Week 2 Understanding Infrared Imaging
Answer the following questions about infrared images (you can rename this Word
file and type right into this document to record your answers), if there is something
you are not sure about after reading the Solutions which appear below, please send
your answers via email to mduclos@deapgroup.com
Above on the left is a photo of an interior wall finished with horizontal tongue &
grooved paneling. The right photo is an infrared image taken after a blower door has
been running for several minutes to bring cold air in through leaks in the building
envelope. Darker colors such as red and purples in the infrared image indicate
colder areas; lighter colors such as yellow and near-whites indicate warmer
temperatures. Would you say that the cold spots are predominantly a result of
thermal bridging, or of air leaks? Why?
Here are two images of a sloped ceiling area on the third floor of a house, in a
finished space in the attic. As before, the infrared image is on the right, and darker
areas are colder. A thermal bridge would be the result of a solid conductive material
penetrating the thermal boundary (such as a wood rafter or a steel beam); an
insulation void would be a space in a framing cavity in the building enclosure that
should have been insulated but wasn’t (such as an empty rafter bay or stud bay). In
this case, would you say the cold spots are a result of thermal bridges or of
insulation voids?
Here on the right we see a sort of mottled texture on an exterior wood-frame stud
wall. Do you think the dark (cold) spots are the result of a thermal bridge, or an
uneven blown-in insulation project?
Here we see an exposed masonry chimney in a kitchen. You can see in the righthand thermal image that the chimney is the coldest surface in the room. The
chimney carries down through the plane of the insulated basement ceiling to the
basement floor. It also extends up through the insulated attic floor through the
roofline above. Would you call this a thermal bridge? What do you think some
strategies for dealing with this would be?
In this final infrared image on the right (this time in gray scale, which is a more
traditional but less flashy way of presenting these images), you can see the vertical
lines of the wall studs. They read lighter than the adjacent wall cavities, which
means they’re warmer than the adjacent wall cavities. Why would this be? If the
studs read warmer than the wall cavities, can they still be considered thermal
bridges?
Solutions start on the next page !
Week 2 Understanding Infrared Imaging – Solutions
Answer the following questions about infrared images (you can rename this Word
file and type right into this document to record your answers), if there is something
you are not sure about after reading the Solutions which appear below, please send
your answers via email to mduclos@deapgroup.com
Above on the left is a photo of an interior wall finished with horizontal tongue &
grooved paneling. The right photo is an infrared image taken after a blower door has
been running for several minutes to bring cold air in through leaks in the building
envelope. Darker colors such as red and purples in the infrared image indicate
colder areas; lighter colors such as yellow and near-whites indicate warmer
temperatures. Would you say that the cold spots are predominantly a result of
thermal bridging, or of air leaks? Why?
The darker colors are due to air infiltrating from the outside driven by the pressure
difference caused by the blower door. Likely the rough opening of the window is not
air sealed (it may even contain counter weights, or ‘sash weights’ in a very old
home) and so more air is infiltrating near the window through the tongue and
groove paneling.
Here are two images of a sloped ceiling area on the third floor of a house, in a
finished space in the attic. As before, the infrared image is on the right, and darker
areas are colder. A thermal bridge would be the result of a solid conductive material
penetrating the thermal boundary (such as a wood rafter or a steel beam); an
insulation void would be a space in a framing cavity in the building enclosure that
should have been insulated but wasn’t (such as an empty rafter bay or stud bay). In
this case, would you say the cold spots are a result of thermal bridges or of
insulation voids?
There appear to be areas behind the drywall that are missing insulation. The
warmer areas appear to be rafters and strapping, which have a higher R value than
air. It is likely air is freely circulating behind the drywall cooling the surface of the
drywall by convection, because there is no insulation there to impede the
convection.
Here on the right we see a sort of mottled texture on an exterior wood-frame stud
wall. Do you think the dark (cold) spots are the result of a thermal bridge, or an
uneven blown-in insulation project?
The irregularity of the colder spots presents the appearance of a poorly installed
blown in insulation. Thermal bridging caused by wall framing is much more linear
and regular. Dense packing using the tube method properly done would result in a
much higher quality installation.
Here we see an exposed masonry chimney in a kitchen. You can see in the righthand thermal image that the chimney is the coldest surface in the room. The
chimney carries down through the plane of the insulated basement ceiling to the
basement floor. It also extends up through the insulated attic floor through the
roofline above. Would you call this a thermal bridge? What do you think some
strategies for dealing with this would be?
This appears to be a fairly strong thermal bridge, conducting heat from the living
space not only up and out of the house, but also down into the basement. There
could be a significant convection loop carrying heat up along the sides of the interior
walls of the chimney, with cool air falling down the middle of the chimney to replace
it. Removing the drywall and installing some type of fire rated insulation (such as
mineral wool board) against the chimney would reduce the heat transfer from the
conditioned space. If this home were undergoing a heating system change, possibly
as part of a Deep Energy Retrofit project, it might be possible to remove the
chimney, by far the best solution, which would reclaim some living space lost to the
chimney, or it could be used as a duct chase for a ventilation system on the floor
above.
In this final infrared image on the right (this time in gray scale, which is a more
traditional but less flashy way of presenting these images), you can see the vertical
lines of the wall studs. They read lighter than the adjacent wall cavities, which
means they’re warmer than the adjacent wall cavities. Why would this be? If the
studs read warmer than the wall cavities, can they still be considered thermal
bridges?
The vertical white bars appear to be studs, and it appears to be heating season. It
appears the wall cavities are mostly or entirely un-insulated, and so the wall surface
over the cavities are cooler than at the studs, because the wood is a better insulator
than the air in the cavities.
At first glance this might appear to be a cooling season situation, with sun on the
exterior walls and the studs acting like a thermal bridge to conduct the sun warmed
exterior wall heat to the interior. The tip-off is that the bedpost is most likely at
room air temperature, and it is much warmer than the studs.