Block and Tackle vs Constant Force Window Balances

The two most common window balances in modern vertically hung windows are block and tackle balances and constant force balances. Learn the differences between the two and find out which we think is better in this quick post.

What are window balances?

Window balances are the devices in your double-hung or single-hung windows that make it easy to open and close your window. These devices have been used in windows for hundreds of years and have advanced with modern technology. There are four types of window balances, two of the most common window balances in modern windows are block and tackle balances, also known as channel balances, and constant force coil window balances.

Constant force window balances and block and tackle window balances aren’t as visible as older balance systems like the cord and weight or spiral balance so some homeowners may not even be familiar with the term. For a general overview of window balances, check out our Window Balances 101 post.

What’s the difference between block and tackle vs constant force window balances?

Block and tackle balances are very different from constant force balances but they’re both designed to accomplish the same task––to smoothly operate a vertically hung window.

Block and Tackle Window Balances

At a glance, the block and tackle, or channel window balance, looks like a combination of the cord and weight balance and the spiral balance. Like the cord and weight balance, the block and tackle systems use cords and pulleys and like the spiral balance, it uses a spring as a counterweight. In this device, the stretchy cord moves with the sash controlling the tension on the spring as the window is opened and closed.

Constant Force Window Balances

The constant force window balance is different from block and tackle, cord and weight, and spiral balances because it uses a stainless steel coil instead of pulleys, cords, and springs. It uses a simpler design that allows the balance to operate smoothly without losing tension over time.

Which is better block and tackle or constant force window balance?

Both are good balances and much more durable than their predecessors. Our preference is for the constant force balance. In our opinion, windows with constant force sash balances are easier to open and close than those with other balances. Windows with constant force balances also feel more secure in the jamb than those with block and tackle window balances. We’ve noticed that some windows with block and tackle balances, particularly sideload windows, have a lot of wiggle room around the sash and while this may not be a problem we prefer the sash to feel fit and secure.

Constant force window balances rarely break down and if they do they’re usually covered by a lifetime parts warranty. Replacing a constant force window balance is an easy process as long as you can identify and source part. Additionally, these balances should never lose tension or rust. Other balances like the block and tackle, for example, have many moving parts that can wear down, rust, bend, or break. While they can usually be replaced, they’re more likely to fail than the constant force balance.

Take a look at the video below to watch one of our team members operating windows with block and tackle and constant force window balances. You won’t notice much of a difference unless you visit a showroom and try operating both types of windows yourself but our choice for balance goes beyond how they feel. We prefer the constant force balance system for its durability and warranty.

Which is more common, block and tackle or constant force window balances?

Based on the windows in our showroom and research online, block and tackle balance systems are currently more common than constant force window balances. Block and tackle balances are used on wood, fiberglass, and composite windows while constant force balances are more common on vinyl windows. Both systems can be installed on hung window frames made of all materials, the last statement is just an observation from the products we have direct experience with.

To learn more about block and tackle or constant force window balances check out the related blogs below. We cover everything from operation and repairs to which window vendors use block and tackle or constant force balances in their single- and double-hung windows.