Modern Double Hung Sash Window Design With an Eye to Historical Influences

Time has proven double hung sash windows to be an excellent design. In some cases these windows have lasted hundreds of years. The revival in the popularity of sash windows has caused many manufacturers to exploit this highly profitable market.

Many people are spending a lot of money on what they think will last them a lifetime. There is a problem, modern sash windows have a different set of criteria on the design from the traditional designs. Demands on a modern window can have a negative effect on the performance that made the traditional sash windows so successful over hundreds of years.

The new demands of maximising profitability and complying with current regulations are adding complexity to the simplicity of the original design. Adding complexity is a real problem for the maintenance in the years to come. If in twenty to thirty years time, components aren't available the window will have to be ripped out and replaced. A two hundred year old window can still be easily maintained and repaired to this day. The problem is similar to those facing plastic windows installed only twenty years ago.

Influences on a design have to be considered and understood before any re-design can be successful in the long term. Without this comprehension, the designer can't make the right choices so the original successful features can be lost.

The design of Double Hung Sash Windows evolved over time starting in the mid 1600's. Each stage in the Sash Window history has been tried, and proved. Advances in glass and glazing technology have driven many of the variations to the basic design. These changes where incorporated in preceding design. We can't identify any serious failures as these windows will have been scrapped long ago..

Current legislation requires the installation of sealed unit double glazing. This advance in fenestration is the biggest challenge so far to the traditional sash window. Large proportions of modern makers have chosen to ignore or are ignorant of problems that this new glazing can cause. The result will be many disappointed customers a few years down the line. They will have to pay for expensive remedial work or be even more disgruntled when the specialist components used are out of production.

There are some good manufacturers who have done well incorporating double glazing in to sash window designs. The existing solutions from modern timber window design have been applied directly to sash windows. These windows have a good chance of performing well over many years. Unfortunately the technology for glazing these windows is adapted from casement style windows where the frame design is fairly heavy in appearance.

Most sash windows with double glazing being produced today don't have the aesthetic elegance of traditional designs. Also a number of the details highlight the modern construction. Whilst making windows that comply with the modern demands of energy conservation, we have to accept some changes to the aesthetics. The latest double hung window designs should be see in the light of past changes. It's another chapter in long history. History will forget the failures, although many individuals won't. Modern windows don't have to be replicas but they do need to be honest.

When judging a new design, we should ask:

a) Are any of the details detracting from what looks right?

a) Is the design in sympathy with the building style and proportions?

c) Has the design been detailed to maximise longevity?

d) Is maintenance and future repair possible and straight forward?

The answers need assessing in a historical context. With continuity, a successful, evolving design can have the best chance of lasting hundreds of years. Good designs will perform to modern standards and survive the test of time.

A project to design and build high performance double glazed, double hung sliding sash windows should start with a look at the historical background. As I've been working on a design that combines the best of modern technology with traditional craft, reference to the past has been invaluable.

Working this way will give me windows with high performance that will out-last me. The cost per unit will be lower than equivalent PVC alternatives. They will add value to the house whilst the energy bills will be lower. The published plans and information will be invaluable source those with some basic skills and a desire join generations of craftsmen making sustainable architectural joinery.

Andy Bell is a designer exploring the application of modern technological advances to traditional craft based designs. The resulting plans can be built using basic woodworking tools and only require a moderate skill level. The History of Double Hung Sash Windows and project progress are on his iDoStuff website