SOME USEFUL FACTS & FIGURES
Here are some figures about household heating/energy loss and the cost benefits of doing a lot of draught-proofing and adding magnetic-strip secondary glazing (or for a very cheap short-term fix, seasonal glazing film (like cling-film))
(2020 note: this information was collated in 2016 from the Energy Saving Trust, buildingconservation.com and English Heritage )
• 18% of all household energy is lost through windows alone, 26% through roofs and 33% through walls
• 30% of heat lost in a home can be due to draughts
• Comprehensive draught-proofing can reduce fuel bills by 20%+ per year
• Curtains reduce heat loss by 41%
• Blinds and shutters reduce heat loss by 51%
• Insulated shutters reduce heat loss by 61%
• Modern roller blinds reduce heat loss by 22%
• Double glazing reduces heat loss by 55%  (U-value 3.14)
• Magnetic-strip secondary glazing reduces heat loss by 63% (U-value 2.70)
• Magnetic-strip secondary glazing can be around 15+ times cheaper than double-glazing
• Draught-proofing (using draught-proofing strips) around windows can reduce energy loss by 80%
• Seasonal glazing film can increase temperatures in your home by 10% and costs from £2 per window

Extracts from an English Heritage 2010 publication titled 'Energy Efficiency in Historic Buildings: secondary glazing for windows':
'• The benefits of double glazing over other methods of window upgrading are often overestimated. Much of the comfort and energy efficiency benefits of new double glazing come from the reduction of draughts that will result from well-fitted window frames with integral draught-proofing. ... With continual improvements in the performance of secondary glazing it may even be possible for the performance of secondary glazed windows to exceed that of new double glazing.
• Heat losses from a typical traditional window are predominantly through gaps around the window. With larger windows the proportion of heat lost by conduction through the glass tends to be greater.
• In terms of noise reduction, double glazed units are no better than single glazed units; and can be slightly worse for traffic noise. The important criteria for noise reduction are that the windows are well fitted and draught-proofed. Secondary glazing, with its larger gap between the panes, is a better sound insulator.'

Hiya, really enjoyed your video, can I ask when in East Sussex you get this from?

This is by very far the best explained video of how to install magnetic secondary glazing 👍👍👍

Thank you so much for taking the time to create it 🙏

Thanks

Late to the party but this is such a helpful video - thanks from Dulwich!

What a lovely relaxed, informative instructional video.
Did you put the piece that is to stick to the window frame on to the sheet, press it against the window frame, take off the sheet and that left the magnetic strip on the window?
That is very clever if I have understood that correctly.

Best secondary glazing video ever! With regard the protruding beads, how is this overcome? 🙏🏽

Hi.  thanks for the video.   Did you find that this blocked out noise.    We live in a semi rural area but get noise from the motorway half a mile away - -  we have double glazing and can still hear the road noise inside.   Also thegap that we would have between the double glazing an the acrylic seconday glszing is only about 2 inches ----  is that ok ?

yThank you from Manhattan  ©2026

Many thanks. Like one of the other commentators below, I was intending to build rather bulky secondary glazing, but will now give this a try. A very clear and well presented video without the usual verbiage and nonsense one comes across. Well done!

Big thanks for this video.  Still perfectly relevant 10 years on

Great stuff come on more tips please.

thank you, took your advice to install my own 2nd glazing, hopefully all goes well.

We live in rented property, may I ask if this strong enough for me to put  cat flap on as I try to find solution to put cat flap for my cat. And I think window will be ideal.

What a great video!! Thank you for making this xx

yes this is a gift and a lucky find, as I was about to construct wooden frames and use 4mm glass. Perhaps a small saving on cost there but an awkward and unsafe option to this much more discreet and manageable system

some big windows, so used 4mm acrylic on those with the 1" magnetic strips but plenty of the small windows, which seem fine with the 3mm 1/2" strips. The plastic came from Trent Plastic of Gainsborough Lincs who provide  a great family like service and delivery with prices way better than all the other options. B&Q do a great deal with the magnetic strip, again much better than anybody else, with free delivery. Used two 30m rolls, one of each wide.

the guy who made the plastics delivery was curious where it was being used, but said he had a quote for one  new fitted window for much more that the fourteen windows I have now secondary double glazed

God bless you.

This video is an absolute gift! So helpful, thank you. I have a very tall sash window - maybe about 2 metres tall. I'm thinking it's too large for one sheet and I might need to do two square style panes. Little worried about how to maintain a tight seal with the split. Has anyone dealt with a large window? Thank you :)

Did you batten at the window cill at the base of the sheet? What is the bottom of the acrylic sheet fixed to if the sill is level and comes in beyond the acrylic sheet?

Brilliant,thank you.