Why choose acrylic secondary glazing for your home?

What is acrylic secondary glazing exactly?

Do you feel drafts or cold coming from your window, but replacing the glass isn't an option? For example, because you have single glazing, want to preserve stained glass, or live in a listed or historic building. An acrylic secondary glazing panel is then a practical solution. You place an acrylic sheet, also known as PMMA or acrylic glass, in front of the existing window, usually on the inside of the frame. This keeps the original window intact while adding extra comfort. plexiglass a sheet (PMMA, also known as acrylic) fitted in front of the existing window, usually on the inside of the window frame. This leaves the original window intact, whilst adding extra comfort.

How does secondary glazing improve insulation?

The principle is simple: an insulating layer of still air is created between the existing glass and the acrylic panel. This air gap reduces heat loss and helps minimise cold draughts around the window. This is the insulating effect of secondary glazing. The benefits are most noticeable in rooms that cool down quickly or where condensation regularly forms on the original glass. For the best performance, the secondary glazing should fit tightly within the window frame to minimise air circulation around the edges.

A More Comfortable Home Without Major Renovations

An acrylic secondary glazing panel is an excellent choice for homeowners who want to improve comfort without undertaking major renovations. In bedrooms, living rooms, home offices, or older properties with single glazing, an additional acrylic panel helps reduce cold spots around windows and creates a warmer, more comfortable indoor environment. It is also ideal if you want to preserve the character of your home, such as stained glass or original timber window frames, because the existing window remains fully visible and untouched. This allows you to make your home more comfortable, energy-efficient, and enjoyable to live in, one step at a time.

Benefits of Acrylic Secondary Glazing for Your Home

Thermal Insulation: Upgrade Single Glazing Towards Double-Glazing Performance

An acrylic secondary glazing panel is a practical way to significantly improve the insulation of single-glazed windows without replacing the entire window frame. Acrylic (PMMA), also known as acrylic glass, has a thermal conductivity of approximately 0.19 W/mK. In practice, installing a 4 mm acrylic secondary glazing panel on a single-glazed window can reduce the overall U-value to around 2.7 W/m²K, which is comparable to older double glazing. By comparison, standard single glazing typically has a U-value of 5–6 W/m²K. This improvement helps reduce heat loss, increases indoor comfort, and can contribute to lower energy consumption. secondary window Single glazing can achieve a U-value of around 2.7 W/m²K. This is similar to older double glazing. By way of comparison, single glazing usually has a U-value of around 5–6 W/m²K.

Thanks to this improvement in insulation, heat loss through the window can be significantly reduced. In homes with single glazing, energy savings of up to around 20% are achievable, depending on factors such as the airtightness of the window frame, the width of the insulating air gap, and the total glazed area.

Sound Insulation and Added Protection

In addition to improving thermal insulation, acrylic secondary glazing provides extra comfort and protection. The combination of a second glazing panel and an insulating air gap offers several additional benefits:

• Reduces draughts by allowing you to achieve a better seal on the inside of the window.
• Reduces outside noise, especially from traffic or playing children;
• Protects delicate stained glass or decorative glass from impacts and cracks;
• Reduces condensation on the inside of the window, provided that adequate ventilation is maintained.

For acrylic secondary glazing, clear, dimensionally stable sheet material is usually the preferred choice. You can find suitable options in our range of plastic sheets, and we can also help you with custom sizes and practical installation advice.

Acrylic vs. Polycarbonate: Which Material Should You Choose?

For an acrylic secondary glazing panel, the choice mainly comes down to clarity, scratch sensitivity, and how you want to use the panel: fixed or removable. Acrylic (PMMA) is crystal clear and gives your window a sleek finish. Polycarbonate is a good alternative when impact resistance is the main priority, but it is generally less glass-like in clarity and scratches more easily. For this, view our polycarbonate sheets.

When Should You Choose XT or GS Clear Acrylic?

