How It Works

How are HEAT Scores calculated?

HEAT Score Relative Waste Heat Descriptor
90-100 Very High
75-89 High
50-74 Moderately High
25-49 Moderately Low
10-24 Low
0-9 Very Low

The objective of HEAT Scores is to provide building owners with a simple and intuitive value (between 0 and 100) that can be used to compare the waste heat leaving their home to other homes in their neighborhood, community and municipality. Waste heat typically escapes through poorly insulated doors, windows, walls, ceilings, ductwork, and electrical fixtures (i.e., pot lights) resulting in increased space heating expenses for homeowners and the generation of unnecessary greenhouse gas (GHG) emissions.

Table 1. Heat Score and relative waste heat descriptors

Based on a combination of attributes defined by the Thermal Archetypes project (TAP)1 [1] and unique thermal values generated by the HEAT project, a HEAT Score for each home is calculated by assigning specific weights to the following four criteria: (i) age, (ii) living area, (iii) average temperature of 12 Hot Spots, and (iv) waste heat (calculated from the thermal image of a rooftop).

According to the TAP, homes constructed before 1945 have 3 times less insulation than the homes constructed after 2005. A sample calculation for space heating using insulation levels from TAP suggest that in Calgary, a home constructed before 1945 with a living area of 81 sq.m (composed of 4 external walls and a roof) will cost 2.6 times more than newer homes, while the living area of a larger home (231 sq.m) costs 2.4 times more than a smaller home. This means that age affects energy consumption (slightly) more than living area; consequently age is weighted slightly more than living area. Additionally, Hot Spots represent critical areas of heat loss, thus their importance is appropriately weighted, as is the area of the roof actively wasting heat (i.e., with a temperature greater than the ambient temperature).

We hypothesize that the higher the temperature difference between the average roof hotspots temperature and the optimal rooftop temperature, the higher the probabilty of wasting heat. This hypothesis is being evaluated in a peer-reviewed scientific paper currently in review. Once this research is accepted, we will make it publically available.

1 The Thermal Archetypes project was developed from statistically representative data libraries for 600+K Canadian homes, where it provides default values for (e.g., for insulation and furnace efficiency) while conducting energy analysis.

[1] Parekh, A., and Kirney, C. (2012). Thermal and mechanical systems descriptors for simplified energy use evaluation of Canadian houses, SimBuild Conference Aug 1-3, Madison, Wisconsin, pp 1-8.