The nature of the weatherization business is that improvements are largely invisible. Over time, occupants of weatherized homes will notice comfort improvements and reduction in their energy bills, but the installers and overseers of weatherization improvements need quicker and clearer feedback.
Furthermore, identifying opportunities for weatherization is often a bit of a guessing game for all involved. Comfort complaints and visible problems can indicate some opportunities, however other less apparent opportunities are usually missed with a simple walk-though and interview with an occupant.
Fortunately, there exist tools and techniques that can address both issues. And these tools have become more available as prices have come down and investment in this industry has gone up.
Diagnostic use of infrared cameras and blower doors is the key. And in combination, these two tools offer much more than the sum of their individual parts.
The largest component of energy loss in many buildings is air leakage. On its own, correct use of a blower door and manometer can precisely measure just how large this opportunity is, and investigators can – by feel – locate the exaggerated drafts created by the blower door.
Trained users of infrared cameras can – on their own – find some thermographic signatures of air leakage in a home, but only when drafts are flowing strongly enough in the right direction that the temperature of surfaces near the leak are changed due to the difference in temperature between the ambient air and the leaking air.
From the inside of a building, thermographic signatures of air leakage at the middle and upper half of a building are just not available under natural conditions. While they may be available on the outside of the building, this less controlled environment and the difficulty of observing roofs and ceilings make thermography less effective from the outside.
When an infrared camera is used while a blower door is running, the images change dramatically. The exaggerated drafts now come inward through the entire home which is kept a constant pressure by the blower door. The resulting infrared images illustrating air leakage will be clear, dramatic and consistent.
I have inspected hundreds of homes – both new and existing. Most new homes I look at are being qualified as ENERGY STAR Homes. Even though I verify many required thermal bypass prevention techniques at pre-sheet rock inspections, when the final inspection comes, I still often find overlooked thermal bypasses during an infrared and blower door inspection. My point is that even the best visual inspections during new construction can still miss things that can be caught by a combined infrared and blower door inspection.
The builders that I work with try to maximize building energy performance as predicted through HERS(Home Energy Rating System) Rating, and finding more air leakage to eliminate is very important to these builders. I will sometimes hand them the IR camera and let them continue to hunt for air leakage while the blower door runs as I go about the rest of a HERS Rating. This opportunity to learn is only available through the combined use of the blower door and infrared camera, so I’m happy for them to take advantage of it as long as I am on site.
For existing homes, the same techniques can be used to identify air leakage issues that are completely hidden from sight otherwise. And, of course, the thermal camera can verify the presence, absence or ineffectiveness of insulation in the building cavities at the same time.
Unexpected circumstances come up frequently and there are many ways that images and blower door findings can be misinterpreted, so training and certification in the use of both tools is very important. Training and certification for general building science including the correct use of blower doors is available from BPI and RESNET in week-long courses.
Training in infrared thermography is not provided as part of these programs. So, in addition to general building science and blower door training, I recommend taking a certification course on the use of thermography for weatherization.
A dedicated individual with this training and certification will be very well equipped to identify and verify the most thorough and effective improvement work in this increasingly important field.
Mike is the principal of Advanced Building Analysis, LLC and will be teaching introductory courses in the combined use of thermography and blower doors through special 1 day workshops arranged by NESEA. The first of these trainings is scheduled for April 22 in Manchester, NH. For more information and to register please contact Pamela Lester at NESEA at 413-774-6051 x 14 or [email protected] .
