Solar Glare Analysis

APPENDIX E

for the proposed

701 Dexter Avenue N Development

Master Use Permit No. 3033099-LU

Prepared for Alexandria Real Estate October 2020

EA Engineering, Science, and Technology, Inc., PBC 2200 Sixth Avenue, Suite 707 Seattle, WA 98121 (206) 452-5357

2200 Sixth Avenue, Suite 707 Seattle, Washington 98121

Telephone: 206.452.5357 Fax: 206.443.7646

www.eaest.com

Table of Contents

Section I – Overview Purpose of the Study ...................................................................................... 1 Project Overview ............................................................................................ 1

Section II – Analysis

Approach ........................................................................................................ 6 Background Information ................................................................................. 6 Findings .......................................................................................................... 7 Potential Mitigation Measures ...................................................................... 14 Significant Unavoidable Adverse Impacts .................................................... 14

List of Figures

Figure 1 - Vicinity Map .................................................................................... 2 Figure 2 – Existing Conditions ......................................................................... 3 Figure 3 - Site Plan .......................................................................................... 4 Figure 4 - Building Elevations .......................................................................... 5 Figure 5 - Reflected Solar Glare – March 21st Vernal Equinox ......................... 9 Figure 6 - Reflected Solar Glare – June 21st Summer Solstice ........................ 10 Figure 7 - Reflected Solar Glare – September 21st Autumnal Equinox ........... 12 Figure 8 - Reflected Solar Glare – December 21st Winter Solstice ................. 13

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701 Dexter Avenue N Development 1 Solar Glare Analysis

Section I – Overview

Purpose of this Study The purpose of this Solar Glare Analysis is to evaluate light and glare-related impacts -- specifically reflected solar glare -- resulting from glazing associated with the 701 Dexter Avenue N Development that is proposed for the south half of the block that is bordered by Dexter Avenue N on the east, Roy Street on the south, Aurora Avenue N on the west, and Valley Street on the north.1 The focus of the analysis is the probable impact to motorists on Aurora Avenue N, Dexter Avenue N and Mercer Street during the AM and PM peak traffic hour periods, as well as the probable impact to residences in the vicinity.

Project Overview The proponent is submitting a Master Use Permit (MUP) (#3033099-LU) for the 701 Dexter Avenue N Development project, which would involve construction of a new 11-story mixed-use shell and core building with approximately 233,999 sq. ft. of office and lab uses, 1,451 sq. ft. of street level retail and below-grade parking for 260 vehicles, 27 of which are off-site accessory stalls for a future development at 800 Mercer. See Figure 1 for a vicinity map, Figure 2 for existing conditions, Figure 3 for a site plan, and Figure 4 for building elevations. Principal exterior building materials would include unitized curtain wall, floor-to-ceiling vision glazing and shadowbox spandrel on the bulk of the south, east and west facades. Protruding volumes at the eastern mass would be outlined with metal panel frame elements that surround the perimeter of the corresponding volumes of roof terraces, with wood-veneer laminate soffits and metal panel flanking walls. Materials on the west portion of the north facade would include concrete shear wall clad with metal panel outboard, and a rainscreen metal panel cladding system on the east portion of the north facade. The curtain wall slot between the two northern core walls would have a maximum of 45% vision glazing in a unitized curtain wall system. The lobby and retail spaces at ground level would consist of a two-story continuous vision glass stick-built curtain wall with protruding glazed entry vestibule. Site preparation and construction could begin in July 2020 with building occupancy by December 2022. It is our understanding that any glazing and/or glass panels on the façade of the building would be consistent with the City’s Energy Code requirements. Reflectivity would be dictated by the nature of glass that is employed and the requirements set forth by the City's Energy Code. However, it is our understanding that no excessively reflective surfaces (i.e., mirrored glass, or polished metals) that go beyond what is required to meet energy-related code provisions are proposed anywhere on the exterior of the project. The proposed project would also include landscaping and pedestrian improvements to upgrade the existing pedestrian features and landscaping on the site and in that portion of the ROW that adjoins the site. Street trees adjacent to the site would be preserved as possible and replaced when removal is necessitated for construction.

1 This analysis has been prepared by EA Engineering, Science, and Technology, Inc. PBC. Staff at EA have

prepared reflected solar glare analyses for approximately 80+ buildings and structures -- predominantly in the downtown Seattle and Bellevue areas.

