Smith, Donald- ELNorthampton, MA August 16, 2021
212 Main St.
Northampton, MA 01060
Trinity Solar No.
1260 Westhampton Road 2021-08-610491
Northampton, MA 01062
Trinity Solar | 4 Open Square Way, Suite 410 | Holyoke, MA | (413) 203-9088
MA License No. 56687
RE: SMITH, DONALD RAYMOND; SMITH, LISA A
To the Building Official:
The following information constitutes a summary of the relevant design criteria and recommendations for the support of a
new photovoltaic [PV] system on the existing roof framing components at the above-referenced location.
Criteria is as follows:
1. Existing roof framing:
Pre-fabricated roof trusses are 2x4 at 24 o.c.;
2. Roof Loading:
• 4.33psf dead load (pounds per square foot - PV panels, mounting rails & hardware)
• 5.1psf - existing roof loads (1.1psf - 2x4 framing, 1.5psf roof sheathing, 2.5psf shingles)
• Ground Snow Load - 40psf - per AHJ (Authority Having Jurisdiction)
• Wind criteria - Exposure Category B, 117 mph wind equivalent to 23.09psf wind pressure
3. Existing Roof modification - none required; existing roof framing is acceptable for PV installation.
This installation design is in general conformance with the manufacturers’ specifications and complies with all
applicable laws, codes, and ordinances – specifically the International Building Code (2015 edition) and the
International Residential Code (2015 edition), including all Massachusetts regulations and amendments.
The spacing and fastening of the mounting brackets is a maximum of 48” o.c. between mounting brackets (staggered)
and is secured using 5/16” diameter corrosive-resistant steel lag bolts. A minimum of 2½” of penetration (embedment)
per lag bolt is required, which will resist all stated loads above – including wind shear. Per NDS Section 11.1.4,
clearance holes - equal to the diameter of the shank - need to be bored into a primary framing member for the
full-length of the threaded portion of the bolt to avoid splitting of the framing member.
Regards,
Ihor Bojcun, PE
Structural Engineer - Trinity Solar