HomeMy WebLinkAboutLA188492 -16394 Falbrook Dr 2.22.21Wyssling Consulting
76 North Meadowbrook Drive
Alpine, UT 84004
Scott E. Wyssling, PE, PP, CME office (201) 874-3483
swyssling@wysslingconsulting.com
February 10, 2021
Everlight Solar Construction PO Box 930550 Verona, WI 53593
Re: Engineering Services Burke Residence 16394 Fallbrook Drive, Lakeville, MN 5.480 kW System
To Whom It May Concern:
Pursuant to your request, we have reviewed the following information regarding solar panel installation on the roof of the above referenced home:
1. Site Visit/Verification Form prepared by an Everlight Solar representative identifying specific site information including size and spacing of rafters for the existing roof structure. 2. Design drawings of the proposed system including a site plan, roof plan and connection
details for the solar panels. This information was prepared by Everlight Solar and will be utilized for approval and construction of the proposed system. 3. Photographs of the interior and exterior of the roof system identifying existing structural members and their conditions.
Based on the above information we have evaluated the structural capacity of the existing roof system to support the additional loads imposed by the solar panels and have the following comments related to our review and evaluation:
Description of Residence: The existing residence is typical wood framing construction with the roof system consisting of truss system
with all chords constructed on center. The attic space is unfinished and photos indicate that there was free access to visually inspect the size and condition of the roof rafters. All wood material utilized for the roof system is assumed to be Doug-Fir #2 or better with standard construction components. The existing roofing material consists of composite asphalt shingles. Photos of the dwelling
also indicate that there is a permanent foundation. A. Loading Criteria Used
115 MPH wind loading based on ASCE 7-16 C 27 degrees
7 PSF = Dead Load roofing/framing Live Load = 20 PSF Snow Load = 50 PSF
3 PSF = Dead Load solar panels/mounting hardware
Total Dead Load =10 PSF
The above values are within acceptable limits of recognized industry standards for similar
structures in accordance with the Minnesota Residential Code (2018 IRC). Analysis performed of the existing roof structure utilizing the above loading criteria indicates that the existing rafters will support the additional panel loading without damage, if installed correctly.
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B. Solar Panel Anchorage
1. The solar panels shall be mounted in accordance with t IronRidge Solar Installation Manual http://ironridgesolar.com/). If during solar panel installation, the roof framing members appear unstable or deflect non-uniformly, our office should be notified before proceeding with the installation.
2. Maximum allowable pullout per lag screw is 235 lbs/inch of penetration as identified in the National Design Standards (NDS) of timber construction specifications for Doug-Fir (North Lumber) assumed. Based on our evaluation, the than what is allowable per connection and therefore is adequate. Based on the variable factors for
the existing roof framing and installation tolerances, using a threa imum
sufficient factor of safety. 3. Considering the roof slopes, the size, spacing, condition of roof, the panel supports shall be placed
no greater than 48 c. 4. Panel supports connections shall be staggered to distribute load to adjacent trusses. Based on the above evaluation, it is the opinion of this office that with appropriate panel anchors being utilized
the roof system will adequately support the additional loading imposed by the solar panels. This evaluation is in conformance with the Minnesota Residential Code (2018 IRC), current industry standards, and is based on information supplied to us at the time of this report.
Should you have any questions regarding the above or if you require further information do not hesitate to contact me.
Very truly yours,
Scott E. Wyssling, PE Minnesota License No. 57927
THESE SHEETS, DESIGNS, AND SPECS ARE PROPERTY OF SUN INCORPORATED. NO PART SHALL BE DUPLICATED OR USED FOR NONE OTHER THAN ITS SPECIFIC PROJECT WITHOUT WRITTEN CONSENT FROM SUN INCORPORATED.MOUNT SHEETSheet: 5File: SUN-SERVER Sun Incorporated Jo s Master E uipment MOUNTS QUICK MOUNT QMPV-datasheet-QMHSS-LS-Quic Hoo SM-we .pd Missing or invalid re erenceSheet: 2File: SUN-SERVER Sun Incorporated Jo s Master E uipment MOUNTS QUICK MOUNT QMPV-datasheet-QMHSS-LS-Quic Hoo SM-we .pd Missing or invalid re erence