What is magnetic secondary glazing?

A sheet of plastic on the inside of your window, which can be easily put up and down because it's held on by strong magnets.This is a good, lower cost way to stop cold getting in your windows - and it can be used in listed buildings and conservation areas because it makes no change to the building.


  • Economical. You can buy ready-cut sheets to fit your windows yourself. More expensive but still less than any alternative, use a contractor. It only takes a few minutes to install. 
  • Unobtrusive. You can paint over the steel strip which remains in place when the secondary glazing is removed. The magnetic adhesive strip remains on the secondary glazing – you can choose white or brown adhesive.
  • Major saving in heat loss (better insulation gap than double glazing); also eliminates draughts and condensation.
  • Easy to remove; store e.g. behind chest of drawers/back of wardrobe/under bed.


  • Not ideal for windows which you open frequently. If the window is sash or a two light casement, it is possible to ‘park’ the removed half on top of the other. It is also possible to fix the secondary sheet on the opening frame, but this reduces the effectiveness of the heat insulation and does not help with preventing draughts. Sash window draughts can be separately eliminated and the sashes made to work smoothly by a franchise called Ventrolla.
  • May be impractical for windows over c.2.5 x 1.5 metres.
  • For larger windows, add pegs or a batten at the bottom to support the sheet if necessary – in some circumstances wind conditions can break the magnetic bond, but this can very easily be countered by fixing a single small plastic clip each side and on top.


  • There are two options for sash windows.  If you do not need to open the window in the winter, use a single sheet over both sashes.  If you need to open one of the sashes from time to time, use separate sheets that meet on the centre line of the top rail of the bottom sash.  A batten can then be permanently or temporarily fixed to the top rail of the bottom sash onto which the metal tapes can be fixed to receive the magnetic tapes on the sheets.
  • There needs to be a level timber surface a little over 1cm wide to receive the tape (no need to remove any paint). Some windows may have a corner moulding – if it is recessed, the adhesive surface needs to be beyond this; if protruding (however slightly) the protrusion needs to be planed off.
  • Polycarbonate and PET don’t yellow or deteriorate over time (unlike Perspex / polystyrene). PET is fully recyclable. You can use glass sheets too, but that’s a bit risky because of extra weight and sharp edges.
  • Cleaning: don’t seem to need it. Never use special cleaners or anything but a soft cloth –ordinary window cleaner spray and a cloth when replaced at beginning of winter is enough.


  • There are contractors who will supply cut sheets from your measurements, or will come and measure, or even supply and fit. Or you can employ a local carpenter, or you can do it yourself. 
  • If you choose to fit yourself rather than using a contractor, send accurate measurements to the supplier who will probably supply the sheets with the magnetic tape already adhered to the sheet and the metal tape adhering to that by magnetism. All you need to do is remove the masking tape and carefully place the sheet and both tapes in position, pressing home so the metal strip adheres to the wooden frame (try it first before removing masking tape to check fit and positioning!).  If the tapes are supplied separately in a roll, you have to fix the metal tape to the window frame and the magnetic tape to the sheet. Fit the least important-looking window first!
  • If you have an arched topped window, and the supplier will not cut to a curve, it is possible to do this yourself by locating the centre of the circle, placing several pieces of drafting tape on the centre point and using a drawing pin and string to mark the curve for cutting with a scriber.  If it’s not a circle arch, the cutting line can be marked using a template.  The adhesive metal and magnetic tapes can be fitted by making frequent small cuts into them so that they ‘bend’.

Some contractors (may be others via google):

www.magneglaze.co.uk  (MrRichard Cutts)

www.nigelsecostore.com (Echoeasy) www.diyplas.co.uk (www.diyplas.co.uk/product.asp?catid=3&subcatid=369)

Buying separately:

Formerton Sheet Sales - Units 5-7 Lower William Street, Northam, Southampton SO14 5QE  tel:02380 332761

www.indigoplc.com (for reels of steel & magnetic strip)

your local glazier