Source: EA, Google Maps, 2019

701 Dexter Avenue N Development Solar Glare Analysis

Figure 1

Vicinity Map

Project Site

Source: EA, Google Maps, 2019

Figure 2

Existing Conditions

Project Site

Source: ZGF, 2020

Figure 3

Site Plan

Project Site

Source: ZGF, 2020

Figure 4

701 Dexter Avenue N—Elevations

North Elevation East Elevation West Elevation

Telephone: 206.452.5357 Fax: 206.443.7646

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Section II -- Analysis

Approach This Solar Glare Analysis has been prepared consistent with provisions of Seattle’s Land Use Code and acceptable methodology2 for projects within the City. The methodology that has been used involves a trigonometric/planimetric approach for determining reflected solar glare impacts. This analysis primarily evaluates reflected solar glare impacts resulting from glazing on the façade of the proposed building during four key periods of the year – vernal equinox (approx. March 21st), summer solstice (approx. June 21st), autumnal equinox (approx. September 21st), and winter solstice (approx. December 21st). The glare diagrams that are contained in this analysis include adjustments for:

• the gradients of Aurora Avenue N., Mercer Street, and Dexter Avenue N, based on street profile information;

• adjacent buildings; and,

• daylight savings time, which affects vernal equinox, summer solstice and autumnal equinox.

Background Sources of Light and Glare While the light from vehicle headlights and reflective solar glare from glazing and other specular surfaces on vehicles can cause temporary glare impacts associated with a development project, the principal source of glare associated with most development projects is sunlight reflected from specular surfaces on building facades. Factors influencing the amount of reflective solar glare that may occur include: weather (e.g., cloud cover); building height, width and orientation of the façade; percent of the façade that is glazed or composed of specular material; reflectivity of the glass or specular surfaces; design relationship between the glazed and non-glazed portions of the façade (e.g., glass inset from the sash, horizontal and vertical modulation); the color and texture of building materials that comprise the façade; and the proximity of other intervening structures or landscaping. Principal sources of light that presently occur proximate to the project site include streetlights along adjacent roadways; light from headlights of vehicles operating on adjacent streets and vicinity; and building lighting (interior and in some instances low-level exterior) in the immediate area of the site. Existing streetlight fixtures are approximately 30 ft. tall and the lamps are cobra-style (cobra lamps function by lighting a broad area).

2 City of Seattle; Department of Community Development. 1979 and 1980. Light and Glare Study, Phase I and

Light and Glare Study, Phase II.

Telephone: 206.452.5357 Fax: 206.443.7646

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Factors that Affect Solar Glare Structures and, to an extent, vegetation can mitigate the environmental impacts of reflected solar glare from glazing. Such can occur if these mitigating factors are located between the sun and the glass or specular surface or between the reflective surface of the façade and the area potentially affected by reflected solar glare. While coniferous and/or evergreen vegetation typically afford the greatest amount of mitigation, at times deciduous vegetation can also restrict the amount of solar glare that is reflected from glazing -- from approximately late April to late October when leaves are present. Between late October and late April, while the amount of glare restriction afforded by deciduous trees is substantially less (influenced by the density of the branches), even during this time of the year they can partially restrict the amount of reflected solar glare emanating from glazed surfaces below a height of 20-30 ft. While Figures 5-8 have been adjusted to compensate for existing buildings and the surrounding topography, they depict a worst-case scenario in that they cannot accurately depict the following factors that would further limit the extent of possible reflected solar glare:

• the mitigating effect of existing and/or proposed on-site trees and street trees; and

• the extent of façade modulation and building materials that are proposed.

Glare Conditions of the Proposed Project

The 701 Dexter Avenue N Development would be located in Seattle’s South Lake Union neighborhood and would consist of a new 11-story mixed-use building with approximately 217,000 sq. ft. of office and lab uses, 1,700 sq. ft. of retail space, and below grade parking for 217 vehicles.

Stationary sources of light (e.g., interior lighting, pedestrian-level lighting, illuminated signage) from the 701 Dexter Avenue N Development would be visible from locations proximate to the project site. Specific information relative to stationary building light fixtures, signage, façade materials (in terms of specular or reflective characteristics) and glazing would be provided as part of the construction-level plans associated with the City’s Building Permit process. Light fixtures would be shielded and directed away from adjacent properties. It is our understanding that the building facade would not include highly reflective glazing or materials. At times during the construction period, however, required area lighting of the job site (safety requirements) would be provided, which would be noticeable within the immediate vicinity of the project site.

Findings

Summary of Findings

The analysis indicates while motorists on Aurora Avenue N, Dexter Avenue N and Mercer Street could occasionally experience reflected solar glare from the south, east and west façades of the proposed building during the AM and PM peak hour, such glare would primarily be outside of the cone-of-influence3 and would not be expected to cause problems for motorists nor differ substantially from periodic glare from stationary and mobile sources that motorists typically experience.

