Sucking Heat Through a Straw

When designing and constructing new homes and buildings limiting heat and cooling loss especially now is a top priority. However existing homes and buildings, particularly very old structures are a much larger problem.

Recently I was hired to perform and energy assessment on an antique town owned building. As is common in my part of the world old brick buildings are quite prevalent. In fact brick making was a major industry in the town I grew up in here in Connecticut. My father actually worked in one of factories as a summer job. He had a scar on his forehead from a brick he failed to catch as a memento of that summer's employment.

Brick is a great building material but a lousy insulator. It is marginally better than concrete as far as thermal transfer with an R value of less than one per four inches. What that means is brick for all intents and purposes does not insulate against thermal loss.

To demonstrate this principal here is a picture of an exterior wall which is at the extreme right of the photo. The heating duct, which is un-insulated, can be seen to the left at the ceiling. An un-insulated heating duct at the ceiling in the center of the room is like shooting yourself in both feet.  The duct is blowing heat toward the exterior wall.

Now looking at the infrared image of the photo we see how the heat distributes through the space. The upper portion of the wall is relatively warm, around 62 º F, but the lower areas are very cold around 47 º F. The heat from the ducts is not wending its way down the wall simply due to thermal dynamics. The cold wall is sucking up the available heat like water through a straw.

This phenomenon occurs in all homes and buildings to a varying extent. Depending on the insulation and amount of air infiltration it can be minor to significant.

A final thermal image from the exterior of building shows the heat loss from a different perspective. The differential is much more subtle, but detectable. The upper portion of the wall is about 3 degrees warmer than the lower. The front of building has been warmed from the sun. I have added a second palette of the image which more readily shows the temperature variations.

Depending on materials and construction the amount of thermal sucking action of a building can often readily be determined through thermal imaging. Infrared brings a whole new perspective on energy loss.

James Quarello
SNEC-ASHI President
NRSB #8SS0022
JRV Home Inspection Services, LLC

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