HomeMy WebLinkAboutEngineer LetterGODWIN ENGINEERING AND DESIGN, LLC 8378 Foxtail Loop, Pensacola, FL 32526 | (850)712-4219 | chad@godwineng.com February 3, 2021 To: St. Lucie County Building Division 2300 Virginia Avenue Ft. Pierce, FL 34982 Re: Knowlton – Residential PV Roof Mount Installation
5207 Indian Bend Ln.
Fort Pierce, FL 34951
Plan Reviewer,
This letter is regarding the installation of a new roof mounted Solar PV System on the existing
residential structure at the address above. I have reviewed the attachment plan and have
determined that the roof mounted PV system is in compliance with the applicable sections of the
following Codes as amended and adopted by the jurisdiction:
2020 Florida Building Code 7th Edition, FBC
ASCE 7 Min. Design Loads for Buildings & Other Structures
Per 2020 FBC, the Roof Mounted PV system will be subject to the following design criteria:
Design Wind Speed(Vult) - 160mph 3sec gust, Exposure Category – C
The PV System consist of the modules, railing, and connection hardware. The system will add a
dead load of approximately 3 psf to the roof.
The existing roof covering is Asphalt Shingle with min. ½” plywood decking and 2” x 4” roof trusses
24” O.C. The roofing, decking, and roof trusses are in good condition. The existing structure will be
adequate for supporting the additional PV dead load and wind loads.
The securement method of the PV system is to be flush mounted to the asphalt shingle roof with the
Ironridge railing and the Unirac Flashlocs. The attachments can be attached up to 48” apart in roof
zone 1, and 24” apart in roof zones 2, 2, & 3. The mounts should be staggered, where possible, to
allow distribution of the design loads evenly to the structure. The mounts shall be installed with a
min. 5/16” lag screw with minimum 2-5/16” thread length.
Please see attached documents and contact me should you have any questions.
Sincerely,
D.Chad Godwin, PE 81360
Exp. 02/28/2021
Donnie C
Godwin
2021.02.04
15:02:42
'00'06-
RiskCategory II Table1.5Ͳ1 Load,PSfBasicWindSpeed(Ult) 160 Figure26.5Ͳ1B 3WindSpeed(asd) 124 IBC1609.3.1 0RoofAngle 24 °0EffectiveWindArea 10.00 ft2 26.20 n/aWindLoadParameters n/aWindDirectionality Kd 0.85 Table26.6Ͳ1n/aExposureCat. B,C,orD C Section26.7 n/aTopographicfactor Kzt 1.00 26.8or26.8.2 n/aGroundElevationFactor Ke 1.00 Table26.9Ͳ1n/aVelocityExposureCoefficient Kz 0.85 Table30.3Ͳ10ArrayEdgeFactor gE 1.50 29.4.4 n/a
SolarPanelEqualizationFactor ga 0.80 Fig.29.4Ͳ8seecalc
VelocityPressure qp 28.41 psf
qh=0.00256KzKztKdKeV2 n/a
MeanRoofHeight h 15.00 ft
0.4h 6.00 ft
360 in
3.00 ft
RoofZoneSetBack a 3.00 ft
12r2e3
GCp Ͳ1.40 Ͳ2.00 Ͳ2.00 Ͳ2.00 uplift
GCp 0.70 0.70 0.70 0.70 downward
p=qh(GCp)(gE)(Ȗa)Ͳ47.73 Ͳ68.18 Ͳ68.18 Ͳ68.18 psf uplift
p=qh(GCp)(gE)(Ȗa)23.86 23.86 23.86 23.86 psf downward
ModuleLength C ft
ModuleWidth B ft
ModuleArea A ft2
TotalDesignLoad(Uplift)Pdesign Ͳ47.73 Ͳ68.18 Ͳ68.18 Ͳ68.18 psf
TotalDesignLoad(Downforce)Pdesign 23.86 23.86 23.86 23.86 psf
DesignLoadperModule Tup Ͳ867.57 Ͳ1239.39 Ͳ1239.39 Ͳ1239.39 lbs
Tup=A*Pdesign
DesignLoadperModule Tdown 433.79 433.79 433.79 433.79 lbs
Tdn=A*Pdesign
DistributedLoad(Uplift)Pdist.Up Ͳ131.85 Ͳ188.36 Ͳ188.36 Ͳ188.36 plf
Tup/B*2
DistributedLoad(Down)Pdist.Down 65.93 65.93 65.93 65.93 plf
Tdn/B*2
RailspanBetweenAnchorPointsL 4222ft
PointLoadperMount(Uplift) R Ͳ527.40 Ͳ376.71 Ͳ376.71 Ͳ376.71 lbs
PointLoadperMount(Down) R 131.85 65.93 65.93 65.93 lbs
SpecificGravity G 0.55 0.55 0.55 0.55 Table11.2A,NDS2005,page68(SYP)
DiameterofLagScrew D 5/16 5/16 5/16 5/16 In
PulloutValueofW 306.8697 306.8697 306.8697 306.8697 lbs/in
W=1800G3/2D3/4
#ofLagscrews 1111
ThreadLengthTd 2.3125 2.3125 2.3125 2.3125 In TableL2,NDS2005
DesignPulloutValueperMount Wt 709.6363 709.6363 709.6363 709.6363
Wt=W*#ofLags*Td
SAFTEYFACTOR SF 1.35 1.88 1.88 1.88 Calculation:SF=Wt/R(Uplift)
12r2e3
MaxCantilever M 16 8 8 8 in Maxrailspan*33%
Snow,SSelfͲStraining,T
Wind,W
WindͲonͲIce,Wi
ASCE7Ͳ16CHAPTER29WINDLOADSͲRooftopSolarPanelsMinimumDesignLoadsͲPart1:Enclosed(Hip,h<60ft,20°<ɽ<27°)LoadTypesDeadLoad,DWeightofIce,DiRain,REarthquake,EFluid,FRoofLive,LrFloodLoad,FaLateralEarthpsi,HLiveLoad,L
MaximumCantileverfromLastattachment
Table1.1ͲPulloutValueforSingleLagScrew
10%ofleasthorizontaldim
leasthorizontaldim
5.53
3.29
18.18
Figure30.3Ͳ2G(Hiproof,h<60ft,20°<ɽ<27°)
Zone
DesignCalculationsfortheUseofAttachmenttoRoofTruss/Rafter
Donnie C
Godwin
2021.02.04
15:02:55
'00'06-