The Frame Game: Should I Choose Timber Or uPVC Frames For Double Glazed Sash Windows?
Sash windows may be old-fashioned, but their beauty, practicality and ease of use has not diminished over the years. They remain a popular and highly decorative choice for your home's windows. However, in these cash-strapped and environmentally conscious times, installing double glazed windows makes more sense than ever, and this can present some issues with sash window design. The increased weight and structural stresses presented by double glazing mean that the material you choose to frame your sash windows is all-important, and choosing between the two most popular options -- traditional timber and modern uPVC -- can be a challenge.
Timber window frames are generally the aesthete's choice. Choosing timber gives you an enormous amount of aesthetic versatility, with a wide variety of woods bringing different colours, shades and grain patterns to the table. Their attractiveness may even add to the resale value of your home.
In terms of durability, timber frames have an undeserved reputation for fragility, when in actual fact they can outlast even uPVC windows. However, this long lifespan is highly contingent on proper care and maintenance, and this goes double for double glazed sash windows -- the extra weight involved in sash window construction and operation means that choosing a suitably robust wood is vital. You will also have to check for cracks, abrasions and splinters on the frames for the lifetime of your windows, as they can cause damaging leaks and hinder the smooth operation of your sashes. Application of a suitable wood treatment every so often will prevent rotting, as well as diverting the attentions of wood-boring insects -- treatments that contain borates or lead acetate are very effective.
As you can imagine, the price for combined beauty and durability can be high, and timber sash frames can be significantly more expensive than uPVC equivalents. However, choosing reclaimed or engineered wood can defray costs significantly, and heavy discounts can be found if you having extensive replacement work done.
The modern popularity of uPVC windows is easy to understand, and glaziers offer an array of double glazed sash windows framed in uPVC. Perhaps the main reason for their popularity is their enormous durability. uPVC windows can take a serious beating from both accidental damage and environmental factors, and are immune to mould and insect attack. uPVC also contains special stabilising compounds that prevent early perishing in intense sunlight, so they will not become brittle and crumbly with age like old and outdated PVC windows. Crucially, uPVC frames have a small but vital amount of flexibility, which allows them to endure the shifting weights of heavy sash windows without cracking or splitting at key weak points.
However, uPVC is generally not considered to be nearly as attractive as real wood, and many homeowners wish to avoid the common, plain white frames often associated with inexpensive uPVC windows. To get around this, high-end uPVC, particularly that used in double glazed windows, is available in a few colours to avoid the dreaded all-white look. It can even be printed with artificial wood grain that looks remarkably convincing from a short distance. uPVC is also difficult to repair and restore, so any windows that suffer unpleasant visible damage will almost certainly need to be replaced.
Despite the impracticality of repairs, however, purchasing and maintaining uPVC double glazing is generally considerably cheaper than timber framed models.