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31B-044 (3)
�1hc��in�nriti4-ZL Optimize Engineering Co., LLC P.O. Box 264•Farmville•VA 23901 3 ,19 Ph: 434.574.6138.E-mail: grichardpe@aol.com Richard B. Gordon, P.E. President April 6,2016 Northampton Building Department Northampton,MA Re: Solar Electric Panels Roof Structural Framing Support To Whom It May Concern: I hereby certify that I am a Licensed Professional Engineer in the State of Massachusetts. Please note the following conclusions regarding framing structure, roof loading,and proposed site location of installation: 1. Existing roof framing: Conventional wood framing roof 1-2 is 2x6 at 20"o.c.with 7'-4"span and roof 3(garage)is 2x6 at 26"o.c.with 10'-5"span(horizontal rafter projection). This existing structure is definitely capable to support all of the loads that are indicated below for this photovoltaic project after sister rafters with a 2x6 using(2)10d nails V o.c. Use of(2)Guard DogTm FMGDO02 screws is approved, or equal shear strength of approx. 120 Ib, V o.c.at areas where little space is available only with remainder of member secured with(2)10d nails V o.c. If do not sister,then install a 2x4 @ 26"o.c. knee wall over an interior bearing wall to limit span of rafters between supports to 8'-6". 2. RoofLoadinq • 4.33 psf dead load (modules plus all mounting hardware) • 24 psf snow live load(40 psf ground snow live load reference) • 4.5 psf dead load roof materials • Exposure Category B, 90 mph wind uplift live load of 11.97 psf(wind resistance) 3. Address of proposed installation: Residence of Bob Walsh, 21 Summer Street Northampton MA This installation design will be in general conformance to the manufacturer's specifications,and is in compliance with all applicable laws,codes,and ordinances,and specifically, International Residential Code/ IRC 2009.The spacing and fastening of the mounting brackets is to have a maximum of 64"o.c.span between mounting brackets and secured using 5/16"x,3%" length corrosive resistant lag bolts. In order to evenly distribute the load across the roof rafters,there shall be a minimum of 2 mounting brackets per rafter &min. 2" penetration of lag bolt per bracket,which is adequate to resist all 90 mph wind live loads including wind shear. The mounting brackets shall alternate between adjacent rafters for better distribution of roof load. Penetration to be 3" minimum of anchors for modules mounted within 18" of ridge and edges of roof. Very truly yours, Optimize Engineering Co., LLC Richard/B.Gordon, P.E. R `' aF M SQ740,, Massachusetts P.E. License No.49993 c�yG MECHANICAL ENGINEERING ELECTRICAL ENGINEERING 2 yPRO©' CIVIL ENGINEERING RGo oN�+ 2 h46GNP`g3 441, April 7, 2016 To: Building Dept. LDEVEOF 8^{ 2016 From: Rachel Bruso—Trinity Solar p <` ;vs Subject: Revised Engineer Letter Attached please find the revised engineer letter for 21 Summer Street, property owned by Bob Walsh. If there are any questions, please feel free to let me know. Thank you very much! T AAachels Rachel.Bruso@trinitysolarsystems.com 413-203-9088 Ext. 1511 Trinity Solar 4 Open Square Suite 410 Holyoke, MA 01040