How Do You Design an HVAC System for a Custom Home in Ontario?
The question sounds simple. The answer has six steps, each of which depends on the one before it — and each of which, when skipped or done in the wrong order, produces a system that either fails the permit office, fails the homeowner, or both. This is the complete process, written for Ontario's climate zones and building code, from the load calculation that starts everything to the permit package that ends the design phase.
If you're already past the background and need a permit-ready HVAC design for a specific municipality — Collingwood, Oro-Medonte, Barrie, Muskoka, or anywhere else in Ontario — jump to the quote form at the bottom. If you want to understand what you're paying for first, keep reading.
Every step in a proper Ontario custom home HVAC design feeds the next. Skipping or reordering them is where most design problems begin.
CSA F280 Heat Loss
Room-by-room load at your municipality's design temperature. The number every other decision comes from. See our heat loss service.
System & Equipment Selection
Furnace, heat pump, boiler, or hybrid — chosen against confirmed load numbers, not against square footage or habit.
Distribution Design
Duct layout, radiant circuit plan, or hydronic distribution — sized to deliver each room's load. See our HVAC design service.
Ventilation & Permit Package
HRV/ERV design, MVDS, Schedule 1, BCIN stamp — all formatted for your municipality's portal. See our HRV/ERV service.
The CSA F280 heat loss calculation is the document that tells you what the house actually needs — how much heat each room loses at your municipality's design temperature, and how much cooling each room gains on the summer design day. Every equipment sizing decision, every duct size, every radiant loop length, every zone boundary — all of it flows from this number. You cannot correctly design an HVAC system without it. You can guess. Guessing is not design.
In Ontario, design temperatures vary significantly by municipality. Collingwood and Wasaga Beach use -22°C. Barrie and Oro-Medonte use -24°C. Muskoka municipalities use -28°C. The GTA and York Region use -18°C. A calculation prepared with the wrong design temperature produces wrong load numbers — and wrong load numbers produce the wrong equipment size, the wrong duct sizes, and a system that either short-cycles or falls short on the coldest nights of the year. Use our free design temperature lookup tool to confirm your municipality before ordering any report.
The calculation also needs to be room-by-room, not whole-house. A single total load number for the whole home tells the equipment selector the total capacity needed — but it tells the duct designer nothing about how to distribute that capacity, and it tells the radiant designer nothing about which zones have higher loads and need tighter tubing spacing. Room-by-room results are what a real design is built from. See our CSA F280 heat loss calculation service for what this produces and what it costs.
Selecting the equipment before the load calculation is done. It happens constantly — a supplier quotes a furnace based on square footage, the homeowner approves it, the permit package gets assembled around the pre-selected equipment, and the calculation that comes back produces a load number that doesn't match. Either the equipment is wrong (now replaced after installation) or the calculation gets massaged to justify the pre-selected unit (now the permit package is dishonest). Starting with the load calculation costs less and produces a better result. Our permit rejection guide has the full accounting of what going out of order costs.
Once the loads are confirmed, the system selection is a matching exercise — not a preference exercise. The confirmed design-day load, the home's construction type, and the local climate zone together narrow the options considerably.
Cold Climate Heat Pump
Best for Zone 5–6At -18°C to -24°C, a CCASHP-certified unit can often serve as the sole heat source for a well-insulated home — no backup required. For Zone 7 (Muskoka), backup heat is more commonly needed. The load calculation determines whether the heat pump covers the design-day load alone. See our cold climate heat pump Ontario guide for the full sizing analysis by climate zone.
Forced Air — Gas Furnace
Most Common in OntarioStill the dominant system type in Ontario custom homes. A high-efficiency condensing furnace (96%+ AFUE) sized to the confirmed load is a reliable, well-understood system that installers know and permit offices are familiar with. Works well with all distribution strategies. Equipment selection must be based on the calculated load — not manufacturer defaults or installer habit.
Hydronic Radiant + Boiler
Best for High-Performance BuildsA condensing boiler or cold climate heat pump serving a hydronic radiant slab or gypcrete system is the highest-comfort option for Ontario custom homes — particularly on ICF or high-performance framed builds where supply temperatures can stay low and efficiency stays high year-round. Requires the most detailed design work. See our radiant heating design service for the full process.
