Ontario · Energy · area guide · checked October 8, 2026

Heat loss calculations in Durham Region

A heat loss calculation is how a heat pump or furnace gets sized, and its key input is the design temperature. In Durham Region, the National Building Code's 2.5% January design temperatures run from −20°C at Whitby (Brooklin) to −24°C at Cannington, so a calculation for a house near Cannington starts from a colder number than one near Whitby (Brooklin). Here's what that means for Port Perry, Uxbridge and Brock and the rest of the area.

A kitchen table with a house floor plan, a laser measure, a tape measure and a laptop showing the plan

Design temperature

−20°C to −24°C

NBC 2020, January 2.5%

Heating degree-days

4,357

Lindsay Frost

Standard

CSA F280-12

Registered organizations

23

many offer F280 reports

How Durham Region is built

Durham Region's houses by when they were built Ten house shapes, one for each tenth of Durham Region's 19,285 houses. Before 1961: 24%, 1961–1990: 42%, 1991–2000: 13%, 2001 or later: 21%. Older houses glow hotter.
  • Before 1961 24%
  • 1961–1990 42%
  • 1991–2000 13%
  • 2001 or later 21%
Each house stands for one in ten of Durham Region's 19,285 houses (single-detached, semi-detached, row, duplex and mobile homes), drawn by when it was built. The glow shows the usual pattern: older houses tend to be leakier and less insulated. Snowfall scales with heating degree-days. Sources: Statistics Canada 2021 Census (table 98-10-0233-01), Environment and Climate Change Canada 1981–2010 climate normals (Lindsay Frost) and the National Building Code 2020 January design temperature for Port Perry.

This page covers north Durham: the townships of Scugog (Port Perry), Uxbridge and Brock. Oshawa, Whitby, Ajax, Pickering and Clarington have their own pages, which also cover their hamlets.

Design temperatures across Durham Region

The National Building Code of Canada 2020 says the 2.5% January design temperature is the value ordinarily used to design heating systems. Its climate table lists these Ontario locations in or next to Durham Region:

Location in the code’s tableJanuary 2.5% design temperatureHeating degree-days
Port Perry−22°C4,260
Uxbridge−22°C4,240
Cannington−24°C4,310
Whitby (Brooklin)−20°C4,010

Environment and Climate Change Canada's 1981–2010 climate normal at Lindsay Frost (30.6 km from the middle of the area) is 4,357 heating degree-days a year, with a January mean of −8.4°C.

What CSA F280-12 asks for

The code requires the heating capacity for a house to be worked out with CSA F280, using the code's own design temperatures, and its list of referenced documents names the 2012 edition, CSA F280-12. The calculation works out how much heat each room loses on the design day, from the house's actual walls, windows, ceiling insulation and air leakage.

At −20°C to −24°C, a cold-climate heat pump sized to the calculation can carry most of the season, and the number shows how much backup heat the coldest days need.

What the calculation needs from your house

Of the 19,285 houses in Durham Region (single-detached, semi-detached, row houses, duplexes and mobile homes), 24% were built before 1961 and 66% before 1991, according to the 2021 Census. In an older or renovated house, the walls, windows and air leakage rarely match the original plans, so ask the designer to measure rather than assume. Have this ready:

  • Room dimensions and ceiling heights, or a floor plan.
  • Window and door sizes and types, room by room.
  • Insulation levels in the attic, walls, basement and any floor over an unheated space.
  • A blower door result from an EnerGuide evaluation, if you've had one.
  • Where the ducts, radiators or baseboards run, so the heat can be delivered room by room.

What it costs

There's no standard published price for a standalone F280 calculation, so ask two or three providers for a written quote that names the deliverable: the room-by-room F280 report, not just an equipment size. Many energy advisors bundle it with an EnerGuide evaluation, which also gives the calculation measured air-leakage data instead of an assumption. Ask whether a rural travel fee applies. The CSA F280 heat-loss calculation explains the method and typical cost bands.

Communities we cover in Durham Region

Every town, village and hamlet below is part of this page, grouped by municipality (2021 Census population).

  • Township of Scugog 21,581Caesarea, Greenbank, Nestleton Station, Port Perry, Prince Albert
  • Township of Uxbridge 21,556Goodwood, Leaskdale, Udora
  • Township of Brock 12,567Beaverton, Cannington, Sunderland

Covered on city pages: Pickering (Brougham, Claremont, Greenwood, Whitevale); Clarington (Hampton, Newcastle Village, Newtonville, Orono); Whitby (Ashburn); Oshawa; Ajax.

NRCan-registered service organizations serving Durham Region

NRCan's list of service organizations (checked October 8, 2026) shows 23 organizations registered for postal codes in Port Perry and Uxbridge (L9L, L9P). Registration means an organization lists those postal areas, not that it has an advisor in town: confirm they travel to your community, and ask about wait times and travel fees.

Only assessments from the seven HRSP-approved organizations qualify for the $600 Home Renovation Savings rebate and its assessment-path upgrade rebates; each listing below says whether it's one of them.

Source: NRCan list of service organizations, checked October 8, 2026, matched by forward sortation area (L9L, L9P). Call to confirm your road is covered.

Heat pump programs in Durham Region

Heat loss calculations in Durham Region: common questions

What design temperature is used for heat pump sizing in Port Perry?

The National Building Code 2020's climate table gives −22°C for Port Perry, −22°C for Uxbridge, −24°C for Cannington and −20°C for Whitby (Brooklin). Provincial codes can use their own climate tables, so ask which value the calculation uses.

What is CSA F280-12?

The 2012 edition of CSA F280, Determining the required capacity of residential space heating and cooling appliances. The National Building Code 2020 requires heating capacity for a house to be determined with it.

How much does a heat loss calculation cost?

There is no standard published price. Ask two or three providers for a written quote for the F280 report, and ask whether it costs less bundled with an EnerGuide evaluation and whether a travel fee applies.

Who does F280 calculations in Durham Region?

Many of the 23 NRCan-registered organizations that list Port Perry and Uxbridge postal codes offer them, as do HVAC designers. Ask for the F280 report itself, not just an equipment size.

Get matched with a registered advisor in Durham Region

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