[RE-wrenches] Roof flashings on L-feet in high snow load conditions

[Troy Harvey]

Ray, we engineer every system using the ASCE structural load manual. Roof snow load has to be below 113 SQFT (for high snow load modules) after taking the ASCE slippery surface reductions based on slope. 


thanks,

Troy Harvey
---------------------
Principal Engineer
Heliocentric
801-453-9434
taharvey at heliocentric.org



On Nov 13, 2012, at 4:21 PM, toddcory at finestplanet.com wrote:

> ray,
>  
> this has been a learn by trial and error learning experience. i know 12/12 is ok and 5/12 is not... so somewhere in between those two pitch angles there is change.
>  
> the latest pole mount i did was a dpw rack with 3 kW on an 8" pole. i am attaching a 100 kb pix of this monster!
>  
> todd
>  
>  
>  
>  
>  
>  
> On Tuesday, November 13, 2012 11:12am, "Ray Walters" <ray at solarray.com> said:
> 
> HI Todd;
> 
> That's very interesting.  What roof pitch does that happen?  I'm guessing that at a step enough tilt, the frame damage is alleviated?
> Also on your tall pole mounts what pole design do you use?  I've tried telescoping type, and guy wires on tall poles.
> 
> Ray
> 
> On 11/13/2012 12:08 PM, toddcory at finestplanet.com wrote:
> I have never had good results with roof mounted pv in our heavy (mount shasta) snow area. the snow tends to creep down the glass and peel the bottom of the frame off the module... and then the glass breaks as it has no support in that area.
>  
> so, around here... i do pole mounts.... WAY up in the air.
>  
> todd
>  
>  
>  
> On Tuesday, November 13, 2012 8:04am, "Troy Harvey" <taharvey at heliocentric.org> said:
> 
> Hi all,
> We have been doing PV installs for years with L-feet and silicone without problems ever. Even still, gravity flashings seem attractive in shingle roofs, to provide a second level of security, and a more professional install (at least in perception). But the cost of these systems in significant in high snow load areas where we often have L-feet every 2 feet on center, to evenly load the structure below. In todays costs, the feet could cost as much as 33% of the panel value.
> I'm wondering what other people are doing in high snow load areas?
> Also. I have noticed that there is a flip side to the risks. We have found that unless you have good quality shingles, on a preexisting roof, that sometimes the adhesive sticking the shingles together is stronger than the low quality shingles themselves - adding risk of trying to shoe horn flashing in after the fact. Your experience?
> 
> thanks,
> 
> Troy Harvey
> ---------------------
> Principal Engineer
> Heliocentric
> 801-453-9434
> taharvey at heliocentric.org
> 
> 
> 
> 
> 
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