Standard window glass blocks most UVB rays but lets the majority of UVA rays pass straight through, which is why furniture still fades and skin still tans near a sunny window. Low-E coated glass, the kind used in modern replacement windows, blocks up to 99% of both UVA and UVB rays. If your windows are older single-pane or basic double-pane units, they’re doing far less than you think.
Key takeaways:
- Ordinary glass filters most UVB rays but does little to stop UVA, which is the type that fades fabric and ages skin.
- Low-E coated glass can block up to 99% of UV rays while still letting visible light through.
- UV damage is a leading cause of faded flooring, curtains, and furniture in Canadian homes.
- ENERGY STAR™ certified windows in the GTA typically use Low-E coatings paired with argon gas fills for both UV control and heat performance.
- Upgrading old windows is usually a more effective fix than adding film to worn-out glass.
What Does Glass Actually Block?
Plain glass blocks most UVB radiation, the shorter, more intense rays behind sunburn, but it does a poor job with UVA, the longer wavelength that travels deeper into skin and fades materials over time. That’s according to the Skin Cancer Foundation, which notes that UVA rays pass through ordinary windows year-round, in every season, even on cloudy days.
This matters more than most homeowners realise. You might feel safe sitting by a window on a winter afternoon, away from direct sun. But UVA doesn’t need direct sunlight or summer heat to do its work. It’s the quiet cause of a sofa that fades unevenly, hardwood that yellows near a patio door, and skin that ages faster on the side of your face nearest the glass.
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Why Does Uv Protection Matter For A Home?
UV exposure through untreated glass fades flooring, upholstery, and artwork, and it adds to cumulative skin exposure even indoors. A home with older glazing lets far more UVA through than one with modern Low-E glass, which changes both your interior’s lifespan and your family’s daily sun exposure.
Fading isn’t just cosmetic annoyance. Replacing sun-damaged hardwood or a bleached sectional costs real money, and it happens gradually enough that most people don’t connect it to their windows until the damage is obvious. Artwork, photographs, and leather furniture are especially vulnerable, since UVA breaks down pigments and dyes at a molecular level over months and years.
There’s a comfort angle too. Rooms with poor glazing often run hotter in summer because UV and infrared radiation both pour through the glass along with visible light. That extra heat gain pushes your air conditioning to work harder, which ties UV performance directly to your energy bills, not just your furniture.
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How Low-E Glass Changes The Picture
Low-E, short for low emissivity, is a microscopically thin metallic coating applied to glass that reflects infrared and ultraviolet energy while still letting daylight through clearly. It works like a selective filter: visible light passes, but the wavelengths that cause fading and heat gain get bounced back before they reach your living room.
TotalSeal windows use Low-E 272 and Low-E 366 coatings, which reflect infrared heat and help keep interior warmth in during Ontario winters while cutting the UV load coming through the glass. An optional interior i89 coating adds a further layer of reflectivity, cutting heat loss by an estimated 10 to 15%.
The numbers back this up. According to industry testing summarised in guidance from ENERGY STAR Canada, Low-E coatings are a core requirement for certified window performance in the Canadian climate zone. Combined with an argon gas fill, which TotalSeal windows also use to improve glazing efficiency by roughly 25 to 30%, the assembly does double duty: less UV fading indoors, less heat loss in January.
| Glass type | UV blocked (approx.) | Visible light | Typical use |
| Single-pane clear glass | Blocks most UVB, little UVA | Full | Older homes, unrenovated |
| Standard double-pane, no coating | Blocks most UVB, some UVA | High | Basic replacement windows |
| Low-E coated glass | Up to 99% of UV | High, glare reduced | Modern ENERGY STAR™ certified windows |
| Laminated glass with UV interlayer | Near total UV block | High | Skylights, specialty glazing |
“A Low-E coating is doing two jobs at once: keeping heat where you want it and cutting the UV that fades your floors,” says a senior product engineer at TotalSeal. “Homeowners usually notice the temperature difference first, but the UV protection is what saves your furniture over the next ten years.”
Do You Need Window Film Or New Glass?
Window film can add UV protection to existing glass, but it’s a patch, not a fix, and it works best on glass that’s otherwise in good condition. If your frames are draughty, your seals have failed, or your glass is fogging between panes, film won’t solve those problems, and full window replacement is usually the better long-term investment.
Window film is worth considering if your current windows are structurally sound but you want extra UV and glare control on a budget, particularly on south or west-facing rooms that get intense afternoon sun. It’s a reasonable stopgap, especially for renters or homeowners not ready for a full renovation.
