HomeMy WebLinkAboutSOLAR ARRAY INSTALL - 18-00003 - 583 Maple Dr - Solar InstallVSE Project Number: U2001-1514-171
December 20, 2017
Blue Raven Solar, LLC
ATTENTION: Scott Gurney
1220 S. 630 E., Suite 430
American Fork, UT 84003
REFERENCE: Karen Abegglen Residence: 583 Maple Drive, Rexburg, ID 83440
Solar Array Installation
To Whom It May Concern:
We have reviewed the documents and photographs relating to the installation of the solar array at the above-referenced site.
Based upon our review,it is our conclusion that the installation of the solar array on this existing roof will not adversely
affect this structure.It is our understanding that the structural components of the existing roof framing are in good condition
and free of damage.The design of the solar panel racking (mounts,rails,etc.)is by the manufacturer or contractor.Please
note a representative of Vector Structural Engineering has not physically observed the roof framing.
Design Parameters
Code: International Building Code, 2012 Edition
Risk Category: II
Design wind speed: 115 mph (3-sec gust) per ASCE 7-10
Wind exposure category: C
Ground snow load: 50 psf
Existing Roof Structure
Roof structure: 2x4 manufactured trusses @ 24" O.C.
Roofing material: composite shingles
Connection to Roof
Mounting connection: (1) 5/16" lag screw w/ min. 2.5" embedment into framing at max. 48" O.C. along rails
2 rails per row of panels, maximum panel height = 5'-6"
Conclusions
Our conclusion regarding the adequacy of the existing roof is based on the fact that the additional weight of the solar array is
3 psf or less.In the area of the solar array,other live loads will not be present or will be greatly reduced.Regarding snow
loads,because the panels are slippery and unobstructed,effective snow loads will be reduced in the area of the solar array.
The member forces in the area of the solar panels are not increased by more than 5%;thus,the stresses of the structural
elements are not increased by more than 5%.Therefore,the requirements of Section 3403.3 of the 2012 IBC are met and 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: U2001-1514-171
Karen Abegglen Residence
12/20/2017
The solar array will be flush-mounted (no more than 6"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.
Regarding seismic loads,we conclude that any additional forces will be small.With an assumed roof dead load of 10 psf,
solar array dead load of 3 psf,and affected roof area of 33%(maximum),the additional dead load (and consequential seismic
load)will be 9.8%.This calculation conservatively neglects wall weight.Because the increase is lateral forces is less than
10%,this addition meets the requirements of the exception in Section 3403.4 of the 2012 IBC.Thus the existing structure 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 shall 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.Particular attention must be paid to the maximum allowable
spacing of connections and the location of solar panels relative to roof edges.Connections to existing roof framing must be
staggered so as not to overload any existing structural member,except at array ends.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.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 assumes no responsibility for the
effects of snow falling from roofs onto other roofs, property or persons due to the installation of the solar array.
VECTOR STRUCTURAL ENGINEERING, LLC
ID Firm License: C2269
12/20/2017
_______________________________________________________
Wells Holmes, P.E.
ID License: P-12264 - Expires: 10/31/2019
Project Engineer
Enclosures
WLH/cbw
12/20/2017
651 W. Galena Park Blvd., Ste. 101 / Draper, UT 84020 / T (801) 990-1775 / F (801) 990-1776 / www.vectorse.com
JOB NO.:U2001-1514-171
SUBJECT:WIND PRESSURE
PROJECT:Karen Abegglen Residence
Label:Note: Calculations per ASCE 7-10
SITE-SPECIFIC WIND PARAMETERS:
Basic Wind Speed [mph]:115 Notes:
Exposure Category:C
Risk Category:II
Importance Factor, I:
ADDITIONAL INPUT & CALCULATIONS:
Height of Roof, h [ft]:15 (Approximate)
Comp/Cladding Location:Hip?No
Enclosure Classification:
Zone 1 GCp:0.9 Figure 30.4-2B (enter largest abs. value)
Zone 2 GCp:1.7 (enter largest abs. value)
Zone 3 GCp:2.6 (enter largest abs. value)
α:9.5 Table 26.9-1
zg [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
GCpi:0 Table 26.11-1 (largest abs. value)
OUTPUT:Equation 30.9-1
Zone 1 Pressure, p [psf]:22.0 psf (1.0 W, Interior Zones*)
Zone 2 Pressure, p [psf]:41.5 psf (1.0 W, End Zones*)
Zone 3 Pressure, p [psf]:63.5 psf (1.0 W, Corner Zones* within a)
(a= 3 ft)
Solar Panel Array
Gable/Hip Roofs 7° < θ ≤ 27°
Enclosed Buildings
Components and Cladding Wind Calculations
piphGCGCqp
VECTOR STRUCTURAL ENGINEERS
JOB NO.:U2001-1514-171
SUBJECT:CONNECTION
PROJECT:Karen Abegglen Residence
Lag Screw Connection
Capacity:Demand:
Lag Screw Size [in]:5/16
Cd:1.6 NDS Table 2.3.2
Embedment1 [in]:2.5
Grade:
Capacity [lbs/in]:205 NDS Table 12.2A 1 13.2 4.0 12.0 158
Number of Screws:1 2 24.9 4.0 12.0 299
Prying Coefficient:1.4 3 38.1 3.0 9.0 343
Total Capacity [lbs]:586
Demand< Capacity:CONNECTION OKAY
SPF (G = 0.42)
Pressure
(0.6 Wind)
(psf)
Max
Tributary
Width (ft)
Max. Trib.
