Posted: 17 September 2013
I would argue it is possible to produce double glazed period timber sash windows that would be appropriate in many historic buildings. It is possible for example to use high quality, antique style glass, which is designed to recreate the wavy reflection of traditional handblown crown and cylinder glass. Float glass is seen as perfectly flat, uniform with an unblemished appearance, which, to purist conservationists, does little to contribute to the visual character of a period building. This antique glass in combination with carefully designed timber windows, without modern joints produces elegant period sight lines in keeping with historic buildings. Also an internally glazed window negates the need for glazing beads externally, thus reproducing traditional putty sightlines.
The ability to improve and achieve high thermal and acoustic performance in buildings ensures their longer-term use and maintenance.
I hope the various Conservation bodies will eventually adopt a sensible approach with regards to replacement timber windows. The manufacturers have worked hard to produce designs that all but they approve of. Therefore alienating Conservation officers and planning from even the sensible majority who appreciate all they do to protect our historic buildings.
There is also definitely a problem with some conservation offers latching onto the marketing blurb with regards to thin double glazed units. Why are they putting forward certain proprietary slender double glazed units that many in the industry and beyond do not believe meet the required standards?
I agree that in very important historic properties it is not appropriate to replace the windows. However, in a grade II property and in Conservation areas where the proposed timber replacement windows meet all but the “nose to the window inspection” they should be considered. Why not work with timber window manufacturers to establish the criteria of design and performance that would be accepted in certain buildings?
Private homeowners want to retain the character of their period properties and do not want to necessarily use plastic windows, they do however need to have the option of using wooden windows. The public do not consider the suggestion by English Heritage that we use timber shutters or heavy curtains as a sensible way forward in this day and age.
Although secondary glazing is sometimes considered an option to assist the performance of a single glazed product, as opposed to specifying a double glazed unit in the first instance, secondary glazing has its own inherent problems and simply fails to meet the thermal and acoustic performance required today. Secondary glazing looks unsightly in an elegant, period property and produces the double reflection all parties are trying to avoid. It is often associated with ventilation problems and condensation; can hinder safe egress in an emergency and is difficult to clean internally. Lastly, without question, people hate it and it detracts from their internal living environment, which to them is as least as important as the external envelope.
MD at Lomax + Wood (Ambassadoor) Timber Windows and Doors
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