Draft Project Impact Report - Boston Redevelopment Authority

Exeter Residences/888 Boylston
5.5 Solar Glare Analysis
Introduction
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Environmental.docx
the Project includes the addition of a 27 story building to an existing low-rise
structure. The effect from the increased height of 888 Boylston from the previously
approved plan is minimal. These changes will, of necessity, require a change in the
view of the site and sky plane when viewed from the adjacent public streets and
sidewalks.
This section includes an assessment of the potential solar glare impacts from new
program and mitigation strategies, if necessary, to offset potential heat gain and glare
impacts. Although the Prudential Center Redevelopment FPIR/FEIR did not include
a solar glare analysis, the discussion presented in the NPC/PNF and this DPIR
demonstrates conformance with the Article 80 Review guidelines and responds to
agency comments generated from the NPC/PNF filing.
The Exeter Residences building is a predominantly masonry building with
residential scale fenestration that is expected to have a limited solar glare and heat
gain effect on the surrounding buildings. The masonry shaft will have cantilevered
glass bays that rise up the entirety of the north façade.
888 Boylston is proposed to be a fully glazed building set back 92-feet from the
Boylston Street curb (77-feet from the property line), and buffered from the street by
street trees and plaza plantings. As a fully glazed building, there is a potential for
glare and heat gain effects on neighboring streets and buildings as discussed below.
There are two general types of solar glare and they are commonly referred to as
“spot glare” and “scattered glare.” The first originates as a reflection from smooth
façade buildings which creates a glare with an equal level of intensity as the source
object. The second originates as porous surfaced buildings diffuse the light as it’s
reflected thereby decreasing the intensity of the glare and making it appear scattered.
Reduced intensity alleviates squinting and general discomfort for pedestrians and
drivers.
Since the normal human viewing range is commonly defined as an angle 30 degrees
above to 45 degrees below the horizontal, and 65 degrees to the left or right of the
forward line of sight, solar glare angles located outside of these parameters have little
to no effect. In addition, glare angles that run perpendicular to the observer (e.g.
pedestrian, automobile driver) have no adverse impacts. In some cases lower solar
altitude angles produce glare (distant glare) within the discussed viewing range,
however the solar intensity is decreased due to the greater expanse of atmosphere
DRAFT - Environmental Protection 5-32