Wooden Sash Windows London

Double glazing existing single glazed sash windows, a good idea?

If you have sash windows and you live in the UK then you have probably heard about the possibilities of replacing 4mm glass with a slim-line double glazed unit to upgrade your single glazed sash windows to double glazed sash windows.

If you have not then I will explain.

The idea first came to fruition around 12 years ago but didn™t become popular due to technological limitations of double glazed units at the time making it near on impossible to hide the old fashioned large double glazing spacer behind the inner moulding of each window.

Glass companies soon exploited the initial idea and came up with new double glazed units with much smaller discreet spacers and very slim units that had all the same thermal benefits of traditional double glazed units.

This new line of slim-line double glazing has now made it possible for property owners to double glaze existing sash windows in period houses without compromising the properties original architectural heritage.

People living in conservation areas that previously could not have double glazed sash windows due to the massive change in the appearance of the window can now do so without stepping on the local conservation officers toes!

This development has seen a huge rise in the amount of companies providing this service and as you might imagine there are also many chancers trying their hand at doing it too!

Be warned if the process is not done correctly or the wrong glass is used you may end up with sash windows that end up falling apart a year or two after the work is done, or if the gaskets are exposed to sun light and not properly hidden behind the beadings of the window they will degrade and you will have misted up windows.

It is far better to have the windows inspected by a reputable sash window company like Mortice and Green first to confirm suitability and then make sure the company carrying out the sash window work knows what they are doing and is using the correct materials and glass.

There are other options to upgrading your sash windows that are comparable in price and in some ways better too. One way is to have the fixed box frame fully restored and have reproduction sash windows manufactured to replace the old single glazed windows.

The new sash windows should be identical in every way other than the fact they will have been designed for slim line double glazed units as opposed to 4mm glass.

Once fitted, the replacement sash windows will provide the same level of thermal protection as complete replacement sash windows, with far less costs and hassle than replacing the entire box sash window.

You should also remember that a double glazed sash window that is fitted into a box frame that is not properly draught proofed is not going to be any better than a single glazed sash window! The double glazed window relies on the window to be properly insulated against draughts.

You would be surprised to hear just how many windows I see across London every month that are double glazed but not draught proofed, I often wonder just what the heck the so called œsash window repair expert was thinking as he fitted the new double glazed sash windows into the draughty un-insulated box frame? It is a real puzzle¦

If you are considering having reproduction sliding sash windows made then why not give us a call? We can double glaze your existing sliding sash windows or if you prefer we also manufacture solid Oak double glazed reproduction sash windows as well!

Sash Windows in the Balance

There are many styles of sash window but all have one common denominator, they all have an operation that requires the weight of the window to be supported to allow ease of opening.

The earliest examples of the sliding sash window had an operation whereby the window would slide horizontally without need for the window to be supported but since around the 18th century most sash windows were designed to slide vertically.

Traditional œhung sash windows reply on a weight system with each window connected to sash cords that are strung over a pulley wheel and attached to a cast iron weight inside the box frame. This cast iron weight is approximately half the weight of the sliding sash, with one on each side they equal the same as the sash window. With the weight of the window balanced by the sash weights the window will lift open and stay open in whatever position the user may choose.

Modern sash windows can sometimes utilise a system referred to as the spiral balance mechanism. The spiral balance is effectively a metal rod that runs up the centre of a strong spring connected at one end. The spring and rod assembly is shrouded within a plastic tube to keep it straight and also for cosmetic reasons. The spring is connected to the box frame sash window run by a screw and the spring is tensioned by turning the metal rod against the spring thus creating tension. Much like some cheap weight lifting and fitness machines the spring mimics the action of gravity by the pulling force of the tensioned spring.

Both sash window balance systems work well but neither a failsafe and will certainly require repair and maintenance over the years.

The most reliable system is, as most professional sash window experts will tell you, the traditional weighted sash window system.

The most common issue with a box sash window is broken sash cords but other problems can occur especially if you replace glass. Older box sash windows will have been weighted for 3mm glass, modern glass is 4mm for safety reasons. This means that if you ever need to re-glaze an old sash window the glazier will no doubt use 4mm glass and you will then unwittingly have increased the windows weight by around 25% The window will then require the sash balance weights to be adjusted to ensure the window still functions as intended. The same would go for spiral balanced windows although the remedy would be simpler as you would only need to increase the tension on the spring to account for the twenty five percent increase in the sash windows weight.

If your sash windows seem to drop closed when you open them or if the top sash slide open on its own then it is likely that you will need either sash cord repairs and or sash window make weights added to the existing sash weights.

All the issues discussed in this article and more can all resolved by visiting our home page or by calling us on 020 7118 9191. We take care of all types of sash window repair work including sash cord replacement, spiral balance replacement and window rebalancing.

Double glazing existing single glazed sash windows, a good idea?

Sash Windows in the Balance