Secondary Glazing Cost: Is It Cheaper Than Double Glazing?

How much does secondary glazing cost?

Professional secondary glazing costs between £150 and £350 per square metre installed, depending on the system type, glass specification, and installation complexity (Energy Saving Trust, May 2026). For a typical window measuring 1.5 m² (e.g. a standard sash window around 1.2m wide by 1.5m tall), expect to pay £225-£525 per window.

DIY secondary glazing kits cost £50-£150 per window for basic magnetic or clip-on acrylic systems. More sophisticated DIY sliding or hinged systems cost £150-£300 per window but require accurate measuring and basic carpentry skills.

These prices include the secondary glazing unit (frame, glass or acrylic, seals, and hardware) plus professional fitting where relevant. They do not include any repairs to the existing primary window, which may add £50-£200 per window if draught-proofing, sash cord replacement, or repainting is required.

Secondary glazing costs by type

The type of secondary glazing system affects both cost and performance. Here are typical costs per square metre for professionally installed systems:

Fixed secondary glazing: £150-£250 per m²

Fixed secondary glazing is the cheapest option. The secondary pane is screwed or clipped into a permanent frame attached to the window reveal or existing window frame. It cannot be opened for ventilation or cleaning unless fully removed (Selectaglaze product data, 2026).

Fixed systems are best for windows you rarely or never open, such as upper-floor sash windows, landing windows, or side panels in bay windows. They offer the best acoustic and thermal performance for the price because there are no moving parts or potential air leakage paths.

Hinged secondary glazing: £200-£300 per m²

Hinged (side-opening or top-opening) secondary glazing allows you to swing the secondary pane open for access to the primary window for cleaning and ventilation. Hinged systems use friction stays or lockable hinges and are held closed with magnetic catches or cam locks.

Hinged units are ideal for windows you open regularly but where you want the secondary glazing to remain in place year-round. They work well in living rooms, bedrooms, and home offices where you want both insulation and occasional ventilation.

Sliding secondary glazing: £250-£350 per m²

Horizontal or vertical sliding secondary glazing runs on tracks fitted to the window frame or reveal. Sliding systems allow easy access to the primary window without the space requirement of a hinged pane. They are the most versatile option for frequently used windows.

Sliding secondary glazing is the most expensive system because it requires precise fabrication and multiple moving parts. However, it offers the best combination of access, aesthetics, and day-to-day usability for windows in kitchens, bathrooms, and other high-use rooms.

Lift-out secondary glazing: £100-£180 per m²

Lift-out panels are lightweight acrylic or thin glass panes held in place by magnetic strips or plastic channels. They can be removed entirely in summer and stored away. Lift-out systems are the cheapest secondary glazing option and popular for DIY installation.

Lift-out panels work well for seasonal use (installed October to April) and in homes where aesthetics matter, as they can be stored when not needed. They are less durable and weathertight than fixed or hinged systems but adequate for most domestic windows.

Secondary glazing vs double glazing: cost comparison

Replacing single-glazed windows with double-glazed units costs significantly more than adding secondary glazing. Here is a direct comparison for a typical sash window (1.5 m²):

Secondary glazing typically costs 40-60% less than full double-glazed window replacement (Historic England, updated March 2026). For a typical house with 12 single-glazed sash windows, secondary glazing costs £3,600-£6,000 compared to £10,800-£18,000 for full double-glazed replacements.

The thermal performance difference is relatively small. Secondary glazing on a single-glazed window achieves a U-value of around 1.8-2.2 W/m²K, while a modern double-glazed sash window achieves 1.4-1.8 W/m²K. Both represent a 60-70% reduction in heat loss compared to bare single glazing (4.8-5.2 W/m²K).

For noise reduction, secondary glazing often outperforms double glazing because the larger air gap (typically 100-150mm) between the primary and secondary panes is more effective at blocking sound than the narrow 12-20mm gap in a sealed double-glazed unit. This makes secondary glazing particularly attractive for homes on busy roads or near railways.

When is secondary glazing better value than double glazing?

Secondary glazing offers better value in several scenarios:

Listed buildings and conservation areas

If your home is listed or in a conservation area, replacing original windows with double glazing may require planning permission and is often refused. Secondary glazing is usually permitted because it is reversible and does not alter the external appearance of the building (Historic England guidance, 2026).

