22B-026 21 Corticelli Engineer 2018-11-19VSE Project Number: U1982-0892-181
November 13, 2018
Trinity Solar
ATTENTION: Phil Smith
4 Open Square Way, Suite 410
Holyoke, MA 01040
REFERENCE: Lindsay Slabich Residence: 21 Corticelli Street, Northampton, MA 01062
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 will require retrofit in order to support
the proposed solar panel installation.The existing rafters of roof 1 must be retrofit by installing a new 2x6 the full length of
the existing rafter. Install the new 2x6 rafter with 16d sinkers at 6" O.C. staggered. Roof 3 is permitted to remain unaltered.
Design Parameters
Code: Massachusetts State Residential Code (780 CMR Chapter 51, 9th Edition (2015 IRC))
Risk Category: II
Design wind speed: 117 mph (3-sec gust) per ASCE 7-10
Wind exposure category: C
Ground snow load: 40 psf
Existing Roof Structure
Roof structure: true 2x4 rafters @ 24" O.C.
Roofing material: asphalt shingles
Roof slope: 40°
Connection to Roof
Mounting connection: (1) 5/16" lag screw w/ min. 2.5" embedment into framing at max. 72" O.C. along rails
Conclusions
Based upon our review,we conclude that the existing structure will require retrofit in order 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 attached calculations verify the adequacy of the roof to support the solar array after the
aforementioned retrofit is complete.
651 W. Galena Park Blvd., Ste. 101 / Draper, UT 84020 / T (801) 990-1775 / F (801) 990-1776 / www.vectorse.com
VSE Project Number: U1982-0892-181
Lindsay Slabich Residence
11/13/2018
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.
The attached calculations verify the capacity of the connections of the solar array to the existing roof against wind (uplift),
the governing load case.
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.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, LLC
11/13/2018
_______________________________________________________
Wells Holmes, S.E.
MA License: 54240 - Expires: 06/30/2020
Project Engineer
Enclosures
WLH/koc
11/13/2018
651 W. Galena Park Blvd., Ste. 101 / Draper, UT 84020 / T (801) 990-1775 / F (801) 990-1776 / www.vectorse.com
JOB NO.:U1982-0892-181
SUBJECT:WIND PRESSURE
PROJECT:Lindsay Slabich Residence
Label:Note: Calculations per ASCE 7-10
SITE-SPECIFIC WIND PARAMETERS:
Basic Wind Speed [mph]:117 Notes:
Exposure Category:C
Risk Category:II
Importance Factor, I:
ADDITIONAL INPUT & CALCULATIONS:
Height of Roof, h [ft]:20 (Approximate)
Comp/Cladding Location:Hip?No
Enclosure Classification:
Zone 1 GCp:1.0 Figure 30.4-2C (enter largest abs. value)
Zone 2 GCp:1.2 (enter largest abs. value)
Zone 3 GCp:1.2 (enter largest abs. value)
α:9.5 Table 26.9-1
zg [ft]:900 Table 26.9-1
Kh:0.90 Table 30.3-1
Kzt:1 Equation 26.8-1
Kd:0.85 Table 26.6-1
Velocity Pressure, qh [psf]:26.9 Equation 30.3-1
GCpi:0 Table 26.11-1 (largest abs. value)
OUTPUT:Equation 30.9-1
Zone 1 Pressure, p [psf]:26.9 psf (1.0 W, Interior Zones*)
Zone 2 Pressure, p [psf]:32.2 psf (1.0 W, End Zones*)
