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Home My WebLink AboutSmith, Alex Letter SS VECTOR E n G I n E E R S VSE Project Number:U3507.0137.221 February 25,2022 TruNorth Solar LLC ATTENTION: Donna Pickard 3735 Dunlap St.N. Arden Hills,MN 55112 REFERENCE: Smith,Alex Residence: 5906 Benjamin Street Northeast,Fridley,MN 55432 Solar Array Installation To Whom It May Concern: Per your request, we have reviewed the existing structure at the above referenced site. The purpose of our review was to determine the adequacy of the existing structure to support the proposed installation of solar panels on the roof as shown on the panel layout plan. Based upon our review,we conclude that the existing structure is adequate to support the proposed solar panel installation. Design Parameters Code: 2020 Minnesota Residential Code(2018 IRC) Risk Category:II Design wind speed,Vult: 115 mph(3-sec gust) Wind exposure category: C Ground snow load,Pg: 50 psf Connection to Roof Mounting connection: (1)5/16" lag screw w/min.2.5"threaded embedment into framing at max.48" o.c.along rails Install(2)rails per row of panels,evenly spaced;panel length perpendicular to the rails shall not exceed 70 in Rail cantilever shall not exceed 50%of connection spacing Conclusions Based upon our review, we conclude that the existing structure is adequate to support the proposed solar panel installation. The glass surface of the solar panels allows for a lower slope factor per ASCE 7, resulting in reduced design snow load on the panels. The gravity loads, and thus the stresses of the structural elements, in the area of the solar array are either decreased or increased by no more than 5%. Stress decreases or increases of no more than 5% are considered acceptable. Therefore,the structure is permitted to remain unaltered. The solar array will be flush-mounted (no more than 10" above the roof surface) and parallel to the roof surface. Thus, we conclude that any additional wind loading on the structure related to the addition of the proposed solar array is negligible. The attached calculations verify the capacity of the connections of the solar array to the existing roof against wind (uplift), the governing load case. Increases in lateral forces less than 10% are considered acceptable. Thus the existing lateral force resisting system is permitted to remain unaltered. 651 W. Galena Park Blvd.,Ste. 101/Draper, UT 84020/T(801)990-1775/F(801)990-1776/www.vectorse.com VSE Project Number: U3507.0137.221 Smith,Alex Residence YE C T O R 2/25/2022 E M G I n E E R s Limitations Installation of the solar panels must be performed in accordance with manufacturer recommendations. All work performed must be in accordance with accepted industry-wide methods and applicable safety standards. The contractor must notify Vector Structural Engineering, LLC should any damage, deterioration or discrepancies between the as-built condition of the structure and the condition described in this letter be found. Connections to existing roof framing must be staggered, except at array ends, so as not to overload any existing structural member. The use of solar panel support span tables provided by others is allowed only where the building type, site conditions, site-specific design parameters, and solar panel configuration match the description of the span tables.The design of the solar panel racking(mounts,rails, etc.) and electrical engineering is the responsibility of others. Waterproofing around the roof penetrations is the responsibility of others. Vector Structural Engineering assumes no responsibility for improper installation of the solar array. Vector Structural Engineering shall be notified of any changes from the approved layout prior to installation. VECTOR STRUCTURAL ENGINEERING,LLC LICENSED m PROFESSIONAL ENGINEER — 02/25/2022 Brett Veazie,P.E. I hereby certify that this plan,specification or report Project Engineer was prepared by me or under my direct supervision and that I am a duly Licensed Professional Engineer under the laws of the State of Minnesota, Enclosures Brett D.Veazie, License No.56392, Expiration Date:30-June-2022 BDV/rsl 651 W. Galena Park Blvd.,Ste. 101/Draper, UT 84020/T(801)990-1775/F(801)990-1776/www.vectorse.com JOB NO.: U3507.0137.221 YETO R SUBJECT: WIND PRESSURE n G 1 n E E R S PROJECT: Smith, Alex Residence Com onents and Cladding Wind Calculations Label: ISolar Panel Array Note: Calculations per ASCE 7-10 SITE-SPECIFIC WIND PARAMETERS: