BLD2024-0939_Structural_Calculations_7.19.2024_9.31.48_AM_4388815VECTOR
E M G I M E E R S
VSE Project Number: U4703.0900.241
June 4, 2024
Infinity Solar USA
6405 E Mill Plain
Vancouver, WA 98661
REFERENCE: Steven Handley - Edmonds Wa Residence: 23109 97th Avenue West, Edmonds, WA 98020
Solar Array Installation
To Whom It May Concern:
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: 2021 Washington State Residential Code (2021 IRC)
Risk Category: II
Design wind speed, Vult: 115 mph (3-sec gust)
Wind exposure category: C
Ground snow load, Pg: 20 psf
Seismic design category: D
Existing Roof Structure
Roof structure: 2x6 rafters @ 16" o.c.
Roofing material: rolled asphalt
Roof slope: 9°
Connection to Roof
Mounting connection: (4) #14 wood screws w/ min. V 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 68 in
Rail cantilever shall not exceed the lesser of 50% of the connection spacing or maximum cantilever allowed by
manufacturer
Connections shall be staggered so as not to overload any existing structural member
Conclusions
Based upon our review, we conclude that the existing structure is adequate to support the proposed solar panel installation.
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.
651 W. Galena Park Blvd., Ste. 101 / Draper, UT 84020 / T (801) 990-1775 / F (801) 990-1776 / www.vectorse.com
VSE Project Number: U4703.0900.241
Steven Handley - Edmonds Wa Residence
Y To R 6/4/2024
fl G I fl E E R S
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. Regarding seismic loads, we conclude that any additional forces will be small. Conservatively
neglecting the weight of existing wall materials, the installation of the solar panels represents an increase in the total weight
(and resulting seismic load) of 4.2%. Increases in lateral forces less than 10% are considered acceptable. Thus the existing
lateral force resisting system is permitted to remain unaltered.
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. 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 panels, solar 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
WA Firm License: 2202
06/04/2024
Wells Holmes, S.E.
WA License: 51006 - Expires: 10/06/2024
Project Engineer
Enclosures
WLH/bpp
651 W. Galena Park Blvd., Ste. 101 / Draper, UT 84020 / T (801) 990-1775 / F (801) 990-1776 / www.vectorse.com
ECTOR�,
n G I n E E R S
PROJECT: Steven Handley - Edmonds Wa Residence
CHECK INCREASE IN OVERALL SEISMIC LOADS
Estimated Roof Dead Load
10.0
Solar Dead Load
3.0
% Roof Covered
14%
Equiv. Total Dead Load
10.5
Addt'I Seismic Weight
4.2%
psf
psf
psf
JOB NO.: U4703.0900.241
SUBJECT: SEISMIC LOADS
Conservatively neglecting the weight of existing wall materials, the installation of the solar panels represents an
increase in the total weight (and resulting seismic load) of 4.2%. Increases in lateral forces less than 10% are
considered acceptable.
YEECTOR®
fl G I E R S
PROJECT: Steven Handley - Edmonds Wa Residence
Com onents and Cladding Wind Calculations
Label: Isolar Panel Array
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 7° < 6 <_ 20°
Enclosure Classification: Enclosed Buildings
Zone 1, 2e GCp: 2.00 Figure 30.3-213
Zone 2n, 2r, 3e GCp: 2.92 (negative coeff.)
Zone 3r GCp: 3.50
a:
Zg [ft]:
Kh:
Ke:
KZt:
Kd:
Velocity Pressure, qh [psf]:
YE.
WIND PRESSURES:
Zone 1, 2e, p [psf]
Zone 2n, 2r, 3e, p [psf]
Zone 3r, p [psf]
9.5
Table 26.11-1
900
Table 26.11-1
0.85
Table 26.10-1
0.99
Table 26.9-1
1
Equation 26.8-1
0.85
Table 26.6-1
24.1
Equation 26.10-1
1.50
Section 29.4.4
JOB NO.: U4703.0900.241
SUBJECT: WIND PRESSURE
Note: Calculations per ASCE 7-16
Zone 1, 2e Ya: 0.78 Fig.
