Thermal Building Inspections 

Building inspections have become more popular since Part L of the latest building regulations recommended thermal checks on new buildings for losses. HIPS inspections can also involve Thermal Imaging.

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 include:

• 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

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 mould 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 an infrared imager, 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.

Infrared Inspection of Roofs

Flat roof membranes are the waterproof barriers between the outside elements and the interior of buildings. They come in a variety of materials and designs, and must be able to expand and contract, resist high winds and the effects of solar radiation and withstand foot traffic. It is easy to see why roofs leak.

Normally there is little or no water within a flat roof assembly. When a leak develops, water enters the assembly and, depending on the type of insulation system, is either absorbed by the insulation or runs to the cracks between the non-absorbent insulation. When water enters the roof assembly it is there for a long time, sometimes the life of the roof.

Thermal capacitance is the physical property of a material’s ability to store heat. The materials in roof assemblies have relatively low thermal capacitance, especially when compared to water. Water requires a lot of energy to raise its temperature and likewise must release a lot of energy to cool.

The physics used for thermal roof inspections is that dry roof insulation heats up and cools down faster than wet roof insulation. Infrared inspection goes beyond simply finding a leak by locating the extent of the moisture invasion of the insulation. To do this we require solar heating of a sunny day. Then at night, after the sun goes down and the roof surface begins to cool, the dry roof insulation cools faster than wet roof insulation.

• Was it a clear sunny day?

• Is it a clear night (for good radiation cooling)?

• Is there little or no wind?

• Is the roof surface dry?

• Is the roof clear of snow, dirt and debris?

The type of insulation used on a roof will result in an infrared image that is characteristic of how that particular insulation absorbs water. Absorbent roof insulation acts similar to a sponge. The water migrates by capillary action throughout a complete roof board before it jumps to the adjacent board. This results in a checker board thermal pattern.

Non-absorbent roof insulation creates a much different pattern when it becomes wet. The water is not absorbed and runs to the edge of the roof board. The water tends to collect at the edges of the boards resulting in a window frame pattern. Different patterns may result from other less common insulating systems.

There are many conditions that can produce thermal patterns that may look like they were created by wet insulation but are not, and others may mask the true condition of wet insulation. The ASTM specification C-1153 titled “Location of Wet Insulation in Roofing Systems Using Infrared Imaging” suggest performing verification of suspected wet insulation by core methods. The following are some examples of situations that may result in poor infrared inspections:

• Insulation with different R-values or different absorption characteristics which are commonly found in repaired areas

• Different internal building temperatures

• Extra gravel or bituminous left from construction

• Warm or cold air exhausting onto roof

• Re-radiation of heat from south or west facing walls

• Wind

• Internal sources of heat or cold such as lights, heaters, and steam pipes

• Dirt, vegetation and debris

• Walkway pads and buried steel plates

• Blisters

• Water ponding, steam plumes and water spray

During the winter thermographers use the same process, however, winter surveys are more difficult because the temperature differences are usually less than on summer surveys (5°F vs. 20°F). If the building is heated, the added heat flow from the building through wet insulation will help enhance the winter thermal patterns.

Moisture Detection - A key to Prevention of Mould Growth

Mould has existed in our environment long before the recent awareness of its presence in homes and businesses. The impact of mould on health is dependent upon the concentration of spores in the immediate area and the allergic effect on an individual. Potential health problems associated with mould exposure can take the form of allergic reactions or asthma. The problem is not limited to homes. Commercial buildings with moisture accumulation due to condensation or leaks are a candidate for mould growth.

According to the U.S. Environmental Protection Agency, there is no practical way to eliminate mould spores in an indoor environment. The best way to control mould growth is to control moisture. Mould can begin growth in as little as 24 hours. Roof leaks and water pipe leaks are common sources of water accumulation that may cause mould growth. Mould has closed public schools and caused companies to spend millions of dollars on environmental tests and remediation. Clearly, there is more reason to become aware of roof conditions, before water begins dripping on a building owner’s head.

Moisture present in roofs and walls can be detected with a sensitive infrared camera under the right conditions. Infrared roof inspections are performed most effectively after sunset, when the roof gives off its heat energy accumulated during the day. The heat capacity of moisture soaked roof insulation is greater than that of dry insulation. As a result, the moisture soaked roof areas appear quite clearly when performing an infrared scan.

Similarly, it is possible to detect moisture located behind interior walls with an infrared camera, under the right conditions. The temperature difference created by the presence of moisture on the inside surface of a wall will appear differently than the surrounding area.

Infrared inspection is a fast, non-invasive method to discover moisture intrusion within the building envelope. It  does not directly detect the presence of mould, rather it may be used to find moisture where mould may develop. The limitations to obtaining accurate infrared images pertain to the ability of the surface being scanned to emit heat energy. Gypsum (dry wall) in interior walls emits quite well, whereas highly reflective surfaces do not. Since the temperature difference between the wet and the dry wall are very slight, a sensitive infrared camera must be used.

The Thermogram shows a burst hot water pipe behind a skirting