24A-006 (5) %vcTPR
2 I9_ Qo-( UTAH OFFICES
Sandy
Layton
E n e I n E E R s St. George
Project Number: U1982-0186-171
April 24,2017
Trinity Solar
4 Open Square Way,Suite 410
Holyoke.MA 01040
ATTENTION: Phil Smith
REFERENCE: Michael Grygorcewicz Residence:35 Terrace Lane,Northampton,MA 01060
Solar Panel Installation
Dear Mr.Smith:
Per your request, we have reviewed the attached layout and photos relating to the installation of solar panels at the
above-referenced site.The following materials and components are proposed in the installation of the solar panels.
Roof Structure:2x6 Rafters at 16 in O.C.
Roof Material:Composition Shingles
Mounting Connections:5/16-Lag Screw with 2.5"Embedment at 6'O.C.maximum.
Based upon our review, it is our conclusion that the installation of solar panels on this existing roof will not adversely
affect the stmcture of this house. The design of solar panel supporting members is by the manufacturer and/or installer.
The adopted building code in this jurisdiction is the 2009 International Residential Code and ASCE 7-05. Appropriate
design parameters which must be used in the design of the supporting members and connections are listed below:
Ground snow load:40 psf per Massachusetts amendments to the IRC(verify with local building department)
Roofsnow load:28 psf per Massachusetts amendments to the IRC(verify with local building department)
Design wind speed: 92 mph(3-sec gust)
Wind exposure:Category C
Our conclusion regarding the adequacy of the existing roof is based on the fact that the additional weight related to the
solar panels is less than 3.5 pounds per square foot In the area of the solar panels,no 20 psf live loads will he present.
Regarding snow loads,it is our conclusion that since the panels are slippery,effective snow loads will be reduced in the
areas of the panels. The attached calculations verify the capacity of the connections against wind, the governing load
case. Solar panels will be flush-mounted, parallel to and no more than 6" above the roof surface. Thus, it is our
conclusion that any additional wind or seismic loadings related to the addition of these solar panels is negligible.
During design and installation,particular attention must be paid to the maximum allowable spacing of attachments and
the location of solar panels relative to roof edges. The use of solar panel support span tables provided by the
manufacturer is allowed only where the building type, site conditions, and solar panel configuration match the
description of the span tables.Attachments to existing roof joist or rafters must be staggered so as not to over load any
existing structural member. Waterproofing around the roof penetration is the responsibility of others. All work
performed must he in accordance with accepted industry-wide methods and applicable safety standards. Vector
Structural Engineering assumes no responsibility for improper installation of the solar panels.
Please note a representative of Vector Structural Engineering has not physically observed the roof framing. Our
conclusions are based upon the assumption that all structural roof components and other supporting elements are in
good condition,free of damage and deterioration,and are sized and spaced such that they can resist standard roof loads.
Very truly yours,
VECTOR STRUCTURAL ENGINEERING,LLC
tk cm
Roger Alworth,P.E. I
Principalal 4 '
RTAirsl
04/24/2017
9138 S. State St., Suite 101 /Sandy. UT 840701 T(801)990-1775 /F(801) 990-1776/www.vectorse.com
S/ ECTCR JOB NO.: U1982-0186-171
E n e I n e E R s
PROJECT: MICHAEL GRYGORCEWICZ RESIDENCE SUBJECT: WIND PRESSURE
Components and Cladding Wind Calculations
Label: Solar Panel Array Note: Calculations per ASCE 7-05
SITE-SPECIFIC WIND PARAMETERS:
Basic Wind Speed [mph]: 92 Notes:
Exposure Category: C
Occupancy Category: II
Importance Factor, I: 1.00
ADDITIONAL INPUT& CALCULATIONS:
Height of roof, h [ft]: 25 (Approximate)
Comp/Cladding Location: Gable/Hip:iti±nfs 7°<9 5zr,
Enclosure Classification: Enclosed Buildings
Zone 1 GCp: 0.9. Figure 6-11C (enter largest abs. value)
Zone 2 GCp: L7 (enter largest abs. value)
Zone 3 GCp: '26 (enter largest abs. value)
a: 9.5 Table 6-2
zv [ftj: 900 Table 6-2
Kh: 0.945 Table 6-3
Kr: 1 Equation 6-3
Kd: 0.85 Table 6-4
Velocity Pressure, qh [psf]: 17.4 Equation 6-15
GCp;: 0 Figure 6-5 (largest abs. value)
OUTPUT: p=qh[(GCp)-(GCp;)j
Zone 1 Pressure, p [psf]: 15.67 psf(1.0W, Interior Zones*)
Zone 2 Pressure, p [psf]: 29.60 psf(1.0W, End Zones*)
Zone 3 Pressure, p [psf]: 45.26 psf(1.0W, Corner Zones* within a)
(*a=assumed=3')
%VECTOR JOB NO.: U1982-0186.171
EFIGIFIEERS
PROJECT: MICHAEL GRYGORCEWICZ RESIDENCE SUBJECT: CONNECTION CAPACITY
Lag Screw Connection
Capacity: Demand:
Lag Screw Size: 5/16
Cd: 1.6 Pressure Max Max. Trib.
