Insulating window reveals

Thermal imaging shows that some of my windows suffer from significant thermal bridging. One solution would be to insulate the window reveals.

I don’t mind hiding some of the frame but I need to keep usable access to the glazing beads in case I ever need to replace the sealed units. To increase insulation space slightly and reduce thermal bridging further I am thinking of removing existing plaster and insulating direct to the brick.

Thin insulation which nevertheless has a low U-value is the order of the day. As far as I know that is aerogel territory. I have found a few companies that supply aerogel insulated window reveal board (I haven’t dared ask the prices yet).

Can anyone tell me whether all aerogels are equal, and if not explain the differences?

Does anyone have good experience with aerogel?

Any other advice on insulating window reveals gratefully accepted.

I used wood fibre that was then plaster skimmed. The boards are a standard thickness but may vary with manufacturer. I would suggest horses for courses- not all windows will need the thinnest material. I used Udi from Back to earth.

Now the next stop for me - fitting windows to be thermally efficient !!
I feel very fortunate to have found a fitter who is communicating well with me and being very patient while I try to explain how I want these windows fitted :sweat_smile:
Incidentally , he appeared on one of those home DIY rescue programmes with Melinda Messenger. I think he is a joiner - not just an actor!! :smile: - he does fit windows !!

Anyway, I explained about our community and changing standards , demand in market for fitters committed to gaining experience in these areas and he’s not been put off !! Quite the opposite, he is very interested to find out more.
I said I would find him a video / information link about insulating window reveals .
I found this link , but I’m not sure if there is better out there to share … @cc_staff

see what you think.
Also, tapes … does anyone have a preference . Compriband seems to be a make that is out there.

an example of installing windows with insulating tapes

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My own treble glazed windows, fitted by Everest, were installed without tape, foam or silicone. There was a void between brick and frame, covered to a lesser extent by trim. I have carefully filled the voids with foam myself and then painted over the foam with Blowerproof.

The state of the windows was discovered by a professional airtightness test and combined thermal survey. It was well worth the money considering what it discovered.

The windows were bought just before I discovered Passivhaus windows. :angry:

Hi i have used tape after removing 75mm of plaster/plasterboard from the reval.
Re-Filled the gap with foam and plasterboard over the top.
What is more important is to close the cavity, you may have open cavity on top and on the botton under the windowboard

Thanks. That looks good although the cavity part doesn’t apply to my house in the modern sense. The walls are “solid” with random small and possibly in some cases interconnected gaps.

Where I have needed to do work around a window I have painted the masonry with two coats of Blowerproof before re-covering. In the few cases where the gaps are larger I have filled, or at least bridged, with foam before painting with the Blowerproof.

Interestingly the row of soldier bricks above the first floor lintels seem to be pointed but not mortared! As the next layer is the roof plate they don’t need to take much weight. I filled those gaps carefully and in stages to avoid disturbing the bricks.

Here is a horror show for you! I came back to this and almost went ballistic after I specified and provided the use of compressible tape at the wall window frame junction. No disguise to the sunlight bypassing the frame.

I used wood fibre insulation board followed by plaster skim to insulate reveal

I hope you didn’t pay until the work was done to the specification. If you gave the spec in advance it forms part of the contract. At most pay for the widow itself as that is now in your possession.

I have learnt the hard way never to leave a tradesman unsupervised.

I believe our walls are solid wall.
We’ve decided upon Eurocell windows - their prices and u -values are A* double glazing which apparently achieve a u-value of 1.2 . we just need to check what the standard glazing is and if there are any additional costs for the energy efficiency coatings and argon.
Eurocell don’t provide a fitting service though , but we have found a joiner who fits windows and so far is on board for fitting with tapes, despite having not used them before. I sent him a how to video, which I already posted in our thread.
So far, I can understand that there should not be any cavity between the brickwork and the window frame, that good window measuring and use of correct size tape is key to bridging any gaps between the brick and the frame.
I think my main concern is in being an old house, how square are the window apertures are likely to be. I’m imagining uneven brick surfaces when the old windows are removed !!

My questions now are how to choose the right type and size of tape.
Also, the talk using a tool to push the tape in as it expands is throwing me off visually.
I know it expands quickly in warmer temperatures and is best kept in the fridge @lloydham prior to installation to delay expansion and allow more time to get the frame in.

Also, I did see that Eurocell have cavity solution kits called Cavalok , but they seem to be for cavity walls , not solid wall.

I feel like we need our own tutorial for windows here on our forum … @mattfranklin how can we get our window fitters trained in this essential kind of window fitting ??
Have I missed a trick - Is there a youtube link from CC for window fitting which members can access.

My experience with 1.1W/m²K is very good. The only problems are where the install wasn’t done appropriately. The windows are fine.
For comparative purposes, the Passivhaus standard for the cool temperate zone is 0.8W/m²K for windows.

Please see the above for Vitaseal tapes. I found these easy to use and effective as I have used them to insulate door openings. Nowt wrong with asking questions!


I had some 25mm insulation board i just cut to size foamed and taped in place.

Now rebranded as Xpanda.

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A bit late for some but this is really informative. How to install a window, using the illbruck i3 system. - YouTube

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