We talk a lot about your home's building envelope—that protective barrier between inside and outside. Windows and doors are its most visible openings, but how important are they for energy efficiency?

Surprisingly, windows and doors rank much lower than people expect for home energy efficiency! Unless there are major issues, improving your windows and doors is supplemental — updating your attic & basement insulation, fixing up your ducts, and air sealing is foundational.  

The danger we’re trying to point out is this: it is SO tempting to convince yourself (or be convinced!) that high-end windows will quickly pay themselves back in lower energy bills. But if you blow the whole home improvement budget on windows and doors —meaning you don’t have any cash left for foundational fixes — you won’t see the energy efficiency improvements (or the drastically lower bills) that you hope for.  

So, read on if:  

• you’ve already taken (or are planning to take) those foundational steps  

• your windows and doors are VERY old (30-40 years plus) 

• your windows and door have never been replaced  

A Shortcut for Buying the Right Windows and Doors in Toronto 

There’s A LOT to dive into with windows and doors. A quick search gets you stuck in terminology quicksand (take U-Factor and the Solar Heat Gain Coefficient for example). Fortunately for the non-engineers out there, ENERGY STAR came up “Energy Rating,” or ER.  

ER turns the whole picture of the energy performance of windows and doors into a single number. You’ll usually see this written as ER - [insert number] online. A higher ER means better performance...and higher cost, of course —don’t get carried away!  

For Toronto, ENERGY STAR recommends any window or door with an Energy Rating of 29 or higher. These will probably be double pane windows, or doors with an insulated inner core, but that’s enough for most Toronto homes!  Having that number in mind when you talk to your installer or make the trip to Home Depot will stop you from overpaying. 

That’s it? 

There are some other considerations, but the Energy Rating gets you 90% of the way there— buying windows and doors doesn't have to be hard!  

Here are three final things to consider before your purchase:  

1. Installation. A high ER window can fail if it’s not installed airtight. Without an airtight installation, air will leak out around the frame and waste energy. Ask your installer if they’re certified by the Window Wise program—this shows they’ve done extra training and take airtight installation seriously.  

2. The material the frame is made of. Vinyl is common, but it has lots of toxic byproducts in its manufacturing process. Wood looks nice and has a lower impact, but it needs much more maintenance to keep airtight over time (wood shrinks and warps more than vinyl). Fiberglass frames are a good balance of the two — low maintenance and low impact. 

3. Large, south-facing windows need special consideration. You'll want to control how much sunlight enters in winter and how much heat they reflect in summer. This is worth a chat with an installer, though. The optimal choice comes down to your home’s unique features.  

Now let's cover something more fun: rebates! 

Can I Get Money Back On My Windows and Doors? 

Yes! Not a lot, but something is better than nothing. We have a Home Improvement Money Back Cheat Sheet, but here’s the summary for windows and doors: 

The Ontario Home Renovation Savings Program gives $100 per “rough opening” (that just means per frame, so a typical bay window would have three “rough openings”).  

The home on the left has 5 rough openings (3 from the bay window, one from the window above, and one in the basement) . The home on the right has 12 (the 5 small windows above the tall panes of the bow window all count as separate rough openings). Each door would count as its own rough opening.   

To qualify for this rebate, you must: 

• Meet the homeowner eligibility criteria  
  

• Complete pre and post project energy assessments with a certified Energy Auditor  
  

• Complete at least one other improvement (that includes insulation, air sealing, and/or a heat pump water heater).  

Also, the doors and windows you install must be approved for the program to be eligible. NRCan has a full, searchable database that covers windows, doors and many more appliances. 

Our article covers eligibility and the application process in depth, but one helpful tip we’ll share here is that installers can help you with paperwork—it's worth asking them about that while you’re collecting quotes.  

Can I make my current windows insulate better? 

This video has tips for making old windows better insulated (we love this channel!).

Diving Deeper 

We’ve included a more detailed summary of what makes windows and door energy efficiency below, but again, ENERGY STAR’s Energy Rating wraps all of this up into one number to make purchasing decisions easier.  

What Makes a Window Energy Efficient? 

Windows combine these features prevent air leaks: 

• Double or Triple Panes: Having more than one sheet of glass, with space in between, creates a buffer that slows down heat transfer. 
  

• Invisible Coatings (Low-E): A microscopically thin layer reflects heat back where you want it—keeping warmth in during winter and out during summer. 
  

• Gas Fills (Argon or Krypton): These inert gases between panes insulate better than regular air. 
  

• Quality Frames: Vinyl, fibreglass, or composite frames limit drafts and keep the structure snug. Wood looks great but it'll need more maintenance to keep its airtightness over time. 

What Makes a Door Energy Efficient? 

Doors combine multiple energy efficiency feature together:  

• Insulated Cores: The best doors have a foam-filled center wrapped in steel or fibreglass.  
  

• Glass Panels Done Right: If you want glass in your door, look for double or triple glazing, Low-E coatings, and gas fills—otherwise that glass will leak hot or cold air. 
  

• Seals & Weatherstripping: A lot of hot or cool air escapes on the bottom edge of the door, so quality seals and DIY friendly add-ons like door sweeps are crucial. 

At the end of the day, windows and doors are the finishing touches, not the foundation, of an energy efficient home. The Energy Rating number is your purchasing shortcut — you don’t need to splurge on the fanciest option to get solid results.