3 A key consideration for motorists is the effect of potential solar glare on a driver’s cone-of-influence. The cone-of-

influence is typically defined as the driver’s viewing area and is within approximately 20 degrees of the horizontal in the direction of vehicle travel. This represents the most sensitive viewing area for motorists. Glare impacts that occur outside the cone-of-influence, while noticeable, are considered less critical.

Telephone: 206.452.5357 Fax: 206.443.7646

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Results of the Analysis Figures 5-8 depict reflected solar glare from the facades of the proposed 701 Dexter Avenue N Development at two times each day during each of the four key days of the solar year -- vernal equinox (approx. March 21st), summer solstice (approx. June 21st), autumnal equinox (approx. September 21st), and winter solstice (approx. December 21st). The two times of the day (8 AM and 5 PM4) reflect the two peak hour traffic periods for Aurora Avenue N, Dexter Avenue N and Mercer Street. It should be noted, however, that solar glare-related impacts may also occur at other times of the day and days of the year. Also, because of the earth’s rotation, the duration of reflected solar glare impacts will vary – from several minutes5 for a stationary observer to substantially less for a mobile observer. Vernal Equinox – Approximately March 21st (refer to Figure 5). Climatic data indicate that March

typically has 3 clear days, 6 partly cloudy days and 22 cloudy days.6

• At 8 AM, reflected solar glare would extend from the south façade of the proposed building to the southwest toward Aurora Avenue N and from the east façade to the northeast toward Dexter Avenue N. While noticeable, the reflected solar glare on both streets would be outside of the cone-of-influence for drivers and would not be expected to cause problems for motorists nor differ substantially from periodic glare from stationary and mobile sources that motorists typically experience. Reflected solar glare would not affect Mercer Street at this time of day.

• At 5 PM, reflected solar glare would extend from the west facade of the proposed building to the northwest towards Aurora Avenue N and from the south façade to the southeast toward Dexter Avenue N. While noticeable, the reflected solar glare on both streets would be outside of the cone-of-influence for drivers and would not be expected to cause problems for motorists nor differ substantially from periodic glare from stationary and mobile sources that motorists typically experience. Reflected solar glare would not affect Mercer Street at this time of day.

Summer Solstice – Approximately June 21st (refer to Figure 6). Climatic data indicate that June

typically has 5 clear days, 8 partly cloudy days and 17 cloudy days.7

• At 8 AM, reflected solar glare would extend from the east façade of the proposed building to the east toward Dexter Avenue N. While noticeable, the reflected solar glare would be outside of the cone-of-influence for drivers and would not be expected to cause problems for motorists nor differ substantially from periodic glare from stationary and mobile sources that motorists typically experience. The north façade of the building would primarily be concrete and would not reflect solar glare. As well, incoming sun would largely be blocked by adjacent buildings to the north of the site. Neither Mercer Street nor Aurora Avenue N would be affected by solar glare at this time of day.

4 8:30 AM and 4 PM for winter solstice because sunrise occurs slight before 8:30 AM and sunset occurs slightly

after 4 PM. 5 The rate of change of the sun’s angle relative to the earth varies widely by season – from about 5 degrees

horizontally and 2 degrees vertically every 15 minutes in June to 3 degrees horizontally and 1 degree vertically every 15 minutes in December.

6 U.S. Dept. of Commerce, NOAA, 1992. 7 Ibid.

Source: EA Engineering and Google Earth, 2019

701 Dexter Avenue N Solar Glare Analysis

Figure 5

March 21st — Vernal Equinox — Pacific Daylight Savings Time

Note: The solid color within the glare outline repre-sents the actual glare from the proposed building that would be experienced in the surrounding area. The area that is not shaded represents the potential glare

1” = 268.57’

701 Dexter Ave. N

Dexter Yard, 14-story

building to be built

701 Dexter Avenue N DevelopmentSolar Glare Analysis

Figure 6

June 21st — Summer Solstice — Pacific Daylight Savings Time

1” = 268.57’

701 Dexter Ave. N

Telephone: 206.452.5357 Fax: 206.443.7646

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• At 5 PM, reflected solar glare would extend from the west facade of the proposed building to the west toward Aurora Avenue N, and from the south façade to the southeast toward Dexter Avenue N. While noticeable, the reflected solar glare on both streets would be outside of the cone-of-influence for drivers and would not be expected to cause problems for motorists nor differ substantially from periodic glare from stationary and mobile sources that motorists typically experience. Mercer Street would not be affected by solar glare at this time of day.

