What’s your Building Science Climate Zone?

Posted in Builders, Dealers, Framers on March 16, 2015

Knowing your climate zone and building accordingly is one of the basic tenants of building science. Moisture, extreme temperatures and inclement weather require completely different building techniques to ensure longevity and efficiency. When you know your building climate zone you can select techniques and materials that are safe, cost effective, and efficient to install and provide an energy efficient building envelope.

Climate zones are defined by two parameters; temperature and moisture which are combined to create hygrothermal maps. There are eight major climate zones in North America based on heating degree-days, average temperatures and precipitation. The Building Science website has its own climate zones map: “Building Profiles for residential construction were developed by BSC to be appropriate for specific climates. The profiles include building cross sections, enclosure and mechanical design recommendations, field expertise notes, material compatibility analysis as well as climate challenges. Each climate has multiple profiles listed as there is more than one possible solution for design and construction of a high performance building within a single region.”


In the early 2000s the US Department of Energy’s Pacific Northwest National Laboratory combined a number of disparate climate resources into the IECC’s current climate zone map. Using information from the 4,775 US weather sites, the PNNL created a definitive map with includes eight climate zones and three moisture zones which produce 24 potential climate designations. Climate zones are based on county borders to enable builders to easily determine the climate zone their build falls into. The map has been adopted by the IECC and Energy Star.

The International Energy Conservation Code (IECC) map shows the climate zones here:

Temperature divisions are determined by degree days. An explanation of degree days from the degreedays.net site:

“Degree days are essentially a simplified representation of outside air-temperature data. They are widely used in the energy industry for calculations relating to the effect of outside air temperature on building energy consumption.

Heating degree days“, or “HDD“, are a measure of how much (in degrees), and for how long (in days), outside air temperature was lower than a specific “base temperature” (or “balance point“). They are used for calculations relating to the energy consumption required to heat buildings.

Cooling degree days“, or “CDD“, are a measure of how much (in degrees), and for how long (in days), outside air temperature was higher than a specific base temperature. They are used for calculations relating to the energy consumption required to cool buildings.”

For example, the base temperature for Toronto is 18°C. On a day with an average temperature of 10°C, the city would rack up 8 heating degree days (HDDs).

Moisture zones are divided into three categories. ‘Moist’ (A) is based on precipitation and falls outside of the marine climate zones.

‘Dry’ (B) is calculated on annual mean temperature as well as precipitation. Here the formula is 0.44 x (TF – 19.5), where TF is the annual mean temperature in Fahrenheit.

‘Marine’ (C) is a temperate zone where the warmest months don’t exceed 72 °F and winter temperatures range between 27 and 65 °F.

Being cognizant of the climate zone in which you are building will help you to utilize advanced technologies and appropriate energy efficiency techniques in your building design.

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