A cold climate heat pump paired with a gas furnace backup covers the efficiency advantage of the heat pump at moderate temperatures while ensuring the furnace handles the design-day load if needed. This pairing works particularly well in Zone 6 and 7 municipalities where design temperatures are cold enough to push some heat pumps below their comfortable operating range. The load calculation determines at exactly what outdoor temperature the furnace needs to take over — that crossover point drives both equipment selections.
Distribution design is where room-by-room load results become physical systems. For a forced-air or heat pump system, this means duct layout: trunk and branch sizing, supply and return locations, diffuser placement, and airflow balancing. For a hydronic radiant system, this means PEX loop layout, circuit lengths, manifold locations, zone boundaries, and supply temperature targets. Both require the room load numbers to do correctly.
The most common distribution design failure in Ontario custom homes is undersized returns. A supply system that can deliver 1,200 CFM to the house is useless if the return path can only move 600 CFM — the system develops positive pressure in supply rooms, negative pressure in return rooms, and the home never reaches temperature balance. Correct duct design sizes supply and return together, routes the trunk to serve the longest runs first, and places returns to capture air from every occupied zone. This is documented in the mechanical drawings that accompany the permit package.
For radiant systems, the distribution design is inseparable from the load calculation — tubing spacing is selected to deliver the confirmed room load at a target supply water temperature, and that target supply temperature then drives the boiler or heat pump selection. The chain runs from load number to spacing to supply temperature to equipment. Change any one input without recalculating the others and the system is unbalanced at design day. See our radiant slab design guide and radiant manifold layout guide for the specifics.
CSA F280 Report
Room-by-room heat loss and cooling load at your municipality's design temperature. BCIN-stamped. The first document and the foundation of everything else.
Mechanical Drawings
Duct layout or hydronic distribution drawn over your floor plans. Equipment schedule, duct sizes, supply and return locations. BCIN-stamped on every page.
MVDS — Mandatory 2025
The Mechanical Ventilation Design Summary documents your HRV or ERV system per CAN/CSA-F326. Mandatory since January 1, 2025 under OBC 2024. Applications without it are returned before review.
Schedule 1 Declaration
Signed and stamped by our BCIN-registered designer. A separate form from the drawings — commonly omitted. See our HVAC permit requirements guide for the complete checklist.
The design temperature is the single most location-specific input in an Ontario custom home HVAC design. Every municipality has one. Every calculation must use the right one. Look up any Ontario municipality →
| Municipality | Design Temp | Zone | HVAC Design Notes | Local Guide |
|---|---|---|---|---|
| Collingwood | -22°C | Zone 6 | Georgian Bay wind exposure affects infiltration; ski chalet setback strategy matters | Guide → |
| Wasaga Beach | -22°C | Zone 6 | CityView portal; Road Occupation Permit required with application | Guide → |
| Midland | -22°C | Zone 6 | Cloudpermit; Planning sign-off before Building Division accepts application | Guide → |
| Barrie | -24°C | Zone 6 | Counter and email accepted; most straightforward Simcoe submission process | Guide → |
| Oro-Medonte | -24°C | Zone 6 | Cloudpermit only; Zoning Certificate required before permit application | Guide → |
| Muskoka (Huntsville / Bracebridge) | -28°C | Zone 7 | Six separate municipalities; backup heat more commonly needed for heat pumps | Guide → |
| King City / York Region | -18°C | Zone 5 | Township of King building dept; best conditions for all-electric heat pump strategy | Guide → |
How do you design an HVAC system for a custom home in Ontario?
In four steps, in order: (1) CSA F280 room-by-room heat loss calculation at your municipality's design temperature; (2) equipment selection — furnace, heat pump, boiler, or hybrid — sized against the confirmed load; (3) distribution design — duct layout or hydronic radiant circuit plan sized to deliver each room's load; (4) ventilation design and permit package — HRV/ERV MVDS, Schedule 1, BCIN stamp, formatted for your municipality's submission portal. Every step feeds the next. Reversing or skipping steps produces design problems that show up either at the permit office or after move-in. Our HVAC design and mechanical drawings service covers steps 3 and 4 in full.
