Tuesday, 21 June 2016

Window Types

image: freedigitalphotos
Window Frame Types Timber, PVC and metal are three common frame materials used in domestic windows. Here we consider some troublesome issues with each, and examine possible solutions.

Timber was always the traditional choice for window frames and remains a popular contemporary choice, especially for double glazing. Hardwood is the more durable option though treated softwood is also used. Regular maintenance, and weatherproofing every five years with paint or wood stain, should avoid timber defects and guarantee a long serviceable life.

Wet rot is a common problem with older windows. Poor maintenance can lead to shrinkage and cracks in putty seals causing rainwater leaks, and leaky guttering above can also cause rainwater penetration. In either event, the result is wet rot which will require urgent attention to prevent further decay.

Wet rot can be treated in a number of ways: by splicing in new wood, though this involves partially dismantling the frame; by removing just the defective wood and using resin to make good the damaged section; or, if there is major decay and a viable repair is impossible, by replacing with a new frame. Resin is the quickest and most cost-effective option involving no removal of glass or dismantling of the timber frame. This type of repair, and subsequent repainting, can easily be completed in a day.

Alterations to Building Regulations, requiring double glazing to be fitted in both new homes and extensions, have made PVC the preferred choice for window frames in the last two decades. They have been marketed as an affordable, energy-saving product requiring no maintenance beyond installation. In reality, double glazing often develops condensation problems over time when moisture penetrates the seals and seeps into the void between the glass plates. New glass, with fresh seals, can be fitted into the frames to remedy this.

Some PVC frames are also prone to discolouration due to the use of lead in the manufacturing process (now discontinued). Due to manufacturing advances, more recent PVC windows are more reliable than earlier models and have improved energy-saving specifications.

Curving metal frames, a 'Steel' product dating from the 1920's, were used to form a 'suntrap window' as a prominent design feature for the home. Poor thermal insulation creating condensation was their weak point, thus many of these single-glazed windows have been replaced. Because of their rigidity, metal frames are very prone to distortion where there is structural movement. Windows that bind or stick in operation, usually resulting in loose, worn or damaged components, are strong evidence that movement is present. Rust can also attack metal frames. If severe, this can only be cured after removal of the frame. Acid or abrasion treatments can be used on surface rust but severe corrosion requires welding in a new metal section.

The strength of aluminium has been elegantly employed in the design of modern slimline windows, improving upon what could be achieved with timber and PVC frames. Yet aluminium's high conductivity means that unwanted heat transfer through the frame can cause condensation, unless, as with current designs, some form of 'thermal break' is used to defeat this.

For the best information and advice visit You Choose Windows. We can help you with a question regarding box sash windows.