Magnetic secondary double glazing

 

What are the benefits?

Savings - Insulating 5 windows cuts average heating bills by 7% or more.
Comfort – cuts draughts and removes cold spots near windows.
Cheap! Costs as little as £60 per sash window versus £600-900 for uPVC, or £1200-1500 for conservation grade replacements.
Simple to fit.
Unobtrusive – you can hardly see it.
Easy to take down.


What products are out there?

The main product is Easyfix Magnetglaze made by Tubeway, but also sold on many other websites. This comes in two forms:-

Standard Magnetglaze (the most common version), which comes as 2 rolls of flexible self adhesive magnetic and steel tape. Steel tape comes in white, but can be painted to match the window.
Magnetglaze Pro, which is in the form of rigid strips of plastic framing, with integral magnetic backing, in 2.4m lengths, which are cut to fit the glazing panel to form a frame. This comes normally in white, but also brown.

Alternatively, some sites (e.g. Indigo) sell larger rolls of tape (similar to standard magnetglaze), which work out a lot cheaper if you are doing several windows.


Where are the instructions?

Tubeway’s website has a useful page which has downloadable instruction sheets for both systems, as well as demonstration videos and prices. Although they are good, it is worth also looking at the very good video for fitting standard Magnetglaze made by Lambeth Council.


Where can I get it?

Standard Magnetglaze - Tubeway sell it direct via their website. Their 3 x 5m pack (enough for 3 windows) costs £60.72, including VAT and postage, or £20.18 per 5m kit.

Ebay has lots of sellers at around £25 for a 5m kit plus £3 postage, so does Amazon.

Alternatively, Indigo’s equivalent version of standard magnetglaze comes as a 30m roll costing £46.68, including delivery and VAT, which is about £10 per 5m. Indigo…

Magnetglaze Pro – Tubeway sells a 10 length pack for £78.66 (incl. VAT) (enough for 5 largish windows, but check your own measurements).

Brighton and Hove Plastics sells individual 2.4m lengths for £8 each and you’d need about 2 per window.

   
Magnet Glaze                  Indigo kit                        Magnet Glaze Pro


What glazing material should I use?

Tubeway warn that their system is not suitable for glass sheets, only plastic, presumably due to safety concerns if a sheet became dislodged and fell on someone. TTL can only go along with that advice, but Jill Goulder has successfully used glass at 8 Wille Cottages, so anyone thinking of using it may want to check hers first. Jill also advises using a batten or studs at the bottom to support heavier sheets such as 4mm glass or acrylic, possibly with a clip at the top.

     
The recommended sheet is Acrylic (trade names Perspex, Plexiglas), which is UV protected, so it won’t yellow with age, and is very strong. Acrylic is actually clearer than glass.

PETG is not quite as clear as acrylic and is not as polished, but is still perfectly ok. Both acrylic and PETG are recyclable. Styrene is cheaper, but will yellow with age and become brittle. Polycarbonate is by far the strongest, but about double the price, for no real advantage.

Sheets vary in thickness from 2mm to 4mm, depending on size of window. The sheet supplier will advise, but Jill recommends 4mm as it's stiffer and easier to handle.

 

Where can I buy sheet Acrylic and what will it cost?

There is no supplier in Lewes and Lewes Glass don’t like dealing with plastics, but can order it in cut to size. However, they only go to Brighton and Hove Plastics in Portslade, so you might as well buy it from them direct. B&H Plastics keep most materials in stock and can usually cut to size while you wait, but not on Saturdays. Alternatively, you can ring though the dimensions and they will cut ready for you to collect. Make sure though that it will fit in your car!

Their standard costs for acrylic are £43/sq.m. for 3mm and £54/sq.m. for 4mm. A 3mm sheet measuring 1300mm x 1000mm would cost about £50/60.

There are numerous sheet cutting websites, but because of the high delivery costs they don’t seem to work out cheaper than Brighton and Hove Plastics. It’s also nice to support local businesses anyway. 


 

Is it worth buying a complete kit rather than separate components?

Some sites offer a complete service. You send them your window dimensions and they’ll send you an acrylic sheet cut to size plus sufficient magnetic glazing strips.

This tends to work out a bit more expensive, but you do get everything delivered to your door.
Nigel’s Eco Store in Brighton quotes around £120 for PET for a medium window, which compares with £60/70 for the cheapest tape plus B&H acrylic. If you’re tempted, get exact dimensions and compare quotes.  Beginners might like to go down this route first, with a couple of windows, and then branch out once they feel confident.

 

Prices correct as at November 2012.

Our thanks to Neil Williams of TTL Energy group for all of the information above.