Secondary Glazing is a cost-effective way to improve the temperature of your home and reduce condensation. By adding a discrete extra layer of glazing placed inside your window frame, it helps insulate existing single and double-glazed windows. Cut-to-size secondary glazing is a customisable approach that precisely addresses the unique needs of your home, ensuring a snug and discreet fit within your window frame.
Secondary glazing also reduces sound pollution and enhances the security of your property. As an innovative approach to window insulation, it offers a range of benefits that extend far beyond its initial cost-effectiveness.
It is also easy to install yourself, we cut the acrylic to size and then you just need to add magnetic tape (sold separately) to your window frame and to the plastic sheet and stick it to the window! You can check out our step by step guide below.
For windows larger than 800mm we recommend using a thickness of at least 4mm, and our magnetic tape for larger windows.
Reduces heat loss and saves on your energy bills
When you install secondary glazing into your property, you achieve the same benefits of double glazing such as less condensation and improved heat transfer. Despite this, secondary glazing is more cost-effective and can reduce heat loss via windows by around 65% - which is 10% more than double glazing.
With a large enough gap between the window and the secondary glazing you could see a 4°C improvement in room temperature resulting in a considerable saving on your heating bill. This is exactly what Mark from Lancashire has experienced, he recently sent us the results from his personal experiment on the effectiveness of his secondary glazing which he has fitted to his existing double glazing:
"When considering the cost of secondary glazing I calculated that if it paid for itself within 2-3 years it was worth it. I only have one month's figures to work on but an indicative 4°C saving means it will reach breakeven point in the winter months of the first year." Read Mark's full findings.
Since our secondary glazing is made of clear acrylic, it can easily be cut to size for any window - even if your windows are circular. Acrylic is also easier to fit than glass due to its lightweight qualities. Due to the optical clarity that acrylic provides, there’s no noticeable difference between the visibility or light transmission of your single-glazed windows and the results of secondary glazing.
Installing secondary glazing is a fantastic option for those who are looking to insulate against noise, such as those in multi-storey buildings, or with buildings against the road. Once it is fitted, secondary glazing has been found to reduce noise by up to 80% without needing to be fit to the exterior of the frame.
Can be used on listed buildings
If you are unable to replace your existing windows with double glazing, secondary glazing is an ideal alternative which is just as beneficial. Acrylic secondary glazing is compatible with period properties and historic homes. It doesn’t detract from the external character and look of the windows of heritage properties but gives all of the insulating benefits without causing condensation.
Acrylic secondary glazing can be removed easily, meaning when the seasons change, the panels can be removed until the winter. Some people choose to keep their secondary glazing on their windows all year round as it also works to keep out dust, dirt and pollen.
Secondary glazing is more difficult to break than single-pane windows - so it gives more protection to your home.
Share your Secondary Glazing photos with us to feature on our website. Simply mention @cutmy.uk on Instagram or upload a photo and tag us!
It's so easy to install secondary glazing at home. Follow these simple six steps to do it yourself:
Step 1: Clean the frame ready for application.
Step 2: Measure and cut the steel tape (thinner tape) for the window frame. For a cleaner look in the corners, you can cut the steel tape at a 45-degree angle for a miter join.
Step 3: Apply the steel tape to the window frame. Make sure to leave no gaps in the corners so that it is as air-tight as possible.
Step 4: Peel off the protective film from the acrylic.
Step 5: Cut and apply the magnetic tape (thicker tape) to the edges of the acrylic sheet.
Step 6: Snap onto the window frame and peel off the final protective film.
Whether you choose our white or black magnetic tape, we recommend putting the thinner steel tape on the frame of your window and the thicker magnetic tape on the acrylic. This is because if you want to take the secondary glazing off in the summertime, you are only left with a thin, more discrete tape that matches your window frame colour. You can also then apply the Perspex again when winter comes back around.
Secondary Glazing Key Features
Clear Perspex® acrylic, polycarbonate, and high-impact polystyrene sheets give excellent optical clarity, ranging up to 92% light transmission, higher than most types of glass, making our clear plastic sheets an advantageous option for use in windows or as a skylight.
Clear Perspex® acrylic sheets are incredibly durable, so are often used as a secondary glazing alternative to glass, as it is resistant to impact and is shatterproof, making it a safer option. Further, clear plastic sheets are particularly useful for sheds and around the home with children and pets.
Comparably, our polycarbonate is 300 hundred times stronger than glass and 30 times stronger than our Perspex® acrylic sheets, as well as being shatter-resistant. You can expect at least 20 years of continued use from these long-lasting panels without showing signs of deterioration.
Clear acrylic sheeting is UV and weather-resistant, as well as being resistant to prolonged exposure to sunlight. In addition, clear acrylic sheets are also resistant to most chemicals and have a low moisture absorption rate, so clear plastic sheets are useful for a host of different environments and are perfect for outdoor applications.
