Thermal imaging and dampness

penitrating damp
penetrating damp

When assessing excess water in a building you have two main categories of non-destructive site tools available: Moisture meters and thermal imaging camera to assess dampness.  The thermal imaging camera can find problems early, allowing them to be recorded and corrected before becoming serious and more costly repairs.

It is important to remember thermal imaging cameras cannot directly detect dampness, but they see thermal moisture pattern images and it’s the shape of this pattern which helps in the diagnostic process in conjunction with a conductivity moisture meter which uses  two pins to measure the conductivity between the pins on the surface to be tested for dampness.

penetrating damp from roof parapet defect
roof parapet causing penetrating damp

When using an infrared camera, you create a thermal imaging of a building dampness defect this helps the inspector to understand the problem by supplying a thermal pattern of the defect, which maybe outside the human visible light spectrum. also, thermal imaging is a rapid non-invasive dampness diagnostic method.

How does the camera work?

It detects infrared radiation emitting from an object it energy which is radiant, conduction or convection, the camera detects this using a sensing chip which has thousands of detectors and at the same time it creates a pattern of temperatures on a surface (using and mathematical formula) in to thermal image of the area.

hidden down pipe
hidden down pipe

In a building inspection the thermal imaging camera can help

  • Find defects in underfloor heating systems
  • See areas of energy loss
  • Detect missing or defective insulation
  • Find air and dampness infiltration points
  • Detect moisture in insulation, in roofs and walls, both in the internal and the external structure.
  • Detect mould and badly insulated areas in the building
  • Locate thermal bridges in the building
  • Find water ingress in flat roofs
  • Detect escapes of water in hot-water pipes
  • Show thermal pattern to help detect construction defects.
  • Help in the monitoring of the drying out of buildings
  • Detect activity in insect hives etc.

Something to keep in minded when investigation.

external thermal image

To get good infrared imaging at 10oC temperature variation is needed.  Therefore, it is better to carry out this work outside the summer period.  Using an infrared camera during daytime to assess a building should be avoided due the effect of solar radiation which is massive and shading effects of clouds on the building as the camera is extremely sensitive.  The camera is most accurate when it is used a 90 degree from a surface.

The emissivity of a material affects the accuracy of temperature given by the camera and there is an entire range of there settings.

Working inside a building removes some of the issues created by the sun.  The warmer the building is internally the better the data you get in the thermal image.  Were possible create an under pressure in the building, this will massively improve thermal data and help find areas were moisture can penetrate the building.

corner thermal problems

Corners and other surfaces will create anomalies. For instance, you will see yourself thermally in the glass of a window.  At night when inspecting lead flashing I could see my high vis jacket.  Corners my look dark on the camera screen but you can check this out by holding the camera parallel to the wall.  One time I found a hot spot on a floor with underfloor heating, but it turned out that it was due to a young child sitting on it.  To show how sensitive the camera can be I pointed into a dark steading and suddenly saw a hot spot moving around, it was a blue bottle flying around.  Carry out the inspection by yourself as operator is a source of energy.

By taking the camera of auto it will stop it recalibrating and changing the temperature span.  This helps in better understanding the thermal images.

The colour palette you select for the inspection is important in helping you decide whether the is a minor problem or a significant problem.  I my opinion the high colour pallet is good for a quick assessment, but you should then switch to the Iron colour pallet to assess the significance. 

You must continually question the data you are receiving during an inspection and do they match the real world.

Defects in underfloor heating

underfloor heating
underfloor heating

In a radiant flooring heating system, heat is provided by hot-water pipes or electric wires in the floor. As the thermal energy moves due to conduction, they warm up any surface around then the air above by convection and radiation.

This system is good as it does not take up space like other wall mounted heating systems.  But their invisibility can also be a problem as how can you find where the defect is with the underfloor heating system? The only rapid and efficient way you can do this is by using thermal imaging.

Defects in insulation

Finding defects in external insulation can be more challenging than internal insulation due to the effect of solar radiation during the day.  By heating the building internally during the cold months and inspecting the area at night you should get some usable images due to conduction.  Due to the chilling effect of the wind on the building envelope the thermal imaging should also be carried out on a still night.

missing insulation
missing insulation

Internally the quality of the insulation installation can be relatively easily to assess, except where it has been installed within the cavity of a wall.  This is done by heating the building and then creating an under pressure.

Air leakage of the building.

A blower door fan is used to assess air leakage in a building
blower door fan

Air leakage is uncontrolled ventilation, and excessive air flows into the house during windy and wintry weather due to over pressure on one elevation and under pressure on the opposite side, this creates a suction effect on one side of the building and air (which may be damp) is rapidly draw into the building.  This leads to heat loss with cold draughts.

A blower door test will give air leakage information and combined with the infrared camera will help find defect areas and direct repair measures. 

This air tightness test is now used to detect the amount of air which is lost through leaks in the new building’s as they use high-quality insulation which needs an unbroken air/vapour control barrier to meet high U values.

Nigel Foster