Flexible secondary glazing

[Mart]

We have some secondary glazing - PVC sheets with a rubber seal held on by clips. They're in a pretty bad state of repair and I'm reluctant to put them back up.

I've been thinking about options and wanted to run past you all.

Flexible 0.5mm PVC sheet, cut to size with magnetic strip around all sides with magnet stuck around frame.

Pros - lightweight, easy to store, easy to remove, airtight

Cons - may not be taught so visibility impaired, may not keep well over summer rolled up, might not actually work(!).

 

[Mrs McG]

I wouldn’t think you’ll get much thermal insulation from 0.5mm?

 

[jamest]

Yeah, that's a PVC film not a sheet. It would be about twice as 'insulating' as clingfilm. Perhaps it's 0.5 cm thick. . . you can get a surprising improvement in u-value by a sheet a few mm thick it would seem (https://www.researchgate.net/public...ass_Windows_Using_Secondary_Glazing_in_the_UK), so it would work

 

[Kearn]

We have some secondary glazing - PVC sheets with a rubber seal held on by clips. They're in a pretty bad state of repair and I'm reluctant to put them back up.

I've been thinking about options and wanted to run past you all.

Flexible 0.5mm PVC sheet, cut to size with magnetic strip around all sides with magnet stuck around frame.

Pros - lightweight, easy to store, easy to remove, airtight

Cons - may not be taught so visibility impaired, may not keep well over summer rolled up, might not actually work(!).

I think you might be combining both the options
- the film is designed to go directly onto the glass, not a great thermal fix, but can serve a purpose if the only option. I believe there are removable versions, I’d be wary of the durability.

- the magnetic option is 3-6mm thick Perspex panels, which are held in place by the magnetic tape, sometimes aided by clips if the size and weight are too great. These are great where your recess allows a seal, but obviously won’t work with all profiles. There are many suppliers out there who cut to size, ideally one panel per window section, such that any opening casements can be used by just removing the one panel. Which admittedly might be a pain to store. However this route traps the necessary pocket of air which will give the thermal improvement. Similar to what you have, but probably lighter for removal and a better seal with the continuous magnetic strip compared to the occasional plastic clips which on ours I don’t trust to hold the panels up let alone form an airtight seal!

*as soon as the windows here are restored and decorated, the old secondary stuff is all in the skip replaced by 4mm magnetic panels.

 

[Mart]

Thats precisely it, a hybrid approach between the firm perspex panels and the temporary shrinkwrap / hairdryer treatment.

My understanding (may be wrong) that the real benefit was through airtightness to stop draughts rather than any thermal benefit from a thicker perspex secondary panel.

 

[jamest]

With a secondary glazing sheet, it's the air trapped between the glass and the perspex that provides almost all the insulating effect, though perspex does have a higher thermal resistance than glass. Of course, if you have leaky windows, an added benefit would be stopping draughts. If you want the trapped air insulating effect to be most effective, it would be best to prevent any draughts through the glass window in the first place.

 

[Niall]

We've got a Georgian hunk of sandstone in a conservation area and just bit the bullet for replacement double glazed sashes in the main house.

It's got a small utility off the main house, solid flagged flood, drafty and a bit damp despite the boiler and a radiator. It's got two old single glazed windows well painted shut. Currently can't get her dry/warm enough to dry clothes.


This vid makes it look very simple, is there any pitfalls doing it full DIY if you can get some PVC cut?

How much impact does it make?

 

[CliffordPope]

We fitted some sheets of Perspex a few years ago. My observations are;

1) It's quite vulnerable to scratching, and even wiping with a cloth needs doing very gently or it dulls the whole surface. Polycarbonate I believe is better, but is more prone to shattering and is much more expensive.
2) Spiders will get inside the gap and you have to take it all down to clear the webs. Newly-hatched spiders are tiny. Heaven knows what they eat - each other probably!
3) Excellent for reducing draughts, but strong gusts of wind bow the sheets and pull the magnetic strips apart. The magnets are too weak and I had to keep adding more plastic clips to hold vulnerable points. The more clips you have the more fiddle it is removing, and refitting. In the end you begin to think why have the magnets at all and just use clips?
4) The magnetic strips become very brittle over time, and break apart easily. It's almost impossible to clean off the remains of the strips and the glue to fit new strips.
5) The metal strips glued to the frame go rusty and break away.
6) The strips, both metal and magnetic, delaminate over time and pull away from the bonded adhesive strip.
7) If you have large sash windows the panels are difficult to handle and a nuisance to store.
8) They are, at least when new, almost invisible.
9) They do make the room warmer, and best of all, can eliminate draughts from old windows.

 

[Stevers]

I've used the old Polycell aluminium frame system to secondary glaze two of my narrower sash windows, one of them in a shower room, and the other a workshop that had been a pantry. I used glass for longevity, and am just a satisfied customer planning to go on to fit their horizontal sliding sash kits to some of our bedroom windows to reduce condensation and noise from the road outside.
https://www.uksecondaryglazing.co.uk/hinged-pane-kits/
These kits are good value, and have eliminated condensation and draughts from the shower room window that were previously epic. The one in the shower room has been installed for the best part of twenty years, the workshop one about ten years. Both will outlast the house, and have helped to preserve the original sash windows in good condition.