What Are Window Energy Ratings?

May 13, 2019

One of the most commonly asked questions about windows is: “What does a window energy rating mean?”

There are lots of resources online to help explain the answer to this question, but often the explanation doesn’t always take into account your particular situation.

Here is Bavarian’s basic explanation of everything you need to know about window energy efficiency and window energy ratings: Read more about energy ratings here

What is the purpose of window energy ratings?

The purpose of window energy ratings is to provide you with a number that indicates how well the window will provide energy insulating properties. This means it will indicate how effectively the window will do the following:

Keep the heat inside during the winter
Keep the cool air inside during the summer
Allow light to pass through the glass
Allow air leakage to pass through the glass and frame

What is a U-rating?

U-value is a standardized measurement, used to determine how much heat flows through one area into another area. Or, in simple terms, how fast the heat inside will transfer to the outside (AKA heat loss).

When selecting which windows and doors to purchase and install in your home, you will want to ask about the U-value. The lower the U-value, the slower the heat loss. The lower the U-value, the better.

If you install windows with a low U-value, they will provide better insulation and will help you reduce how often your furnace or AC is running. This can result in reduced energy bills.

If you want to know more about u-ratings, click here for the Government of Canada’s more in-depth description.

What is an ER rating?

An Energy Rating (ER) is a formula that measures the U-value, air leakage, and the benefit of solar gain. Once calculated, it provides a rating to show which products have the highest potential for annual energy savings. The higher the ER rating, the better the value.

Both the U-value and the ER rating are important considerations when selecting new windows and doors.

Energy Star requirements indicate that Canadians, depending on which zone they live, should select products offering a U-value from 0.21 to 0.32 and ER ratings from 34 to 21. Click here to learn more about Energy Star ratings on the Natural Resources of Canada website.

Selecting your windows solely based on an ER-rating doesn’t address issues in Southern Ontario like solar heat gain which can be intense in the summer months. It’s generally recommended to select a window with a low U-value and high solar heat shield — and it rejects damaging UV rays. The more solar protection in your window, the more your interior will be protected from fading and damage from ultraviolet rays. This type of glass will provide you with the most comfort year-round. Bavarian’s supplier, Cardinal Glass, offers excellent options for your windows.

Why is a U-rating more important than an ER-rating?

Selecting your windows solely based on an ER-rating doesn’t address issues in Southern Ontario like solar heat gain, which can be intense in the summer months.

It’s generally recommended to select a window with a low U-value and high solar heat shield — as it rejects damaging UV rays. The more solar protection in your window, the more your interior will be protected from fading and damage from ultraviolet rays.

What are Energy Star® windows?

Energy Star® certified windows have been tested by accredited laboratories to ensure that they meet the desired energy performance criteria.

The sticker that you see on your windows will inform you that your windows have been tested and the results have been confirmed by a third-party — so you can rest assured that you are purchasing inspected windows.

There are many kinds of windows that are eligible for Energy Star® certification, including:

Windows (hinged, sliding, non-openable, tilt-turn)
Skylights (flat-glazed, domed, tubular)
Sliding glass doors (single or multiple sliding panels)
Hinged doors (single or double leaf*)
Folding doors
Tilt-turn doors
Sidelites
Transom windows
And more

For more information about Energy Star® rated windows and how to know what windows to install in your home, contact the experts at Bavarian Windows.

Keep your home energy-efficient with new windows

When you think of coming home, you think of a cozy place, a comforting place, a warm place. The last thing you want is to get out of the cold and come into a drafty, damp, and chilly space. If you find this happening in your home, odds are it’s time to replace your windows.

Today, windows are constructed using advanced technology for superior energy efficiency and optimal performance. Windows and doors are constructed to resist the forces acting on them (e.g. sun, wind, rain, snow), including:

Reducing heat loss with specially formulated glazing to resist heat loss
Reducing radiant transfer with Low-E coatings to better insulate
Reducing air leakage with durable weatherstripping and closings

Installing new windows is a great way to keep your heat where it belongs, inside your home. There are a huge variety of windows and doors to choose from. It all comes down to your style and your budget.

How do you find air leaks?

If you’re wondering if your home needs new windows, here are some simple tests that you can perform to check:

Test the edges of your windows and doors with your bare hand. If you feel the wind blowing against your skin, you know you have a leak.
Light a candle and hold it, carefully, near the edges of your windows and doors. A candle will flicker in a smaller draft than you can feel with your hand. If the candle flickers you will be able to determine where there are air leaks.
You can purchase an air leak detector and point it at areas of concern. If leaks are detected, the light will display.
Hire an expert. A professional will be able to conduct a thorough audit of your home and will have the precision tools to accurately measure air leakage. Some energy professionals will also conduct a ‘blower door test’ to determine your home’s air-tightness. Contact REEP for expert air leak detection.

At Bavarian Window Works, we offer customers a huge selection of energy-efficient windows. Come and learn more by visiting our showroom.