HomeMy WebLinkAboutJOSE GIL - Eng LetterDaniel W. Dunzik Architect LEED-AP
370 Burnt Hill Rd. Skillman NJ. 08558 908-872-3664
StudioGdesign@comcast.net
Re: Proposed Photovoltaic Solar Panel Installation
Dear Plan Reviewer:
Roof Type:
Attachment System:Wind Zone 1 Wind Zone 2 Wind Zone 3
3. Solar Modules shall be UL-1703 rated. Refer to manufacturers specifications sheets.
4. Positive drainage of the system shall be so as not to void the existing roof warranty.
6. Please refer to the attached structural calculations.
Daniel W. Dunzik, RA. LEED-AP
FL. Lic. No. AR98795
Fastener Max Spacing (in.)
72 48 0
July 14, 2020
Jose Gil
6306 EMERSON AVE
Certification: I have reviewed the engineering testing reports for the racking and attachments to be used on this
project and I certify that the products are capable of supporting the code required loads and are suitable for this
installation when installed in strict compliance with the manufacturers printed instructions.
Regarding the solar panel array installation on the above referenced project please note that an inspection was
performed by a representative of the Architect/Engineer of Record, and analysis of the existing structure was
conducted. There is adequate structural capacity for the installation of the array with the following recommendations:
FORT PIERCE, FL 34951
1. The array will be installed on the existing roof. The roof framing is constructed of 2"x4" wood trusses @24" o.c.
spanning 12'11'' with a top chord length of 14'9'' with intermediate supports at 1/2 points, making the effective longest
span equals 7'5'' with 1/2" plywood sheathing. The new array (See Site map by contractor) will add 2.63 Lb. / Sf.
overall to the roof. No additional structural support is required for the roof structure.
5. All aspects of the installation shall comply with the Florida Administrative Code, 2017 Florida Building Code -
Residential Sixth Edition, ASCE-7-10, 2017 Florida Building Code – Energy Conservation, Sixth Edition, 2014
National Electric Code, All Local Governing County and Municipal Ordinances adopted by reference or enacted by
law. All components used meet the criteria of the Florida Solar Energy Center.
If you have any questions relating to this matter, please contact me at your earliest convenience. Thank you.
2. The attachment system shall be secured to the roof and shall be in strict compliance with manufacturers printed
instructions. The attachment system shall be UL 1703 approved tested. Provide 6 mil. vapor barrier between
dissimilar metals. Provide water tight gasket and sealant at all penetrations. Attachments shall follow panel rows as
specified by the system manufacturer’s installation manual. The panel angle shall match the roof slope. Reference
summary table below:
min. 5/16” x 4” long stainless-steel lags with a min.
embedment of 3” into the rafters
Shingle
“SnapNrack” “Ultra Rail” ®
Fastener Info:
Daniel W. Dunzik Architect LEED-AP
370 Burnt Hill Rd. Skillman NJ. 08558 908-872-3664
StudioGdesign@comcast.net
Gravity Load Calculation Criteria
Structural Design Loads per ASCE 7-10
Dead Loads = 10 psf + 2.6 psf (new solar panels) = 12.6 psf
Roof Live Load = 20 psf
Ground Snow Load = 0 psf
Wind Load Calculation Criteria
Wind Loads per ASCE 7-10, Ch. 30 method 1
Using an area of 10 SF, wind loads from Figure 30.5-1:
Zone 1 = -42.1 psf Roof Slope = 23 degrees Roof Mean Height = 15 ft
Zone 2 = -73.4 psf Basic Wind Speed = 160 mph
Zone 3 = -108.5 psf Exposure = B
Per section 2.4.1, ASD combo = D + 0.6W:
Zone 1 = 2.6 psf + 0.6(-42.1 psf) = -22.7 psf
Zone 2 = 2.6 psf + 0.6(-73.4 psf) = -41.4 psf
Zone 3 = 2.6 psf + 0.6(-108.5 psf) = -62.5 psf
Check Attachment to Wood Truss
Use 5/16 dia. Lag screw w/ 3" embedment into 2 in. wide roof rafter
Lag Screw Spacing:Lag Screw Tributary Area:
Zone 1 = 72" o.c. max Zone 1 = (72" o.c. max)^2 / 144 = 36 SF
Zone 2 = 48" o.c. max Zone 2 = (48" o.c. max)^2 / 144 = 16 SF
Zone 3 = 0" o.c. max Zone 3 = (0" o.c. max)^2 / 144 = 0 SF
Lag Screw Forces:W = 266lb/in (Table 12.2A, 2015 NDS)
Zone 1 = 22.7 psf x 36 SF = 817 lb < W', OK Cd = 1.6 (Table 2.3.2, 2015 NDS)
Zone 2 = 41.4 psf x 16 SF = 662 lb < W', OK Ct = 1 (Table 2.3.3, 2015 NDS)
Zone 3 = 62.5 psf x 0 SF = 0 lb < W', OK W' = W x embed x Cd x Ct
W' = 266 lb/in x 3 in. x1.6 x 1 = 1276.8 lb
July 14, 2020