What is Secondary Glazing?

All aspects explained

Secondary glazing is a fully independent window system retrofitted on the room side of a primary window.

Secondary glazing is used to enhance the thermal, acoustic and security performance of existing windows. As a reversible adaptation it is generally acceptable for Listed buildings. Effective secondary glazing relies on good seals to maximise the benefits, so each window opening is measured to close tolerance and bespoke frames and timber grounds produced to achieve the closest fit. Glass is carefully selected to meet specific thermal, acoustic or security requirements. Frames are designed to blend in with the existing primary window and to complement the interior aesthetic.

The anatomy of Selectaglaze secondary glazing

The anatomy of Selectaglaze secondary glazing
Aluminium profiles of Selectaglaze secondary glazing
The framing sections are made to exclusive Selectaglaze designs using aluminium alloy. This strong, lightweight material is extruded to form the slender, complex shapes needed to accommodate seals, fixings and specialist hardware.
The forming of aluminium frames for arched and shaped secondary glazing - Selectaglaze
Selected sections can be curved and shaped to match the primary window. For more details see the arched and shaped windows section of the website.
The RAL colour chart providing a multitude of options for secondary glazing
Polyester powder paint in a wide range of RAL colours in flat, metallic or textured finishes including wood-grain effect.

The standard colour is HIPCA white semi-gloss.

Anodised in natural Silver, Analok Bronze or Black, and a limited range of other colours.

Both paint and anodized finishes are very durable with long life expectancy and minimal maintenance.
Gaskets which hold glass in place in aluminium secondary glazing frames
Glass is held in position by PVC nitrile gaskets, available in white or black, or specialist bonding tapes in systems that offer high levels of security.
Weatherseals to provide draught exclusion in secondary glazing
Sliding units are fitted with twin silicone-treated, grey polypropylene pile seals.
Hinging units are fitted with high performance Q-Lon seals (in white or black). This material has excellent memory and will retain its original shape for years, maintaining optimum sealing and acoustic performance.
Rack of glass ready to be put into aluminium secondary glazing frames
Glazing and safety is covered by BS 6262-4:2018 ‘Glazing for buildings. Code of practice for safety related to human impact’ and Approved Document K, Requirement K2 – Protection from falling, Requirement K4 – Protection against impact with glazing.

Glass thickness varies from 4mm 28mm depending on the product and application.

Other glazing applications include:
Enhanced Thermal
  • Low emissivity glass (hardcoat)
  • Sealed glass unit (various specifications)
Enhanced Acoustic
  • Acoustic laminates
  • Toughened
  • Laminated
Solar control
  • Body tinted
  • Patterned
  • Opaque laminate
  • Screen printed or etched
  • Switchable glass
  • Sealed unit with integral blind
  • Anti-reflective glass
  • Low iron glass
  • Anti-bandit laminates
  • Polycarbonate sheet
  • Glass/polycarbonate composites
FSC certified timber used for Selectaglaze secondary glazing sub frames
Custom timber grounds can accommodate splayed or out of shape openings. All timber grounds and sub-frames are made from certified timber products.
Variety of handles and locks for selectaglaze secondary glazing
There is a range of handles, finger pulls and locks which are specific to each product. Please check the ironmongery tab on each product page to see the available options.
Sealant used for the finishing of secondary glazing installations
Timber grounds, sub-frames and aluminium frames are bedded on an acrylic sealant to provide a lasting perimeter seal.
Diagram showing the effect of the cavity between primary and secondary glazing to reduce dB levels
The cavity is the distance between the existing window and the new secondary glazing. This plays an important role when noise is an issue, the bigger the cavity the higher the insulation levels.

Secondary glazing to suit any design, shape or style of window

Whether the primary window is square or not, there will be something in the standard products range or the specialist shaped and curved treatments, that would suit the opening, match the sightlines and provide a discreet treatment.

Product sustainability – recycling and waste

Both main materials are carefully managed and extensively recycled.
  • Aluminium
    Optimized cutting programmes reduce usage, and all cutting waste is recycled. An estimated 90% of aluminium used in buildings is recycled at ‘end of life’

  • Glass
    Optimized cutting programmes minimise waste. Broken glass (cullet) is recycled in a number of ways, some being turned into new glass and some into alternative materials such as road surfacing
Find out more about product sustainability here

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