42004
5 March 2025

Tom Coles of Mitchell& Dickinson answers your questions on beating the draughty window challenge in period and listed properties

Pictured left isCosyGlazing,the advanced secondary glazing solutionfromMitchell & Dickinson; while picture right is the company's MD, Tom Coles

Mitchell & Dickinsonspecialises in delivering bespoke insulation solutions for period homes and listed buildings in the UK.

How expensive is it to secondary-glaze one window; why not buy a new window?

Price is dependent on the type of window. Installing CosyGlazing to a sliding sash window or an arched topped stone mullion window is much more complex than a casement window. If you live in a listed property, replacing windows isn't usually an option - and why would you want to put an original window in landfill when you can restore and insulate it?

Is secondary glazing less expensive than replacement windows?

Again, this very much depends on the style of the window; replacement windows are not usually an option or desirable in period or listed buildings.  A hybrid solution may be best. For example, sashes may need to be replaced while the frames, which can be restored to good order, do not.

How does insulation keep my home cooler in the summer?

A well-insulated loft will definitely help keep your home cooler in the summer as the heat that penetrates through your roof will be trapped in the loft.  A sloping ceiling can also be insulated with wood fibre insulation for exactly the same reason. It is equally important that heat is retained in the winter and expelled in the summer; a building must not overheat as this will damage the fabric of the structure.

I've heard people can't get mortgages for homes with spray foam insulation. Is your sheep's wool insulation acceptable to mortgage lenders?

Yes...

You treat your wool with borax. What is this?

Borax is a natural mineral used to treat sheep's wool to prevent insects (including moths) from eating the wool.

Are there areas in my home that would not be suitable for your insulation?

We take a whole-house approach to insulation, so one of our experts would visit your home to enable us to offer the right insulation advice. We have a range of solutions for listed buildings including deep restoration, draughtproofing, secondary glazing and vacuum glazing (Fineo) to choose from.

Will I save money?

Yes! In a typical period home, 30% of heat is lost through draughts, 20% through single glazed windows and 10% through the loft.  When employing Mitchell and Dickinson's bespoke solutions depending on your building's nuances, it is possible to reduce heating bills by 50%.

Will it be too hot in summer?

No.  We future proof all buildings in a project so that you can open and close windows all year round. This may sound simple but the windows will not contract or expand and "get stuck" - as is common with old buildings.

Will it reduce noise?

Many of our customers report a significant reduction in noise having installed CosyGlazing and/or draught proofing, although everyone's tolerance to sound is different so we don't guarantee noise reduction. If noise reduction is important to you, in addition to improved thermal efficiency, there are modifications we can suggest.  The initial discussions with a customer determine the main objectives of a project and, if noise is key, then we will develop a solution focussing on acoustics.

What about condensation?

In the majority of cases, installing CosyGlazing reduces condensation, although we cannot guarantee it will eradicate it entirely.

Do I need planning permission for a listed property?

You don't need planning permission. It is, however, the homeowner's responsibility to check with their local conservation officer as to whether Listed Building Consent or a Certificate of Lawfulness is required. Many conservation officers are fully supportive of our installation methods and, therefore, don't require any permissions to be sought. We "handhold" our clients from the start to the finish of a project and, therefore, help with any external challenges. We have great relationships with Conservation Officers who we deal with and, more often than not, spend time on site with them so all is fully understood.  As a business, we are happy to install our insulation measures without Listed Building consent as CosyGlazing is reversible - it is attached using magnetic strips - and cannot be seen from the outside.

What if I have large or oddly shaped windows?

Not a problem! CosyGlazing and draught proofing can be installed on windows of all shapes and sizes; we often install in windows with arched tops.

Will I still be able to open the windows?

Yes. We can install CosyGlazing to sash windows in a way that allows you to open both the top and bottom sashes without having to remove the secondary glazing. It is the same with traditional casement windows although sometimes we do need to fit slightly modified hardware.

For further information the Mitchell & Dickinson, please clickhere

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With compliments:
Taylor Alden
Email:media@tayloralden.co.uk