Secondary Glazing
Secondary glazing is an independent pane fitted inside the existing window, and for listed buildings it is often the most practical way to cut heat loss, draughts and noise without altering historic fabric. Because it is reversible and leaves the original window untouched, conservation officers generally prefer it to replacement or to altering sashes for double glazing. Systems range from slim aluminium frames and magnetic or lift-out acrylic panels to purpose-made timber units matched to the existing joinery. Firms here survey, make and fit to the irregular openings normal in old buildings.
What this category covers
- Slim-framed aluminium and timber secondary glazing systems
- Magnetic and lift-out panels for occasional or seasonal use
- Acoustic secondary glazing for traffic and aircraft noise
- Bespoke units for curved, arched and irregular openings
- Survey and fitting into out-of-square period reveals
Cocoon Window Insulation
Cocoon Window Insulation supplies and fits bespoke magnetic secondary glazing and draught-proofing ...
Conservation Secondary Glazing Ltd
Conservation Secondary Glazing Ltd supplies the CSG system, a patented secondary glazing ...
Gecko Glazing
Gecko Glazing is an Edinburgh company offering a patented secondary glazing system ...
Invision Secondary Glazing
Invision Secondary Glazing installs bespoke aluminium secondary glazing nationwide, working in partnership ...
JH Building Restoration Ltd
JH Building Restoration Ltd is a heritage restoration and refurbishment contractor based ...
Mitchell & Dickinson
Mitchell & Dickinson specialise in what they call integrated insulation for period ...
Sash Windows Northwest
Sash Windows Northwest is a sash window restoration specialist based in Leyland, ...
Storm Windows Limited
Storm Windows is a family-run manufacturer and installer of bespoke secondary glazing ...
Specifying secondary glazing on a period building
Position the frames to disappear. The best installations align frame members with the existing glazing bars and sit within the reveal or behind the shutters, so from outside and from across the room the original window still reads as the window. Ask to see photographs of comparable installations before ordering.
Match the gap to the purpose. A cavity of around 20mm gives good thermal performance; noticeably better acoustic performance needs a wider gap, typically 100–150mm, which is worth planning for if traffic or aircraft noise is the main reason for the work.
Keep it openable and ventilated. Windows still need to open for ventilation, cleaning and escape, and trapped moisture between the panes can cause condensation on the original glass and decay in the joinery. Systems that open easily and allow some air movement avoid this.
Confirm the consent position. Because secondary glazing is reversible and internal, it is often acceptable on listed buildings, but it does usually require Listed Building Consent, and officers will want to see how frames relate to shutters, panelling and glazing bars.
Questions to ask
Is secondary glazing acceptable on a listed building?
It is generally the preferred option, because it is reversible and leaves the historic window intact. Listed Building Consent is normally still required, and officers will look at how the frames sit within the reveal and relate to shutters and glazing bars.
How does secondary glazing compare with double glazing for noise?
For noise it usually performs better. Acoustic insulation improves with a wide air gap, and secondary glazing can have a cavity of 100mm or more, whereas a sealed double-glazed unit has only a few millimetres. Different glass thicknesses in each pane improve it further.
Will it cause condensation on my original windows?
It should not, if the installation allows a little ventilation and the seals are sensible. Problems arise when moist internal air is sealed into the cavity. Systems that open easily and are fitted with this in mind avoid condensation on the historic glass.
Directory information is provided to help visitors identify potentially relevant specialists and suppliers. Inclusion does not constitute a recommendation, approval or guarantee by Tuscan Foundry Products. Please check current services, credentials, availability and suitability directly with each business.