Secondary glazing is also the preferred solution for homes with original features like Victorian sash windows or Georgian glazing bars, where replacement would harm the building's character and value.

Noise reduction priority

If reducing external noise is your main concern, secondary glazing with a 100-150mm air gap typically outperforms double glazing. Traffic noise, aircraft noise, and railway noise are all reduced more effectively with secondary glazing because low-frequency sound requires a wider air gap to block.

For maximum noise reduction, acoustic-grade secondary glazing with laminated glass can achieve sound reduction of 45-50 dB, equivalent to cutting perceived noise by around 75-80%. This level of performance is difficult and expensive to achieve with replacement windows.

Rented properties and temporary installations

Secondary glazing is fully reversible. If you are a tenant or plan to move within a few years, lift-out or magnetic secondary glazing systems can be removed without damaging the property. This makes secondary glazing attractive for renters or homes where you want flexibility.

Budget constraints

If you need to improve multiple windows but have a limited budget, secondary glazing allows you to treat more windows for the same cost. For example, £5,000 will buy secondary glazing for 12-15 windows but only replace 5-7 windows with double glazing.

The energy savings are similar in percentage terms (both reduce heat loss by around 60-70%), so treating more windows with secondary glazing often delivers better whole-house performance than replacing fewer windows with double glazing.

DIY secondary glazing: how much can you save?

DIY secondary glazing can cut costs by 50-70% compared to professional installation. Basic magnetic acrylic systems cost £50-£100 per window and take 30-60 minutes to fit with no special tools required.

DIY sliding or hinged systems using aluminium extrusions and polycarbonate or glass panels cost £100-£200 per window and require accurate measuring, cutting, and drilling. You will need a tape measure, drill, saw (for cutting extrusions), and screwdriver. Most suppliers provide full installation instructions and cutting services.

For a typical house with 10 windows, DIY secondary glazing costs £500-£1,500 in materials compared to £3,000-£5,000 for professional installation. The trade-off is time (expect 1-2 hours per window for DIY fitting) and finish quality (professional installations are generally neater and better sealed).

DIY secondary glazing is most cost-effective for:

• Lift-out seasonal panels (easiest to fit, no permanent fixings)
• Fixed panels on rarely-opened windows (simplest construction)
• Homes with simple rectangular windows (no curves or unusual shapes)
• Tenants who cannot make permanent alterations

Professional installation is usually worth paying for on complex windows (bay windows, arched tops, odd shapes), sliding systems (require precise alignment), and when installing more than 10-12 windows (time saving becomes significant).

Does secondary glazing qualify for VAT relief?

Secondary glazing installed in a residential property qualifies for the reduced 5% VAT rate under the energy-saving materials scheme. This applies to both supply and professional installation (HMRC Notice 708/6, April 2026).

The 5% rate saves around £40-£70 per window compared to the standard 20% VAT rate. Make sure your installer applies the reduced rate; most reputable secondary glazing companies do this automatically, but DIY kits purchased retail are charged at 20% unless explicitly advertised as energy-saving materials.

Note that double-glazed replacement windows do not qualify for reduced VAT; they are charged at the standard 20% rate unless installed as part of a renovation of a property that has been empty for at least two years.

Ongoing costs and maintenance

Secondary glazing has minimal running costs. Most systems require only occasional cleaning (wipe both sides of glass once or twice per year) and checking that seals and catches remain in good condition.

Professional aluminium-framed secondary glazing typically lasts 20-30 years with no component replacement. Acrylic panels may scratch or yellow after 10-15 years in direct sunlight but can be replaced at low cost (£30-£60 per panel for DIY, £80-£150 per panel for professional). Hinges and friction stays may need replacing after 10-15 years (£20-£40 per window).

In comparison, double-glazed sealed units can suffer from misting or seal failure after 10-20 years, requiring full unit replacement at a cost of £150-£350 per window. Secondary glazing avoids this problem because the air gap is not sealed, so condensation between panes is less common and easier to resolve when it occurs.

Related guides

• Secondary Glazing for Sash Windows (period homes cornerstone guide)
• Double Glazing Cost Guide
• DIY Secondary Glazing: Step-by-Step Guide