated blower into the open front door jamb. By exhausting the interior air at very high rates he created a vacuum in the home. This pulls warm or hot air through any defects in the building envelope. This allowed the use of his next bit of magic – Infra-red imagery in real-time.


Uninsulated areas of the ceiling where the wall joins – normal for 10 year old homes

Two hours of inspection revealed many openings that he included in his report to the homeowner. I have included of few of the images from that report:

Doggy door

Doggy Door to garage area

Recessed ceiling light fixture

Leaking recessed ceiling lighting fixture. There were dozens in this home.

Plumbing wall openings at top plate

During construction the top plate was left unsealed around plumbing stacks allowing heat and moisture into the home


The largest leak was from an open flue on a gas fireplace

Most of the problems found on this inspection called for repairs by trades other than HVAC. Also, some of the leaks will not be practical to correct. But the reason I am posting this is to let you know that here is a relatively inexpensive method to discover definitive answers to where the moisture is coming into your home. Or why your heating and cooling utility bills are higher than you expect.

Mark found aluminum windows that are leaking, flooring that was not caulked to the baseboards, etc.

With a report such as this any homeowner can develop a plan that allows them to know up front what the costs of correction will be with a reasonable expectation of success.

Once this plan is complete we will follow up with a second test. With that new measurement, we will calculate the size of an outside air duct to pressurize the home. This duct pulls in outside air, dehumidifies it and allows it to exit at low rates through the leaks that remain to be repaired.

The customer can monitor the hygrometer on the thermostat to evaluate the effectiveness of the corrections. I will post the results in this space when we’re finished.

About Swinson AC Co

Residential Air Conditioning and Heating Contractor in Central Baldwin County Alabama and the Eastern Shore 964-9009 990-0998
This entry was posted in Air Conditioning, Ductwork, Humidity, Mold, Odors, Technology and tagged , , , , , . Bookmark the permalink.

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