With a higher impact tolerance to acrylic sheeting, clear polycarbonate sheets make a stronger, long-lasting alternative to both acrylic and glass. At its thickest point polycarbonate is also resistant to bullets, and its brake form is a tenth of an inch thick.
Clear cast Perspex® acrylic sheeting is easy to fabricate and can be cut, drilled and shaped to any requirements, so it’s a flexible material to work with. The cut surfaces can be polished and sanded easily for a more professional finish to your sheeting.
HIPs work out at one-third of the price of clear acrylic relative to square meter sheets, allowing secondary glazing to become an accessible inexpensive task to complete.
All of our secondary glazing plastic options are equally easy to clean, with just warm soapy water and a microfibre cloth needed to ensure a hygienic finish.
|Maximum Sheet Size||3050mm x 2030mm|
|Available Thicknesses||2mm, 3mm, 4mm, 5mm|
|Light Transmission||> 92%|
|Fire Rating||UK Class 3 Fire Rating|
|Water Absorption||0.2% (24 h, 23oC) at dry state 50 x 50 x 2mm – 40mg to ISO 60, Method 1|
|Manufacturers Tolerances||+/- 10% plus 0.4mm (e.g. 5mm cast sheet could vary from 4.1mm to 5.9mm)|
|Cutting Tolerances||+/- 1mm|
Frequently Asked Questions
Will secondary glazing really save me money on my heating bills?
With a large enough gap between the window and the secondary glazing you could see a 4°C improvement in room temperature. This is exactly what Mark from Lancashire has experienced, he recently sent us the results from his personal experiment on the effectiveness of his secondary glazing which he has fitted to his existing double glazing:
Mark sent us this photo of his secondary glazing set up, as you can see there's an amazing 5.3°C difference between the thermometer inside the room to the one on the other side of the secondary glazing.
What do you use for secondary glazing?
Secondary glazing can be done with a clear acrylic or polycarbonate sheet, attached into place with a removable fastener such as our magnetic tape, allowing you to remove the secondary glazing during the warmer periods.
How much does secondary glazing cost?
This will depend entirely on the size of your window. For a window measuring 635 x 890 mm, which is a fairly common window size in the UK, our 3mm plastic secondary glazing kit would cost only £55.41 - when compared to the cost of buying new uPVC casement windows, labour costs, and a plasterer to refinish the internal areas round the window, you'll be saving hundreds.
What thickness do I need?
We recommend 4mm for secondary glazing. This thickness offers improved insulation properties and enhanced protection against noise and drafts. It is a common choice for secondary glazing in residential buildings and provides a good balance between insulation and affordability.
2mm: Only to be used on very small windows. 2mm offers basic protection but may not provide significant insulation or soundproofing benefits.
3mm: A good budget option for small windows under 800mm, still lightweight and suitable for basic insulation and protection against drafts. It provides better durability than 2mm and more rigidity.
4mm: Our recommended thickness, you'll certainly notice the improved insulation properties and reduction in condensation, noise and drafts. Any window larger than 800mm will benefit from the rigidity of 4mm.
5mm: Thicker acrylic provides the maximum enhanced insulation and soundproofing benefits. It is suitable for areas where noise reduction and thermal insulation are crucial, such as homes located near busy streets or commercial areas. 5mm is ideal for large windows over 1.5m but it will be heavy so you'll need our thicker magnetic tape and a windowsill or wooden baton to rest it on to take the majority of the weight.
Can perspex be used for double glazing?
Due to the optical clarity that acrylic provides, there’s no noticeable difference between the visibility or light transmission of your single-glazed windows and the results of secondary glazing. Often a preferable alternative to double glazing, particularly for heritage properties, acrylic doesn’t detract from the external character and look of the windows but gives all of the insulating benefits without causing condensation.
Does plastic secondary glazing work?
When you install secondary glazing into your property, you achieve the same insulating benefits of double glazing such as lower energy bills and improved heat transfer. Secondary glazing can reduce heat loss via windows by around 65% which is 10% more than double glazing.
How do you measure secondary glazing?
Using a measuring tape, measure the height and width of the frame you are attaching the glazing to then add on the width of the magnetic tape. It is also worth considering that not all windows are perfectly shaped so measurements will need to be taken in multiple places for a truly accurate end result.
Will it help with condensation problems?
Secondary glazing can be very effective at preventing condensation and mould growth on windows in cold climates. However, this does work best if the secondary glazing has a breathable gap between the panes rather than a fully sealed unit. This allows some airflow which helps prevent the build-up of condensation.
How do I open or clean my windows?
As our secondary glazing kits are magnetic, you can simply remove the plastic sheet for quick and easy access for cleaning or extra ventilation.