Window spacers hold your glass in place, and an important thing is the material they are made from.

window spacersMost windows, and all efficient windows, have at least two panes of glass. They are held together by a window frame on either side and also by something called spacers, which sit at the edge of the glass between the two panes. They are inserted into a window assembly and fixed to that spot using a sealant to keep them from moving.

Spacers also prevent fogging and condensation on windows by sealing the area between the glass. That area is often filled with a gas that helps block heat transfer, and spacers prevent this gas from leaking.

Spacers are a small part of a window, and you don’t need to think very much about them or spend lots of time considering the options before you buy. But there’s one thing to make sure of: Spacers should be made of a material that won’t conduct heat through your windows. It’s important to avoid ones made only of metal.

This is because metal conducts heat. In cold weather, metal spacers often let warm air escape your house, leaving you more reliant on your indoor heater to keep temperatures stable. That can mean higher monthly utility bills. In hot weather, metal spacers allow outside heat to infiltrate your house, leading to similar consequences.

Choose spacers that are made of non-metal materials, such as rubber or foam, which are often the most efficient. The material embedded in some of these non-metal spacers will contract, expand, and return to its original shape depending on the conditions outside. This helps keep moisture at bay, which reduces the possibility of mold forming in your home.

Spacers can also be made of composite materials that mix metal and other things, and these are often called warm-edge spacers. Although not widely used, metal spacers can be made efficient if they have a “thermal break” – some other material between the metal on their outsides, such as a hard polyurethane in the middle, with the metal parts on the outside like a sandwich. It’s just not common for spacers to be metal with a thermal break.

Before buying windows, ask the window dealer for information on the spacers of the windows you’re considering. You’ll surprise the salesperson with your knowledge!

For more details, see our spacers page in the Types and Parts of a Window section of this website. The Window Selection Tool will create a bespoke list of efficient windows right for your home and climate.