The final piece of the puzzle of window purchasing is actually a performance standard that wraps the U-Value and solar heat gain co-efficient and Canadian Standards Association (CSA) A440 standard for vinyl windows into one. It’s called the Canadian Energy Rating (ER) System for windows and doors. The window or door ER number really is the bottom line for the homeowner interested in energy-efficient fenestration products for their home.
A window’s ER rating is an indicator of its overall performance based on three qualitative factors: 1) the solar heat gain of the window 2) how much heat the window loses through the frames, sealed glass units and spacer system and 3) heat loss through air leakage. A single number, or measurement, is established using complex scientific calculations and computer modeling. Basically, the higher the number, the more energy efficient the window or door is. The range for most Energy Star approved windows is between 25 and 35 ER points.
However, there are a few things that you should keep in mind when comparing the ER numbers of different windows and doors. Firstly, most fixed windows will have higher ER numbers than operating ones. This is because fixed windows tend to have more glass and less frame area than operating windows. This translates into more solar heat gain and less heat loss through frames and, therefore, a higher ER number. Secondly, fixed windows tend to be more airtight than operating ones. That being the case, they will cause less heat loss and a give a higher ER number.
When shopping for new windows and doors, then, you should compare the ER numbers within each window category. That is, compare one company’s fixed window ER number to that of another company. It wouldn’t make sense to compare, say, the ER number of a casement window from company A to the ER number of a double hung window from company B.
The Canadian Energy Rating (ER) system for windows and doors is a major helpful tool in giving consumers the information that they need to make good decisions about which windows and doors to buy for their home. It is easy to understand and useful for comparing one product to another. It is, nevertheless, just one thing to consider.
A good shopper will buy from a company with a good track record of window and door installations, since the quality of the installation is as important as the quality of the window or door itself. Where possible, the consumer would be well advised to purchase from a company that both manufactures and installs its own windows and doors, so that there can be no finger-pointing between the contractor and manufacturer if a problem with the window or door should ever occur. Warranties, number of years in business and company accreditations are also important factors to consider when choosing a company to replace your windows and doors.