CSA F280 Heat Loss & Sizing Ceiling Guide
How CSA F280-12 affects HVAC sizing for BC new builds: capacity rules, sizing ceiling limits, overheating protection, and why HOT2000 is not approved.
CSA F280-12 ("Determining the Required Capacity of Residential Space Heating and Cooling Appliances") is the standard referenced in the BC Building Code (Sentence 9.33.5.1.) for sizing residential heating and cooling systems. Unlike HOT2000 annual energy simulations, F280 performs peak-load calculations. Its room-by-room and block-load outputs dictate ductwork sizes, register placement, and appliance capacities.
BC Building Officials enforce strict "capacity sizing limits" based on F280. Heating capacity must meet or exceed calculated heat loss, while nominal cooling capacity must meet or exceed 80% (or 100% if satisfying overheating clauses) and must not exceed 125% of calculated gain (except for ground- or water-source heat pumps) to prevent short-cycling. Short-cycling reduces comfort, wastes energy, fails to manage summer humidity, and shortens compressor lifespans.
A common residential compliance error is attempting to use energy modeling software for mechanical sizing. The BOABC Handbook states explicitly that HOT2000 and the Passive House Planning Package (PHPP) are NOT approved to perform CSA F280 calculations. Apollo utilizes F280-verified design software (such as TECA's calculator) to produce reports that match the energy model, drawings, and built conditions.
Review the rules building officials check during plan review.
- Heating Sizing: The installed space heating system capacity must meet or exceed the calculated peak heat loss.
- Cooling Floor: Installed cooling capacity must meet or exceed 80% of the calculated peak heat gain (or 100% if sized to satisfy the 9.33.3.1.(2) overheating protection).
- Cooling Ceiling: Nominal cooling capacity must not exceed 125% of calculated gain (except for ground/water source heat pumps) to prevent short-cycling and comfort issues.
- Timing: Sizing calculations should be completed at the building-permit stage and no later than framing inspection so as-built ducting can accommodate the equipment.
Design cooling capacity to comply with the 26 °C overheating clause.
- BCBC 2024 Sentence 9.33.3.1.(2) requires mechanical cooling to hold ≤ 26 °C in at least one living space during peak summer design temperatures.
- A whole-house cooling system sized via standard CSA F280 typically satisfies this requirement.
- If cooling is provided only to a single "refuge room," a separate F280 calculation must be performed for that room because F280 is not designed for single-room internal boundaries.
- Single-zone cooling calcs should follow the TECA/HVAC-DC "Guideline on Single Zone Cooling in Dwelling Units" Version 1.0a (March 14, 2025) and its voluntary submission checklist.
Ensure calculations use verified tools, not energy models.
- F280 calculations must be performed using software from the hvacdc.ca verified list (e.g. TECA Heat Loss & Heat Gain Calculator, Right-F280).
- HOT2000 and PHPP are annual simulation tools, not peak load calculators, and are not approved for F280 compliance under Article 9.33.5.1.
- Apollo runs the energy model in HOT2000 and F280 sizing in a separate, hvacdc.ca-verified tool.
- Modellers must coordinate window, insulation, and ventilation inputs between both models so they do not conflict.
Send details to start an F280 heat-load calculation.
- Floor plans with room names, window sizes, and ceiling heights.
- Elevations, building sections, foundation details, and project orientation.
- Window and exterior door U-values and SHGC.
- Wall, roof, floor, slab, and foundation insulation assemblies.
- Mechanical equipment preferences (furnace, heat pump, boiler) if already considered.
What builders ask before booking.
Is a CSA F280 calculation required in BC?
Yes. BCBC Sentence 9.33.5.1 requires CSA F280-12 calculations to size space heating and cooling equipment for all new Part 9 residential construction.
Can I use my HOT2000 model for F280 sizing?
No. The BOABC Handbook states that HOT2000 and PHPP are not approved for CSA F280 compliance. Sizing must be done in a separate hvacdc.ca-verified program.
What are the cooling capacity boundaries checked by building inspectors?
The installed cooling system must meet or exceed 80% (or 100% if satisfying overheating requirements) of the calculated peak heat gain, and must not exceed 125% of that gain (unless it is a ground- or water-source heat pump) to prevent short-cycling.
How do I size cooling for a single "refuge room" to meet code?
Under the BCBC 2024 overheating clause, cooling a single room requires a dedicated room-level F280 calculation. You should follow the TECA/HVAC-DC "Guideline on Single Zone Cooling in Dwelling Units" Version 1.0a (March 14, 2025) and submit its checklist.
Send the drawings and project basics.
Jesse Cummings reviews the file and returns a quote - base compliance package and applicable add-ons, priced by stage - within one business day after receiving the drawings and project basics.