DIY Secondary Glazing Kits: An Honest Review

Shrink film kits

A sheet of clear film taped to the architrave and shrunk tight with a hairdryer. Cost is trivial. It genuinely stops draughts and reduces condensation on the original glass, and for a single winter in a rented flat it is defensible value. What it will not do is reduce noise meaningfully, because it has almost no mass. It also cannot be opened, it tends to detach in a warm room, and the tape often takes paint with it in spring.

• Very cheap and quick
• Real draught and condensation benefit
• Negligible acoustic benefit
• Single season, tape can damage paintwork

Magnetic acrylic panels

An acrylic sheet held to a steel or magnetic tape strip around the reveal. A clear step up from film: it has some mass, it seals reasonably, and it can be taken off in summer and stored. It suits small windows, rented property and rooms where you want reversibility above all. The limitations are that acrylic scratches easily, discolours over years, flexes on larger panels, and cannot match the acoustic performance of laminated glass. Storage of the panels also becomes a nuisance in a small flat.

Self assembly framed kits

Aluminium or plastic sections cut to length with a corner joint system and glass or acrylic supplied to size. These can produce a genuinely decent result if the opening is a true rectangle, if you can measure accurately, and if you are comfortable cutting and sealing. Where they fail is on the two things period property always presents: openings that are not square, and reveals that need packing and continuous sealing rather than a push fit.

What DIY cannot buy

Three things. Deep cavities, because kits fit close to the existing glass and there is no subframe. Acoustic laminated glass in a frame stiff enough to carry it. And a continuously sealed perimeter on an out of square opening. Those three are exactly what an acoustic result depends on, which is why noise is the application where DIY consistently disappoints.

When DIY is the right call

Choose a kit if you rent and cannot make permanent fixings, if you need a fix for one winter, if the window is small and rarely used, if your problem is purely draughts or condensation rather than noise, or if the budget genuinely will not stretch and doing something beats doing nothing. There is no shame in a film kit on a spare bedroom.

When it is a false economy

Choose professional installation if noise is the driver, if the property is listed or in a conservation area where appearance and reversibility will be scrutinised, if the openings are arched, bayed or out of square, if the windows are large or high level, or if you want the window to still be usable and to last twenty years. A kit that has to be replaced three times, plus the paintwork it damaged, is not cheap.

The middle path

Several customers start with film on the least important windows and have us do the bedrooms and the front bay properly. That is a perfectly rational allocation of money, and it usually reveals the difference clearly enough that the rest follows the year after.