Double Glaze and Re-glaze Existing Sash
Glass replacement is one of the most common services that we provide. Whether you are looking to improve the thermal performance of your windows or reduce the noise, we will install double glazing into existing windows or supply and fit double-glazed hard wood sashes to fit within your original box or Casement Window. This is an extremely efficient method to improve your home’s heat efficiency. What is more, it is a less expensive and less disruptive process than replacing the whole box and the windows.
How to Re-Glaze Your Existing Sash Windows
The Installation Process
- We remove just the glass from your existing frames
- Install new double-glazed panes inside the same timber box
- Your period sash remains completely unchanged
- Typically completed in 2–3 days per window
What Improves (And What Stays The Same)
- Glass becomes double-layered (internal only)
- Thermal efficiency improved
- Sound reduction improved
- Your heritage frame & external look stay intact
Why Renew Glazing Instead of Replacing Sashes?
- Preserve original character & heritage value
- Lower cost than full sash replacement
- Faster installation (minimal disruption)
- Maintains listed building compliance
- Proven in 1000s of London homes
How We Re-Glaze Your Sashes – Start to Finish
Free Home Survey (No Obligation)
- We assess your existing window frames for condition
- Check for timber rot, draft issues, structural soundness
- Present glazing choices (slimline, acoustic, vacuum, etc.)
- Provide transparent, fixed quote
Ordering & Prep
- Custom-cut glass fabricated to match your frame dimensions
- Confirmed installation date scheduled
- You receive a briefing on what to expect
Installation Day
- Typically 2–3 days for most homes
- Old glass carefully removed (recycled responsibly)
- New double-glazed units installed in your original frames
- System tested, workspace cleaned
- Immediate performance improvement noticed
Aftercare & Warranty
- 5-Year Guarantee on glass + 3-Year Workmanship Warranty
Making your home more energy efficient
At Restore My Window our double-glazing services provide security, comfort, and value to your property. In our offer, you will find double-glazed sash units of different thicknesses, depending on how thick your existing windows are. Around 25% of the heat loss in an average property is through the windows and doors. Therefore, installing double glazing is a good way of making the home a more energy-efficient environment, and also reducing those monthly utilities costs.
Main reasons to choose Double Glazing
- Reduces the outside street noise levels
- Easy to maintain
- Optimum security
- Cost-Effective solution
- Adds an Insulating Layer
There is a variety of glazing options that will suit your property:
- Acoustic glass
- Security glass
- Single glazing
- Slimline double glazing
- Fineo vacuum glazing
- 12mm up to 25mm double glazing
Want an idea of the cost? Request a free quote now.
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Frequently Asked Questions
The cost of double glazing for existing frames varies depending on the size of your sash windows, the glazing unit thickness (typically 12mm to 28mm), and the type of glass chosen, whether that’s standard double glazing, slimline double glazing, acoustic glass, or Fineo vacuum glazing. At Restore My Window, retrofitting double-glazed units into existing sash frames is significantly more cost-effective than a full window replacement, as the original box frame and surrounding joinery are preserved. To get an accurate figure for your property, we recommend requesting a free quote, we cover all London boroughs and can assess your frames in person.
Yes, fitting double glazed units into old sash windows is one of our most popular services at Restore My Window. We install double-glazed hardwood sashes directly into your existing box frame, meaning there is no need to disturb the surrounding plasterwork, brickwork, or period joinery. This makes it an ideal solution for Victorian and Edwardian properties across London, where preserving the original sliding sash mechanism and architectural character is important. We offer glazing unit thicknesses to suit the depth of your existing sashes, so the double glazing fits precisely without altering the look of your windows.
Double glazing refers to replacing your existing single-pane glass with a sealed insulating unit made of two panes of glass with a gap in between, this significantly improves thermal performance and noise reduction. Re-glazing, on the other hand, is the process of replacing a broken, cracked, or failed pane of glass within an existing frame, restoring it to its original condition without necessarily upgrading to a double-glazed unit. At Restore My Window we offer both services for existing sash windows, whether you’re looking to upgrade your home’s energy efficiency with double glazing or simply need a damaged pane replaced, our team can advise on the right solution for your frames and budget.
Timber sash windows do typically carry a higher glazing cost than standard uPVC windows, primarily because the work requires specialist joinery skills and bespoke double-glazed units tailored to the exact dimensions of each sash. However, the investment is well justified, retrofitting double glazing into existing timber sash frames preserves the heritage character of your property, avoids the need for full replacement, and adds measurable value in London’s period housing market. At Restore My Window, we specialise exclusively in timber sash and casement windows, so our pricing reflects the craft involved while remaining a far more economical option than replacing the entire window unit.