Traditionally, all sliding sash windows were operated by cast iron weights. A box is built into each side of the window, which houses the weights. This is then attached to a piece of sash cord, which travels over a pulley in the top corner of the window and attaches to the sash that will be moving. The weight is chosen to closely match the weight of the sash, so that a perfect counterbalance is achieved and movement of the otherwise heavy window is effortless.
The use of weights and pulleys in newer sliding sash windows has reduced, and has largely been replaced by the spiral balances system. These function using similar principles of counterbalancing, but achieve it through the use of two springs inside a PVC tube. Spiral balances are normally visible on the inside of the window and can look unsightly. However, we have developed a spiral balances cover, which is a thin timber cover paint matched to the window and allows total concealment. This makes the windows with spiral balances almost perfectly reflect the style of those with weights and pulleys.
Each system has advantages and disadvantages, and the right system for you will depend on your location, the reveals in the window opening and the desired impact you are hoping for. Weight and pulley systems have an unmistakeable historic feel, they fit neatly behind traditional reveals, the systems last longer (many decades) and repair only requires fitting a new sash cord. Spiral balances systems fit neatly into all building/reveal profiles without reducing light, they are typically a few hundred pounds cheaper and the systems are very durable (life-spans of 65 years have been simulated in the labs, but are not typical).
If you want to talk to discuss the benefits of either system, or how they might work in your home, then please do give us a call.