What are the Most Energy Efficient Windows?

In an age of constantly rising energy prices, many home and business owners are looking for every way they can to improve efficiency and decrease electricity bills. Windows have improved efficiency levels substantially in the last two decades as consumer attitudes changed to demand higher efficiency home improvement products.

There are several types of windows on the market today, all claiming to be energy efficient, but we are often asked: “what are the most energy efficient windows?” This question has several possible answers and we’ll explain the components, features and styles that typically provide the highest levels of energy efficiency.

Window Frame Materials

There are four common types of window frames available on the market today: wood windows, vinyl windows, fiberglass windows and aluminum windows. Of these four, wood, vinyl and fiberglass frames are all energy efficient – although some more than others. Aluminum frames on the other hand are not very energy efficient. Although wood as a building component is relatively energy efficient, wood windows typically have one major disadvantage versus vinyl and fiberglass windows – they do not have an insulated air cavity to improve efficiency. Vinyl and fiberglass window frames have a hollow pocket that can be filled with insulating material with a better insulating value than wood. When comparing fiberglass to vinyl, the differences are not as significant. Fiberglass does not expand or contract during hot or cold weather, so there is less opportunity for air leakage around the window – making fiberglass frames the most energy efficient type of frame on the market.

Window Low-E Glazing

Window glazing is relatively new when compared to other energy efficiency measures added to windows in the last 20 years. Older windows typically had no window glazing or a single glazing with a low-e coating. Multiple low-e coatings, like those on our Zo-e-shield glass windows, are necessary to maximize energy loss through your windows by as much as 30 percent! Our map below shows expected energy savings with our Zo-e-shield coated windows:

Zo-e-shield Energy Savings

Type of Window

Different types of windows can have very different levels of energy efficiency. For example, a fixed window panel (i.e. a picture window) will have the lowest amount of air leakage as there are less areas for air to infiltrate the window. Single-hung windows and double-hung windows are the most popular types of windows installed in houses today and have air leakage rates that are among the highest of all window types. Awning windows and casement windows, on the other hand, have very low air leakage rates due to their hinged sashes that create a tighter air seal.


Above all, the most energy efficient type of window is a window that is properly installed. Even a window that is manufactured to be the most energy efficient window on the market can be a major source of air leakage if it is improperly installed. If you are planning on having new windows installed in your home or business, be sure to choose a trained and certified window contractor. If you need assistance finding a professional window contractor, our dealer locator can help you find one in your area. Alternatively, contact us directly and we can recommend a window installer in your area.