Explore our Guide To Window Balance Systems to learn more about the different technologies and the better option for you as a consumer. Note, we aren't going to get very technical in this article, we don't want your falling asleep this early in the day (or night depending on when you are reading this.)
Basically, a window balance system allows the sashes on a single and double hung window to be opened smoothly and with as little friction and difficulty as possible.
There are two main types of balance systems, the constant force and the block and tackle variety. These two system account for perhaps 95% of all American made windows manufactured and sold today; . For most consumers, I would say there is really only one thing you need to know, the block and tackle balance system is a better and slightly more expensive system. If you see that a company uses the block and tackle as one of their features, they get a plus in their column. I always remember that block and tackle is the better option by saying "b before c" - block before constant (maybe I just have a bad memory!)
Jim R. - Site Editor - 2015
The traditional (read old) box sash windows used a weight that was attached to a length of cord that was looped over a pulley. This weight component was located in the window frame itself and affixed to the sash frame. This pulley system allowed the window sash to lift up and down, but it was clunky and occasionally had to be rebalanced if you switch out glass etc. These older wood windows were clunky for a number of reasons, not just the balance system!
The constant force balance system, sometimes referred to as a coil spring balance, is the less expensive option that is used today. It is probably the more popular option for manufacturers due to the low cost and ease of transportation. In this system, there are 2, 4, 6, or 8 spring coils that, taken together, equal the sash weight. The result is a smooth, easy to use and quiet lifting motion on the hung windows.
Block and tackle balance system also use spring force that serve as a counterbalance to the weight from the window sash. Like the more traditional approach, the block and tackle use a cord and pulley system that helps smoothly and effectively open and shut hung windows. These systems offer easier replacement of parts if there should be an issue down the road. There are also hybrid systems, but most window manufacturers use one of these main options.