Pros of adding film to existing glass:
- Lower upfront cost than replacing windows
- Can be installed quickly without disrupting the frame
- Adds UV and glare reduction to glass that’s still in good shape
Cons of adding film to existing glass:
- Doesn’t fix draughts, failed seals, or old hardware
- Can void some glass warranties if applied incorrectly
- Films degrade and need replacing every several years
If your windows are older than 15 to 20 years, replacement glass with a built-in Low-E coating gives you UV protection, better insulation, and a fresh warranty all in one step. It’s the difference between treating a symptom and fixing the underlying issue.
What This Looks Like In A Real GTA Home
Picture a west-facing living room in Mississauga with original 1990s double-pane windows. By late afternoon, the sun pours in, the rug near the window has visibly lightened, and the room feels like a greenhouse even with the air conditioning on. That’s a textbook case of UV and infrared radiation passing straight through uncoated glass.
“When we measure homes like that, the glass is usually the whole problem,” says a lead installation manager at TotalSeal. “Swap in a Low-E unit with the right coating for the room’s exposure, and clients tell us the room stops feeling like a sunroom within the first afternoon.”
The fix isn’t just about picking any replacement window. Orientation matters: a south or west-facing room in the GTA benefits from a coating tuned to block more solar heat gain, while a north-facing room can prioritise warmth retention. This is exactly the kind of detail a proper in-home consultation sorts out before you order anything.
How To Check If Your Current Windows Are Doing Their Job
A few simple checks tell you whether your glass is pulling its weight. Look at fabric, flooring, or artwork near south and west-facing windows for uneven fading compared to the rest of the room. Hold your hand near the glass on a sunny day; if it feels noticeably hot, you’re likely getting a lot of unfiltered solar radiation, UV included.
You can also check your windows for an ENERGY STAR™ certification sticker or ask your original installer what glass package was used. Homes built or renovated before Low-E coatings became standard, roughly before the early 2000s, are the most likely candidates for an upgrade. If you’re unsure what you’re working with, a free consultation and a cost estimator can give you a realistic sense of what an upgrade involves before you commit to anything.
Common Mistakes Homeowners Make With UV And Glass
The biggest mistake is assuming all glass performs the same, when coating type, gas fill, and glazing count make a significant difference. A second common error is buying window film as a permanent fix for windows that actually need full replacement due to failed seals or draughty frames.
Another mistake is ignoring orientation. Homeowners often choose the same glass package for every window in the house, when a south-facing kitchen and a shaded north bedroom have very different UV and heat exposure. Matching the coating to each room’s sun exposure gets better results than a one-size-fits-all order.
Making The Switch To UV-Smart Glazing
If your home’s furniture is fading, your energy bills are climbing, and your windows are showing their age, upgrading to Low-E glazing solves several problems with one project. It’s not just about comfort on a sunny afternoon, it’s about protecting what’s inside your home for the long run. A free consultation is the simplest way to find out exactly what your current glass is letting through and what a modern, ENERGY STAR™ certified replacement would change.
Frequently Asked Questions
Can You Get A Sunburn Through A Window?
Sunburn from standard glass is unlikely since it blocks most UVB, the ray responsible for burning. UVA still passes through, which contributes to skin ageing and tanning rather than a burn, over longer exposure times.
Does Tinted Glass Block More UV Than Clear Glass?
Tinted glass can reduce glare and some visible light, but tint alone doesn’t guarantee strong UV blocking. A proper UV-rated coating or laminate does more for UV protection than colour tint does.
Do Car Windows Block UV Rays?
Windscreens are laminated and block nearly all UV, but side and rear car windows are usually plain tempered glass and let significant UVA through, which is why drivers often see more sun damage on one side of the face.
Is Low-E Glass Worth The Extra Cost?
Low-E glass typically pays back through lower energy bills and less fading, so most homeowners find it worthwhile, particularly in a climate with strong summer sun and cold winters like the GTA’s.
Do Curtains Or Blinds Block UV As Well As Glass?
Curtains and blinds block more UV than glass alone since they stop light entirely when closed, but they also block the view and daylight, so most homeowners prefer glazing that filters UV while keeping the room bright.
How Long Does A Low-E Coating Last?
A Low-E coating is baked or applied during manufacturing and typically lasts as long as the window’s insulated glass unit itself, often 20 years or more, unlike surface films that need periodic replacement.
