Perspex magnetic tape secondary glazing (split at meeting rail)

From 8:12 in the YouTube clip above, you can observe a sheet of acrylic magnetic strip secondary glazing being removed and applied from/to a sash window.

What would you think about the idea of having this sheet of acrylic split along the horizontal at the meeting rail? There would therefore be two sections of acrylic.

It would mean the lower section of acrylic would only have to be removed if you wanted to slide the sash up to air a room, rather than a larger and more cumbersome section of perspex.

I wonder to what extent such a split would reduce the heat/sound insulation properties of the secondary glazing? If not a huge amount, then this may be acceptable in order to make the perspex less cumbersome. Any thoughts? Thanks.

I'd be worried the top sheet would slip down with gravity. As one sheet it generally is sat on the window sill to stop this. Having said that it depends on the size you will be using. As goes heat/sound loss, yu would need to build up the edges , where the sheets overlap , to ensure the magnetic tape meets...if it is ' taped ' all round , with no gaps ,I can see no difference being noticed

ronniecabers said:

I'd be worried the top sheet would slip down with gravity. As one sheet it generally is sat on the window sill to stop this.

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I've only seen this system on YouTube, so that's a good point I hadn't considered. I suppose a baton could be placed horizontally along this section (at meeting rail) to act as a sill for the upper section of perspex.

ronniecabers said:

Having said that it depends on the size you will be using.

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The upper section of perspex would be 98 cm wide (38.5") x 60 cm high (23.5") .

According the the clip above, the one sheet of perspex would be applied to meet where I have marked a red line in the image below. In my case this would give one perspex sheet a gap of 6.5 cm between the glass and the perspex.

Perhaps one other option would be to apply the upper 98 cm wide x 60 cm high perspex sheet to the red line, then apply the larger lower perspex sheet to the blue line i.e. directly onto the lower sash. This would allow the lower sash (with perspex applied) to slide up as normal and behind the upper section of perspex.

Obviously the gap would be much reduced for the lower section, and also it would not be covering the meet between the lower sash and the staff (stop) bead. However, it would mean the perspex for the larger lower sash would not have to be removed to slide this window.

Possom said:

What would you think about the idea of having this sheet of acrylic split along the horizontal at the meeting rail? There would therefore be two sections of acrylic.

Click to expand...

Yes, this is one of the options that magneglaze offers (http://www.magneglaze.co.uk/sashWindows.php) though I don't see exactly what they're doing at the middle...