Condo Media - February 2013 - 28

by Bret Monroe
and Lew Harriman

TECHNOLOGY

Heat Seekers
Thermal Cameras and Commercial Building Inspections
fter years of confusion and
fear of technology, the worldwide interest in reducing energy consumption has put a new
emphasis on diagnosing the location
and extent of heat leakage into and
out of building enclosures and on
troubleshooting potential structural
issues or damaged locations. Thermal
infrared cameras have become standard
tools for the building inspections
focused on these issues.
Consider a simple example of a hotel
stairwell with an odor problem. The
infrared camera shows a temperature
pattern, which suggests that cool water
is escaping the fan-coil unit’s drain pan
and wetting the carpet. Such wet
materials grow the mold and bacteria,
which produce odors.
The images below show an example of
outward air leakage from the top of a
tall building due to the stack effect during cold weather. Warm air escaping
through open joints near the top of the
building creates a slight suction at the
base of the building. Cold air leaks in at
the base of the building to replace the
outward-flowing air at the top, resulting in wasted energy and cold drafts.

To understand the use and the limitations of infrared imaging for moisture
detection, it helps to understand
infrared energy and the cameras, which
can see it.

Thermal Cameras

All surfaces above absolute zero emit
electromagnetic waves in the infrared
region. These wavelengths are almost all
much longer than visible light, although
at the edge of human perception,
infrared laser pointers emitting light at
about 0.75 microns are a familiar technology. Slightly beyond that wavelength
are the near-infrared waves, which can
be seen with “night-shot” image
enhancement in conventional video
cameras. Then, 10 times longer than
those wavelengths and beyond the range
of conventional optics are the middle
infrared wavelengths between seven and
14 microns. This range is called “thermal infrared” because when surfaces are
between -40° and +400°F they emit
quite a bit of radiation in this range.
The strength of their emission can be
sensed and measured with special optics,
and used to show surface temperature
patterns.
Infrared technology was
developed originally for
military purposes. It’s the
basis of heat-seeking missile guidance systems. But
the cost of thermal imaging cameras has come
down as economies of scale
have reduced manufacturing costs. For example, the
cost of a camera with a
low-res imaging array of
160 x 120 pixels has
dropped from over $20,000
Warm air escaping from open joints shows the location and relative
magnitude of heat leakage from a tall building during cold weather.
10 years ago to less than

CONDO MEDIA • FEBRUARY 2013

$3,000 today. And the cost of a highres camera with a sensor of 320 x 240
pixels has come down from $40,000
10 years ago to between $8,000 and
$12,000 today, depending on which
features they include. These more economical prices have made thermal
cameras cost-effective for moisture
inspections as well as more complex
energy investigations.

Inspection Examples
Let’s suppose a pipe breaks in an
office. After the obvious water is
removed with wet-vacuums, the building is surveyed in preparation for drying. After water ponds on the floor, it
wicks up into the wall board, pulled by
capillary suction. The thermal camera
shows the moisture pattern as a band
of cool surface near the base of the
wall. That’s because the evaporating
moisture takes just a bit of heat from
the wall itself. Modern infrared cameras can resolve a temperature difference of less than 0.2°F between
adjacent pixels, so the fact that the
moist area may be only 1.5°F cooler
than the rest of the wall is no obstacle
to forming the image.
It’s interesting to note the insulating
effect of the base molding. Of course
the wall board behind that base molding is still wet. But that fact is not perceptible in the infrared image. This
illustrates the important point that
these cameras do not “see inside
walls.” Nor do the camera images
“penetrate” into the wall. Although it
shows very useful images, an infrared
camera can only see the patterns created by the emission of infrared energy
from surfaces. Meters must be used to
confirm the presence of excess moisture. Then the investigator’s skill must

Condo Media - February 2013

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