34 Summer Street LetterVSE Project Number: U1876.1774.201
June 22, 2020
Boston Solar
55 Sixth Road
Woburn, MA 01801
REFERENCE: Bombardier, Jessica Residence: 34 Summer Street, Salem, MA 01970
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: Massachusetts State Residential Code (780 CMR Chapter 51, 9th Edition (2015 IRC))
Risk Category: II
Design wind speed: 127 mph (3-sec gust) per ASCE 7-10
Wind exposure category: C
Ground snow load: 50 psf
Designed for snow guards: Yes
Existing Roof Structure
Roof structure: 3x5 rafters @ 30" O.C.
Roofing material: asphalt shingles
Roof slope: 35°
Connection to Roof
Mounting connection: (1) 5/16" lag screw w/ min. 2.25" embedment into framing at max. 30" o.c. along rails
Use (4) #10 wood screws at rail ends as required.
Racking system: SnapNrack
Conclusions
Based upon our review,we conclude that the existing structure is adequate to support the proposed solar panel installation.
See attached calculations.
651 W. Galena Park Blvd., Ste. 101 / Draper, UT 84020 / T (801) 990-1775 / F (801) 990-1776 / www.vectorse.com
VSE Project Number: U1876.1774.201
Bombardier, Jessica Residence
6/22/2020
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.Because the increase in lateral forces is less than 10%,this addition meets the requirements of the
exception in Section 807.5 of the 2015 IEBC as referenced in 780 CMR Chapter 34,9th Edition.Thus the existing lateral
force resisting system is permitted to remain unaltered.Any non-structural changes to the plans will not affect the
conclusions in this letter.
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, LLC
06/22/2020
_______________________________________________________
Jacob Proctor, P.E.
MA License: 54953 - Expires: 06/30/2022
Project Engineer
Enclosures
JSP/ych
06/22/2020
651 W. Galena Park Blvd., Ste. 101 / Draper, UT 84020 / T (801) 990-1775 / F (801) 990-1776 / www.vectorse.com
JOB NO.:U1876.1774.201
SUBJECT:WIND PRESSURE
PROJECT:Bombardier, Jessica Residence
Label:Note: Calculations per ASCE 7-10
SITE-SPECIFIC WIND PARAMETERS:
Basic Wind Speed [mph]:127 Notes:
Exposure Category:C
Risk Category:II
Importance Factor, I:
ADDITIONAL INPUT & CALCULATIONS:
Height of Roof, h [ft]:25 (Approximate)
Comp/Cladding Location:Hip?No
Enclosure Classification:
Zone 1 GCp:1.0 Figure 30.4-2C (enter negative pressure coefficients)
Zone 2 GCp:1.2
Zone 3 GCp:1.2
α:9.5 Table 26.9-1
zg [ft]:900 Table 26.9-1
Kh:0.95 Table 30.3-1
Kzt:1 Equation 26.8-1
Kd:0.85 Table 26.6-1
Velocity Pressure, qh [psf]:33.2 Equation 30.3-1
GCpi:0 Table 26.11-1
PRESSURES:Equation 30.9-1
Zone 1, p [psf]:33.2 psf (1.0 W, Interior Zones, beyond 'a' from roof edge)
Zone 2, p [psf]:39.8 psf (1.0 W, End Zones, within 'a' from roof edge)
Zone 3, p [psf]:39.8 psf (1.0 W, Corner Zones, within 'a' from roof corner)
(a= 3 ft)
Solar Panel Array
Gable Roofs 27° < θ ≤ 45°
Enclosed Buildings
Components and Cladding Wind Calculations
()()piphGCGCqp−=
JOB NO.:U1876.1774.201
SUBJECT:CONNECTION
PROJECT:Bombardier, Jessica Residence
Calculate Uplift Forces on Connection
Pressure
(0.6 Wind)
(psf)
Max Connection
Spacing1
(ft)
Max Trib.
Area2
(ft2)
Max Uplift
Force
(lbs)
Zone 1 19.9 2.5 7.0 139
Zone 2 23.9 2.5 7.0 167
Zone 3 23.9 2.5 7.0 167
Calculate Connection Capacity
Lag Screw Size [in]:5/16
Cd:1.6 NDS Table 2.3.2
Embedment3 [in]:2.25
Grade:
Nominal Capacity [lbs/in]:205 NDS Table 12.2A
Number of Screws:1
Prying Coefficient:1.4
Total Capacity [lbs]:527
Determine Result
Maximum Demand [lbs]:167
Lag Screw Capacity [lbs]:527
Result:Capacity > Demand, Connection is adequate.
Notes
1. 'Max Connection Spacing' is the spacing between connections along the rails.
2. 'Max Trib Area' is the product of the 'Max Connection Spacing' and 1/2 the panel width/height perpendicular
to the rails. (2) rails per row of panels. Length or panels perpindicular to the rails shall not exceed 67".
SPF (G = 0.42)
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.
VECTOR STRUCTURAL ENGINEERS
JOB NO.:U1876.1774.201
SUBJECT:GRAVITY LOADS
PROJECT:Bombardier, Jessica Residence
CALCULATE ESTIMATED GRAVITY LOADS Roof Pitch: 8.4 :12
ROOF DEAD LOAD (D)
Increase due to
pitch
Material weight
[psf]
Asphalt Shingles 1.22 2.0
1/2" Plywood 1.22 1.0
Framing 1.00 3.0
Insulation 1.22 0.5
1/2" Gypsum Clg.1.22 2.0
M, E & Misc 1.00 3.5
Total Original Roof DL
PV Array DL 1.22 3
DL:1.22
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):w/ Solar Array
Roof Slope [x:12]:8.4
Roof Slope [°]:35
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]:0 ASCE 7-10, Section 7.3.4
Unobstructed Slippery Surface?No ASCE 7-10, Section 7.4
Slope Factor Figure:Figure 7-2b ASCE 7-10, Section 7.4
Roof Slope Factor, Cs:1.00 ASCE 7-10, Figure 7-2
Sloped Roof Snow Load, ps [psf]:35 ASCE 7-10, Equation 7.4-1
Design Snow Load, S [psf]:35
1.00
35
Design material
weight [psf]
2.4
1.2
3.0
0.6
2.4
3.5
13.2
3.7
#VALUE!
Existing
35
8.4
35
50
C
Fully Exposed
0.9
1.1
II
1.0
35
0
No
Figure 7-2b
Abbrev GRADES
Fbxx
(psi)
Fvxx
(psi)
g
(lb/ft3)
JOB NO.:U1876.1774.201 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:Bombardier, Jessica 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 35 20 13 CRITERIA (L/)DTL DLL DDL LSL LSL (1.3X106E)1,700 400 42
Solar 3.7 A(BLANK)180 240 STL36 GRADE 36 STEEL 21,600 14,400 490
STL46 GRADE 46 STEEL 27,700 16,500 490
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)
DLLallow
(in)
1.5DL
GLB
Camb Check
Rafter 5.75 2.5 9.2 (1)SPF#2 3x5 1.00 1.15 1.00 370 370 532 1048 317 1553 0.072 0.383 0.049 0.288 0.51 M
29,000,000
2,000,000
1,300,000
1,400,000
1,600,000
1,600,000
1,400,000
Exx (psi)
1,800,000
29,000,000
29,000,000
1,700,000
1,800,000
1,900,000