The higher initial cost of sash chain, compared to sash cord, is offset by the chain's longer useful life.
Chain should be selected for material, load rating and size.
Material: Sash chain is available in plated steel, bronze, and, to a limited extent, brass.
A bronze or brass chain will outlast a plated steel chain, as it will not rust.
Load Rating: A sash weighing 30 lbs. will place a static load of 15 lbs. on each of the two sash chains that suspend it. Suddenly raising, lowering, or stopping the travel of a sash, however, will create an instantaneous load exceeding the normal static load by many times.
For this reason it is advisable to select chain with the highest load rating practical for the size of the pulley.
Size: Sash chain is manufactured in trade sizes determined by width, links per foot, and gauge of material.
As stated above, chain should be selected for the maximum load carrying capacity that will fit the pulley groove.
Estimated Length: For double-hung windows, the approximate total required amount of chain can be calculated by the following formula:
(1/2 the sash opening height + 2 feet) x 4.