Jump to content

uPVC Window Frames - Improving insulation


Recommended Posts

For a long time now i've known about Liniar's Glazing Flipper, basically a trim which attaches to the middle of the profile with a rubber flipper as the name suggests, which creates a barrier to the outer half (where the frame drainage holes are located) and the inner half, and always thought it was such a brilliant idea, since the drainage holes will allow air to move freely around the 5mm gap all around the glazing, bypassing all of that expensive triple glazing, and thats irrespective of whether the beading fits tightly or not...but of course with anything brilliant, you can never get hold of it.


Then when i was looking for something else, joint backer rod (the stuff you use to fill a deep hole to stop you having to use so much caulk) popped up, and i thought now that would certainly do the job, as its flexible, waterproof, cheap and hopefully airtight when compressed (even if its not it should be far better than just an empty gap), so i've bought 10m of 10mm rod just to give it a go, and will report back if its made any difference. I'll put it on a window where i can do one pane and leave the other so its a reasonable comparison.

  • Like 1
Link to comment
Share on other sites

Arrived today so thought may as well get it in place on my afternoon off. Did one fixed pane on one window and one opener on another, fiddly as expected but not overly so, pushed the rod in to roughly where the centre pane of glass sits in the 3G unit


beading’s off



absolutely hate the duck tape they use when it’s perished, tidied it up best I could, you can see the gap clearly and I could feel the breeze coming through at this point.





just used a filling knife to gently push it in all around the perimeter. I will report back with some results and before I buy any more rod

  • Like 1
Link to comment
Share on other sites

Brilliant idea Mike. Is this why the likes of internorm etc glue the glazing ( I think) in the frames? 


As per internorm site:

I-tec glazing ensures maximum security and safety for your home! The glass pane is fitted into the frame precisely. The remaining gap between glass and window frame is filled with adhesive and afterwards, the glue joint is concealed beneath the cover bead. This creates all around fixing without any gaps, this optimises the, thermally insulated and soundproofed window.

Link to comment
Share on other sites

Taken a few readings using an IR non contact thermometer, not much wind today.


the fixed frame showed an improvement of between 0.3 and 0.5C between the ‘improved’ and original frame.


the opener showed between 0.0 and 0.1C improvement.


on a day which is quite still I’d say this makes sense, so the opener has drainage holes but they drain into the main window profile which then drains externally, so any air movement would have a longer more complex route.


can’t comment on sound insulation as both of the treated areas are at the back of the property away from road side.


I have ordered another 50m of rod to complete the other windows, which all in moneywise will be around £20.


will try and remember to take some acoustic readings on my phone before and after when I do a window at the front facing the road, and also take additional reading’s temperature wise when we are forecast some strong wind which I think is due this week.

  • Like 2
Link to comment
Share on other sites

  • 2 weeks later...

This one isn’t very scientific, but may be something…


So I went back on the heating graphs for that room (which i have since retrofitted with the backer rod completely now) to a day where the heating was on the day before (so the starting temp was the same) and the night temps were very similar to a night since I’ve done the works (which were consecutive days as it turned out), and got the following result:


Before - Temp just before the heating comes on - 14.2C


After - Temp just before the heating comes in on - 15.0C


As an aside, this may seem generally a low temperature but this room is only on heat schedule til 4pm and has a lot of glazing, even though it is triple glazed (between 1.0 and 1.1Uw).


Make of it what you will, all a bit finger in the air this part

Edited by MikeGrahamT21
Link to comment
Share on other sites

  • 1 month later...

Managed to get everywhere completed now.


Living Room (-2C Night)

Before - Temp just before the heating comes on - 15.7C

After - Temp just before the heating comes in on - 15.8C


Bedroom (0C night) - Least accurate as the reading comes from TRV which on a night is behind curtain, though both values came from same device in same situation.

Before - Temp just before the heating comes on - 13.7C

After - Temp just before the heating comes in on - 14.8C


Dining (0C night)

Before - Temp just before the heating comes on - 14.8C

After - Temp just before the heating comes in on - 15.1C


Did some acoustic readings before and after for the 'roadside' windows, and achieved a 1dB drop on all 3 windows.

The temperature readings are probably very finger in the air stuff, i've tried to marry up days with similar temperatures and the previous day where i was in all day to make it as good a comparison as I could.


I noticed the newer uPVC windows i've got have a larger gap around the glass in some cases, but not always, so it could be difficult to say exactly what size backer rod would be perfect. I think for the majority the 10mm stuff has been idea, and even tight in some cases, but then on others i've had to double it up and 20mm would have been a better choice.


All in all, i think for the small outlay in money and effort, its certainly worthwhile considering, especially if you are fitting new windows and have the beading off anyway.

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...