Building Science-Heat Movement in Pictures

I’ve talked a few times on this blog about how a home can lose heat in a cold climate. Thermodynamics tells us heat moves from a warm space to a cold one by one of three methods; convection, conduction or radiation. This blog is going to show visually how a structure loses heat by way of several thermal images photographs.

We can’t completely stop heat loss.  Increasing the R-value of surface will only slow the loss.  Building codes have been changing, and a lot of those changes are because of a better understanding of building science.  In my climate for example, wall insulation recently increased from a minimum of R-19 to R-21.  Now that’s not a big change, but over the life of the structure, it will add up.  Another recent code requirement, buildings are required to meet a certain air tightness value.  Same thing, over the life of the structure, there will be a reduced energy need along with added comfort and if done correctly, a more durable structure with better indoor air quality.  The following pictures show the movement of heat through our buildings.

An uninsulated concrete block basement at -10 degrees.

I’ve shown this picture several times on both Instagram and on this blog. This shows heat moving from a conditioned or warm basement through concrete and to the outside during a very cold day. The scale on the right side of the pic shows the temperature range, from -7.5° F to 13° F. The temperature of the air at the time of the photo was -10° F. The basement wall is 23° warmer than the air temperature. Loosing heat!

Radiant heat in a garage slab with two rows of uninsulated concrete block.

This picture looks very similar to the last. I was called to this property for an energy audit and learned that this garage had in-floor heat tubing connected to an electric boiler. The slab was heating two rows of concrete blocks secured on top of the concrete slab by way of conduction and then moving the heat to the outside. Not an efficient way to heat a structure!

eThermal Imaging of cold air infiltration under poorly sealed bottom plate.

Another picture I’ve shown before on this blog. This photo was taken with my blower door in operation during a test of a home built in the 1930’s. The flooring systems of that time would have included 2x floor joists and 1x floor boards run diagonally across the floor joists. Sill seals at the bottom plate were not used. All the small gaps in the 1x board extending to the outside create spaces for air to move into the home. Stack effect would equalize the pressure of the home by moving conditioned air out of the building, through the roof and upper areas. Heat loss though air movements-convection.

A woodstove in operation.

This picture shows the heat produced by a woodstove. Notice the different purples on the brick walls near the stove. The lighter purple is heat moving from the woodstove to the brick. This is an example of heat moving by radiation. Both these walls are exterior and the heat will be moved by conduction to the outside where the temperature is much cooler.

Thermal imaging of recessed light fixtures during a blower door test.

Recessed lighting installed in an unconditioned attic are notorious for leaking air. This photo shows air moving through the fiberglass insulation present in the attic, through the fixture and into the room while conducting a blower door test. When the blower door is not running the opposite occurs. Heat during the winter months will move up through the metal housing and into the attic. Heat produced from an incandescent light bulb will act like a chimney and intensify the stack effect.

A roof truss separating conditioned and unconditioned space.

This pic shows an unconditioned attic on the other side of this wall. The purple lines are framing members of the truss which are causing these areas to be cooler. I have been in homes where the owners smoke or burn candles and a faint line appears on the surface of the drywall, usually on a ceiling, where each wood framing member is located. This is called ghosting and is caused by the colder area being damper than the surrounding surfaces, which hold the fine particulates produced from smoke or candles.

A thermal image of the outside of a building during the winter.

This photo shows the 1952 Cape I recently purchased. I was aware of the heat loss through the roof, was a little surprised at the heat moving through the side wall of the shed roof dormer. A lack of air sealing where the roof and side wall meet is causing conditioned air to move through the framing. Something I will be fixing (and blogging about) next summer.

Thermal image of a standard electric water heater. The purple pipe is the cold incoming water and the yellow is hot outgoing water.

A good picture of an electric hot water heater losing heat. In my energy audit report, I usually suggest using pipe insulation and a water heater blanket to reduce heat loss. I’ve heard the argument that losing some heat doesn’t amount to much because it is helping to heat the building. That statement is true, but…the purpose of this electric water heater is to heat water, not condition the living space, and heating with electricity is one of the most expensive ways to heat a home.

I have many more thermal imaging photos that I will periodically share in future blogs. I also post several photos each month on my Instagram account. Follow me at Northernbuiltpro.

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