Listed properties boast character and charm where they give us a brief insight into historic architecture and building techniques. These buildings have stood the test of time, however, living in a period property can feel cold and noisy due to poor draught proofing and inadequate glazing.

Upgrading windows within listed properties can be difficult as planning permission is needed from your local authority, the cost of new replacement windows can be expensive and can lead to a loss of character and charm from the overall aesthetic. Secondary Glazing has grown in popularity due to its thermal and soundproofing capabilities; it can also be installed within listed properties and conservation areas.

Listed buildings and period properties are unique in style and contribute to English and Scottish heritage. As of 2016, there were 377,587 listed buildings in England classified into three groups:

  • Grade I – 2.5% of all listed buildings are classified as Exceptional Interest.
  • Grade II* – 5.8% of all listed buildings are classified as Particular Interest.
  • Grade II – 91.7% of all listed buildings are classified as Special Interest.

What is Secondary Glazing

Secondary glazing involves fitting a discreet internal window in addition to your existing, single, double and triple glazed window. It’s a cost-effective and efficient way to insulate and soundproof your windows and preferred for the use within Listed Buildings and Conservation areas. Secondary glazing can reduce noise levels by up to 80% (54dB) and can decrease heat loss by as much as 65%.

Our tips for specifying Secondary Glazing

1. Understand if you need planning permission. Secondary glazing is often installed within listed properties to enhance thermal and acoustic insulation. The installation does not change the fabric of the building and is entirely reversible. It is discreet and unobtrusive meaning that it can’t be seen from the exterior of the building, it complies with modern construction and conservation regulations. We do recommend that you speak with your local authorities planning department or local conservation officer who will be able to give you further advice.

A quick and easy google search for your local area will give information and contact details of the planning department within your local authority. Simply visit Google and type “Listed Buildings & Conservation Areas” and your area, this Google search should return more information and advise.

2. Consider why you need Secondary Glazing and what option will provide you with optimum performance. If your listed property is cold and draughty or suffers from poor acoustic insulation, we recommend different glass types and installation methods. Installing secondary glazing closer or further apart from your primary window will affect either acoustic or thermal performance.

Thermal Insulation: Secondary glazing can block incoming draughts and prevent heat from escaping through your primary windows. For maximum heat reduction, we recommend the installation of a glass which has a Low-E coating.

This specially designed Low-E coating is thinner than a human hair and is applied to the glass, it does not compromise the amount of light that is transmitted through the glass. Low-E glass reflects heat waves into the room keeping homes warm, this in turn will reduce energy consumption. For enhanced thermal performance Granada Glazing recommend that the secondary glazing is installed no greater than 80mm away from your primary window. The air-filled cavity acts as an insulator where the Low-E glass will reflect heat into the room.

*Secondary glazing with 28mm double glazed unit is only available in our heritage hinged unit. The figures above assume that secondary glazing is installed 80mm glass to glass and thermal measurements are taken from the glass centre.

Acoustic Insulation: Secondary glazing can turn the noise of a diesel bus into a whisper as it can often reduce noise levels by up to 80% (54dB). Key to blocking noise is to install the secondary glazed system 150mm to 200mm away from your primary window.

For acoustic insulation we would recommend the installation of acoustic laminated glass, this glass will offer optimum acoustic performance. 6.8mm acoustic glass is a 0.8mm acoustic PVB (Polyvinyl Butyral) sandwiched between two 4mm glass panes. Cars, trains and planes often emit low-frequency noise which can be challenging to block, acoustic glass has been designed to block these lower frequency sound waves. Acoustic laminated glass is designed to reflect sound waves where the PVB acoustic layer absorbs the sound.

3. What style of Secondary Glazing should I select? Secondary glazing is available in multiple styles which will complement and match the function of your primary window. Special consideration should be given for cleaning, maintenance and ventilation. We advise that a secondary glazing style is selected that matches the aesthetic of your primary window, this will ensure that the secondary can’t be seen from the outside and blends seamlessly into the room.

Secondary Glazing Styles:

Vertical Sliders: Vertical sliders are used in conjunction with traditional box sash windows. A tilt in option is available which enables both panels to tilt into the room for easy cleaning. They slide up and down where both panels operate on spiral balances. These spiral balances allow the window to remain open in any given position.

Horizontal Sliders: Horizontal sliders are often installed where access to the primary window is essential. The panels slide horizontally within the frame and can be individually lifted out to give full access for cleaning and maintenance. For added durability, the panels slide on high-quality brass rollers.

Hinged Units: With one pane of glass hinged units offer an unobtrusive view and are a popular choice to be installed in conjunction with doors and large windows. Hinged units are discreet and provide minimal impact on a windows site lines.

Fixed Panel: Our most simple secondary glazing product, typically used when there’s a minimal area available for fixing into.

Lift Out: Lift outs provide one of our most cost-effective solutions – ideal for when limited access is required. They can be lifted out of the frame to give total access to the primary window for cleaning and maintenance.

Arched Units: Secondary Glazing can be arched in-house to match all styles and types of primary glazing.

4. Ask to see information and the portfolio of your chosen installer

Secondary glazing boasts exceptional acoustic and thermal performance, for optimum performance; it is essential that it is specified and installed correctly. Noise and heat can penetrate the smallest of holes, through creating a tight seal whilst installation will prevent heat escaping. Secondary glazing should look discreet and blend seamlessly into any room, and we recommend that trims are scribed in to give a clean and neat finished aesthetic. Granada Glazing partner with over 3000 trade installers across the UK where we can advise a local installer to carry out the survey and installation of the secondary glazed units.

Our bespoke secondary glazed units are designed for listed properties and are engineered on state of the art CNC machinery. This ensures all frames are manufactured with tight seals to prevent heat loss and offer exceptional acoustic performance. We can powder coat in over 200 Ral colours and arch frames in-house which ensure quality and durability. For more information on our secondary glazed units or to speak with us for advice, please talk to us directly by telephoning 01909 499 899 or email

Get in touch
Please tick here to confirm you understand our GDPR policy.