Extreme Weather PSA: How Cold Ontario Winters Affect Your Windows

Ontario winters are no joke. Between bitter cold, high winds, ice storms, and sudden temperature swings, extreme weather can put even the best-built homes to the test. During this time of year, many homeowners notice changes around their windows — most commonly interior condensation — and wonder if something is wrong.

The short answer? In most cases, your windows are working exactly as they should.

Below, we break down how extreme weather impacts windows, why condensation happens, and when it’s normal — especially if you’ve recently installed new, energy efficient windows.

How Extreme Cold Impacts Windows

During prolonged cold snaps, your windows and doors are exposed to:

• Freezing and thawing cycles that place stress on seals and frames
• Rapid temperature differences between indoors and outdoors
• High winds that increase pressure on glass and frames
• Reduced airflow near windows when blinds or shutters are closed

These conditions can cause temporary and harmless changes, even in high quality windows.

Why Interior Window Condensation Occurs

Interior condensation happens when warm, moisture filled indoor air comes into contact with a cold glass surface. When outdoor temperatures drop significantly — especially below 20°C — the interior pane of glass cools enough for moisture in the air to settle on it.

This is most common when:

• Indoor humidity rises above 30%
• Warm air cannot circulate against the glass
• Tight sealing blinds or shutters block room heat from warming the window

High quality windows with LowE + argon glass are designed to manage indoor humidity levels up to about 30%, but during extreme cold, some condensation — particularly along the bottom of the glass — is completely normal.

In fact, many homeowners (including us) see up to 1 inch of condensation along the bottom of the glass on very cold mornings. Once blinds are opened and warm air reaches the glass, the condensation typically evaporates naturally.

New Windows? Don’t Panic

If you’ve recently installed new windows and are noticing condensation for the first time, this often causes concern — but it’s usually a good sign.

Modern, energy efficient windows seal your home far more tightly than older windows. That improved seal keeps heat in, but it can also make winter moisture more noticeable.

Condensation does not mean your new windows are defective.

It often means:

• Your home is well sealed
• Warm air is staying inside where it belongs
• Indoor humidity has fewer escape points

What Happens in Extreme Cold ( 20°C and Below)

With double pane LowE argon glass, the interior pane can only stay about 12–15°C warmer than the exterior glass. When outdoor temperatures drop far enough, condensation on the interior glass may:

• Increase temporarily
• Freeze along the bottom edge
• Appear more noticeable when blinds remain closed

This is normal physics — not window failure.

Will Condensation Damage My Windows?

The good news:

• Condensation will not damage vinyl windows
• If it dries quickly, it will not cause mould
• Temporary winter condensation is common in well sealed homes

Interestingly, if you experience no condensation at all during extreme cold, you may notice overly dry air — often felt as static shocks or dry skin.

Balancing Indoor Humidity Matters

Managing humidity is about balance, not elimination.

• Hardwood floors require 25–30% humidity in winter to prevent excessive drying, shrinking, and gaps
• Humidity that’s too high in summer (above 55–60%) can cause floors to swell or buckle

A small amount of winter condensation is often a sign you’re maintaining a healthy indoor environment.

Do Triple Pane Windows Reduce Condensation?

Yes. Triple pane windows with wider spacers and multiple LowE coatings provide:

• Higher insulation (R value)
• Warmer interior glass surfaces
• Reduced condensation in extreme cold compared to double pane windows in the same conditions

They’re an excellent option for homeowners looking for maximum comfort and performance.

When Should You Be Concerned?

While most winter condensation is normal, you should reach out if you notice:

• Persistent moisture that does not dry
• Water pooling on sills
• Visible damage to surrounding materials
• Condensation between glass panes

If something doesn’t look or feel right — or you simply want peace of mind — we’re always happy to help.

We’re Here to Help

At Oakville Windows & Doors Inc., we believe an informed homeowner is a confident homeowner — especially during extreme Ontario winters.

📍 Visit our showroom: 1380 Speers Rd, #7, Oakville

📞 Call us: 905 827 3200

🌐 Learn more: www.oakvillewd.com

If you have questions about condensation, window performance, or upgrading for better insulation, our team is always here to help — no matter how cold it gets outside.