May 4, 2009

TONY COLANTONIO, PUBLIC WORKS AND GOVERNMENT SERVICES

Thermographs can capture air leakages from the tops of buildings

Technology

Imaging proving the right tool for moisture and mold

PETER KENTER

correspondent

Moisture and mold-related issues continue to stalk the construction industry, resulting in expensive remediation projects and the odd lawsuits.

The tool fast gaining a reputation as a way to nip those issues in the bud is the infrared imager which can pinpoint temperature anomalies to detect moisture inside a building envelope before it becomes a problem.

Like all technology, the devices continue to decrease in price as they improve in quality, complexity and ease of use.

“Over the past five years, equipment costs have come down due to the proliferation of low-resolution equipment in the 10,000 to 20,000 pixel range, said Tony Colantonio, Building Enclosure Architect, Public Works and Government Services Canada.

He said such low-res systems are suitable for applications where distance to object is less than five meters which is most interior inspections, especially for residential.

“With the availability of low-cost imagers, we’ve seen more and more restoration companies and builders using the technology,” he said

“While the price of the equipment continues to decrease, the cost and time commitment for proper equipment operation and inspection training hasn’t.”

And that’s key, he said, since disciplinary knowledge and training are more significant than the cost of the equipment in the successful integration of the technology into the construction industry.

Colantonio said thermography is an excellent tool for locating invisible defects, including electrical and mechanical system problems, hidden moisture accumulation within wall and roof assemblies, defective insulation, voids in wall and structural components, unwanted openings in wall and roof assemblies leading to air leakage, and pest infestations.

“All these defects can be identified with appropriate thermographic equipment in the hands of inspectors with expertise,” said Colantonio.

However, thermography requires specialized training, both in identifying the proper conditions for infrared thermography and in understanding the results of the inspection.

Last year the National Master Specification Directorate introduced four new sections dealing with thermographic assessments; 02 27 13 — Building Envelopes, 02 27 16 — Roofing, 02 27 19 — Mechanical Equipment, and 02 27 23 — Electrical Equipment.

They identify not only equipment requirements but also certification requirements for both equipment operators and report writers for each application.

Where there’s a lack of relevant standards, specific procedures are spelled out for each assessment application.

“Thermographic results also need to be corroborated by other methods,” said Colantonio. “Results are often suspect when inspectors don’t have disciplinary expertise in the area of their inspection. A visual inspection can sometimes help explain some anomalies found with thermography but good thermal images always help determine where to do exploratory openings.”

Exterior walls can be grouped into five distinct types: masonry, architectural pre-cast, metal and glass curtain wall, insulated steel assemblies, and—for low-rise and residential buildings—wood and steel frame.

“Within these generic types of walls there is considerable variation in the type of cladding, insulation and assembly configuration of components required to control moisture and air migration,” said Colantonio.

He added that vapour retarders control vapour diffusion while air barriers control air movement from the exterior through to the interior.

However, he said, air movement can transport 10 to 100 times more moisture through unintentional openings in the air barrier assemblies than vapour diffusion through the leakiest vapour barrier or retarder.

“You need to not only detect the moisture, but understand how it’s entering the building enclosure,” he said.

Among the questions to be asked: is the moisture coming from inside the building or entering from outside?

Placing buildings under positive or negative air pressure for extended periods of time can help to pinpoint breeches in the building enclosure, as moisture-laden air either enters or leaves the building, he said.

It’s imperative to differentiate the source of the moisture accumulation between interior and exterior sources, since remedial actions will vary considerably, Colantonio added.

Similarly, an inspector needs to differentiate between thermal patterns created by surface penetration of water, and patterns created by air leakage from the building interior in cold winter conditions.

A good thermographic scan also depends on suitable weather. Readings differ from winter to summer and in dry or wet weather. A thermograph (thermal image) taken shortly after a heavy rain will show significantly different results from one taken a few days later. Thermal images taken during the day will differ considerably from those taken at night. If thermal images are obtained under specific conditions, the inspector may only have a limited time to obtain meaningful results.

“We currently have 300,000 pixel equipment in the commercial marketplace and there are one mega-pixel cameras under development,” said Colantonio.

“As with digital camera development, we’ll see increased spatial resolution in infrared equipment over the next decade and it may be accompanied by better thermal resolution.

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