Written by: Luke Cheverie
Reviewer: Editorial Team
An egress window is more than a basic basement window. It's a legal safe exit, sized and placed so anyone inside has a way out in an emergency. This is exactly why Ontario building code requires one in any basement bedroom or livable space.
To qualify as egress, a window needs to meet a few specific things, not just "open wide enough":
A clear opening of at least 3.8 sq ft, with no single dimension of that opening less than 15".
The clear opening has to be achieved in one motion — unlock it, open it, done. No removing sashes, no disconnecting hardware, no special knowledge required.
In some cases, there are also requirements for how high the opening sits off the finished floor, plus other conditions depending on your specific basement.
Not every window style can meet that bar. Of the common basement window shapes, three are built to qualify:
Casement: hinges on one side and swings fully outward
Slider: one sash slides horizontally
Hopper: hinges at the top and opens up and inward
Which of the three qualifying styles is right for your basement depends on your specific opening, your window well, and (most importantly) what your local municipality allows. That's because most basement windows are below-grade: set lower than the ground outside, sitting in a dug-out window well rather than open air. That's what creates the snow, ice, and clearance issues.
At Nordik, we believe every homeowner should feel confident about what they're choosing and why. Here's what you need to know.
The Three Main Egress Window Styles
As mentioned above, there are technically three egress-capable window shapes on the market, here's the real breakdown.
Casement Egress Windows
Casement windows hinge on one side and swing fully outward, giving you the entire opening to climb through (or escape a fire through, which is the whole point), plus the most glass area for natural light. That same full-swing design means the sash compresses tightly against the frame when closed, giving casements the best air seal of the bunch.
That seal is backed by real numbers, Nordik’s RevoCell® double-pane casements carry an Energy Rating of 40 thanks to a 4.5" solid-core microcellular PVC frame doing the insulating work.
Where casement runs into trouble is the outward swing itself. Casements aren't always allowed as a below-grade egress window. Many municipalities restrict or prohibit them in basement window wells because snow and ice buildup can block the sash from opening outward when you need it most. Casement is more commonly permitted in above-grade situations, or where the window well is unusually large.
If casement is what you have your eye on, confirm with your local building department before you plan around it.
Sliding Egress Windows
Instead of swinging outward, a slider moves one sash horizontally so you only get about half the opening width, but that trade-off buys you something a casement can't offer (almost no outward clearance needed). If your window well is shallow, or your rough opening is wider than it is tall, this style often solves the exact problem a casement runs into.
That space-saving design doesn't cost you on efficiency, either. Our RevoCell® double-pane sliders still hit an Energy Rating of 40. This makes it the practical pick when your basement's layout calls the shots, not the spec sheet.
Hopper Windows
Hopper windows hinge at the top and swing up and in. The hopper-style wood windows were the common basement window in Ontario homes built before the 1970s, and the style has simply stuck around because it works.
In fact, hopper is the egress style Nordik installs most often. Because the sash tilts inward rather than swinging out, there isn’t a snow-or-ice clearance issue to worry about, which is a big part of why so many municipalities are comfortable with it..
Most existing hopper windows in older homes already meet (or are very close to meeting) current egress requirements, which is a big part of why replacement (rather than a style change) is usually all that's needed. And with RevoCell® technology, hopper is arguably the best all-around choice for most basements today, with its strong energy performance, no clearance concerns, and broad acceptance from local building departments.
Which Egress Window Style Is Right for Your Basement?
Every basement has its own quirks: the well, the wall, the light you're chasing, and what your local building department will actually sign off on. The right style is the one that fits your space and clears code in your municipality, not just the one that looks best on paper.
Here's how to figure out which one that is.
When Your Window Well Is the Deciding Factor
Casement needs the most from your window well. Meaning enough depth and width for the sash to swing fully open without hitting the sides.
A slider is more forgiving on depth since it slides instead of swings, so it functions perfectly, even in a shallow well as long as there's enough width. It's also generally unaffected by snow-and-ice clearance rules.