Basic Wind Speed [mph]: 115 Notes: Exposure Category: C Risk Category: II ADDITIONAL INPUT & CALCULATIONS: Height of Roof, h [ft]: 15 (Approximate) Comp/Cladding Location: Gable Roofs 27°< 0 <_45° Enclosure Classification: Enclosed Buildings Zone 1 GCp: 1.0 Figure 30.4-2C (enter negative pressure coefficients) Zone 2 GCp: 1.2 Zone 3 GCp: 1.2 a: 9.5 Table 26.9-1 z9 [ft]: 900 Table 26.9-1 Kh: 0.85 Table 30.3-1 KZt: 1 Equation 26.8-1 Kd: 0.85 Table 26.6-1 Velocity Pressure, qh [psf]: 24.4 Equation 30.3-1 GCp;: 0 Table 26.11-1 PRESSURES: p = q, GCp — GCpi Equation 30.9-1 Zone 1, p [psf]: 24.1 psf (1.0 W, Interior Zones, beyond 'a' from roof edge) Zone 2, p [psf]: 29.0 psf (1.0 W, End Zones, within 'a' from roof edge) Zone 3, p [psf]: 29.0 psf (1.0 W, Corner Zones, within 'a' from roof corner) (a= 3 ft) JOB NO.: U3507.0137.221 YETO R SUBJECT: CONNECTION n G In E E R S PROJECT: Smith, Alex Residence Calculate Uplift Forces on Connection Pressure Max Trib. Width 1 2 Max Trib. Max Uplift (0.6 Dead -0.6 Wind) Area Force (psf) (ft) (ft2) (Ibs) Zone 1 12.7 4.0 11.7 148 Zone 2 15.6 4.0 11.7 182 Zone 3 15.6 4.0 11.7 182 Calculate Connection Capacity Lag Screw Size [in]: 5/16 Cd: 1.6 NDS Table 2.3.2 Embedment3 [in]: 2.5 Grade: SPF (G = 0.42) Nominal Capacity [Ibs/in]: 205 NDS Table 12.2A Number of Screws: 1 Prying Coefficient: 1.4 Total Capacity [Ibs]: 586 Determine Result Maximum Demand [lbs]:l 182 Lag Screw Capacity [lbs]:1 586 Result: Capacity > Demand, Connection is adequate. Notes 1. 'Max Trib. Width' is the width along the rails tributary to the connection. 2. 'Max Trib Area' is the product of the 'Max.Trib Width' and 1/2 the panel width/height perpendicular to the rails. (2) rails per row of panels. Length of panels perpendicular to the rails shall not exceed 70". 3. Embedment is measured from the top of the framing member to the beginning of the tapered tip of the lag screw. Embedment in sheathing or other material is not effective.The length of the tapered tip is not part of the embedment length. JOB NO.: U3507.0137.221 YET O R SUBJECT: GRAVITY LOADS n G I n E E R S PROJECT: Smith, Alex Residence GRAVITY LOADS Roof Pitch: 7.0 :12 Design material Increase due to Material weight ROOF DEAD LOAD (D) weight [psf] pitch [psf] Composite Shingles 2.3 1.16 2.0 1/2" Plywood 1.2 1.16 1.0 Framing 3.0 3.0 Insulation 0.5 0.5 1/2" Gypsum Clg. 2.3 1.16 2.0 M, E & Misc 1.5 1.5 Total Existing Roof DL 10.8 PV Array DL 3.5 1.16 3 ROOF LIVE LOAD (Lr) Existing Design Roof Live Load [psf] 20 ASCE 7-10 Table 4.3-1 Roof Live Load With PV Array [psf] 0 2020 MRC, Section R324.4.1.1 SNOW LOAD (S): Existing w/ Solar Array Roof Slope [x:12]: 7.0 7.0 Roof Slope [°]: 30 30 Ground Snow Load, pg [psf]: 50 50 ASCE 7-16, Section 7.2 Terrain Category: C C ASCE 7-16, Table 7.3-1 Exposure of Roof: Fully Exposed Fully Exposed ASCE 7-16, Table 7.3-1 Exposure Factor, Ce: 0.9 0.9 ASCE 7-16, Table 7.3-1 Thermal Factor, Ct: 1.1 1.1 ASCE 7-16, Table 7.3-2 Risk Category: 11 II ASCE 7-16, Table 1.5-1 Importance Factor, Is: 1.0 1.0 ASCE 7-16, Table 1.5-2 Flat Roof Snow Load, pf [psf]: 35 35 ASCE 7-16, Equation 7.3-1 Minimum Roof Snow Load, pm [psf]: 0 0 ASCE 7-16, Section 7.3.4 Unobstructed Slippery Surface? No Yes ASCE 7-16, Section 7.4 Slope Factor Figure: Figure 7-2b Figure 7-2b ASCE 7-16, Section 7.4 Roof Slope Factor, Cs: 1.00 0.66 ASCE 7-16, Figure 7.4-1 Sloped Roof Snow Load, Ps [psf]: 35 23 ASCE 7-16, Equation 7.4-1 Design Snow Load, S [psf]: 35 23 JOB NO.: U3507.0137.221 TO R SUBJECT: LOAD COMPARISON E n G I n E E R S PROJECT: Smith, Alex Residence Summary of Loads Existing With PV Array D [psf] 11 14 Lr [psf] 20 0 S [psf] 35 23 Maximum Gravity Loads: Existing With PV Array (D+ Lr)/Cd [psf] 25 16 ASCE 7-10, Section 2.4.1 (D +S)/Cd [psf] 40 32 �ASCE 7-10, Section 2.4.1 (Cd=Load Duration Factor=0.9 for D,1.15 for S,and 1.25 for Lr) Maximum Gravity Load [psf]:1 40 1 32 Ratio Proposed Loading to Current Loading: 1 82% OK The gravity loads, and thus the stresses of the structural elements, in the area of the solar array are either decreased or increased by no more than 5%. Stress decreases or increases of no more than 5%are considered acceptable.Therefore,the structure is permitted to remain unaltered. JOB NO.: U3507.0137.221 yT O R SUBJECT: SOLAR LAYOUT n G I n E E R S PROJECT: Smith, Alex Residence 'f PLANVIEW AREA IS 2609 SQUARE FT ARRAY AREA 814 SQUARE FT _ ►. ARRAY IS 31% OF PLANVIEW AREA - 18" Setback from ridge 36" Pathway to ridge ..' lot- :'r,<71 L 4b