Comparing Insulation Solutions for Single Glazed Sash and Other Timber Windows: Double Glazing vs. Conventional Secondary Glazing vs. Gecko Glazing

When it comes to improving the energy efficiency and reducing the noise and condensation associated with single glazed sash and other timber windows, choosing the right insulation solution for your windows is key. Secondary glazing and double glazing are two popular options, each with their own benefits and drawbacks. Let’s dive into a comprehensive comparison to help you make an informed decision, and outline why Gecko Glazing, our unique form of secondary glazing, is the best solution of all.

What is Double Glazing?

Double glazing involves completely replacing existing single glazed windows, or just the glass in existing frames, with sealed units consisting of two panes of (usually ‘low emissivity’) glass separated by a layer of air or an inert gas such as Argon or Xenon. This provides improved insulation and noise reduction and increases property values.

In heritage areas, it is usually not allowed, or desirable, to replace timber windows with UPVC double glazed windows. Usually, timber replacements mimicking the originals is the option of choice.

Advantages:

• Good thermal insulation, reducing heat loss significantly and improving comfort
• Largely eliminates condensation
• High levels of noise reduction.
• Enhances property value for many homes.
• Often better sealed than original windows, so reduces draughts

Disadvantages:

• Extremely high cost, particularly for custom or heritage properties, so providing an extremely poor return on investment
• Requires the removal of original windows, potentially altering the property’s character and requiring heritage building fabric to be sent to landfill.
• Disruptive, time consuming and invasive installation.
• High embodied carbon due to the production and transportation of new materials. Therefore not an environmentally positive option. 
• Thermal performance is not nearly as good as, for example, UPVC triple glazing, and little better than secondary glazing. 
• Quality and expected lifespan of replacements, especially timber frames, are generally lower than those of windows being replaced. 

What is Conventional Secondary Glazing?

Conventional secondary glazing involves fitting additional panes or panels over the existing window frame. Typically it consists of a vertically or horizontally sliding, aluminium framed system. It tends to be better for heritage or listed properties as it retains the original windows while improving insulation.

Advantages:

• Significantly reduces heat loss.
• Reduces noise substantially
• Largely eliminates condensation.
• Around half the price of replacement double glazing, so a better return on investment.
• Somewhat easier installation.
• Preserves the original building fabric, so better for heritage buildings.
• Can completely prevent draughts

Disadvantages:

• May not match the thermal or acoustic performance of high-quality double glazing.
• Generally inhibits window opening and can obstruct shutters
• Generally visually quite obtrusive
• Draughts reduced ‘too much’, such that inadequate ventilation is allowed, potentially increasing damp issues
• Not a DIY option
• Still quite expensive relative to benefits

Gecko Glazing

Advantages:

• Significantly reduces heat loss, often by up to 50%.
• Largely eliminates condensation
• Around 80% cheaper than replacement double glazing, so an excellent return on investment.
• Completely non-invasive and reversible, making it ideal for heritage buildings.
• Extremely fast and easy installation with minimal disruption.
• Can be installed DIY, further reducing cost
• Almost invisible once installed, maintaining the original appearance of the property and preserves the original building fabric.
• Very low embodied carbon, so a far better choice environmentally.
• Does not obstruct existing windows or shutters in any way

Disadvantages:

• May not match the thermal performance of high-quality double glazing, but will provide largely the same performance as conventional secondary glazing
• Do not prevent draughts by themselves. Installation of brush strips is advisable as the best way to reduce draughts without compromising ventilation. 
• Does not reduce noise as much as conventional secondary glazing.

Which Solution is Right for You?

The choice between double glazing, conventional secondary glazing and Gecko Glazing will depend on your budget, property type, and priorities. If you own a listed or heritage property, secondary glazing is likely the best option, offering significant energy savings while preserving the historic building fabric. Conventional secondary glazing may be best if reducing noise is your primary objective, but otherwise Gecko Glazing is likely to provide the best combination of features at lowest cost. For those looking to replace old windows that are failing entirely, double glazing may be the better choice—albeit with a much higher upfront cost.

Conclusion

Double glazing, conventional secondary glazing and Gecko Glazing all have their strengths, but Gecko Glazing stands out for its affordability, ease of installation, and suitability for heritage homes. It’s a smart, sustainable choice for homeowners looking to reduce heat loss, improve comfort, and preserve their property’s charm.

Learn more about how Gecko Glazing can transform your windows here.