Zone 2n, 2r, 3e Ya: 0.78 29.4-8
Zone 3r Ya: 0.78
Equation 29.4-7 p = q h (GC p)(Y E)(Y a)
56.2 psf (1.0 W )
82.1 psf (1.0 W )
98.3 psf (1.0 W )
(a = 3 ft)
Y
ECTOR y
n G i n E E R S
PROJECT: Steven Handley - Edmonds Wa Residence
Calculate Uplift Forces on Connection
Zone 1, 2e
Zone 2n, 2r, 3e
Zone 3r
JOB NO.: U4703.0900.241
SUBJECT: CONNECTION
Pressure Max Trib. Width 2 Max Trib. Max Uplift
(0.6 Dead -0.6 Wind) Area Force
(psf) (ft) (ft) (Ibs)
31.9
4.0
11.3
362
47.4
4.0
11.3
538
57.2
4.0
11.3
648
Calculate Connection Capacity
Wood Screw Size:
Cd:
Embedment3 [in]:
Grade:
Nominal Capacity [Ibs/in]:
Number of Screws:
Prying Coefficient:
Total Capacity [Ibs]:
Determine Result
Notes
#14
1.6
1
SPF (G = 0.42)
121
4
1
774
NDS Table 2.3.2
NDS Table 12.213
Maximum Demand [Ibs]: 648
Wood Screw Capacity [Ibs]: 774
Result: Capacity > Demand, Connection is adequate.
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 68".
3. Embedment is measured from the top of the framing member to the beginning of the tapered tip of the wood
screw. Embedment in sheathing or other material is not effective. The length of the tapered tip is not part of the
embedment length.
ECTOR
r1 G 1 r1 E E R S
PROJECT: Steven Handley - Edmonds Wa Residence
JOB NO.: U4703.0900.241
SUBJECT: GRAVITY LOADS
GRAVITY LOADS Roof Pitch: 1 1.9 :12
Design material
Increase due to
Material weight
ROOF DEAD LOAD (D)
weight [psf]
pitch
[psf]
Rolled Asphalt
2.0
1.01
2.0
1 /2" Plywood
1.0
1.01
1.0
Framing
3.0
3.0
Insulation
0.0
0.0
1/2" Gypsum Clg.
0.0
1.01
0.0
M, E & Misc
0.0
0.0
Total Existing Roof DL
6.0
PV Array DL
3.0
1.01
3
ROOF LIVE LOAD (Lr)
Existing Design Roof Live Load [psf] 20 ASCE 7-16 Table 4.3-1
Roof Live Load With PV Array [psf] 0 2021 IRC, Section R324.4.1.1
SNOW LOAD (S): Existing w/ Solar Array
Roof Slope [x:12]:
Roof Slope [°]:
Ground Snow Load, pg [psf]:
Terrain Category:
Exposure of Roof:
Exposure Factor, Ce:
Thermal Factor, Ct:
Risk Category:
Importance Factor, Is:
Flat Roof Snow Load, pf [psf]:
Minimum Roof Snow Load, pm [psf]:
Unobstructed Slippery Surface?
Slope Factor Figure:
Roof Slope Factor, Cs:
Sloped Roof Snow Load, ps [psf]:
Design Snow Load, S [psf]:
1.9
1.9
9
9
20
20
C
C
Fully Exposed
Fully Exposed
0.9
0.9
1.1
1.1
II
II
1.0
1.0
14
14
20
20
No
Yes
Figure 7-2b
Figure 7-2b
1.00
1.00
14
14
20
20
ASCE 7-16, Section 7.2
ASCE 7-16, Table 7.3-1
ASCE 7-16, Table 7.3-1
ASCE 7-16, Table 7.3-1
ASCE 7-16, Table 7.3-2
ASCE 7-16, Table 1.5-1
ASCE 7-16, Table 1.5-2
ASCE 7-16, Equation 7.3-1
ASCE 7-16, Section 7.3.4
ASCE 7-16, Section 7.4
ASCE 7-16, Section 7.4
ASCE 7-16, Figure 7.4-1
ASCE 7-16, Equation 7.4-1
ECTORm
M G 1 n E E R S
PROJECT: Steven Handley - Edmonds Wa Residence
Summary of Loads
D [psf]
Lr [psf]
S [psf]
Maximum Gravity Loads:
JOB NO.: U4703.0900.241
SUBJECT: LOAD COMPARISON
Existina With PV Arrav
6
9
20
0
20
20
Existing With PV Array
(D + Lr) / Cd [psf] 21 10 JASCE 7-16, Section 2.4.1
(D + S) / Cd [psf] 23 25 JASCE 7-16, 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]:l 23 1 25
Maximum Member Forces:
(-.Pr)NAFTRV
Span(ft) 15.5 (Approximate)
Solar Panel Array Start, a (ft) 0.9 (Approximate)
Solar Panel Array Length, b (ft) 5.6 (Approximate)
Framing Spacing (ft) 1.3
MEMBER FORCES
Vertical Reaction, V1(lbs)
Vertical Reaction, VZ (Ibs)
Shear Capacity Shear Demand Ratio
743
249
34%
743
239
32%
OK
Existing With PV Array Ratio
Moment @ Center, M (Ibs-ft) 907 1 943 104% JOK
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.