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January/February 2003 issue	In this issue Table of Contents Editor’s Notebook Inside Story Feature: Home at heart À la carte Reverberations

Matters of degrees
Accurate calculations of ‘heating degree days’ and ‘snow loads’ play a critical role in keeping our homes warm and safe
By Steven Fick and Eric Harris

THERE’S COLD, and then there’s snow. We measure one with thermometers, of course, and the other by recording how many centimetres have fallen. But is that enough? Not for oil and natural gas companies or for architects and structural engineers.

To increase the efficiency of heating-fuel delivery systems, a measure of coldness was developed by engineers at the turn of the 20th century to predict fuel consumption. Called "heating degree days," it is based on the assumption that once the outside temperature drops below 18°C, everybody reaches for the thermostat (see map legend).

For example, the coloured bands on the map show that Victoria averages less than 3,000 on this scale, while Resolute hits 12,500. As each winter progresses, energy companies keep a close watch on the accumulation of heating degree days in the areas of their routes and tweak delivery schedules and supplies accordingly.

The map also shows the amount of oil that would be needed to heat a generic house situated at various places around the country. At 50 cents a litre for heating oil, the house in Victoria would cost $720 to heat annually, while in Resolute, it would cost $3,622. (Of course, heating oil is also pricier in remote areas.) Is it any wonder Canadians congregate along our southern frontier?

Snow load is yet another critical factor for any building in Canada. Just ask the architects of Montréal’s Olympic Stadium! A roof in Glacier, B.C. (see chart), must be strong enough to support the equivalent of 40 pickup trucks.

*Click on the section of map you wish to view enlarged

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Snowloads

The best way to protect a snow-laden roof is to stay off it. Every community has guidelines to ensure that its houses and other structures are strong enough to support potential snow loads. Below are baseline snow loads that a 10-by-10-metre flat roof must bear in the following communities:

For snow-load information for other cities, click through this alphabetical listing:

A / B / C / D / E / F / G / H / I / J / K / L / M / N / O / P / Q / R / S / T / U / V / W / Y

SOURCES: METEOROLOGICAL SERVICE OF CANADA, ENVIRONMENT CANADA; INSTITUTE FOR RESEARCH IN CONSTRUCTION,NATIONAL RESEARCH COUNCIL OF CANADA;

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