Thermal imaging of double glazing retrofitting projects

Vacuum double glazing is an equivalent to standard triple glazing and is up to 8 times more energy-efficient than single glazing

Thermal imaging of double glazing retrofitting projects

In this article, we will use thermal imaging of double glazing to demonstrate the superior thermal efficiency of vacuum double glazing as compared to original single glazing and slimline double glazing.

Sash windows double glazing is a core service provided by Chameleon and offers many advantages to homeowners. Especially suitable for those in historic properties wanting to preserve the original character of their windows, some of the key benefits include:

  • Increased thermal efficiency of windows (up to 8 times more vs single glazing)
  • Improved acoustic properties, reducing noise penetration from outside
  • Allows for the preservation of the original window aesthetic with the glass retrofit into the existing frame
  • Saves costs on full replacement of window units

For our retrofit service, we use super-efficient Fineo glass which features a vacuum seal between the glass units rather than the conventional air or gas filling. Due to the vacuum’s superior heat retention properties, it means the gap between the two pieces of glass can be far smaller, making it suitable for use on slimmer profile historic windows.

Thermal camera testing

Improving the thermal properties of sash windows is a central aim of our retrofit service and, as such, is something of great importance to us as a company.

However, in the interests of deepening our knowledge in the areas of its thermal properties and drilling down to obtain more evidence and hard metrics regarding performance (real-life ‘street data’), we purchased a high specification thermal imaging camera.

Comparison points included windows on the same house which hadn’t yet had double glazing installed, and also windows on the same and neighbouring properties which had undergone retrofitting with slimline double glazing offered by other companies in the market.

Case study 1

Here you can see evidence from one of our completed retrofitting projects in Suffolk. The images show a comparison between the top window, which was double glazed with Fineo vacuum-sealed glass, and the ground floor sash window which was not (single glazed).

double glazing sash windows suffolk
thermal imaging of FINEO glass
FINEO Double glazing (green square box). Single glazing (Yellow square box)

At this property in Suffolk, the thermal camera data also shows another point of interest: is the 1st-floor window on the far left in the picture above on the right. 

This is a false window (i.e. a wall from the inside) which, as can be seen in the thermal image, experiences greater heat loss than our installed units (circled green) while making small gains on the single glazing (circled yellow) which shows a high degree of heat loss..

This is another example illustrating the superior thermal properties of our vacuum double glazing.

Double glazing for sash windows thermal imaging

The image on the far left is a normal camera image, central is the thermal camera image in colour and on the far right is the thermal camera image in black and white:

The darker colours (purples into reds) and accompanying intensity of the brightness signify higher rates of heat loss being captured by the thermal camera, and here we can clearly see the bottom window giving off a much greater heat signature than the double glazed Fineo window above. The black and white image on the far right shows us almost no heat signature from the window we retrofitted.

Single glazing and slimline
Thermal imaging of single glazed windows

This second image above from the same project shows a window client had retrofitted with slimline double glazing and we can see little noticeable difference between it and the original signal glazed windows.

Case study 2

thermal images of double glazing

Here windows on the first floor were double-glazed by us as compared to ground floor windows which remained single glazed originals. Whilst showing less contrast than the images from case study 1, we can still see a reduced heat signature in these as compared to the originals and also the front door as another example of a single glazed heat source.

The below thermal imaging also shows the windows we worked on compared to those of a property next door which remained single glaze. The intense orange glow from their windows clearly contrasts against the low heat signature from the Fineo vacuum-sealed windows on the right-hand side:

Case study 3

The below thermal imaging of double glazing from a completed double glazing project in Cambridge gives a good contrast point between the Fineo installed glass and single-glazed door which glows intensely red showing a strong heat loss signature.

vacuum double glazing thermal photographs

Here also we can see the neighbouring house showing a strong heat loss signature from the windows despite being slimline glazed by another company.

Case study 4

In the thermal imaging below, from a retrofit vacuum double glazing job on a property in Cambridgeshire we can see the good thermal properties of the renovated windows with minimal heat signature given off:

vacuum double glazing thermal imaging

Case study 5

At this property, we carried out wooden windows frame restoration, installed draught-proofing seals as well as retrofitted double glazing into existing timber window frames. 

In the thermal images below, we see the windows following Fineo installation give off a very reduced heat signature (excluding the window on the bottom left which remained as the original single glazed casements).

Windows on the second floor remain dark, with purple tones, in the image on the right-hand side, illustrating the very efficient trapping of heat inside the property by the vacuum-sealed windows.

This ultimately means a warmer house and reduced heating bills.

thermal images of windows
Normal photograph and thermal image of the property

Case study 6

This retrofit job on a beautiful Georgian cottage also shows thermal imaging of double glazing that was recently installed by our team. Interesting to note also the bright glow from the chimney (likely heat from a fire) and the contrast between this and the dark purple colour of the windows on the thermal images:

Georgian sash windows double glazing


Vacuum double glazing, as further demonstrated by our thermal camera results, remains the best option on the market for sash windows retrofitting projects.

With gains across numerous areas, from thermal efficiency to noise reduction, there are many reasons why historic homeowners continue to choose retrofit double glazing as the solution to their window issues and as the alternative to full windows replacement.

Please don’t hesitate to contact us at Chameleon Decorators & Windows Restoration for a no-hassle quotation from a member of our friendly team.


How much heat do you lose through single glazed windows?

On average up to 25-30% of your home’s heating and cooling is lost through single glazed windows. 

How to reduce heat loss through windows?

Double glazing retrofitting where the single glazing is replaced with double glazing can reduce heat loss by 74% compared to single glazing. 

How does vacuum glazing work?

Much like a bell jar from science experiments with vacuum-sealed windows the air is simply removed (sucked out) from the gap between the glazing, thus creating a vacuum. This is different to the other gas or air-filled systems on the market.