Insulation Properties of Older Houses: Investigation with a thermal imaging camera

Older houses pose particular challenges with regard to thermal efficiency and sustainability. For this reason Sarah and myself found it extremely useful to borrow the thermal imaging camera to investigate our house- Culhams Farmhouse. The farmhouse was built in 1840 and the original part of the house has solid brick walls although several more modern extensions have cavities and mostly meet today’s building regulation standards. Windows in the original house have thick oak frames and single glazed lead mullions. The property is Grade 2 listed so anything we do has to meet the approval of the conservation officer. Originally the house was built without a damp proof course, but a chemical course was inserted over 40 years ago much to the disapproval of the conservation officer who told us that this should not have been allowed. We don’t appear to have any significant damp issues. Today the house has a modern gas central heating system (boiler replaced 18 months ago) which is supplemented by two log burners (both replaced recently and meet today’s standards) and an open fire. I have purchased a wood moisture meter to ensure I only burn seasoned wood.

Another part of the thermal efficiency jigsaw is how we use the property. It’s relatively large and there are only the two of us rattling around in it so throughout the winter half of it is unused and unheated apart from Xmas. Two downstairs reception rooms are mostly unheated- but the radiators and log fires can bring them up to temperature quite quickly in the event they are needed. Similarly, only one of the bedrooms and both bathrooms have background heating the rest being left completely unheated. The house has two large, cavernous lofts and I have improved the depth of insulation on the one above our bedroom, but the other larger loft doesn’t meet today’s standard for thickness of insulation.

Having set the scene what did the thermal imaging camera reveal? We borrowed it on a cold and frosty night when there was a log fire in the lounge log burner and the radiators were working in the rooms we heat. The camera is very sophisticated with a large instruction manual but in simplistic mode you can forget all this and switch it on then pull and hold the trigger. The screen now reveals the thermal image, and you can walk round the outside of the property to investigate its thermal properties. Black or grey is good but yellow or orange is bad suggesting significant heat loss and red is awfully bad.

How did Culhams Farmhouse fare? The good news is (and somewhat surprising) that the walls of the original structure and all of the roofs were black showing no appreciable heat leakage. Rather surprising is that the image of the downstairs cloakroom, a 1980s addition with a conventional cavity wall construction, clearly showed the outline of its radiator in orange suggesting much greater heat loss from the newer construction. The bad news was the windows, where all of the original window openings with single glazing, showed significant heat loss. The camera was also effective in identifying heat loss through drafts. We have a new extension completed 18 months ago comprising a large kitchen extension and involved excavation of the original kitchen to install underfloor heating which is modern and efficient. (I know that earlier I said the house is too big so you might wonder why we extended- it’s a long story but in essence the space we had wasn’t in the right place). As an aside the kitchen refurbishment made a major contribution to reducing our carbon footprint as we got rid of the solid fuel AGA which used to run 24/7 throughout three seasons and consumed anthracite at an alarming rate. The kitchen extension was built with an insulated cavity wall and no problems were detected here. However, we had windows with solid oak surrounds and also tri-fold doors with solid oak frames. We were warned these might shrink and cause drafts and these were clearly visible on the camera showing as a thin strip of orange along the hinged joints. The other major draft leakage was from the old front door. This is rarely used but is the original oak door, 180 years old. Its warped and has been for years but we have a curtain we can draw across it.

So what are the next steps having seen the thermal imaging? Well, the apparent loss of heat through the solid walls was a huge relief. Solid walls can be a major problem in older properties and options are limited- wall cladding is ugly and, in any event, wouldn’t be permitted in a listed building. Thankfully, the walls at Culhams  are thick (four bricks thick in fact) greater than many older properties and thicker than modern cavity construction albeit without the benefit of high performance insulation. I’m surprised about heat loss through the downstairs cloakroom- I would have expected a 1980s construction to have insulation in the cavity but perhaps not. I will fit a thermostatic valve on the radiator and lower the temperature. I have just bought a load of draft excluder and have started to fix the worst problems. Then there is the question of the single glazed windows! Some were replaced a few years back by a previous owner and had to be handmade- the bill was huge. There is no easy answer to this but I am looking a the possibility of secondary glazing although Sarah and I have yet to agree on this radical step. In the meantime we will continue to draw the thick curtains in the winter months.

All in all, the thermal imaging experience was very good. It provided some reassurance but also focussed attention on where the quick wins are for thermal efficiency. I would recommend it to everyone.


Paul Roper