The property doctor takes a look at windows!
15th March 2012
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A quick look at Windows.

 

Last weekend I undertook a spring clean of the house, and spent time cleaning the inner surface of the windows. Our windows are modern box sash windows, double glazed, and fairly draft free.  The experience however prompted me to take a quick look at windows, functionality, design, and durability.  We are always being asked to look at several sash windows that allow those drafts to sap heat from a room or have the sash cords broken which then need to be replaced.  We have also recently been asked to look at some wooden casement windows in a 13-year-old house, which are in effect rotten, and require replacement. So time for an article.

My starting point has to be to go back to basics.  The main functions of a window are to admit light and air into a room. Once these functions are fulfilled consideration should be given to thermal insulation, possibly sound insulation, fire resistance, and security.  They should in certain circumstances also be designed to allow escape, in the event of a fire. Aesthetically, the design of a window can also enhance the architectural look of a house, whether it is a Tudor house, or a Victorian terraced house.  Houses from the different time periods have characteristic looks.  Putting modern uPVc double glazed window units in a traditional black and white building would look odd, and at the very least have the Conservation Officer from the local authority jumping up and down demanding reinstatement. And rightly so.

There are many variants to the design of a window frame.  Perhaps the oldest are the casement windows. Here a traditional rectangular window frame is built into the wall of the house, a lintel supports the weight from the wall above so that there is no compression pressure exerted on the window frame. Into the frame is fixed a number of smaller window frames that are attached by hinges, to allow easy opening and closing to take place. These windows can be either hinged vertically or horizontally, top or bottom of the window frame, to allow them to be opened. Some windows are hinged in the middle on both sides to allow them to pivot open horizontally.

The next main development in window design was the double hung sash window frame. First introduced in the reign of Queen Anne, they are usually associated with a Renaissance or Georgian type of elevation. They are considered superior to casements both on aesthetic and practical grounds, and if skilfully used can give dignity to a building.  Both the top and bottom windows slide vertically, each window is attached to counter balance weights by a cord running over a pulley.  Opening and closing is made simple as the window is raised, the counterbalance weight drops, thereby making the operation relatively simple and lightweight.

There hangs the problem, excuse the pun. Often the cords attached to the weights break, rendering the window inoperable.  The wooden box frame sometimes distorts, and of course, over the years, the wooden wearing surfaces suffer from wear and tear. Drafts often arise in gaps where the meeting rails of the upper and lower window don’t quite meet. In design terms, there is only a certain maximum width that can be achieved, thereby restricting the maximum area of window that can be used for each room. It is for this reason that casement windows have retained their popularity with designers.

The next big design revolution was the use of double glazed windows.  Two sheets of glass are fixed together in a frame, and a vacuum set up between the glass. Little light transmission is lost, but the thermal insulation properties of the glass are substantially improved.  In countries where severe weather conditions are experienced, they often fit triple glazed units.  Sound insulation is also improved, for say houses that are located in close proximity to a busy road.

Materials used in the manufacture of window frames have also changed over the years.  Originally wood was the main material.  Ideally a hard wood was used, such as oak.  As cost became more of an issue, builders started to use soft woods, perhaps with hard wood sills.  The problem with modern soft wood windows is that they have a restricted life span, and quite often after 15 to 20 years, will need to be changed as they sometimes literally start to fall apart.

Metals such as galvanised steel, and aluminium were often used for the manufacture of frames.  In the older “Crital” style window frame, the galvanising broke down; the expanding rusting metal put additional pressure on the glass, resulting in cracks in the windowpanes. When this occurs, there is little point in repairing the glass; it is best to go straight to replacement.  The early window frames were relatively shallow in depth, thereby making the fitting of double glazed panels very difficult, again reinforcing the decision to replace with more modern units.

The next big development in window design came with the introduction of uPVc window frames.  Early on there were problems with making the material resistant to oxidation by sunlight.  These problems have now been solved, and with modern manufacturing processes, and the use of wood effect colouring, quite often the presence of uPVc window frames can only be confirmed by close examination of the window.

The beauty of this type of window is that it ticks all the right boxes in design terms, light transmission, heat retention, security, flexibility in design and low on going maintenance costs. It may not however fulfil design aesthetics in traditional buildings, particularly if they are listed.  Here quite often it is possible to retro- fit secondary double-glazing to derive the same benefits as from a modern window. 

Whatever the age of a house, windows are perhaps one of the most important design features, affecting overall functuality and appearance. Maintenance of the windows is essential to ensure they are fully functional, but draft free.  As heating costs increase, quite often the capital costs of windows can become relatively cheaper, warranting replacement.

 

Original Blog by Timothy Lea and Griffiths' Tony Rowland, the property doctor.

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Alan J

Member since: 10th July 2012

Whilst running The Best of Evesham I am also locally focussed on doing what I can for the local community in profiling what is going on.A prolific user of Social Media-We offer Social Media Management...

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