Frequently Asked Questions
Whether you’re considering installing, maintaining, or renovating sash windows, we’re here to provide you with all the information you need. In this FAQ section, we’ve compiled answers to some of the most common questions our customers have. If you don’t find the answer you’re looking for here, feel free to reach out to our expert team through our contact form.
General Information
What is secondary glazing?
Secondary glazing is an additional slimline window that sits inside of your existing windows. It offers improved thermal performance, noise reduction, and security — all without replacing your original windows or altering the external appearance of your property.
Will secondary glazing affect the look or condition of my original windows?
No. Incarnation secondary glazing is designed to be discreet and non-invasive, preserving the original character of your windows.
Will I lose the functionality of my existing windows when fitting secondary glazing?
Not at all. Our secondary glazing is designed to allow full access to your existing windows, by placing openers in the same locations as the openers on your primary windows.
What styles of secondary glazing are available?
Secondary glazing is available int eh following styles:
- Horizontal sliders
- Vertical sliders
- Hinged units (side, top, or bottom opening)
- Lift-outs
- Fixed panels
- Shaped units (arches, circles, etc.)
These can be tailored and combined to suit your window layout and access requirements.
Performance & Benefits
What thermal benefits does Incarnation Secondary Glazing offer?
Secondary glazing can reduce heat loss by up to 65%, helping lower your energy bills and improve your property’s EPC rating. Using low-emissivity glass, we can reduce U-values from around 4–5 W/m²K to 2 W/m²K or lower.
Will secondary glazing reduce noise?
Yes. Our systems can reduce noise levels by up to 45dB. In high-noise areas, this can result in up to 80% noise reduction.
How does secondary glazing improve security?
Installed internally, secondary glazing adds a hidden layer of protection. It cannot be opened from outside and can include laminated security glass, making forced entry significantly harder — even if the original window is compromised.
Does secondary glazing stop condensation?
When correctly installed, secondary glazing can help reduce condensation by promoting balanced airflow between panes. However, it does not address damp issues caused by poor insulation, insufficient airflow or structural problems.
Glass & Frame Options
What glass sizes and options are available?
We offer a selection of glass types on our secondary glazing to suit your needs, including:
- 4mm, 6mm, and 6.4mm glass options
- Available in toughened and laminated, variants
These options allow us to tailor your secondary glazing to meet both thermal and
acoustic performance goals.
Can I choose different types of safety or acoustic glass?
Yes. We provide toughened and laminated, in a variety of thicknesses. We also offer patterned and privacy glass and flyscreens as optional extras.
What is the benefit of using a subframe?
A timber subframe makes it easier to install secondary glazing in window openings that aren’t perfectly square or level. The timber can be trimmed and shaped (scribed) to closely match the existing window reveal, ensuring a more accurate fit.
Installation & Maintenance
Is secondary glazing easy to install?
Yes. All units are pre-assembled and can be fitted with minimal disruption. Installation is typically quicker than a full window replacement, and trims are available for a neat finish.
What’s the difference between reveal fixing and face fixing?
- Face Fixing is mounted to the internal face of the primary window, conserving cill space and enhancing thermal insulation.
- Reveal Fixing is installed inside the window recess and is preferred for acoustic projects, offering a larger air cavity (typically 100mm+) for superior soundproofing.
Are the products guaranteed?
Yes. We offer a 10-year guarantee on frames and panels, and 2 years on moving hardware.
Planning & Heritage Properties
Do I need planning permission for secondary glazing?
Usually not. Secondary glazing is installed internally and does not alter the building’s structure, making it suitable for almost any project, including conservation and Grade II listed properties. However, it’s best to notify your local conservation officer.
Can secondary glazing be used in conservation or listed buildings?
Yes. Incarnation Secondary Glazing is ideal for heritage properties and conservation areas. Secondary glazing is recommended by Historic England as an alternative to window replacement..
Support & Next Steps
How do I get a quote or find an installer?
Trade customers can request a quote directly through our website. Homeowners can use our Find an Installer tool to locate a trusted partner in their area.
What support is available for installers?
At Incarnation, we’re committed to supporting our installer network every step of the way. Through our Trade Installer Partner Scheme (TIPS), we offer access to a dedicated Trade Hub packed with resources — from technical documents and installation guides to marketing assets that help you promote and sell secondary glazing with confidence.
If you install secondary glazing, our comprehensive training, product knowledge, and expert support ensure you can deliver the best results for your customers. If you're interested in becoming a TIPS installer, contact us to find out how we can support your business.
