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Home My WebLink AboutENGINEER LETTER - 21-00867 - 625 Autumn Ct - Solar Panels 55 WEST 500 SOUTH, HEBER CITY, UT 84032 T 925.787.3067 U RIGHTANGLEENG.COM November 1, 2021 Horizon PWR 166 Valley Street Providence, RI 02909 RE: Structural Roof Evaluation for the Rawlings Residence: 625 Autumn Court, Rexburg, Idaho As per your request, we have evaluated the roof structure under the proposed solar panel array. The information used to evaluate this structure was gathered by Horizon PWR on behalf of Right Angle Engineering. The roof structure consists of pre-manufactured trusses spaced at 24” on center. The roof material consists of asphalt shingles. The design criteria used to analyze this structure are listed above and included with this letter. The adopted building codes in this jurisdiction are: the 2018 International Building Code, the 2018 International Existing Building Code, and ASCE 7-16. International Existing Building Code (IEBC) 2018 section 806.2 indicates that alterations to an existing building that results in less than a 5% increase in the total stress may be performed without a structural evaluation of the existing building. As demonstrated in the attached calculations, the additional weight of the solar panels will be less than 5% increase in the gravity loading and the stress on the existing roof framing. Based on our assessment we have determined that the existing roof framing will safely and adequately support the additional loads imposed by the solar panels without reinforcement. In order for the loads to be evenly distributed, the roof attachments should be staggered and spread evenly throughout the panel array. Attachment points should be spaced at a maximum of 48” on center. The racking system should be installed per the manufacture’s specifications. There should be a minimum of 65 FlashFoot2 attachment points to the roof. Each attachment should have a 5/16” or 18/8 SS lag screw with 2.5” minimum penetration centered on each truss top chord or rafter. Waterproofing around the roof penetrations is the responsibility of others. Right Angle Engineering assumes no responsibility for improper installation of the solar panels. Regards, Robert D Smythe, P.E. Right Angle Engineering 11/1/21 Design Criteria: Design Wind Speed (ASD)- 115 mph Ground Snow Load- 50 psf Risk Category- II Exposure category- C 2 Design Criteria: Design Wind Speed (3 second gust) 115 mph Exposure Category C Risk Category 2 Mean Roof Height 30 ft Roof Type Gable Roof Building Type enclosed Roof Dead Load- ASCE Table C3-1 Asphalt Shingles 2 psf 5/8" Plywood Sheathing 2 psf Roof Framing 4 psf Insulation 3.85 psf Gypsum sheathing 2 psf Solar Panel Array 3 psf Dead Load Without Panels 13.85 psf Dead Load With Solar panels 16.85 psf Roof Live Load Existing Roof Live Load 20 psf ASCE 7-16 Table 4.3-1 Roof Live Load with Solar Panels 0 psf 2018 IBC 1607.13.5.1 Roof Snow Load-ASCE 7-16 Ground Snow Load (pg) 50 psf Section 7.2 Exposure Factor (Ce) 0.9 Table 7.3-1 Thermal Factor (Ct) 1.1 Table 7.3-2 Importance Factor (Is) 1 Table 1.5-2 Flat Roof Snow Load (Pf) 35 Equation 7.3-1 Slippery surface Slope Factor (Cs) 0.57 Figure 7-2 Nonslippery Surface Slope Factor (Cs) 1 Figure 7-2 Roof Snow Load 35 psf Equation 7.4-1 Reduced Roof Snow Load (Slippery Surface) 20 psf Equation 7.4-1 Load Combinations - ASCE 7-16 Section 2.4.1 Without Solar Panels With Solar panels D + Lr 33.8 psf 16.8 psf D + S 48.5 psf 36.5 psf 3 Solar Array 1- Array One Roof Slope 36 degrees Number of panels 7 Panel Area 122.5 ft^2 Wind Calculations- ASCE 7-16 GCp Zone 1 -1 Figure 30.3-(2A-5B) GCp Zone 2 -1.8 Figure 30.3-(2A-5B) GCp Zone 3 -2.8 Figure 30.3-(2A-5B) Gcpi 0.18 Table 26.13-1 Velocity Pressure (qh) 28.2 psf qh= .00256KhKhtKdV^2 Equation 26.10-1 Kh 0.98 Table 26.10-1 Kht 1 Equation 26.8-1 Kd 0.85 Table 26.6-1 Designed wind pressure (P) psf Equation 30.8-1 P= qh(GCh) - (GChi)) Zone 1 Pressure (P) -33.3 psf Zone 2 Pressure (P) -55.8 psf Zone 3 Pressure (P) -84 psf Roof Connection Shear Capacity 396 lbs NDS 2015 Table 12K Shear tributary area 29.8 ft^2 Pullout Capacity 266 lbs/in Lag screw embedment 2.5 in Total pullout capacity 951 lbs NDS 2015 Table 12.2A Pullout max tributary area 17 ft^2 Factor of Safety 