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Secondary Glazing: The Ultimate Solution for Heritage Homes & Listed Buildings
Secondary Glazing: The Ultimate Solution for Heritage Homes & Listed Buildings
Category: Products / Soundproofing
Reading Time: 5 Minutes
📌 The 10-Second Summary
- The Problem: You live in a Listed Building or Conservation Area and cannot replace your single-glazed windows.
- The Solution: Secondary Glazing adds a discreet internal aluminium frame with a large air gap.
- The Result: Up to 80% noise reduction (better than double glazing) and significantly reduced heat loss.
Secondary glazing is often misunderstood. Many homeowners view it as a “compromise”—an ugly, clunky extra pane of glass you only install if the Council forces you to.
The reality is very different. Modern, slimline aluminium secondary glazing is a high-performance engineering solution. In fact, for acoustic insulation, it creates a barrier that even the best triple glazing struggles to beat.
Table of Contents
1. Why Choose Secondary Glazing?
If you live in a modern house, you replace the windows. But if you live in a period property in Hampshire, that might not be legal—or desirable.
Secondary glazing involves fitting a discreet, slimline aluminium frame with its own glass on the inside of your existing window reveal. This leaves your original timber sash or Crittall windows completely untouched.
2. Head-to-Head: Secondary vs Replacement
Most people assume replacement double glazing is always the best option. But when it comes to noise, Secondary Glazing is actually the superior choice.
3. The Science: The 100mm Gap
The secret isn’t just the glass; it’s the gap. Unlike a sealed unit, secondary glazing allows for a massive air space between the old window and the new pane.
Ideal Gap: 20mm – 50mm. This stops convection currents transferring cold air, acting like a “double skin” for the house to eliminate draughts.
Ideal Gap: 100mm – 150mm. The large air volume dampens sound vibrations. Combined with Stadip Silence acoustic glass, this is the ultimate noise barrier.
4. Styles & Operation
Modern units are designed to align with your existing window sightlines (the bars), making them virtually invisible from the outside.
| Style | Best Used For |
|---|---|
| Vertical Sliders | Sash Windows. The panes slide up and down, counter-balanced by springs, matching the operation of your original window. |
| Horizontal Sliders | Casement / Crittall Windows. The panes slide left to right, allowing easy access to the primary window for ventilation. |
| Lift-Out Units | Fixed Windows. For windows you rarely open but need to clean behind occasionally. Ideally for smaller apertures. |
5. Frequently Asked Questions
Yes, it is very effective. By creating an internal seal, it prevents the warm, moist air inside your home from hitting the cold single-glazed outer window. This stops water droplets forming on the glass.
Absolutely. We design the secondary system to match your primary window. If you have a sliding sash, we fit a sliding secondary unit. You simply slide the inner pane up, then the outer pane up, to get fresh air.
If installed with a 100mm+ air gap and acoustic glass, secondary glazing can reduce noise by over 50 decibels. To put that in perspective, standard double glazing reduces noise by about 30-35 decibels. It is the difference between hearing a car drive by and silence.
📚 KJM Knowledge Hub
Further reading on heritage and soundproofing:
Mark Pearce is a highly experienced specialist in the double glazing industry, having built his knowledge from the ground up through hands-on experience in installation, manufacturing, sales, and business management. Beyond his role at KJM, Mark is a keen blogger, writer, and traveller, often sharing insights on the latest innovations in the home improvement industry.
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