Secondary glazing for original sash windows

Improve energy-efficiency and cut down noise with secondary glazing

At Ventrolla, we know that sometimes double glazing is not the right solution for upgrading your timber sash or casement windows. It may be that you live in a listed building or your property is subject to the regulations of a conservation area. In these cases, secondary glazing is an ideal alternative and we have years of expertise crafting and installing it in homes from the Victorian, Edwardian and Georgian era.

A discreet solution for upgrading authentic timber windows

Secondary glazing is a fully independent internal window, fitted on the room side of an existing window. It’s usually constructed with a lightweight and thin aluminium frame, so it won’t block the sunlight, look ugly or obstruct your view. There are many styles to choose from too, so you can trust us to suggest the most suitable option for your property:

Lift Out Units

Used where the primary window is fixed or where a customer seldom requires access to open the window for ventilation.

Hinged Units

Generally used with casement/hinged primary windows.

Vertical Sliders

Often used on vertical sliding sashes with the meeting rails aligning with the primary window meeting rail.

Horizontal Sliders

Normally used in conjunction with sash or casement windows where full access is required and where there is sufficient space internally to open the casement secondary glazing.

We recommend having your primary windows inspected at the same time as a secondary glazing survey, ask our team for more details.


Elegant, bespoke secondary glazing in two period-style ranges

Our secondary glazing is designed to seamlessly blend into the style of your property. Choose from a traditional or heritage design, below. 

Whichever design you choose, it’s reassuring to know that all products offer a high level of additional security, easy access to the primary windows and secure night ventilation position.


With its slim, discreet aluminium profile, offering minimal sight lines and easy access to the primary glazing, making it a popular choice with homeowners.


Using a slightly thicker, heavy-duty aluminium profile suitable for large-scale commercial installation, as well as smaller applications.

Cut down noise from busy roads

For many homeowners, traffic noise is a key concern. In these instances, secondary glazing with thicker glass can make the world of difference. Well-fitted secondary glazing provides outstanding noise reduction – outperforming double glazing – and our acoustic glass provides maximum sound insulation. The minimum gap between the primary window glazing and the secondary glazing must be 100m – and to achieve a higher acoustic performance, a gap around 150mm is desirable. If the reveal is insufficient to achieve the minimum 100mm gap, the window will require boxing out to the required depth. Our Surveyors will advise on this and any other issues at the time of the survey.

Chilton Dynamics, market leaders in acoustic testing and modelling, found our windows capable of reducing noise levels by over 50dB, enough to quieten the busiest railway line or rumbling road

Make your home feel warmer

A draughty home can be uncomfortable and leave you with expensive energy bills. By creating a second barrier to the elements, secondary glazing is an ideal way to reduce wasteful thermal heat loss. Our bespoke solutions create an insulating layer of air – this is important to the retention of energy as the fitment and seals.

With the right glass, heat loss can be reduced by as much as 65%. For thermal insulation, low-E glass is often the best choice because the glazing has been engineered to provide a range of benefits: The best single glazing insulation  |  Maximum energy conservation  |  Extremely discreet installation  |  Environmentally friendly solution  |  Affordable investment with quick returns

Our installations can exceed Building Regulations’ requirements, offering significant cost savings in the process. They are also sympathetic to traditional buildings, maintaining their appearance and integrity.

Relax in a more secure home

Windows are often seen as a weak point in building security. At Ventrolla, our secondary glazing offers an affordable, discreet and highly effective solution to help counter this problem.

Unlike single windows, secondary glazing offers a range of benefits: Extremely difficult to open from the outside  |  An additional physical barrier against forced entry  |  Outer glazing can act as a vibration-sensitive alarm  |  Tough aluminium frames are securely fixed to resist forcing  |  The use of cutting tools is deterred through a combination of glass, resin and polycarbonate  |  Risk of tampering with locks and catches, or removing glass or glazed panels, is minimised

Can secondary glazing be installed in my listed building?

If your home is listed, in a conservation area or has protected status then secondary glazing is the preferred method of upgrading your home’s energy efficiency and sound insulation. It is advised that before undertaking any work you contact your local conservation officer to check what is and is not allowed before starting any renovation. We have a vast wealth of experience and can help you get permission for works and navigate the process.
You can read our do’s and don’ts of listed building restoration here.

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From secondary glazing to bespoke replacement windows and everything in-between, we can help you:

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