Window replacement in Ontario 2026: when you need a permit, retrofit vs. full-frame, and how to stack the energy rebates
Most window replacement projects start with a quote and a product choice. Both are the wrong starting point.
The U-factor and SHGC rating on a window determine its winter performance in a GTA freeze-thaw climate and whether it qualifies for the 2026 rebate programs. The brand is a secondary decision. But the permit question comes before either of them, because it determines which installation method is available.
When window replacement needs a permit in Ontario
Retrofit replacement installs a new sash and glass unit inside the existing frame, using the existing rough opening. No building permit is required, provided the opening stays unchanged. This covers the majority of residential window replacements in the GTA.
Full-frame replacement is different. Removing the frame and changing the rough opening dimensions requires a permit. So does altering the structural header above the opening, even if you are otherwise doing a retrofit. That distinction catches a lot of homeowners off guard.
Egress is the third permit trigger. Under Ontario Building Code Section 9.6.3, basement windows in rooms used as bedrooms must have a minimum openable area of 0.35 square metres, at least 380 mm wide and 600 mm tall when open. Converting a non-egress window to meet those minimums is a permit-required alteration, regardless of whether the frame stays.
Pull the permit through the contractor or in your own name. Either way, confirm in writing who holds it. Liability for a non-conforming installation falls to whoever is named on the permit. The parallel permit logic for kitchen and bathroom work is covered in the kitchen renovation permits guide if you are running multiple scopes at once.
Retrofit vs. full-frame: the decision that drives the cost
Retrofit uses the existing frame. A new sash and glazing unit goes into the existing rough opening. GTA labour runs $150–$250 per window, and the project often finishes without touching interior trim or drywall.
Full-frame removes everything: frame, nailing fin, interior trim. It is the right call when the frame has rot, moisture infiltration at the sill, mold in the surrounding drywall, or condensation between panes. Condensation between panes usually means a failed seal, and a failed seal often signals a compromised frame, not just a glass problem. GTA labour runs $250–$400 per window because the scope includes reframing, nailing fin integration, and interior finishing.
Signs you need full-frame rather than retrofit: drafts pulling from the frame edges rather than the glass; paint peeling on the interior stool or apron; visible staining or soft spots at the sill; existing windows that are out of square.
ENERGY STAR Zone 2 — the spec that determines rebate eligibility
Ontario falls almost entirely in ENERGY STAR Canada Zone 2. Zone 2 thresholds are a U-factor of 1.22 W/m²K or lower and an SHGC of 0.27 or higher on south-, east-, or west-facing windows.
The U-factor is the number that matters for Ontario winters. It measures heat loss through the glass assembly. A low U-factor also cuts condensation on the interior glass surface during cold snaps. In GTA homes, most trim damage around windows comes from moisture cycling through the frame during those cold-snap cycles, not from the glass failing outright.
Before ordering, confirm the specific product is listed on the Natural Resources Canada ENERGY STAR product finder at nrcan.gc.ca. Not all products marketed as energy-efficient meet Zone 2 thresholds, and the certification number from that database is what you need for rebate claims.
Stacking the 2026 rebates
Three programs are running concurrently in Ontario and can be stacked on the same project.
The Home Renovation Savings Program offers $100 per window opening for ENERGY STAR certified replacements. It runs through November 2026 and needs no pre-authorization or energy audit.
The Canada Greener Homes Grant covers up to $5,000 for eligible upgrades, but requires a pre-authorization application and a pre-upgrade EnerGuide assessment before work starts. The pre-auth step is mandatory. Miss it and the claim is disqualified, regardless of what gets installed.
Enbridge Gas offers rebates up to $5,000 for eligible improvements and can be stacked with the Greener Homes grant on the same project.
The HRSP $100/window is the simplest of the three: file after installation with the ENERGY STAR certification number and the invoice.
What a quote should include
The spec sheet is non-negotiable: U-factor, SHGC, and ENERGY STAR certification number should be on the document before you sign anything. Labour rate should state explicitly whether it covers retrofit or full-frame. Ask whether the stool, apron, and interior trim are included or quoted separately, and whether disposal is in scope. Building permit cost, if it applies, should be a line item.
If a contractor cannot produce an ENERGY STAR certification number for the windows they are proposing, that is a red flag. The certification is searchable by product name on the NRCan product finder.
Save the certification number and the installation invoice. You need both for any rebate claim.
More from home.renovation.reviews
- Related: Kitchen renovation permits guide — what triggers a permit and trade sequencing
- Main site: LF Builders — window replacement and exterior renovation in the GTA
- Blog: LF Builders renovation guides
If you have gone through the HRSP or Greener Homes process and hit a specific snag, the details are worth posting. The pre-auth timing and the EnerGuide booking window are where most claims get stuck. Top contributors earn $RENO tier-up rewards and climb the leaderboard.