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Community and Q&A

Climate Zones – Shouldn’t they account for mountains and coastlines?

canada_deck | Posted in General Questions on

I live in Canada.  The region that I live in is simply called “Climate Zone 5” and so these are the rules that apply:

However, that region contains the Coast Mountain Range and extensive coastline and it seems ridiculous to throw it all in the same category.

For example, I have a waterfront house in that region.  It is not in Tofino but let’s use that as an example.  Tofino receives annual rainfall of about 124 inches and the year with the lowest temperature is January where the mins are 36.3 F.  It rarely snows in Tofino.

Wind is also a major factor in many of these coastal areas.  The trees can’t even grow straight along the waterfront in Tofino.

Contrast that with buildings that are built on the relatively nearby Mt. Washington (on Vancouver Island) which is also thrown into the same “Climate Zone 5” category.  The buildings here are at an elevation of about 1200 m (3600 feet).  It is much colder with annual snowfall of over 37 feet.

I appreciate that it’s difficult to create a building code that takes into account every micro-climate but this over-generalization seems ridiculous.  Perhaps I am reading this all wrong – are you actually allowed to apply the code as-is to mountainous regions and to build to “Climate Zone 5” at ski resorts in this area?

Is there any part of the world where they do a better job of this?

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  1. _Stephen_ | | #1

    Building code is pretty big... Is there a more specific part of it that you are taking issue with that we could discuss?

    1. canada_deck | | #2

      The wall insulation requirements are a good one. Average minimums in Tofino are never below freezing. Mt. Washington is below freezing for a good chunk of the year. Are they really applying the exact same requirement to the alpine chalet and the coastal cabin?

      1. _Stephen_ | | #4

        I mean, apparently they are.

        I think it's just a way to be able to specify the crappiest house you can legally build in large swaths of areas. No one I know built a code minimum house. Plus you still do your manual J calculation based on local data, not your climate zone.

  2. Trevor_Lambert | | #3

    The climate zone map for Canada is pretty much useless. 95%+ of the population is in the same zone, according to it. Windsor to Winnipeg, apparently it's all the same, despite one regularly going to -40 and the other rarely going below -20C. Try looking at the definition of the zones as far as heating degree days go, then look up the climate data for the last 5 years at the nearest major station to you.

  3. Expert Member

    I think what Canada Deck is complaining about is more specific. The BC building code now provides climate-specific building assembly requirements - and these large zones include very different climates. The same thing could be said about the areas covered by the various levels of seismic threat, or the blanket requirement that the coastal area must have rain-screens and certain flashing details.

    I guess the best answer is that the code is a blunt instrument that isn't capable of small distinctions. On a local level, the different micro-climate that a house built in the woods here experiences, compared to that of it's nearby neighbour on the waterfront, reveals the same problem. It simply isn't practical to codify too many distinctions.

  4. jackofalltrades777 | | #6

    I also believe the building department doesn't like creating numerous other climate zones for that area as that creates confusion for their code and plan review. It throws them into a panic and more errors can be made on their end. So the simpler the design category, the easier it is for them to review the plans.

    What you described above is more than a micro-climate difference. We are talking no snow to an area that sees 37 feet of snow. That's a huge difference. So does the snow load on the roof have to be the same in Tofino (which sees no snow) and Vancouver Island which sees 37 feet of snow? That would be ridiculous to require the same roof snow loads. Yet, that is exactly what is happening unless they have an addendum that stipulates low elevation coastal areas in Zone 5 don't require that rating?

    1. Expert Member
      MALCOLM TAYLOR | | #8

      No, the snow loading at Mount Washington is required to be as I recall five time that of Tofino. The climate zones in the code only affect the energy requirements of building assemblies.

  5. JC72 | | #7

    I suppose one could look at their climate zone as it is described on the Koppen Scale in order to dial in their design.

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