[RE-wrenches] Roof Loading request for help

[wes kennedy]

Hi All,

I am fully in favor of standardized permitting, and streamlining the process of installing PV.  With that said, I do think the "one layer of shingles = PV on roof thing" is apples and oranges.  Though the deadloading in psf is similar, PV doesn't sit on the roof, it lands on some sort of attachment, standoff, l-foot, what-have-you.

This leads to pretty high point loading values, doesn't it?  If you spread your 1000 lb array around 300 square feet, you get your 3.3 psf, BUT if it lands on 30 L feet, each of 4 square inches you end up with much higher points of concentrated loading.

Anybody worry  about that? 

Thanks!
Wes Kennedy
NABCEPian
   

--- On Tue, 7/7/09, Joel Davidson <joel.davidson at sbcglobal.net> wrote:

From: Joel Davidson <joel.davidson at sbcglobal.net>
Subject: Re: [RE-wrenches] Roof Loading request for help
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Tuesday, July 7, 2009, 7:13 PM



 








 



Allan,
In most of California (seismic zone 4) residential 
PV systems with solar arrays weighing less than 4 lb/ft2 do not require 
structural engineering if the roof has one layer of composition shingles. The 
reasoning is that roofs are allowed 2 layers of shingles (old set and re-roof 
set) and a layer of shingles weighs 4 lb/ft2 so 1 shingle layer and 1 solar 
array weighing less than 4 lb/ft2 is within the dead weight load limit. Hope 
this helps.
Joel Davidson

  ----- Original Message ----- 
  From: 
  Allan Sindelar 
  To: 'RE-wrenches' 
  Sent: Tuesday, July 07, 2009 5:26 
PM
  Subject: [RE-wrenches] Roof Loading 
  request for help
  

  
  Wrenches, 
  We are currently facing a city 
  permitting bureaucracy that has recently discovered solar – that is, suddenly 
  each department in the permitting and plan review departments is coming up 
  with standards for PV systems. Some of the standards, of course, make no 
  sense.  
     
  PV systems typically add about 
  three pounds per square foot to the loading on a roof. We are facing a city 
  requirement for structural engineering work for standard roof 
  attachment if the mounting approach is to make penetrations into the roof 
  structure. This is a typical requirement that will only add considerable cost 
  to each PV system, and we’re looking to have our ammunition to fight this well 
  stocked in advance. Specifically, are building authorities in other 
  jurisdictions requiring structural engineering work for this type of 
  roof attachment? 
     
  Thanks 
   
  Allan 
     
  Allan Sindelar 
  Allan at positiveenergysolar.com 
  NABCEP Certified Photovoltaic 
  Installer 
  EE98J Journeyman 
  Electrician 
  Positive Energy, Inc. 
  3201 Calle Marie 
  Santa 
  Fe , New Mexico 
  87507 
  505 424-1112 
  www.positiveenergysolar.com 
     
  
  

  _______________________________________________
List sponsored by 
  Home Power magazine

List Address: 
  RE-wrenches at lists.re-wrenches.org

Options & 
  settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive: 
  http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org

List 
  rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out 
  participant 
bios:
www.members.re-wrenches.org


-----Inline Attachment Follows-----

_______________________________________________
List sponsored by Home Power magazine

List Address: RE-wrenches at lists.re-wrenches.org

Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org

List rules & etiquette:
www.re-wrenches.org/etiquette.htm

Check out participant bios:
www.members.re-wrenches.org

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20090710/ec507ddc/attachment-0003.html>