(1.0 Wind) Spacing Area Max. Uplift
Embedment: 2.5 in (psi) (ft) (ftz) Force (Ibs)
Grade: SPF (G = 0.42)
Capacity: 205 lbs/in. emb. Zone 1: 15.7 4 12 188
Number of Screws: 1" Zone 2: 29.6 4 12 355
Total Capacity: 820 lbs Zone 3: 45.3 4 12 543
Demand< Capacity: CONNECTION OKAY
"V E C i O R JOB NO.: U1982-0186-171
E rl G I n E E R S
PROJECT: MICHAEL GRYGORCEWICZ RESIDENCE SUBJECT: GRAVITY LOADS
CALCULATE ESTIMATED GRAVITY LOADS
Increase due to Original
DEAD LOAD (D) pitch loading
Roof Pitch/12 I 5.1
Composite/Asphalt Shingles 4.3 1.09 4.00 psf
1/2" Plywood 1.1 1.09 1.00 psf
Framing 3.0 psf
Insulation 0.8 psf
1/2" Gypsum CIg. 2.2 psf
M, E & Misc 1.5 psf
DL 12.9 psf
PV Array DL 3.0 psf
ROOF LIVE LOAD (Lr)
Existing Design Roof Live Load [psf] 20 ASCE 7-05, Table 4-1
Roof Live Load With PV Array [psf] 11.1111.E 2015 BC, Section 1607.12.5
SNOW LOAD (S): Existing With PV Array
Roof Slope(:12): 5.1 " 5.1
Roof Slope [1: 23 23
Snow Ground Load, pg [psf]: ;40 40 ASCE 7-05, Section 7.2
Terrain Category: 4't - C ; C -„ASCE 7-05, Table 7-2
Exposure of Roof: Fully Exposed [z Fully E4 bbed^`" ASCE 7-05, Table 7-2
Exposure Factor, Ce: 0.9 0.9 ASCE 7-05, Table 7-2
Thermal Factor, q: N1 ' ' t "" ,.,] <{ASCE 7-05, Table 7-3
Risk Category: II <._ II & ASCE 7-05,Table 1-1
Importance Factor, Is: 1.0 1.0 ASCE 7-05, Table 7-4
Flat Roof Snow Load, pt [psf]: 28 28 ASCE 7-05, Equation 7-1
Minimum Roof Snow Load, pm [psf]: 0 0 ASCE 7-05, Section 7.3.4
Unobstructed Slippery Surface? ""No - Yes. 'I ASCE 7-05, Section 7.4
Slope Factor Figure: Figure 7-2b Figure 7-2b ASCE 7-05, Section 7.4
Roof Slope Factor, C3: 1.000 0.783 ASCE 7-05, Figure 7-2
Sloped Roof Snow Load, p3 [psf]: 28 22 ASCE 7-05, Equation 7-2
Design Snow Load, S [psf]: 28 22
�\IECTOR JOB NO.: U1982-0186-171
E rl G I M E E R S
PROJECT: MICHAEL GRYGORCEWICZ RESIDENCE SUBJECT: LOAD COMPARISON
Summary of Loads
Existing With PV Array
D [psf] 13 16
Lr[psf] 20 0
S [Psf] 28 22
Maximum Gravity Loads:
Existing With PV Array
D+L,[psf] 33 16 ASCE 7-05, Section 2.4.1
D+S [psf] 41 38 ASCE 7-05, Section 2.4.1
Maximum Gravity Load [psf]: 41 38
Ratio Proposed Loading to Current Loading: 92.6% OK
The gravity loads in the area of the solar panels are decreased;thus, the stresses
of the structural elements are decreased.Therefore,the requirements of Section
3403.3 of the Massachusetts State Building Code,8th Edition(2009 IBC) are met
and the structure is permitted to remain unaltered.