5 Common HVAC Deficiencies That Delay Ontario Building Permits (and How to Avoid Them)

Getting your building permit approved can be stressful enough—finding out the mechanical/HVAC submission is missing key items (or includes something the reviewer can’t accept) is one of the most common reasons permits get delayed.

Below are five HVAC-related deficiencies that regularly show up in Ontario permit reviews, plus practical ways to prevent them. (Always confirm the exact requirements with the authority having jurisdiction (AHJ) and the current Ontario Building Code/municipal submission requirements for your project.)

1) Incorrect EEDS (SB-12) package selection

The Energy Efficiency Design Summary (EEDS) is the SB-12 compliance form that shows which energy-efficiency “package” (or path) your design is following. A common issue is selecting a package that doesn’t match the rest of the drawings or specifications—especially windows, insulation values, air tightness assumptions, or equipment efficiencies.

How to avoid it

• Make sure the architectural drawings, window schedule, insulation notes, and HVAC equipment specs align with the selected SB-12 package.

• If the design changes (window area, HVAC equipment, insulation), re-check that the selected package is still valid.

• Keep a clean set of supporting documentation (cut sheets, schedules) so the reviewer can verify the inputs quickly.

2) Missing return air inlet (common on split levels or rooms above unconditioned space)

Return air is what allows conditioned air to circulate back to the air handler. If a room has supply air but no practical return path, it can end up pressurized (or under-served), which impacts comfort and system performance.

This can be especially common in:

• Split-level layouts where airflow paths are interrupted by doors and elevation changes

• Rooms over garages or other unconditioned spaces where temperature swings are larger

How to avoid it

• Confirm every supplied room has a return grille or a clear, code-acceptable return air path (for example, transfer pathways that meet the design intent).

• Review the duct layout early—before framing details and bulkheads are finalized.

• Coordinate with the architectural plan so return locations aren’t blocked by millwork or doors.

3) Missing ventilation design and the Residential Ventilation Design Summary (MVDS) form

Permit reviewers often need to see a complete mechanical ventilation design, not just “HRV on plans.” Many municipalities require a Residential Mechanical Ventilation Design Summary (sometimes called MVDS) as part of the submission package.

How to avoid it

• Provide a complete ventilation design showing the principal ventilation strategy, airflow rates, and key components.

• Include the municipality’s required summary form (or an equivalent ventilation design summary accepted by the AHJ).

• Ensure the ventilation drawings match the equipment selections and duct routing shown on the HVAC plans.

4) HRV/ERV not in compliance (including “through-the-wall” HRV/ERV configurations)

Heat Recovery Ventilators (HRVs) and Energy Recovery Ventilators (ERVs) need to be installed and configured in a way that satisfies both code intent and the project’s ventilation design. A recurring permit-review issue is specifying an HRV/ERV setup that doesn’t meet the expected distribution, performance, or configuration requirements.

One example that can raise flags in reviews is using a “through-the-wall” style unit where the design intent requires a ducted, balanced system with properly distributed supply and exhaust.

How to avoid it

• Confirm the ventilation system type and configuration that your AHJ expects for the project.

• Use an HRV/ERV selection that can meet required airflow rates and installation constraints.

• Make sure the drawings clearly show: outdoor air intake/exhaust, distribution points, and how the system integrates with the rest of the HVAC.

5) Missing fire dampers / protection for openings when limiting distance is under 1.2 m

When a wall is close to a property line (or otherwise has a small “limiting distance”), requirements related to protecting openings and penetrations can become more stringent. If the HVAC design includes openings/penetrations that should be protected (and they aren’t), it can trigger review comments—and sometimes expensive late-stage changes.

As your note highlights, this is more than a paperwork issue: adding fire dampers (and related rated details) can be a meaningful cost and coordination impact.

How to avoid it

• Identify walls with limiting distance under 1.2 m early (architect + designer coordination).

• Review any ducts, grilles, vents, louvers, and penetrations that interact with those walls.

• Coordinate the HVAC drawings with the fire protection / architectural details so any required protection is shown clearly on the permit set.

Conclusion

Most HVAC permit delays are preventable when the energy (SB-12/EEDS), ventilation, and HVAC drawings are coordinated as one package. A quick “submission QA” pass—checking returns, ventilation documentation, HRV/ERV configuration, and limiting-distance implications—can save weeks of back-and-forth with reviewers.

If you’re seeing repeated mechanical review comments, Stelos can help you organize and coordinate your permit submission set so gaps get caught early—before they turn into delays or costly rework.