Building
Envelope
The primary
diagnostic procedure for determining the thermal performance of a building
envelope is infrared thermography. It can be used to identify heating and
cooling loss due to poor construction, missing or inadequate insulation and
moisture intrusion. Correcting the defects plays a significant role in
increasing building
efficiency and structural integrity.
Thermography can identify surface temperature variations of the building
envelope, which relates to problems in the structure, thermal bridging, moisture
content and air leakage.
Two primary mechanisms for heat loss in buildings are conduction through the
walls and air leakage. Both can be identified from the surface of the building
with infrared thermography. Early correction of the faults identified can be
made before extensive damage occurs.
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Conductive
Losses
Problems identified
as conductive losses are: missing insulation, improperly installed or compressed
insulation, shrinkage or settling of various insulating materials; excessive
thermal bridging in joints between walls and the top and bottom plates; moisture
damage to insulation and building materials; heat loss through multi-pane
windows with a broken seal; leaks in water pipes; damaged heat ducts; location
of, or leakage in buried steam lines, water lines or underground sprinkler
systems, etc.
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Air Leakage
Air leakage is the passage of air through a building envelope, wall, window,
joint, etc. Leakage to the interior is referred to as infiltration and leakage
to the exterior is referred to as exfiltration. Excessive air movement
significantly reduces the thermal integrity and performance of the envelope and
is, therefore, a major contributor to energy consumption in a building.
In addition to energy loss caused by excessive air leakage, it can cause
condensation to form within and on walls. This can create many problems; reduce
insulation R-value, permanently damage insulation, and seriously degrade
materials. It can rot wood, corrode metals, stain brick or concrete surfaces,
and in extreme cases cause concrete to spall, bricks to separate, mortar to
crumble and sections of a wall to fall jeopardizing the safety of occupants. It
can corrode structural steel, re-bar, and metal hangars and bolts with very
serious safety and maintenance issues. Moisture accumulation in building
materials can lead to the formation of mold that may require extensive
remediation.
Virtually anywhere in the building envelope where there is a joint, junction or
opening, there is potential for air leakage. With the use of the IR-InSight or
FlexCam S infrared imagers, one can identify thermal irregularities on the
building envelope and the thermal pattern discerning whether the pattern
indicates a problem with the insulation, air leakage or the building structure.