When choosing custom-cut acrylic, you will often see two variants: XT and GS. Clear Acrylic XT cut to size (extruded) is more affordable and easy to work with. This makes it a practical choice for a removable acrylic secondary glazing panel in spaces such as a storage room, workspace, or guest room.

Custom-cut Clear Acrylic GS (cast) has a higher surface quality and even sharper optical clarity. If you want the most discreet secondary glazing panel possible for a living room or kitchen, with a premium finish, GS is usually the best choice. Unsure which option best suits your desired secondary glazing insulation, installation method, or how to fix an acrylic secondary glazing panel? We are happy to help you find the right solution.

How to Install Acrylic Secondary Glazing

Measure, Choose the Right Thickness and Order Cut to Size

Measure the frame carefully before ordering an acrylic secondary glazing panel. Take the reveal size, or internal frame measurement, at several points: left, centre and right, as well as top and bottom. Always use the smallest measurement, so the panel fits neatly and you avoid putting stress on the sheet.

Then choose the right thickness. Use 4 mm for small windows, 6 mm for medium-sized windows, and 8 mm or more for larger surfaces or when extra rigidity is required. Order your sheet cut to size, so you do not need to saw it yourself and the edges remain neat. For clear acrylic secondary glazing, custom-cut Clear Acrylic XT and custom-cut Clear Acrylic GS are practical options. View the possibilities in our range of acrylic sheets.

Fixing Methods: Turn Buttons, Profiles and Sealing Tape

Choose a fixing method that matches how often you want to remove the secondary glazing panel. Install turn buttons or mounting clips by screwing them into the window frame and pressing the panel into place; this is useful if you want to remove it quickly. Fit an aluminium frame around the panel if you want a neat finish and extra rigidity. If you prefer to screw directly through the sheet, pre-drill the holes and use rubber washers, allowing enough space for thermal expansion.

Always apply insulation tape or draught excluder tape around the edges to ensure a good airtight seal and better secondary glazing insulation. If there is a risk of condensation, drill small ventilation holes at the top and bottom if the space between the glass and acrylic is not fully sealed. Want to buy an acrylic secondary glazing panel with advice on installation? Feel free to contact our specialists.

Acrylic or Glass: What Are the Practical Differences?

When choosing acrylic secondary glazing, the key considerations are ease of installation, safety, and maintenance. Compared with traditional glass secondary glazing, these are the main differences:

1) Weight: acrylic weighs approximately 50% less than glass. You will notice this immediately when measuring, lifting and installing, especially with larger panels or when working alone. It also generally makes installing acrylic secondary glazing easier.

2) Strength: acrylic is approximately 25 times more impact resistant than glass. This makes it much less likely to break during transport or installation, which is particularly beneficial for indoor applications and windows that are opened and closed regularly.

3) Scratch Resistance: acrylic is more prone to scratching than glass. Clean it with a soft, clean cloth and preferably a cleaner specifically designed for acrylic or plastics, and avoid abrasive cleaners or rough sponges.

In most indoor applications, acrylic is a practical and proven choice for secondary glazing, especially when improving thermal insulation is one of your main goals. If you're unsure which solution is best for your situation, feel free to contact our Kunststof Forte customer service team for expert advice.

Buy Acrylic Secondary Glazing Cut to Size from Kunststof Forte

Want to buy acrylic secondary glazing that fits straight away and neatly aligns with your window frame? Kunststof Forte supplies acrylic cut to size, so you do not need to saw or adjust a standard sheet yourself. Simply provide your measurements and we cut the panel to your specified dimensions. This allows you to start installation quickly and helps prevent gaps that could reduce the insulation performance of your secondary glazing.

For a clear result, you can choose from options such as custom-cut Clear Acrylic XT and custom-cut Clear Acrylic GS. Unsure which version best suits your application, for example for acrylic secondary glazing with magnets, screws or Velcro? We are happy to advise you based on your situation and desired finish.

Is it for several windows or a larger project? Simply request a custom quote. If you have a practical question or need technical advice, please contact our customer service team. You will receive clear guidance, reliable delivery, and the confidence that you are choosing the right material.