Hopper needs the least outward clearance of all three, tilts inward instead of out, and is the style Nordik most often installs or replaces in existing below-grade openings.
Replacing an Older Basement Window
If you already have a hopper, good news: most older hoppers are close to meeting current egress sizing, so a straightforward RevoCell® hopper replacement is often all that's needed. If you're considering switching styles instead, say, to a slider, that's usually more involved, since it can mean widening or otherwise modifying the rough opening.
Casement is not automatically "the standard upgrade" from a hopper. Whether it's even an option depends on your municipality's rules for below-grade outward-swinging windows and how much clearance your well has.
Permits
If your project doesn't require modifying the opening or enlarging the window well, a permit is often not required. If you are changing the size of the opening or the well, plan on a permit as part of the project.
Separately, if your intention is to create a legal rental unit in the basement, that living space needs to be verified through your local building department and permit process regardless of whether the window itself is being modified.
The bottom line is, always check with your local building department before finalizing your window style. Egress rules (including which styles are accepted below grade) vary by municipality, and confirming upfront saves you from planning around a window that won't be approved.
Egress Windows and Energy Efficiency in Ontario
Style affects energy performance: casement achieves the tightest air seal when closed, since the sash compresses against continuous weatherstripping around the full frame. Sliders are slightly less airtight at the sash-to-frame slide path, though still a major upgrade over what they're replacing.
Nordik’s RevoCell®'s 4½" deep microcellular PVC frame applies equally to all styles. The frame isn't a trade-off between styles; it's a baseline advantage across every one of them.
Casement double-pane: Energy Rating 40
Single slider double-pane: Energy Rating 40
Hopper double: Energy Rating 35
Argon-insulated glazing with a warm-edge spacer matters most in basement installations, where the exterior temperature differential is greatest during an Ontario winter.
Frequently Asked Questions
What is the most common egress window style for basements?
Hopper is the most common egress style Nordik installs today. Sliders were actually the most common basement window before the modern hopper style became widely available, and many municipalities still don't allow casement below grade at all, since snow and ice buildup can restrict the sash from swinging outward when it needs to.
What is the difference between a casement and a sliding egress window?
A casement swings fully outward on a hinge, giving you the entire opening as clear space. A slider moves one sash horizontally, so only about half the total width becomes a clear opening, but it needs far less outward clearance.
Can an awning window be used for egress in a basement?
No. Awning windows do not qualify as egress windows under Ontario building code, regardless of their size or energy rating. They're a good ventilation window elsewhere in the home, but not for egress.
Do hopper windows qualify as egress windows in Ontario?
Yes, most older hopper windows already meet, or are close to meeting, current egress sizing requirements, and hopper is one of the most commonly accepted below-grade egress styles. Always confirm your specific opening against current requirements with your local building department.
Which egress window style is the most energy efficient?
Casement style edge out sliders slightly on air seal, thanks to full-frame weatherstripping compression. In practice, the RevoCell® frame itself (not the style) is the bigger factor in overall performance.
What size window well do I need for an egress window?
It all depends on the style. Casement needs the most outward clearance, slider needs the least. Exact minimums should be confirmed with your installer for your specific window size.
Can I replace an old hopper window with a casement or slider?
You can, but it's not always the "standard upgrade" it might seem. Most older hoppers already meet or nearly meet code, so a RevoCell® hopper replacement is often the simplest path. Switching to casement depends on whether your municipality allows outward-swinging windows below grade, and switching to slider or casement typically means modifying the rough opening.
What type of basement window lets in the most natural light?
Casement and hopper are typically about the same as both use a full glass sash for the opening size. A slider lets in a bit less, since only half the sash slides open while the other half stays fixed.
About Nordik
Nordik Windows & Doors manufactures and installs windows and doors for Ontario homeowners. Every product is custom-built in Canada, every installation is handled by Nordik's certified crews, and every job is backed by the 25-Year No-Bull Warranty, covering product, parts, labour, and installation with no fine print.