Secondary Glazing

I have developed a system of secondary double glazing that significantly improves the thermal and acoustic efficiency of single glazed windows. The frames are made form timber and individually designed,made and finished/painted for every installation. Contact me about a feasibility visit and a quote!

There are number of mass produced aluminium products on the market. While these can offer more alternative ways of opening the seconary unit, they are often bulky and obtrusive and can prove very expensive (often as much as replacing the whole window)! My installations cause minimum damage to the existing frame (usually just a few screw holes) and do not change the character of the façade, this makes it ideal for period properties and conservation areas. They are also a very cost effective alternative to the aluminium mass produced product.

I am not able to offer secondary glazing for every window, but I have created solutions for a large number of different window types from Georgian town houses to Dartmoor cottages. I have worked with listed properties and a National Trust property.·

click on images for links

Secondary glazing can give significant noise reduction. Noise reduction of up to 80% can be achieved. Even in less than ideal instalation situations, 50% noise reduction is almost certain.
Secondary glazing will reduce condensation.
Secondary glazing will help make your home more energy efficient and help save you money on your fuel bills.
Secondary Glazing does not change the character of the facade and so is ideal for listed buildings or those in conservation areas. English Heritage guidelines advocate the use of secondary glazing. (see link in technical)
Secondary Glazing can improve a building's rating on a Energy Performance Certificate and can become a factor in a property valuation.
Secondary Glazing will enhance security of the window.

Technical Stuff

Noise Reduction
The cavity makes the difference. Secondary Glazing is the most effective solution for reducing intrusive noise through glazing. The gap between an existing primary window and the secondary unit makes a big difference to the level of noise insulation. Unlike sealed units, where the two pieces of glass are coupled together at a fixed distance (usually 6-20 mm) with a secondary unit the primary and secondary windows act as independent barriers to the transmission of noise. The greater the cavity between them, the better the dampening effect of the combined window.

It is also possible to fit glass of a different thickness in the secondary unit to that of the primary window. When the inner and outer glass have a different mass, higher frequency noise is reduced through the reduction of ‘sympathic resonance’. Using a thicker glass improves performance, particularly at lower frequencies. There are also a range of specialist glasses available to further reduce sound if necessary.

Improved Thermal Insulation
Depending on the nature of the installation, the type of existing window and the type of glassed used in the secondary unit, varying degrees of thermal insulation can be achieved. It is possible to achieve 60 – 70% improvement in each window.
There are specialist glasses which can be used to further improve thermal efficiency however from experience, I have found that the greatest gain in thermal efficiency when fitting secondary panels is through the elimination of drafts. Ill fitting sash and casement windows in many period houses are the greatest cause of heat loss.

Safety, Planning etc.
It is sometimes necessary and sensible to fit laminated or toughened glass in ‘critical locations’ (as defined by part N of The Building Regulations). This will add to the cost.

Living in a listed building or conservation area, means that replacing existing windows with double glazing is often not an option due to planning restrictions. Fitting internal secondary glazing is ideal as it does not require planning permission (with a very few exceptions).

There is information from the Energy Saving Trust on windows generally at

English Heritage produce a guide to secondary glazing historic buildings.


“its CONSIDERABLY warmer in our room this evening. Thank you so much for your expertise and hard work”.
J & J Chagford

“Thanks for your efforts recently, the bedroom was transformed with the secondary glazing. The large draughty bays made it almost uninhabitable in the winter”
P & J St Leonards, Exeter

"the kids rooms are much warmer this winter. We hope to do some more rooms this year" T & I Topsham, Devon.