Tempstar Heat Pump sizing guide in Greater Vancouver

Two houses on the same Burnaby street, built the same year, same footprint. One needs noticeably more heating capacity than the other. One had the attic topped up and the windows replaced; the other still has original aluminum frames and a crawlspace that breathes. That difference is the whole reason sizing gets calculated instead of guessed.

Most homeowners are told a number before anyone has looked in their attic. It usually comes from the size of the old furnace, which itself came from a guess made decades ago, or from a square-foot chart that knows nothing about your windows facing English Bay. Heat pumps are far less forgiving of that shortcut than gas furnaces were, because their capacity moves with outdoor temperature and because they run long, quiet, low-output cycles instead of short blasts.

This guide walks through how a Tempstar heat pump actually gets sized for a Lower Mainland home: what gets measured, why the coastal climate changes the math compared to the Interior, how ductwork limits your choices, and what oversizing and undersizing feel like once you live with them. HeatLand has been sizing and installing heat pumps across Metro Vancouver and the Fraser Valley since 1999. Call (604) 330-3812 for a free written no-obligation estimate.

Capacity is a match to your house, not a match to your old furnace

The number that matters is how much heat your house loses on a cold night and how much it gains on a hot afternoon. Everything else follows from that. Heat pump capacity is usually expressed in BTU per hour or in tons, and a Tempstar model line will publish both a nominal rating and a table of actual output at different outdoor temperatures.

The trap is starting from the equipment you already own. Furnaces in older Vancouver housing stock were routinely installed with enormous margin, sized for the worst imaginable case, then never revisited after the attic was insulated or the windows were swapped. Copying that number forward gives you a heat pump far larger than the house needs.

The second trap is the square-foot chart. It treats a 1970s Coquitlam split-level with a vented crawlspace the same as a well-sealed Port Moody townhouse of identical area. Those two homes do not lose heat at anything like the same rate.

A heat pump also has to satisfy two loads, not one. Your heating requirement and your cooling requirement are different numbers, and in most Lower Mainland homes the heating load is the larger of the two. Sizing to the cooling load alone leaves you short in February. Sizing to the heating load alone can leave a system that cools poorly in July because it cycles too fast to pull humidity out of the air.

The load calculation: what Manual J and CSA F280 actually do

A proper load calculation is a room-by-room accounting exercise. Every surface that touches outdoor air gets entered: wall area and its insulation value, ceiling area, floor over crawlspace or slab, and every window with its area, glazing type and compass orientation. Air leakage gets estimated or measured. Internal gains from people, lighting and appliances get added on the cooling side. Then the software runs the whole thing against your local design temperatures.

In Canada the residential standard is CSA F280; ACCA Manual J is the equivalent widely used across North America and the two land in similar territory. Either one produces the same deliverable: a heating requirement and a cooling requirement in BTU per hour, broken out by room.

That room-by-room breakdown is the part homeowners underestimate. It tells the installer not just how big the outdoor unit should be, but how much air each room needs, which is what determines duct and register sizing. A whole-house number alone will not stop the bonus room over the garage from being cold.

Ask to see the output. A real load calculation is a multi-page document with your address on it and your inputs listed. If a contractor cannot produce one, they did not do one. HeatLand runs the calculation before quoting equipment, and you get the result in writing.

What a technician measures during the home visit

The visit is mostly measuring and looking, and it takes real time. Expect a tech in your attic hatch with a flashlight and a tape, checking insulation depth and whether it is compressed, displaced around pot lights, or missing over the addition. Expect them in the crawlspace looking at the underside of the floor and the state of any ducting down there.

Windows get counted and characterized: single or double glazed, wood, vinyl or aluminum frame, and which direction each faces. A wall of west-facing glass in Kitsilano drives the cooling load hard on a summer evening. North-facing glass barely moves it.

Exterior wall construction gets identified where possible, sometimes from an unfinished basement corner or a cut-in for a receptacle. Ceiling heights get measured, because volume matters and vaulted rooms are not the same as flat eight-foot ceilings.

Then the mechanical side: the existing duct trunk and branch sizes, the return air path, filter location and size, the electrical panel with its main breaker rating and available spaces, and where an outdoor unit could physically sit with the clearances the manufacturer requires. In a strata, the tech should also look at where the unit would sit relative to neighbouring bedroom windows and patios.

None of this is upselling. Every one of those inputs changes the answer.

Coastal design conditions change the math for Metro Vancouver

Sizing is anchored to design temperatures, and those are published per municipality in the BC Building Code climatic data tables. Vancouver, Richmond, Surrey, Abbotsford and Chilliwack do not all share the same numbers, and the Fraser Valley generally runs colder in winter and hotter in summer than the waterfront. Your installer should be using the value for your city, not a regional average.

What makes the coast distinctive is not extreme cold. It is how much of the heating season sits in the mild, damp band just above and below freezing. That is where heat pumps do their best work, and it is why a properly sized unit here carries the house on its own for most of the winter.

Damp air brings its own complication: defrost. Coastal humidity means outdoor coils frost up more readily than they would in a dry climate, and the system periodically reverses to shed that ice. Frequent defrost cycles are normal here, not a fault. A unit sized so tightly that it has no margin will feel that loss of output more.

Salt air matters if you are near the water in White Rock, Tsawwassen, Steveston or along the North Shore waterfront. Outdoor coils and cabinets corrode faster in that environment. That does not change the capacity calculation, but it does change placement, coil protection options and rinse-down maintenance, and it belongs in the same conversation.

