This is a very popular question for sash window owners. The answer is, of course, chain. Chain is going to last a lot longer than a cord. However, it is best to stick to what the sash window has in the first place. Sash windows are usually tailored to suit the home. So, if your window has a cord, there is a good reason for this. Plus, a properly installed and functioning sash cord can last over 60 years!