Heat insulation is perhaps the most common reason for getting double-glazing. However, if the frame is not right the insulation provided by double-glazing is lost. The worst conductors of heat and therefore the best insulators are wood and PVC-u. Aluminium is a relatively good conductor of heat and so is not the best material if this is of primary concern.
The protection against sound is another great attribute of double-glazing and their isn’t really a clear winner. The relative sound insulation properties are therefore of lesser concern that those of say heat.
Security is always a concern and here we have a clear winner. Aluminium is extremely strong and is the material of choice where security is of major concern. This explains why aluminium is commonly seen on commercial premises. Wood and PVC-u have their weak spots. PVC-u expands during hot temperatures and the expansion gaps required can become weak points for intruders.
Another area that has a clear leader is appearance. Wooden frames are easily the most attractive frames. The timeless appeal of wood suits both modern and period properties. In particular, for period properties it is almost mandatory to have traditional looking frames and in particular sash windows. The appearance of the properties can be undermined with PVC-u frames or cheap looking fake wood finishes.
Although wooden frames are the most pleasing on the eye they are also the hardest work. Older frames require a significant amount of attention to prolong their life. The newer wooden frames are treated before being shipped to retailers but they still require the attention. Regular coats of protective paints are needed every four or five years. PVC-u and aluminium frame require very little maintenance and can be cleaned with just an occasional wipe with a damp cloth.
Finally, we look at the cost of the different types of frames. Generally speaking, the cheapest are PVC-u frames, followed by aluminium and finally wood are the most expensive. The economic benefits of PVC-u frames combined with their excellent insulation properties go a long way to explaining their popularity.