Balance point: where capacity meets load on the coldest nights

Heat pump output falls as outdoor temperature falls, while your home’s heat loss rises. Plot both and they cross. That crossing is the balance point, and it is the single most useful number to come out of a good sizing exercise.

Above the balance point, the heat pump carries the house alone. Below it, something has to make up the shortfall, whether that is electric resistance heat in the air handler or an existing gas furnace in a dual-fuel arrangement.

Where you want that balance point to land is a design decision, not a fixed rule. Push it low by choosing more capacity and the system runs unassisted through nearly every night of a Lower Mainland winter, but you may end up with a unit that is oversized for the mild majority of the season and for cooling. Let it sit higher and you accept more backup heat during a cold snap in exchange for equipment that matches the house better the rest of the year.

Variable-capacity Tempstar systems widen that window considerably, because they can modulate down for mild weather instead of cycling on and off. That is a large part of why they suit the coastal climate.

The honest answer for any specific model is in the manufacturer’s published performance tables at each outdoor temperature. Ask your installer to show you the row for your city’s design condition rather than accepting a general assurance.

Backup heat, dual fuel, and what your electrical panel allows

Below the balance point you need supplemental heat, and choosing it is part of sizing rather than an afterthought.

If you are keeping a working gas furnace, a dual-fuel setup lets the heat pump handle mild weather while the furnace takes over in a cold snap. The control switches between them at a temperature you set. Gas work here is TSBC-certified territory, and the furnace must be properly matched, vented and permitted regardless of how little it now runs.

If you are going all-electric, backup usually means electric resistance elements in the air handler. Those elements draw real current, and this is where many Vancouver retrofits hit a wall. A lot of older homes in East Van, New West and the North Shore still have panels with limited capacity and no spare spaces. Adding a heat pump plus electric backup can push you past what the service supports, which means an electrical load calculation, possibly a panel upgrade, and possibly a service upgrade with the utility.

That cost sits outside the equipment itself but very much inside your decision. Find out early. A qualified electrician does the load calculation to the Canadian Electrical Code as adopted in BC.

One more consideration: if you are pursuing CleanBC or FortisBC program paperwork, eligibility and documentation requirements come from those programs directly. Confirm current rules with them before you commit to a configuration.

Ductwork, airflow and static pressure decide what will actually fit

A heat pump moves considerably more air than the gas furnace it often replaces, because it delivers heat at a lower supply temperature. That single fact wrecks more retrofits than any equipment failure.

Here is the mechanism. Gas furnaces produce hot supply air, so a modest volume does the job. A heat pump produces warm supply air, so it needs more volume to deliver the same heat. If your existing trunk, branches and especially your return are undersized, forcing that extra air through them raises static pressure. High static pressure reduces airflow, and reduced airflow reduces capacity and can trigger protective faults.

So the technician should measure. External static pressure across the air handler, checked against what the equipment is rated to tolerate, tells you whether the ducts can support the size you calculated. Undersized returns are the most common problem in older Lower Mainland homes, often a single central return grille that was never adequate.

Remedies range from enlarging the return and adding a grille, to resizing branch runs, to sealing a leaky crawlspace duct system that is currently heating the ground.

If the ducts genuinely cannot be brought up to what a ducted system needs, ductless or ducted mini-split zoning becomes the better engineering answer. Tempstar offers ducted and ductless options, and choosing between them should follow the airflow findings rather than preference.

Oversizing, undersizing, and the strata and permit realities

An oversized heat pump announces itself. It satisfies the thermostat quickly and shuts off, then restarts a few minutes later. Rooms swing warm and cool. In summer it cools the air fast without running long enough to pull moisture out, so the house feels clammy at a temperature that should feel comfortable. The compressor and reversing valve take the wear of all that cycling.

Undersizing is quieter but costs you differently. The unit runs continuously in a cold snap, backup heat engages more often than it should, and your electricity consumption climbs during exactly the weeks you notice it.

Both are avoidable with a real calculation. Neither is fixable with thermostat settings afterward.

Beyond the equipment, two Lower Mainland realities shape the install. First, permits: most municipalities here require a mechanical permit for heat pump installation, gas work requires TSBC-certified fitting and its own permit, and electrical work requires an electrical permit. A licensed contractor pulls these. Skipping them creates problems at resale.

Second, strata. If you are in a townhouse or condo, outdoor unit placement almost always needs written approval, and many bylaws set noise limits or restrict which walls, patios and roof areas can be used. Manufacturers publish sound ratings for their outdoor units, and that documentation is what a strata council usually wants to see.

HeatLand handles the calculation, the permits and the strata documentation. Call (604) 330-3812.

Quick Checklist

• Ask for a written room-by-room load calculation (CSA F280 or Manual J) with your address on it, not a square-foot estimate or a copy of your old furnace’s rating
• Confirm the design temperatures used are the published values for your specific municipality, not a Metro Vancouver average
• Have external static pressure measured on the existing duct system and the return air path assessed before any equipment is selected
• Get an electrical load review of your panel and service before committing to electric backup heat
• Ask to see the manufacturer’s published capacity table for the exact model at your local winter design condition, and where the balance point lands
• Confirm mechanical, gas and electrical permits are being pulled, and secure written strata approval for outdoor unit placement if you are in a strata

Frequently Asked Questions

Reviewed by the HeatLand Heating & Cooling team — licensed, insured, TSBC-certified HVAC contractor serving Metro Vancouver & the Fraser Valley since 1999. Error codes, specifications, pricing and rebate programs vary by model and change over time; confirm details against your unit’s own manual, a written quote, and the manufacturer or CleanBC/FortisBC. If you smell gas or your CO alarm sounds, leave the home and call the gas utility and a licensed technician from outside.