Area2
(ft2)
Max. Uplift
Force (lbs)
Zone
1. 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.
2. 'Max. Trib Area' is the product of the 'Max. Tributary Width' (along the rails) and 1/2 the panel width/height
(perpendicular to the rails).
VECTOR STRUCTURAL ENGINEERS
JOB NO.:U2001-1514-171
SUBJECT:GRAVITY LOADS
PROJECT:Karen Abegglen Residence
CALCULATE ESTIMATED GRAVITY LOADS
ROOF DEAD LOAD (D)
Increase due to
pitch
Original
loading
Roof Pitch/12 2.3
Composite Shingles 2.0 1.02 2.0 psf
1/2" Plywood 1.0 1.02 1.0 psf
Framing 3.0 psf
Insulation 0.5 psf
1/2" Gypsum Clg.2.0 psf
M, E & Misc 1.5 psf
DL 10 psf
PV Array DL 3 psf
ROOF LIVE LOAD (Lr)
Existing Design Roof Live Load [psf]20 ASCE 7-10, Table 4-1
Roof Live Load With PV Array [psf]0
SNOW LOAD (S):Existing
w/ Solar Panel
Array
Roof Slope [x:12]:2.3
Roof Slope [°]:11
Snow Ground Load, pg [psf]:50 ASCE 7-10, Section 7.2
Terrain Category:C ASCE 7-10, Table 7-2
Exposure of Roof:Fully Exposed ASCE 7-10, Table 7-2
Exposure Factor, Ce:0.9 ASCE 7-10, Table 7-2
Thermal Factor, Ct:1.1 ASCE 7-10, Table 7-3
Risk Category:II ASCE 7-10, Table 1.5-1
Importance Factor, Is:1.0 ASCE 7-10, Table 1.5-2
Flat Roof Snow Load, pf [psf]:35 ASCE 7-10, Equation 7.3-1
Minimum Roof Snow Load, pm [psf]:20 ASCE 7-10, Section 7.3.4
Unobstructed Slippery Surface?Yes ASCE 7-10, Section 7.4
Slope Factor Figure:Figure 7-2b ASCE 7-10, Section 7.4
Roof Slope Factor, Cs:0.98 ASCE 7-10, Figure 7-2
Sloped Roof Snow Load, ps [psf]:34 ASCE 7-10, Equation 7.4-1
Design Snow Load, S [psf]:3435
2.3
11
50
C
Fully Exposed
0.9
1.1
II
1.0
35
20
No
Figure 7-2b
1.00
35
JOB NO.:U2001-1514-171
SUBJECT:LOAD COMPARISON
PROJECT:Karen Abegglen Residence
Summary of Loads
Existing With PV Array
D [psf]10 13
Lr [psf]20 0
S [psf]35 34
Maximum Gravity Loads:
Existing With PV Array
D + Lr [psf]30 13 ASCE 7-10, Section 2.4.1
D + S [psf]45 47 ASCE 7-10, Section 2.4.1
Maximum Gravity Load [psf]:45 47
Maximum Member Forces:
LOCATION
GEOMETRY
Span(ft)31.1 (Approximate)
Solar Panel Array Start, a (ft)2.8 (Approximate)
Solar Panel Array Length, b (ft)10.8 (Approximate)
Truss/Rafter Spacing (ft)2.0
MEMBER FORCES
Existing With PV Array
Vertical Reaction, V1 (lbs)1390 1428 OK
Vertical Reaction, V2 (lbs)1390 1403 OK
Moment @ Center, M (lbs-ft)10798 11010 OK
The member forces in the area of the solar array are not increased by more than 5%;
thus, the stresses of the structural elements are not increased by more than 5%.
Therefore, the requirements of Section 3403.3 of the 2012 IBC are met and the
structure is permitted to remain unaltered.
Ratio
House
102%
103%
101%