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. It can also cut noise.
Cheap! Costs as little as £60/80 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.
How does it work?
Self adhesive white flexible magnetic strip is run around the perimeter of a sheet of acrylic and a matching frame of steel strip is fixed around the window for it to attach to. The acrylic sheet is held in place snugly, but is quick and easy to detach for cleaning or storage.
The end result is virtually invisible, but amazingly effective in preventing heat loss and draughts. It cuts window losses by half and has about 80% of the effectiveness of conventional double glazing, at a fraction of the price.
How do I install it?
The best and simplest method is to use a single sheet covering the whole window. Some suggest that sashes can be insulated individually, but we have found this to be impractical.
On a simple window, installation takes less than an hour and is pretty straightforward. See the video below to get a better idea of what’s involved. For those less confident of their DIY skills, the new TTL enterprise SNUG can quote for installation and also advise on draughtproofing and other issues.
A very clear instruction video for fitting magnetic double glazing, made by Lambeth Council, is on YouTube:
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, is in the form of rigid strips of plastic, 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, particularly Indigo, sell larger rolls of tape (similar to standard Magnetglaze), which can work out cheaper if you are doing several windows.
There are also systems using two magnetic strips. They seem more complicated, but may give a stronger grip.
However, quality is important, as the tape has to stay in place indefinitely. Some have found that the cheaper Indigo steel tape can peel with time and it is probably wisest to only go for their best quality adhesive. Magnetglaze tape seems reliable, as the adhesive is thicker, which allows it to better accommodate unevenness.
Where can I get it and what does it cost?
A fuller list of suppliers is given at the end, but here are a few pointers.
Standard Magnetglaze – works out at around £20/30 to tape a single window (5m kit). It can be bought from Tubeway direct, Amazon, ebay and a variety of specialist sites.
Alternatively, Indigo’s best quality equivalent is much the same price.
Magnetglaze Pro – Costs around £15/20 per window (2 lengths) and can be bought online or at Brighton & Hove Plastics.
Magnet Glaze Indigo kit Magnet Glaze Pro
|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. PETG is also somewhat heavier, which can make big sheets a little awkward. 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 we have found 3mm suits most applications and is easy to handle.
Sheets can be cleaned using soapy water or window spray, much the same as glass. However, abrasive pads or cleaners will scratch and must be avoided.
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.
It can be helpful to have a batten or studs at the bottom to support larger, heavier sheets, possibly with a clip at the top (B & H Plastics have these too).
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. It’s best to ring though the dimensions and they will cut ready for you to collect. Make sure though that it will fit in your car!
Approximate costs for acrylic are £40/50/sq.m. for 3mm and £50/60/sq.m. for 4mm. A 3mm sheet measuring 1300mm x 1000mm would cost about £60/70.
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 £70/80 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.
Miscellaneous Practical Details
Although easy to take down, the system is not really suitable for windows opened frequently, such as kitchens and bathrooms.
Big panels can be unwieldy, so maybe not suitable for very large windows.
The standard tape is white faced, to match most windows, but take care when ordering, so as not to accidentally order the brown version (unless your windows are brown of course).
Staff beads (the round edged ones holding the sashes in place) on some windows can protrude, making it awkward to fit panels. This can be overcome by either relocating the beads back, planing them slightly or fixing a frame of slim battens (say 20mm x 5mm) around the frame, so that the magnetic strip is raised.
The system is well established and long lasting. We have known of panels in place for around 20 years.
Based on the experience of Jill Goulder, Neil Williams and SNUG
Brighton and Hove Plastics, Boundary Rd, Portslade BN3 4EF. 01273 421122.