Double Hung Window Systems - Which Type is Yours? Weight and Pulley vs Spiral Balance

For a vertical sliding sash to stay in the open position some form of counterbalance system is needed to offset the weight of the sash.  Most double hung sash windows in Australia use one of the two most viable options; Spring / Spiral Balance System or Weight and Pully System.   When installing Ecobead Parting Bead, the bottom sash will need to be removed in order to get access to the parting bead.  In this blog we talk through how to remove the bottom sash with each system.

Weight and Pulley System:

This is the more traditional system and relies on cast iron, or lead weights to counterbalance the weight of the sash.  The sash is attached to and suspended by lengths of sash cord.  Each sash cord then passes over a sash pulley which is fitted into the window jamb near the top of the opening.  The opposite end of each cord or chain is attached to the counterweight.  The weights are installed in a pocket, or box, built into the side of the window. When the window is correctly weighted, the sash will require little or no effort to operate and will remain open or closed as desired. 

In order to remove the bottom sash the cord needs to be united from the bottom sash to release it, then tied off to hold the cord in place and prevent the cord from slipping back into the box.  After the Ecobead parting bead has been installed, the knot needs to be untied and the cord tied back onto the bottom sash.

Spring / Spiral Balance System:

Though the counterbalance principle is similar to the weight and pulley system, it’s achieved in a different way.  Spiral balances are composed of a spiral rod and spring within a metal or plastic tube.  The rod connects to the spring, which is what provides tension for supporting the sash.  The balance is held in place with a single screw at the top corner of the jamb and one or 2 screws on the bottom sash.  Each sash should have 2 balances (one on each side) to support it properly. 

In order to remove the bottom sash, the spiral balance needs to be unscrewed from the bottom sash.  Care should be taken here as the balance is under tension therefore when unscrewed the balance might spin dramatically to remove the tension. After the Ecobead parting bead has been installed, simply screw the spiral balance back to the bottom sash.