Zone 3 Pressure, p [psf]:32.2 psf (1.0 W, Corner Zones* within a)
(a= 3 ft)
Solar Panel Array
Gable Roofs 27° < θ ≤ 45°
Enclosed Buildings
Components and Cladding Wind Calculations
()()piphGCGCqp−=
VECTOR STRUCTURAL ENGINEERS
JOB NO.:U1982-0892-181
SUBJECT:CONNECTION
PROJECT:Lindsay Slabich 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 16.1 6.0 16.5 266
Number of Screws:1 2 19.3 6.0 16.5 319
Prying Coefficient:1.4 3 19.3 6.0 16.5 319
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.:U1982-0892-181
SUBJECT:GRAVITY LOADS
PROJECT:Lindsay Slabich Residence
CALCULATE ESTIMATED GRAVITY LOADS
ROOF DEAD LOAD (D)
Increase due to
pitch
Original
loading
Roof Pitch/12 10.1
Asphalt Shingles 2.6 1.31 2.0 psf
1/2" Plywood 1.3 1.31 1.0 psf
Framing 3.0 psf
Insulation 0.0 psf
1/2" Gypsum Clg.0.0 psf
M, E & Misc 0.0 psf
DL 7 psf
PV Array DL 4 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]20
SNOW LOAD (S):Existing
w/ Solar Panel
Array
Roof Slope [x:12]:10.1
Roof Slope [°]:40
Snow Ground Load, pg [psf]:40 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]:0 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:0.50 ASCE 7-10, Figure 7-2
Sloped Roof Snow Load, ps [psf]:18 ASCE 7-10, Equation 7.4-1
Design Snow Load, S [psf]:1832
10.1
40
40
C
Fully Exposed
0.9
1.1
II
1.0
35
0
No
Figure 7-2b
0.92
32
Abbrev GRADES
Fbxx
(psi)
Fvxx
(psi)
g
(lb/ft3)
JOB NO.:U1982-0892-181 DFL#1 DFL#1 1,000 180 32
DFL#2 DFL#2 900 180 32
DF1 (5X)DFL#1 5X5 & LARGER 1,350 170 32
SPF#2 SPF#2 875 135 26.2
SP#2 SP#2 1,100 175 34.3
PROJECT:Lindsay Slabich Residence SUBJECT:BEAMS 24F-V4 24F-V4 2,400 240 32
24F-V8 24F-V8 2,400 240 40
LVL (1.9)LVL (1.9X106E)2,600 285 40
DESIGN LOADS:Load Types:Snow Live Dead LVL (2.0)LVL (2.0X106E)2,200 285 42
Roof 32 20 8 CRITERIA (L/)DTL DLL DDL LSL LSL (1.3X106E)1,700 400 42
Solar 3.5 A(BLANK)120 240 STL36 GRADE 36 STEEL 21,600 14,400 490
B 240 480 STL46 GRADE 46 STEEL 27,700 16,500 490
C 600 800 STL50 GRADE 50 STEEL 30,000 20,000 490
Label
Length
'L' (ft)
*Roof
Trib
(ft)
Floor
Trib
(ft)
Wall
Trib
(ft)
Add'l
Live
Load
(plf)
Add'l
Solar
Load
(plf)
Point
Load
From React (A,B)Dist
'a'
(ft)
Point
Live
Load
'PLL'
(lb)
Point
Dead
Load
'PDL'
(lb)# PLIESGrade Size "BM/HDR"D CRITERIACr CD CF,V Ra (lb)Rb (lb)
Mmax
(ft-lb)
Mallow
(ft-lb)
Vmax
(lb)
Vallow
(lb)
DTL
(in)
DTLallow
(in)
DLL
(in)
(SEE
COND
'C')
DLLallow
(in)
(SEE
COND
'C')
1.5DL
GLB
Camb Check
Roof 3 5 2 7.0 (1)SPF#2 2x4 1.15 1.15 1.50 221 221 276 443 195 543 0.165 0.500 0.075 0.250 0.62 M
Roof 1 10 0.68 2.4 (1)SPF#2 2x4 (True)1.15 1.15 1.00 150 150 374 514 140 828 0.451 1.000 0.204 0.500 0.73 M
Roof 1 10 1.32 4.6 (1)SPF#2 2X6 1.15 1.15 1.30 292 292 729 948 265 854 0.451 1.000 0.204 0.500 0.77 M
*Roof trib. adjusted based on the ratio of moment of Inertia.
Exx (psi)
1,800,000
29,000,000
29,000,000
1,700,000
1,800,000
1,900,000
29,000,000
2,000,000
1,300,000
1,400,000
1,600,000
1,600,000
1,400,000
VECTOR STRUCTURAL ENGINEERS
JOB NO.:U1982-0892-181
SUBJECT:SOLAR LAYOUT
PROJECT:Lindsay Slabich Residence