Autumnal Equinox – Approximately September 21st (refer to Figure 7). Climatic data indicate that September typically has 8 clear days, 9 partly cloudy days and 13 cloudy days.8

• At 8 AM, reflected solar glare would extend from the east façade of the proposed building to the northwest toward Dexter Avenue N and from the south façade to the southwest toward Aurora Avenue N. While noticeable, the reflected solar glare on both streets would be outside of the cone-of-influence for drivers and would not be expected to cause problems for motorists nor differ substantially from periodic glare from stationary and mobile sources that motorists typically experience. Mercer Street would not be affected by solar glare at this time of day.

• At 5 PM, reflected solar glare would extend from the south facade of the proposed building to the southwest toward Dexter Avenue N and from the west façade of the building to the northwest toward Aurora Avenue N. While noticeable, the reflected solar glare on both streets would be outside of the cone-of-influence for drivers and would not be expected to cause problems for motorists nor differ substantially from periodic glare from stationary and mobile sources that motorists typically experience. Mercer Street would not be affected by solar glare at this time of day.

Winter Solstice – Approximately December 21st (refer to Figure 8). Climatic data indicate that December typically has 2 clear days, 4 partly cloudy days and 25 cloudy days.9 On this day of the year at 4 PM the altitude of the sun above the horizon is approximately 2 degrees; therefore, reflected solar glare distances are great.

• At 8:30 AM, reflected solar glare would extend from the east façade to the northeast toward Dexter Avenue N and from the south façade to the southwest toward Aurora Avenue N and Mercer Street While noticeable, the glare on all three streets would be outside of the cone-of-influence for drivers and would not be expected to cause problems for motorists nor differ substantially from periodic glare from stationary and mobile sources that motorists typically experience.

• At 4:00 PM, reflected solar glare would extend from the south facade of the proposed building to the southeast toward Dexter Avenue N and Mercer Street, and from the west façade to the northwest toward Aurora Avenue N. While noticeable, the reflected solar glare on all three streets would be outside of the cone-of-influence for drivers and would not be expected to cause problems for motorists nor differ substantially from periodic glare from stationary and mobile sources that motorists typically experience.

8 U.S. Dept. of Commerce, NOAA, 1992. 9 Ibid.

701 Dexter Avenue N DevelopmentSolar Glare Analysis

Figure 7

September 21st — Autumnal Equinox — Pacific Daylight Savings Time

1” = 268.57’

701 Dexter Ave. N

Figure 8

December 21st — Winter Solstice — Pacific Standard Time

8:30 AM

Note: The solid color within the glare outline repre-sents the actual glare from the proposed building that would be experienced in the surrounding area. The area that is not shaded represents the potential glare area that would be interrupted by an intervening struc-

1” = 268.57’

701 Dexter Ave. N

Dexter Yard 14-story building to be built

Telephone: 206.452.5357 Fax: 206.443.7646

www.eaest.com

In summary, while motorists on Aurora Avenue N, Dexter Avenue N and Mercer Street could experience reflected solar glare from the south, east and west façades of the proposed building, such glare would primarily be outside the cone-of-influence and would not be expected to cause problems for motorists nor differ substantially from periodic glare from stationary and mobile sources that motorists typically experience.

Analysis also indicates that at certain times of the year and times of day – assuming that weather conditions are suitable (e.g., not raining or overcast) -- reflected solar glare from the façades of the proposed 701 Dexter Avenue N Development could be noticeable to residents in buildings near to the project site. While noticeable, no significant long-term impact is anticipated, partly due to mitigating effects such as less-reflective building materials being used, building modulation, as well as the fact that reflected glare, if it occurs, would be limited in duration as a result of sun angle changes associated with the earth’s rotation.

Potential Mitigation Measures

In summary, no significant long term, reflected solar glare-related environmental impacts are anticipated for motorists on Aurora Avenue N, Dexter Avenue N or Mercer Street as a result of the proposed 701 Dexter Avenue N Development and no mitigation measures are necessary. The following measures, however, would help to reduce overall light and glare from the project as it relates to the neighborhood surrounding the site.

• Building façade materials are still in the process of being finalized but are anticipated to include glass and masonry/stone. Reflectivity of the glazing will be dictated by the nature of glass that is employed and the requirements set forth by the City's Energy Code. It is anticipated, however, that no excessively-reflective surfaces (i.e. mirrored glass, or polished metals) that go beyond what is required to meet energy-related code provisions are proposed anywhere on the exterior of the project building.

• The proposed street trees, as well as the use of building materials with relatively low-reflectivity at street level would minimize reflective glare-related impacts to pedestrians and motorists.

• Pedestrian-scale lighting would be provided consistent with code, function and safety requirements. Exterior lighting would include fixtures to direct the light downward and/or upward and away from off-site land uses.

Significant Unavoidable Adverse Impacts

No significant unavoidable adverse impacts are anticipated.

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