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BLD2022-1312_Structural_Calculations_9.29.2022_2.48.43_PM_3137054SOLGMN I,' P O W E R September 30, 2022 Subject: Proposed Solar Panel Installation Christopher Glanister Residence, 21732 84th Ave W, Edmonds, WA To Whom it May Concern, Our engineering department has reviewed information, gathered by our field crews, related to the proposed solar panel installation at the above -referenced address. The purpose of our review was to determine the structural adequacy of the existing roof for the proposed installation. Based on our review and analysis of the available information, it is our professional opinion that the existing structure requires a retrofit to ensure structural adequacy to support the proposed installation. The retrofit shall consist blocking between rafters on roof sheathing with obvious water damage. Install additional 2x4 members in between rafters at 48" O.C. spacing. Design Parameter Summary Governing Building Code: 2018 Washington Building Code (2018 IBC) Risk Category: II Design Wind Speed: 110 mph (per ASCE 7-16) Ground Snow Load: 25 psf Roof Information Roof Structure: 2x4 Rafters @ 24" O.C. Roofing Material: Asphalt Shingles (2 layers) Roof Slope: 18 degrees Roof Connection Details RT Minis into 2x rafters or truss top chords at 48" O.C., install per design drawings and manufacturer specs Locations per design drawings Note: Required embedment length excludes the tapered tip of the screw, and embedment into sheathing. Analysis The proposed installation - including weight of panels, racking, and mounts - will be approximately 2.78 psf. In the areas where panels are installed, roof live loads will not be present. Also, where applicable, roof snow loads will be reduced because the slippery surface of the panels will cause the roof to shed additional snow loads relative to the existing roof surface. The reduction of roof live and snow load is adequate to fully or partially compensate for the addition of the panel installation. Because the member forces in the area of the solar panels are not increased by more than 5%, the stresses in the members are not increased by more than 5%, and so per section 806.2 of the International Existing Building Code (IEBC), the structure need not be altered for gravity loading. The proposed installation will be 6" max. above the roof surface (flush mounted) and parallel to the roof surface. Therefore, any increase in wind loading on the building structure from the solar panel installation is expected to be negligible. Wind is the governing lateral load case. Because the increase in lateral loading is not increased by more than 10%, per section 806.3 of the adopted IEBC, the structure need not be altered for lateral loading. Wind uplift on the panels has been calculated in accordance with the relevant provisions of ASCE 7-16. This loading has been used to verify the adequacy of the connection specified above. Connection locations should be in accordance with design drawings. Conclusion When the retrofits detailed in this letter's opening paragraph are performed, the structure will have adequate strength to support the proposed installation. Connections to the roof must be made per the "Roof Connection Details" section above. Copies of all relevant calculations are enclosed. Limitations and Disclaimers The opinion expressed in this letter is made in reliance on the following assumptions: the existing structure is in good condition (apart from the damage which shall be repaired or retrofit per the above); the existing structure is free from defects in design or workmanship; and the existing structure was code -compliant at the time of its design and construction. These assumptions have not been independently verified, and we have relied on representations made by the property owner and his or her agents with respect to the foregoing. The undersigned has not inspected the structure for patent or latent defects. Electrical engineering is beyond the scope of this analysis. Solar panels must be installed per manufacturer specifications. Structural design and analysis of the adequacy of solar panels, racks, mounts, rails, and other components is performed by each component's respective manufacturer and the undersigned makes no statement of opinion regarding such components. This letter and the opinions expressed herein are rendered solely for the benefit of the permitting authority (city or county building department), and may not be utilized or relied on by any other party. If you have any questions or concerns, please contact our office at (8SS)-709-1181, or email me directly at Trevor.Jones@solgenpower.com. Sincerely, Trevor A. Jones, P.E. 30/09/2022 The retrofit shall consist blocking between rafters on roof sheathing with obvious water damage. Install additional 2x4 members in between rafters at 48" O.C. spacing. Additional Retrofit Details and Notes 2 x RAFTER 2 x CEILING JOIST BEARING WALL NEW 2 x BLOCKING AT 48" O.C. OR AT OTHER SPACING AS NOTED IN LETTER ROOF SHEATHING W9- RIDGEBOARD TOENAIL NEW BLOCKING INTO EXISTING WITH (2) 16d NAILS AT EACH CONNECTION. DO NOT PENETRATE PLYWOOD ABOVE. DETAIL NOTES: 1. ALL MEMBERS SHOWN ARE EXISTING UNLESS LABELED (N) OR NEW. 2. RETROFIT REQUIRED ONLY AT ROOF AREAS SUPPORTING SOLAR PANELS AND THAT ARE SAGGING OR SOFT, UNLESS NOTED OTHERWISE IN LETTER. Pictures of poor condition - area to be retrofit (where applies) SOLGr- N P 0 w E R Note: All calculations per ASCE 7 Load Comparison This calculation justifies the additional solar load by comparing existing to proposed gravity loads in the location of the solar panels. Dead Load Asphalt Shingles 1/2" Plywood Framing Insulation 1/2" Gypsum Ceiling M,E, & Misc Solar Panel Total Dead Load Snow Load Ground Snow Load, Pg Exposure Factor, Ce Thermal Factor, Ct Importance Factor, IS Flat Roof Snow Load Slope Unobstructed Slippery Surface? Slope Factor, CS Sloped Roof Snow Load Live Load Roof Live Load Load Combination D+Lr D + S Max. Load % of original Withniit Cnlnr %A/ith Cnl!3r 5 5 psf 1 1 psf 3 3 psf 1 1 psf 2 2 psf 1.5 1.5 psf 0 2.78 psf 13.5 1 16.28 psf 25 1 1.1 1 19.25 18 No Yes 1.00 0.87 19.3 16.7 psf Eqn. 7.3-1 orjurisdiction min. degrees psf 20 1 0 psf 33.5 16.3 psf 32.8 33.0 psf 33.5 33.0 psf 98% Result: Because the total forces are decreased, per the relevant code provisions stated in the body of the letter, the existing roof structure is permitted to remain unaltered. SOLGr- N P O W E R RT Mini Connection Calculation This calculation justifies the connection of the solar panels to existing roof members, by showing the connection capacity is equal to or greater than the uplift force demands. Connection Demand Spacing perpendicular to rail Spacing parallel to rail Effective Wind Area on each connection Roof Angle Wind Speed Exposure Coefficient, K, Topographic Factor, K,t Directionality Factor, Kid Elevation Factor, Ke Velocity Pressure, q, GCp (max) Exposed Panels? (YE = 1.5) Pressure Equalization Factor, Ya Uplift Force Max. Uplift Force / Connection (1.0 WL) ASD Factored (0.6 WL) Solar Dead Load (0.6 DL) Max. Uplift Force (0.6 WL- 0.6 DL) Connection Capacity Connection Type Total Allowable Capacity 32.5 in in ft2 degrees SOLAR PAt ROOF mph ROOF TEC MINI 48 10.8 18 110 0.8 1 0.85 1.00 21.1 psf Mount to existing ratters Center Zones Edge Zones Corner Zones 1/2 panel length Max spacing 1.80 2.57 2.57 No No No 0.79 0.79 0.79 29.8 42.5 42.5 322.9 460.6 460.6 193.7 276.4 276.4 18.1 18.1 18.1 175.7 258.3 258.3 psf Ibs Ibs Ibs Ibs RT Mini into 2x Rafter 447.0 Ibs (per manufacturer) K Compare ASD Factored Demand to Capacity Demand 258.3 Ibs Capacity 447.0 Ibs Result Capacity exceeds demands. Therefore, connection passes.