Heat loss through windows and the benefits of secondary glazing.

Heat loss from windows has always been a major issue, this is mainly through period windows such as sliding sash windows and casement windows, this type of window is usually found in grade I and grade II listed buildings but is also found in millions of Victorian and Georgian properties throughout the United Kingdom.

So how do we overcome this problem, firstly it depends on your budget and limitations due to planning restraints such as listed buildings and conservation areas. If you live in a listed building secondary glazing and draught proofing are your two main avenues to peruse to reduce your heat loss from your sash windows or casement windows. If your property is not constrained by government planning restrictions then you will have more options at hand you could also fit double glazing this of course will reduce heat loss but have disadvantages too, such as disruption to your internal décor and this will be significantly more expensive and of course you will be losing your original period sliding sash or casement windows that fit in beautifully with your period property, this will in many cases reduce the value of your property and its saleability, for the simple reason that people who want to live in period homes prefer period features and your original windows play a major part in the external look of your home.

Current research has shown that heat loss through sliding sash windows and casement windows can be reduced by 60%, this is achieved by reducing conduction and radiation through the windows.

So to conclude secondary glazing your period sash windows and casement windows will drastically reduce your heat loss through your period windows as single glazing is a poor thermal insulator and readily conducts heat, a typical u-value of a single 4mm pane of glass would be 5.4W/m2K and a typical value of a wooden sliding sash or casement Window would be around 4.8W/m2k. Typically fitting Kensington’s secondary glazing system would bring your single glazed windows down to around 2.5W/m2k or with the use of low emissivity glass such as Pilkington K glass or Planitherm glass to around 2.5W/m2k.

A building in scotland through thermal imaging

Heat loss from a building in Edinburgh, most of the windows are single glazed and emitting more heat than the thermal imaging camera can record (the white areas) the windows on the top right have secondary glazing you can see a massive difference as they are cool.


Maintain the character of your home

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Improve thermal performance

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Quality products installed to the highest standards

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More affordable than replacing your windows

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Approved for use in conservation areas

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Areas We Cover

Altrincham, Bebbington, Birkenhead, Bromborough, Cheadle Hulme, Cheshire, Chester, Church Stretton, Denbighshire, Denbigh, Ellesmere Port, Flintshire, Helsby, Holmes Chapel, Knowsley, Knutsford, Liverpool, Llandudno, Lymm, Nantwich, Northwich, Oswestry, Prenton, Prescot, Rainhill, Rhyl, Runcorn, Sale, Shawbury, Tattenhall, Wallasey, North Wales, Warrington, Weaverham, West Kirby, Whitchurch, Widnes, Winsford, Wrexham.

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