2.11 Minimum number of connections 12 Beam Stress IEBC 2018 Section 806.2 Beam Span 14 ft Spacing 2 ft Roof Framing type pre-manufactured trusses Panel Orientation portrait Number of Panels per rafter 2 Panel distance from eave 0 Without Solar Panels With Solar Panels Percent Increase Bending Moment 2376.5 ft-lbs 1785.6 ft-lbs 75.1% Less than 105% Vertical Reaction (V1) 679 lbs 567.3 lbs 83.5% Less than 105% Vertical Reaction (V2) 679 lbs 514.12 lbs 75.7% Less than 105% 4 Solar Array 2- Array Two Roof Slope 36 degrees Number of panels 7 Panel Area 122.5 ft^2 Wind Calculations- ASCE 7-16 GCp Zone 1 -1 Figure 30.3-(2A-5B) GCp Zone 2 -1.2 Figure 30.3-(2A-5B) GCp Zone 3 -1.2 Figure 30.3-(2A-5B) Gcpi 0.18 Table 26.13-1 Velocity Pressure (qh) 28.2 psf qh= .00256KhKhtKdV^2 Equation 26.10-1 Kh 0.98 Table 26.10-1 Kht 1 Equation 26.8-1 Kd 0.85 Table 26.6-1 Designed wind pressure (P) psf Equation 30.8-1 P= qh(GCh) - (GChi)) Zone 1 Pressure (P) -33.3 psf Zone 2 Pressure (P) -38.9 psf Zone 3 Pressure (P) -38.9 psf Lag Screw Connection Shear Capacity 396 lbs NDS 2015 Table 12K Shear tributary area 29.8 ft^2 Pullout Capacity 266 lbs/in Lag screw embedment 2.5 in Total pullout capacity 951 lbs NDS 2015 Table 12.2A Pullout max tributary area 24.4 ft^2 Factor of Safety 2.91 Minimum number of connections 11 Beam Stress IEBC 2018 Section 806.2 Beam Span 14 ft Spacing 2 ft Roof Framing type pre-manufactured trusses Panel Orientation portrait Number of Panels per rafter 2 Panel distance from eave 0 Without Solar Panels With Solar Panels Percent Increase Bending Moment 2376.5 ft-lbs 1810.6 ft-lbs 76.2% Less than 105% Vertical Reaction (V1) 679 lbs 576.4 lbs 84.9% Less than 105% Vertical Reaction (V2) 679 lbs 517.4 lbs 76.2% Less than 105% 5 Solar Array 3- Array Three Roof Slope 36 degrees Number of panels 16 Panel Area 280 ft^2 Wind Calculations- ASCE 7-16 GCp Zone 1 -1 Figure 30.3-(2A-5B) GCp Zone 2 -1.2 Figure 30.3-(2A-5B) GCp Zone 3 -1.2 Figure 30.3-(2A-5B) Gcpi 0.18 Table 26.13-1 Velocity Pressure (qh) 28.2 psf qh= .00256KhKhtKdV^2 Equation 26.10-1 Kh 0.98 Table 26.10-1 Kht 1 Equation 26.8-1 Kd 0.85 Table 26.6-1 Designed wind pressure (P) psf Equation 30.8-1 P= qh(GCh) - (GChi)) Zone 1 Pressure (P) -33.3 psf Zone 2 Pressure (P) -38.9 psf Zone 3 Pressure (P) -38.9 psf Lag Screw Connection Shear Capacity 396 lbs NDS 2015 Table 12K Shear tributary area 29.8 ft^2 Pullout Capacity 266 lbs/in Lag screw embedment 2.5 in Total pullout capacity 951 lbs NDS 2015 Table 12.2A Pullout max tributary area 24.4 ft^2 Factor of Safety 2.91 Minimum number of connections 26 Beam Stress IEBC 2018 Section 806.2 Beam Span 15 ft Spacing 2 ft Roof Framing type pre-manufactured trusses Panel Orientation portrait Number of Panels per rafter 2 Panel distance from eave 0 Without Solar Panels With Solar Panels Percent Increase Bending Moment 2728.1 ft-lbs 2052.7 ft-lbs 75.2% Less than 105% Vertical Reaction (V1) 727.5 lbs 614.2 lbs 84.4% Less than 105% Vertical Reaction (V2) 727.5 lbs 576.7 lbs 79.3% Less than 105% 6 Solar Array 4- Array Four Roof Slope 36 degrees Number of panels 10 Panel Area 175 ft^2 Wind Calculations- ASCE 7-16 GCp Zone 1 -1 Figure 30.3-(2A-5B) GCp Zone 2 -1.2 Figure 30.3-(2A-5B) GCp Zone 3 -1.2 Figure 30.3-(2A-5B) Gcpi 0.18 Table 26.13-1 Velocity Pressure (qh) 28.2 psf qh= .00256KhKhtKdV^2 Equation 26.10-1 Kh 0.98 Table 26.10-1 Kht 1 Equation 26.8-1 Kd 0.85 Table 26.6-1 Designed wind pressure (P) psf Equation 30.8-1 P= qh(GCh) - (GChi)) Zone 1 Pressure (P) -33.3 psf Zone 2 Pressure (P) -38.9 psf Zone 3 Pressure (P) -38.9 psf Lag Screw Connection Shear Capacity 396 lbs NDS 2015 Table 12K Shear tributary area 29.8 ft^2 Pullout Capacity 266 lbs/in Lag screw embedment 2.5 in Total pullout capacity 951 lbs NDS 2015 Table 12.2A Pullout max tributary area 24.4 ft^2 Factor of Safety 2.91 Minimum number of connections 16 Beam Stress IEBC 2018 Section 806.2 Beam Span 18 ft Spacing 2 ft Roof Framing type pre-manufactured trusses Panel Orientation portrait Number of Panels per rafter 3 Panel distance from eave 0 Without Solar Panels With Solar Panels Percent Increase Bending Moment 3928.5 ft-lbs 2829.5 ft-lbs 72% Less than 105% Vertical Reaction (V1) 873 lbs 724.9 lbs 83% Less than 105% Vertical Reaction (V2) 873 lbs 624.9 lbs 71.6% Less than 105%