Northfield is two classroom wings and a cafeteria on reversible DX splits and a gym on a packaged rooftop with a 100 kW gas furnace. It needed two fields the model did not have: a heater's fuel (a gas heater's duty over its efficiency is fuel, never electricity) and a compressor's reversible flag — every circuit used to be a heat pump on heating hours, so the gas rooftop heated with its compressor first and burnt 100 kWh a winter week as a top-up.

A single-zone rooftop could not heat the gym and cool the cafeteria's kitchen in the same hour — 17 unmet cooling hours a winter week — so the cafeteria has a split of its own. The gym's furnace is 100 kW because 60 left it 106 hours short.

On Toronto's year the school reads 52 MWh of cooling, 168 of heating, 39 MWh of electricity and 167 MWh of gas. The heat-pump splits leave the classroom wings 13 unmet heating hours each and the cafeteria 21 on the coldest mornings — no backup heat by design, left in to say what a reversed circuit does at −20 °C.

What it reads on Toronto

Cooling / heating	52 MWh / 168 MWh
Electricity / gas	39.1 MWh / 167 MWh
Gym	held by the 100 kW furnace (60 kW left it 106 hours short); three unmet cooling hours on a 3 m³/s rooftop sized as a packaged unit is
Heat-pump wings	13–21 unmet heating hours a room at −20 °C — no backup heat, by design

What it taught

• Gas is fuel, not electricity; a report that folds it into kWh of power misprices every gas building.
• A cooling-only machine says so (`reversible: false`) or the model runs its compressor backwards in January.
• A heat pump at −20 °C is little of a heater; the case shows the shortfall instead of hiding it behind a backup it does not draw.

The machines

• DX split, 12 kW class — open in the builder
• Packaged rooftop with gas furnace, 3 m³/s — open in the builder

Sources

• Reznor Model X gas duct furnace catalog (80 % certified output)
• EnergyPlus frost derate model for heat pumps
• PVGIS TMY, Toronto

Readings of the shipped model on the building's own PVGIS typical meteorological year; engineering estimates from catalog data and published correlations. The building runs on every plan, including Free, a few times a day.