SNOW MANAGEMENT ANALYSIS

Designing Roofs in Snow Country

Let’s begin at the beginning – there is no perfect building for this type of climate. Problems that currently plague existing buildings in snow country are in large part inherent in their design and therefore very difficult to remediate after the fact. To be effective at designing buildings for snow, a review of potential snow management issues should be conducted at the beginning, during the conceptual design phase, and then reassessed as the project evolves. By correcting snow shed issues while the project is still on the drawing board, costly amounts of money repairing damage from snow shed can be avoided.

 

Our review and analysis of roofs considers the following:
  1. In what direction are the prevailing winds with respect to the site?
    Prevailing winds pick up snow and rearrange it into drifts on the leeward aspects of a building. By knowing which way the wind blows, a designer can ensure that decks, windows, paths and doorways are properly located and protected from these heavy snow deposits.
  2. Where is the snow going when it slides off the roof?
    Locating these snow shed zones ensures that all entrances/ exits, driveways, pathways and stairs are well protected from any sliding snow and ice as well as roof drip. Although various forms of snow retention can be installed to help mitigate these problems in lieu of changing the design, we would recommend that retention never be used as the primary means of defense when trying to protect the public from hazardous conditions.
  3. What type of roofing material is best suited for the snow country climate?
    More damage is done by sliding snow than by any structural failure resulting from the weight of snow. Although there is no perfect material for this climate, low sloped roofs in combination with a high friction roofing material such as cedar shakes, or good quality asphalt shingles can help prevent snow from sliding and go a long way in lengthening the life of your roof and the structure under it.
  4. Do you have adequate ventilation?
    When roof designs get complicated, adequate ventilation is hard to achieve. Poor circulation allows pockets of warm air to get trapped which leads to the formation of ice dams. Ice dams cause damage to roof material which inevitably leads to leaking. A good way to mitigate ice damming and the formation of icicles on your roof is to keep the underside of the roof so cold that heat escaping from the building will not melt the snow. This is called cold roof assembly and is used widely by European alpine communities. Cold roof detailing incorporates a well-insulated ceiling with a generously vented attic space which helps prevent interior warmth from melting the snow

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The hazards of no snow retention – a massive release of snow
 
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The addition of snow clips to retain snow and reduce the width of snow shed trajectory

 

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When snow shed problems can not be resolved, the public must be made aware to avoid these dangerous snow shed zones