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Thermal Imaging Camera Case Study: External Wall Insulation

At Sustainable St Albans, we have two thermal imaging cameras for loan. They have been borrowed by over 500 people across the district over the last seven years. The Camera Team always request feedback and examples from those who borrow the camera to see what it’s being used for. We’re very grateful to JoM for sharing their comparison of two external walls: one that has been insulated as part of a retrofit project, and one that has not.

Here you will see two images of walls in Bedroom 1 and Bedroom 2, taken with a Thermal Imaging Camera. The walls imaged in both bedrooms face north west and never get the sun. The bedrooms are next to each

The outside temperature that day was around -4 Celsius. 

This image shoes a predominantly 'orange and red' thermal imaging camera capturing a temperature range of 12.8-17.8 degrees Celsius

Bedroom 1 has been internally insulated with insulating boards (Celotex, 55mm
insulating board) on all outside walls and the ceiling.

The spot temperature is identified at 15.7 Celsius and the range is 12.8 to 17.8 Celsius. 

The value of insulation is beautifully shown here. It also demonstrates the importance of airtightness – sealing up the insulation boards even further in future would stop any cold coming through the warm surface adding to the overall effect. 

As Celotex is petrochemical based, it may interest readers to know that there are a number of alternatives to Celotex such Diathonite and flexible or rigid wood fibre.

This image shoes a predominantly 'purpleand red' thermal imaging camera capturing a temperature range of 6.9 to 11.9 degrees Celsius. There are yellow squares in the image where pictures are hanging on the wall.

Bedroom 2 has not been insulated.

The spot temperature is 7.3 Celsius and the range 6.9 to 11.9 Celsius.

The Thermal Imaging Camera has measured the spot temperature difference in the walls to be more than 8 degrees, and the highest temperature in the uninsulated room is below the lowest in
the insulated room! 

The bay windows in Bedroom 1 face south west and the bay windows in Bedroom 2 face north east but the home owner didn’t think that explains the dramatic difference in the north west facing walls of the two rooms.

With thanks to JoM for sharing the images and analysis: December 2022.

For further information on insulation and other retrofitting considerations see the book Beginners Guide to Eco Renovation. There’s an extract on the our page Efficient buildings – insulating your home

Sign up to our mailing list to find out when our Thermal Imaging Camera borrowing season opens again in Autumn 2023.

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