Snow Loads [RE-wrenches]

[Jeff Clearwater, Village Power Design]

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Hi Chris,

We treat commercial rooftop arrays in New England 
like you would a multiple level roof and/or as a 
hip roof and apply the snow drift calculations 
for unbalanced snow loads as outlined in the 
applicable state codes as well as the ASCE code. 
We also look at the case where snow/ice might 
build up underneath a tilted array and then also 
fall on top of the array on the next snow storm. 
It makes for some sobering calculations - 
especially when combined with the wind loading - 
but we sleep better at night.  (and do more 
ground mounts!).

Welcome to New England, It's not CA!

Best,

Jeff Clearwater
Village Power Design



>We are experiencing many architects and structural engineers being
>concerned with snow loads and snow drifts resulting from the
>installation of solar modules being installed onto an existing building
>roof, mostly concerned with commercial flat roofs.  How do you all
>handle snow loads for flat commercial roof mounts where the snow from a
>large tilted array could theoretically slip off and accumulate at the
>front of the array and/or where the tilted array captures snow and a
>snow drift accumulates under the arrays?
>
>Technically, these piles of snow create more of a point load versus
>having the fallen snow accumulate evenly over the entire roof.  If the
>existing building’s roof structure was designed to meet minimum loading
>req’ts per Bldg Code, will this redistribution of snow adversely affect
>the roof?  If the front/bottom of the tilted array is 12” or more off
>the roof, will the wind blow the snow from behind the array thru this
>opening, thus NOT creating a snow drift?  What’s the reality of this
>situation?
>
>Chris
>
>
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--
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com
gosolar at villagepower.com
NABCEP (tm) Certified Solar PV Installer

Voice: 413-259-3776
Fax: 413-825-0703
65 Schoolhouse Rd
Amherst, MA 01002
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`~


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