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.
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 toss 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.
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.
Virtually anywhere in the building envelope where there is a joint, junction or opening, there is potential for air leakage. An experienced thermographer 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.
