Windows & Doors
CONTENTS:
Choose The Right Energy Efficient Windows
Factors Affecting Window Energy Efficiency
Windows are one of the weakest points in a home’s thermal envelope.
| Even a well-insulated wall typically performs far better than the window beside it. In Manitoba’s climate, poorly performing windows are a leading cause of high heating bills, cold spots near exterior walls, condensation damage, and uncomfortable drafts in winter. But windows do more than keep heat in. | They control how much solar energy enters your home, how much outside noise you hear, and how much natural light reaches your living spaces. The right windows — properly chosen and installed — can contribute meaningful passive solar heat gain on south-facing walls, reducing your heating load on sunny winter days. For landlords, window performance directly affects tenant comfort and utility costs. | Upgrading inefficient windows in a rental property can reduce heating demand, lower the risk of condensation-related mold, and improve year-round habitability. The next sections below will help you recognize the signs of underperforming windows, understand how performance is measured, and know what to look for when choosing a replacement. |
ENERGY STAR® Certification for Energy Efficient Windows
Energy Rating (ER) for Energy Efficiency Windows
Pro Tip!
A high ER rating does not tell you whether the frame is well-insulated, whether the weatherstripping will hold up over time, or how the window will perform in real-world conditions.
Some lower-cost manufacturers use a strong ER number as a primary selling point — it is worth looking beyond that single figure. Use ER as a filter, not a final answer.
U-factor for Energy Efficient Windows
Pro Tip!
When comparing windows, always insist on whole-window U-factor values. If a salesperson only quotes centre-of-glass performance, ask for NFRC-certified whole-window numbers. Reputable manufacturers will have this data readily available.
R-value for Energy Efficient Windows
Pro Tip!
A note on whole-product vs. center-of-glass ratings:
Manufacturers sometimes quote center-of-glass U-factor, which measures only the glass portion and ignores the frame and edge effects, where much of the real-world heat loss happens.
Whole-product U-factor is always higher — worse — than center-of-glass. Always ask which figure you are looking at, and when comparing products, use only whole-product ratings.
R-value does not appear on official Canadian window labels or ENERGY STAR® Certified documentation. It is, however, commonly quoted by contractors, retailers, and manufacturers — often because homeowners are more familiar with it from insulation products like batts and rigid foam, where R-value is the standard currency.
If given an R-value for windows, divide 1 by it to convert to a U-factor (U = R ÷ 1) for a direct comparison.
Solar Heat Gain Coefficient (SHGC) for Energy Efficient Windows
Pro Tip!
If your home gets a lot of sun in winter, high SHGC windows can give you free heat. If your home gets too hot in summer, low SHGC windows can help keep it cool.
By matching SHGC to the direction of each window, you can take advantage of free solar heat in winter without making your home uncomfortably hot in summer.
Visible Transmittance (VT) for Energy Efficient Windows
Pro Tip!
VT is not always prominently displayed on product labels or in contractor quotes. If natural light is important to you, ask for the VT figure for the specific product you are considering and compare it to your existing windows before committing to a purchase.