What does HVAC design for a Collingwood custom home involve?
Collingwood uses -22°C as its heating design temperature (Climate Zone 6). HVAC design starts with a CSA F280 load calculation at -22°C — the correct number for Collingwood, not Toronto's -18°C or Barrie's -24°C. Georgian Bay wind exposure affects infiltration assumptions for exposed waterfront or hillside properties. For ski chalets and seasonal properties near Blue Mountain, the control strategy must address setback management and recovery. The complete permit package — heat loss report, mechanical drawings, MVDS, Schedule 1 — is submitted by counter or email to the Town of Collingwood Building Department. See our Collingwood heat loss and permit guide for the specifics.
What does HVAC design for an Oro-Medonte custom home involve?
Oro-Medonte uses -24°C (Climate Zone 6) and has the most administratively demanding permit process in Simcoe County: Cloudpermit submission only, and a Zoning Certificate from the Planning Division must be obtained before the Building Division will accept a permit application. HVAC design follows the same four-step sequence — CSA F280 at -24°C, system selection, distribution design, permit package — but every document must be formatted for Cloudpermit upload at the correct file size and naming convention. See our Oro-Medonte permit guide and our new Oro-Medonte radiant guide for the local specifics.
Is a heat pump a good choice for a custom home in Simcoe County or Georgian Bay?
Yes — with correct sizing. In Zone 6 at -22°C to -24°C, a CCASHP-certified cold climate heat pump can cover the full design-day load for a well-insulated home. For high-performance framed or ICF construction, the loads are low enough that the heat pump operates comfortably as the sole heat source. For homes with higher loads — larger glazing area, conventional framing, waterfront exposure — a hybrid configuration with gas backup is more appropriate. The decision hinges on the confirmed load number versus the heat pump's verified output at the local design temperature. Our cold climate heat pump Ontario guide covers this comparison by climate zone.
What is the MVDS and why is it required?
The Mechanical Ventilation Design Summary is a document required under OBC 2024 (in force since January 1, 2025) that demonstrates how the home's HRV or ERV system meets the ventilation requirements of CAN/CSA-F326 and the SB-12 compliance path. It documents the unit's Sensible Recovery Efficiency, airflow rates, and ventilation zone coverage. Every new Ontario home requires it regardless of heating system type. Applications submitted without it are returned as incomplete before any technical review. Our HRV/ERV ventilation design service produces the MVDS as part of every complete permit package.
What is BCIN and why does the HVAC design need to be stamped?
BCIN stands for Building Code Identification Number — the registration credential required under the Ontario Building Code for qualified designers who prepare HVAC and mechanical design documents for permit submission. Every page of every document in the mechanical permit package must carry the designer's name, BCIN registration number, qualification identification number, and signature. A package missing any of these elements is returned as incomplete. Our designers are BCIN-registered and stamp every page of every document as a standard part of every package we produce. See our permit rejection guide for the full list of stamping requirements.
How long does HVAC design take for a custom home in Ontario?
We deliver complete packages in 48 hours after receiving your floor plans and confirming the project details. Complex multi-system projects — radiant plus forced air, multi-zone hydronic, large custom homes with detailed room schedules — may require additional time, which we confirm upfront. The 48-hour turnaround applies to our standard residential HVAC design packages. Send your plans and we'll confirm the timeline before you commit.
Ready to start your HVAC design? Upload your floor plans and tell us your municipality — we'll confirm the design temperature, assess the project, and deliver a complete permit-ready package in 48 hours.
Get Free Quote →Upload your floor plans and tell us your municipality. We'll confirm your design temperature, assess the project, and deliver the complete BCIN-stamped HVAC design package — heat loss report, mechanical drawings, MVDS, and Schedule 1 — formatted for your building department. For full custom ICF builds with all mechanical engineering included, our partner icfhome.ca coordinates complete projects province-wide.
- CSA F280 room-by-room heat loss — correct design temperature confirmed
- System selection guidance — furnace, heat pump, radiant, or hybrid
- Mechanical drawings — duct layout or hydronic distribution
- MVDS — HRV/ERV design for OBC 2024 compliance
- BCIN stamp · Schedule 1 · Municipality-formatted
- 48-hour delivery · Province-wide service