Thermal Imaging

Thermal image from a domestic houseThermal images can give us useful information about how efficient our buildings are.  They can highlight potential problems as well as giving us re-assurance that things we have done to conserve energy are working OK.

CFB has its own thermal imaging camera and is happy to carry out surveys for householders, businesses and community buildings, including schools.  There is a small charge for household surveys, to cover our expenses.

If you would like to book a survey please email or phone / text: 07507 782523.

Understanding thermal images

What is thermal imaging?

A thermal camera creates a thermal image by converting invisible infrared radiation into an image we can see. Thermal imaging is an extremely effective technique for immediately detecting, visualising and recording temperature differences, heat loss and anomalies.

Thermal imaging is best done on a still, dry, cold night at least two hours after sunset. This is due to a number of reasons which you should be aware of when looking at your thermal image:

  • Wind can influence the thermal image, airflows cool down the surface material, lowering the temperature differences between hot and cold areas making it more difficult to pick out ‘hot spots’.
  • Rain or mist can lead to misleading thermal patterns, lowering surface temperatures. Even after the rain has stopped the evaporation of the water cools down the material’s surface.
  • The temperature difference between the inside and outside of the building should be at least 10 degrees C. If your photo was taken with a big temperature difference, heat loss from your building will be clearer; if the temperature difference was small areas of heat loss will be more subtle.
  • During the day, the walls of your house will store heat from the sun. This heat can take at least two hours to disperse after the sun has gone down. Different materials will disperse heat at different rates, so be aware of changes in building materials across your house. Also south facing walls are likely to store more heat during the day than those that are north facing, consider the aspect of your house when looking at your thermal image.

When opening your thermal image you will be given information on when the image was taken, what the weather was like and what the outside temperature was; use this to help you gain a greater understanding of what your image is showing you.

Understanding your thermal image

You should not necessarily be looking at how red your house is or isn’t as a whole but how even the surface colour appears and whether there are any anomalies across the image. Anomalies could signify any of the following:

  • Thermal bridging, where a certain material connects the inside and the outside of the house making it easier for heat to escape from the building for example a door or window lintel.
  • Air leaks
  • Insulation deficiencies

Examples of typical anomalies / heat loss

The temperature gauge attached to the picture should only be seen as indicative, with a clear night sky the temperature can be a lot colder than -8 degrees C.

The image above is a Photoshop rendition of the most common problems found on post WWII houses in which the majority of people in Bradford on Avon live.

Using the temperature gauge above, red or white areas on the house walls, windows or roof indicate heat loss and thus a potential problem.

The area no 1 is a common problem caused by a “corner-effect” where insulation panels join together. This join often allows for heat to leak from a building. This is why many buildings lose a lot of heat along skirting boards, porch recesses, and external chimney breasts. In this case the heat leakage is quite severe and indicates that the insulation in the join or even the roof join was damaged and needs to be repaired.

The area no 2 is yet another example of damage to the roof. Such areas may indicate not only damage to the roof insulation but also damage to the roof itself. This is because water is a very efficient heat conductor and wet insulation is in fact worse than no insulation.
Suggested solution: Check roof and roof insulation for damage.

The area no 3 and similarly area no 8 indicate severe heat loss through the external walls. In both areas this heat loss may be caused by damaged cavity wall insulation as well as a hot object such as a radiator or a boiler placed just behind these areas. Cavity wall insulation can get easily damaged by water leakages. As you can see the area no 3 and especially no 8 are close to the windows. These may be badly fitted and thus allowing for water ingression. It is also a good idea to fit radiator reflector foils or panels behind radiator and boilers. Thermal Imaging tests have proved that these foils and panels reduce heat loss through external walls and thus keep more heat in the house.
Suggested solution: Install radiator reflector foils or panels behind radiator and boilers, check for potential cavity wall insulation damage by examining your window frames for any deterioration and external wall for any holes and cracks that may allow for dampness to seep into the cavity wall insulation.

The areas no 4, 5, 6 and 9 indicate severe heat loss from and around windows. The two windows indicated numbered no 4 indicate a potential gap between the window frame and window lintel that needs to be draught proofed again.   The problem can also be caused – as is the case with the window indicated no 5 – by failure of the seal in the double glazed window unit.   This failure is often revealed by the unit going misty and eventually wet in between the panes. Unfortunately such windows leak a lot of heat around the edges.   Yet even worse are single glazed windows which – as in the case of the window indicated with no 9 – lose a significant amount of heat even if they are in good repair.
Suggested solution: Repair the draft proofing sealant around the window frames as well as the sealant in the double glazed units that go misty in the mornings. Also consider fitting secondary glazing to your single glazed windows or even replacing single glazed windows with double glazed units. Another very efficient way of tackling heat loss through windows is the installation of heavy curtains, using thermal curtain lining, and even window shutters.

The area no 6 indicates yet another heat loss connected to either problematic window construction that allows for water leakage or, as is the case here, the problem lies in construction of the decorative window ledge. It is made of a solid stone slab that has no cavity insulation and thus leaks a lot of heat – especially if there is a radiator placed under the window.
Suggested solution: Unfortunately, there is no easy solution in this case but you might consider placing either external or internal insulation panels to limit the heat loss in the area.

The area no 7 indicates a badly fitted main door that allows draught around the door frame. The door is also fitted with decorative stained glass fitting where the lead has shrunk and lets out a substantial amount of heat.     Suggested solution: Install draft excluders around the door frame and inspect your decorative stained glass or other fitting in your external doors for possible gaps. You may want to consider installing secondary glazing behind any decorative glazing. Also during the coldest month it is a good idea to put a heavy curtain or blanket on a portiere rod behind the external doors.

………… However not all anomalies indicate a heat loss problem.

Examples of non problematic anomalies

Thermal imaging can capture a number of house features and occurrences that are not always problematic.

The image bellow is a Photoshop rendition of the same house showing such features and occurrences.

The area no 1 shows hot area around chimney. This is of course normal if the chimney is in use. Should the chimney area show red even if the chimney was not in use then there is a potential problem with the roof or the roof insulation. It is therefore advisable that you check the condition of your roof and insulation around the chimney if the thermal image reveals hot spot around your chimney.

The area no 2 shows a roof window or a skylight. The actual window appears very cold as it reflects the cold sky. The green circle around the window should be of little concern as it does not appear any hotter than the house walls.

The area no 3 shows the roof lead flashing which reflects the cold sky.

The areas no 4 and no 9 show open windows. It is often difficult to distinguish between an open and severely damaged window. It is therefore advisable that you check the condition of the windows that show heat loss on a thermal image of your house.

The area no 5 shows a typical water heater flue outlet in use. If you use your water heater extensively you might consider investing in a passive flue gas heat recovery device.

The area no 6 shows an object on the external wall that reflects the cold sky but loses no heat.

The area no 7 shows a burglar alarm.

The area no 8 shows an external light with a traditional light bulb or dated energy saving light bulb which often emit more than 100 degrees C. It is therefore advisable that you consider exchanging them for LED light bulbs which are currently among the most energy efficient sources of light.

The area no 10 shows a typical bathroom vent. These are very important for keeping indoors climate free of extensive moisture but also potential causers of extensive heat leaks if they are of a dated construction or kept in a bad repair order.

The areas no 11 and no 12 show typical outside vegetation. This, as well as other objects such as cars, bins, flower pots or hanging baskets, can emit the external temperature, reflect the cold sky or even a nearby source of heat such as street light or a badly insulated house.

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