What should you know about slider windows?


Key points:

  • Although slider windows don’t perform as well as casements, they cost less and still provide acceptable levels of performance.
  • When comparing slider windows consider BOTH their heat loss conductivity (U-Factor) and energy rating (ER) for a true sense of how the window performs.
  • Because slider windows are operated manually, proper operation is crucial to longevity and performance of the window.

Let’s break it down further.

Slider vs. casement: what’s the difference?
If you know anything about modern windows, you’ll probably come to learn that there are two main types of window design: slider and casement. Slider and hung windows differ from casement and awning windows in how they operate, and that in turn, has an effect on their performance.

Slider windows are exactly what their name suggests. The moving part of the window (sash) slides around in a channel to open or close the window.

Casement windows are also sometimes referred to as crank windows. The metal crank hardware moves the sash at an angle away or toward the frame. That’s why casement windows are much easier to operate.

For more in-depth comparisons check out:
Modern Windows Compared: Awning And Casement vs. Slider And Hung
Casement Windows in Edmonton: A Comparison
Awning Windows in Edmonton.

But the big efficiency changer in both of these windows is not the sash itself, but rather how well it works within the window as a system. In slider windows, the area between sash and frame is filled with fiber weatherstripping. Casement windows, on the other hand, have compression seals around the frame. When the window is closed the compression seal fills up the area between frame and sash much better than fiber weatherstripping, ultimately resulting in a more airtight unit.

Another performance difference is in the difference in sash size. Because casement windows only have one sash, they only have one insulated glass unit. Even in single slider windows, there are still two sashes which need to fit into the depth of the window opening. The individual sealed units have to be much thinner and are therefore less efficient.

What are tilt-and-turn slider windows?
When shopping for new sliders, customers often come across tilt-and-turn windows. The sashes in these units can be unlatched to turn at a 90-degree angle to the frame, much like the sash in casement windows.

Although this feature looks very modern especially in a double slider, homeowners often misunderstand its true purpose. While these windows can give you a beautiful unobstructed view, the turn-in in function is intended as a maintenance feature. It allows for cleaning of the outer side of the window from the inside of the house.

Tilt and turn windows look great and modern, but homeowners often misinterpret how to use them.

It is unadvisable to keep the sash in a turned-in position as the weight of the sash can cause stress on the frame resulting in deformation or even breakage. This is especially crucial in triple pane windows because their sashes are much heavier.

Check out: Common Problems With Slider Windows

How to compare slider windows?
Regardless of the window style you decide on, all windows you consider should be ENERGY STAR rated. ENERGY STAR is an international organization that classifies and rates energy efficient products, from household appliances to building materials.

As of January 2020, homeowners no longer have to consider a Climate zone when shopping for windows that are ENERGY STAR® certified in a particular area. A product in Canada is either ENERGY STAR® certified or not, with a single standard applied nationwide.

But keep in mind that if you want to purchase new energy-efficient windows in Edmonton, you should only consider models with a minimum ER (energy rating) of 34 to ensure that these windows meet the Canadian government fenestration standards.

ER Ratings are a number given to windows, based on a calculation of different performance factors. These include things like the U-Factor and Solar Heat Gains. The ER rating has been devised specifically to make it easier for consumers to understand and compare window performance across different manufacturers.

  • U-Factor is a calculation of how conductive a window is, how it is affected by convection heat loss and the emissivity of the glass in the panes. At the very basic level, the lower the U-factor, the better your window is at keeping heat inside.
  • SHGC: The Solar Heat Gain Coefficient is a measure of how much heat from the sun a window gains. Although ideally you want as much heat from the sun in the winter months, most modern windows with high SHGC end up overheating the home. High SHGC factors are great for windows that see very little direct sunlight and can maximize energy gains in those places. The lower SHGC, the less heat from the sun your windows let through.

ER Ratings vs. U-Factor
You can often see window ratings represented in either one of these values. But which one is a better representation of a window’s performance?

An ER number is a more encompassing representation of how a window “transfers” energy. The more heat it gains rather than loses, the more efficient a window is considered.

But the U-Factor directly assesses a window’s resistance to heat loss. This is especially important to consider in Canada as we often have longer nights in the winter where it is essential for a home to retain as much of its heat as possible.

A high ER number may just mean a window gains a lot of energy from the sun. A low U-factor will mean that a window is great at keeping the warm air in.

We have compared triple-pane window performance ratings from top window companies in Edmonton: All-Weather Windows, Durabuilt, Ecoline, Canadian Choice, and McLeod Windows and Doors.

For comparison’s sake, we examined single slider windows with Low-E applications and gas fills to see how they compare. Take note of each window’s U-factor, ER rating, and the company’s value range for each performance metric. It is often possible to improve a window performance with additional features.


Not seeing a company you’re interested in? All this and information about other window companies is publicly available on the National Resources Canada website.

When deciding on new windows, regardless of their type and style, make sure that the windows you consider are ENERGY STAR rated, have a high ER value, and a low U-Factor. Remember also that correct window installation is equally as important as the quality of the product you buy. Even the best windows can’t perform to their full capacity if they are not installed right.

Find out what goes into Ecoline slider windows.

Check out more window replacement articles:
End-Vent Windows, Best Designs to Match Your Sliders
Find Out The Cost of Replacement Windows
One Thing You MUST Know Before Scheduling A Window Replacement Quote

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