Windows and Glass in Newmarket: A Homeowner's Guide
In Newmarket, fogged, cracked or sweating windows in sound frames are usually fixed with new glass, not new windows, and the town's rules make that simple: glass-only work in an existing frame needs no building permit, and in the Lower Main Street South heritage district, repairing broken panes to original specifications is exempt from heritage permits. The housing is mostly single-detached houses built since the 1950s around a 19th-century Main Street. At 4,260 heating degree-days, Newmarket needs about 21% more heating than downtown Toronto, the highest figure in the GTA building-code list, which means more room-side condensation and more sun-driven thermal cracks.
Newmarket is rated at 4,260 heating degree-days, against 3,520 at Toronto City Hall, making it about 21% colder by heating demand and the coldest location in the GTA list.
Glass-only replacement doesn't change the opening, and Newmarket's building rules don't require a permit even for same-size window or door replacement; new or enlarged openings do need one.
The Lower Main Street South Heritage Conservation District covers 72 properties, and repairing broken window panes to original specifications is exempt from heritage permits.
Single-detached houses are 60% of Newmarket's dwellings; duplex units are 7%, a higher share than in Vaughan, Markham or Richmond Hill.
Newmarket's population rose from 5,000 to 11,000 between 1950 and 1970 and reached 87,942 in 2021, so most homes date from the postwar decades onward.
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Newmarket is the coldest place we work. Building-code climate data rates it at 4,260 heating degree-days, against 3,520 at Toronto City Hall. That's about 21% more heating demand than downtown and the highest figure in the GTA list, and it shows up on the glass as more condensation and more winter cracks. In most homes, the fix is new glass in the frame you already have.
The housing is mostly postwar and later: detached houses and townhouses around a 19th-century Main Street that is protected as a heritage district. This guide covers what that stock means for your windows, how Newmarket's cold changes the advice, and the local permit and heritage rules, which are clearer here than in most GTA municipalities.
Newmarket's housing, from Quaker settlement to Highway 404
Newmarket was settled from 1801 by Quaker families from Vermont and Pennsylvania, and its downtown has centred on Main Street for more than a century. Suburban growth came later: the population rose from 5,000 to 11,000 between 1950 and 1970, Upper Canada Mall opened at Yonge and Davis in 1974, and Highway 404 later pulled development east. By 2021 the town had 87,942 people in 31,239 private dwellings.
Today 60% of dwellings are single-detached, 13% townhouses, 13% apartments, 7% semi-detached and 7% duplex units. That duplex share is higher than Vaughan's (3%), Markham's (5%) or Richmond Hill's (3%).
| Housing | Typical era | What we usually find | What tends to fail |
|---|---|---|---|
| Lower Main Street South and downtown | 19th century onward | Older and heritage-sensitive windows | Broken panes, sash and glazing wear |
| Postwar and 1970s–80s subdivisions | 1950s–1980s | Windows often replaced once already | Fogged later-generation units, worn cranks |
| East-side growth toward Highway 404 | Later decades | Original double-pane sealed units | Fogged units past typical life, thermal cracks |
| Duplex and apartment units | Various | Mixed | Seal failure and condensation; landlord or condo rules may decide who pays |
Typical sealed-unit life is 10 to 25 years, and south-facing units often last less than 12. In a 25-year field study of more than 2,400 units, 4.9% had failed by year 10 and 9.2% by year 25. So a house with 20 windows and original 1990s glass will usually have at least one fogged unit, and where the frame is sound, that's a glass-only fix.
How Newmarket's cold affects your glass
By the national building-code climate-zone thresholds, 4,000–4,999 heating degree-days is Zone 6, while downtown Toronto at 3,520 falls in Zone 5. Newmarket has recorded −35.2 °C and averages 122.2 cm of snow a year, against a record low of −31.3 °C at Pearson.
Condensation
The colder the outside pane, the less indoor humidity a window can take before water forms on the room side. At 21 °C indoors, double glazing tolerates about 41–49% relative humidity at −18 °C outside, falling to 32–39% at −29 °C. These are NRC's classic 1960 tables, but the physics hasn't changed: on Newmarket's coldest nights, a house kept near the top of Health Canada's 30–50% range is likely to see its windows sweat.
What helps:
- Drop indoor humidity toward 30% during cold snaps, and check it with a hygrometer.
- Run bath and kitchen fans, and keep blinds open so room air reaches the glass.
- Consider warmer glass on problem windows when their sealed units are replaced. NRC's classic data shows triple glazing tolerating about 49–53% humidity at −29 °C, against 32–39% for double.
Our condensation guide explains the full picture.
Thermal-stress cracks
Glass cracks when its centre and edge are at very different temperatures, at roughly 50 psi of stress per °F of difference. On a sunny morning after a hard frost, the centre of a pane can reach 15–25 °C while the edge in the frame sits at −10 °C or colder. Half-closed blinds, partial shade and heating vents aimed at the glass all add to the risk. A thermal crack starts at the edge and runs straight in. It can't be repaired; the glass or sealed unit is replaced. Read more in our cracked window guide.
Is triple pane worth it here?
More so than downtown, though it's still not an automatic yes. In Toronto, triple glazing costs $150–$300 extra per window, saves $60–$150 a year in heating and pays back in 15 years or more. With about 21% more heating degree-days, we'd expect Newmarket savings to be somewhat higher; that's our estimate, not a measured figure. The clearer win is comfort: at −10 °C outside, the inner glass sits at 16–18 °C for triple against 11–14 °C for double. Triple sashes are also 30–50% heavier, so a triple unit often won't suit an existing frame; for a glass repair, low-E, argon and a warm-edge spacer are the usual upgrade. See our low-E, argon and triple-pane guide.
Permits and heritage in Newmarket
Building permits. Glass-only replacement keeps the existing frame, so it doesn't change the opening at all. Newmarket's rules go further: even "replacing doors and/or windows that are the same size as existing" doesn't need a permit, while "creating new openings for, or increasing the size of, doors and windows" does.
Heritage. Newmarket's historic downtown was recognized as a Provincial Heritage Conservation District in October 2013. The Lower Main Street South Heritage Conservation District covers 72 properties. The Town exempts "repairing broken window panes to original specifications" from heritage permits, while alterations to a property in the district need one. So a like-for-like pane repair can go ahead; only a whole-window swap or a design change needs the Town's approval first.
What we'd do on a Newmarket job
For a fogged or cracked unit in a sound frame, we replace the sealed unit and keep the window. Glass-only replacement runs $350–650 per opening in the GTA, a fraction of the $1,000–1,800 a full-frame window costs. Prices vary with size, glass type and access. On cold-facing windows that sweat, we'll quote a warmer glass option if the frame can take it. On Main Street, we match the original glass so the repair stays within the heritage exemption. If a frame has failed, we'll tell you it's a window-replacement job rather than a glass repair.
Areas of Newmarket we serve
All of Newmarket, from the Main Street heritage district and downtown to the Yonge and Davis corridor and the newer neighbourhoods toward Highway 404. We also serve Richmond Hill to the south.
Next step
If a window in your Newmarket home is fogged, cracked or sweating, start with our Newmarket window repair page and request a free quote. Tell us if your property is on Lower Main Street South and we'll quote a like-for-like repair.