Thermal image surveys

Thermal Imaging is a great way to spot where homes are losing heat. Not keeping warmth in your house equates to higher heating costs – who can afford that?

Having been encouraged by the work carried out by Elham Transition Town group, we decided to start thermal image surveys in Hythe in 2011. A thermal imaging camera is a clever piece of equipment which records the temperature of anything you point it at and the variations in temperatures of everything around it. So you can take a picture of a house with the camera and it will show you which parts are hotter than they should be.

Kent County Council gave us a month-long loan of their thermal imaging camera in 2011 and since then we have surveyed about 60 homes.  We will be borrowing the camera again during February 2013.  As we’re a group of volunteers, we do not charge for surveys and the advice we give is purely for the benefit of householders, on an informal basis. We can show you what the camera is picking up and give you some advice about what you can do to improve things.

The house surveys have to be carried out in the winter, on dull days, about two hours after dusk. If it has been sunny, brickwork can remain warm for several hours and we get misleading readings from the camera. We also ask the householder to have the heating on for most of the day as we need a temperature differential of at least 10 degrees centigrade between the indoors and outdoors.  It makes it more obvious to spot where heat is escaping. It is also better if internal doors are left open so the heat can circulate throughout the house.

After the survey, we can email the digital images to the homeowner and give a quick identification of the problem and our recommendations to improve energy efficiency. Unfortunately, we can’t get pictures of sloping roof surfaces, but we can easily identify hot-spots on a roof where insulation is missing.  We’ve seen several cases of faulty new upvc windows and also older double glazing where the seals have failed. The most striking energy loss is through uninsulated walls, where we can pinpoint exactly where radiators are.  The thermal imaging camera cannot “see” through glass, so you don’t have to worry about spying someone in a bathroom during the surveys.

One our most common recommendations is “get thicker curtains” rather than ripping out good timber windows for UPVC versions. Interlined curtains are very effective and tucking curtains behind radiators keeps heat in. Old wooden or glazed external doors are easily insulated with an interlined door curtain and prevents letter box drafts. Turkey foil behind radiators also works well to radiate heat back into the room. We’ve even identified roosting pigeons, showing up as a mysterious hot area in the eaves of a house.

The camera enables us to see cold and hotspots within the home too. We’ve learnt during the course of the last two years’ surveys that huge temperature differences either side of an uninsulated loft hatch can cause drafts. In fact anywhere with a big temperature differential can cause air movements. One homeowner thought there was a spirit “presence” in the kitchen. It turned out there was a very cold patch on the ceiling and below the kitchen sink, combined with a hot boiler cupboard in the same room.

The camera also picks up temperature differences caused by damp and although not an energy issue, it is useful to know there’s a problem and then be able to rectify it.

To give you an idea of what thermal images look like, a few examples are set out below. Please bear in mind that the scale shows the overall range of temperatures and allocates colours over this scale. So red in one image will be a different temperature to red in another image. The figure stated in Centigrade in the top left corner of the image is the temperature measured in the centre of the image, where the little cross and circle are. So red does not mean something is boiling hot – it may only be 2 degrees centigrade!








A lot of heat is coming out of the small windows, which are single glazed, without curtains.  Heat also coming through the front door and at eaves level.








Modern double glazed window where the seals have failed and is now as effective as a single glazed window.







Heat from a gas fire warming the brickwork at the back of the fireplace.  The flue is on an external wall so the heat goes into the garden.  Architects take note, keep fireplaces on internal walls!








Radiators under the windows of the bay throwing heat outside rather than into the room.