1445+1455 West Georgia St. Solar Reflection Analysis

Reflected Heat Screening Analysis 1445+1455 West Georgia St.

November 2, 2016 RWDI # 1600058

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1445+1455 West Georgia St. Solar Reflection Analysis Vancouver, BC

Reflected Heat Screening Analysis

RWDI #1600058

November 3, 2016

SUBMITTED TO

SUBMITTED BY

Rowan Williams Davies & Irwin, Inc.

Suite 280 – 1385 West 8th Avenue

Vancouver, BC, Canada V6H 3V9

Tel: (604) 730-5688

Jon Barratt, P.Eng.

Project Manager

[email protected]

Ryan Danks, B.A.Sc., P.Eng.

Senior Project Engineer

[email protected]

Dawn Guspie

Associate

James KM Cheng Architects

Suite 200-77 West 8th Avenue

Vancouver, BC, V5Y 1M8

Tel: +1 (604) 873 4333

[email protected]


November 2, 2016 RWDI # 1600058

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EXECUTIVE SUMMARY

RWDI was retained to provide a screening level analysis of

the solar reflections which will emanate from the proposed

1445+1455 West Georgia Development in order to assess

the potential of these reflections to cause thermal impacts

on people and property in the surrounding neighbourhood.

Specific materials have not been decided upon, so RWDI

has made suitably conservative assumptions regarding the

reflectivity of the facade based on our experience with other

facades in a similar climate.

The reflections from the proposed development were

simulated hour-by-hour for an entire year. The peak

intensity of the reflections as well as their frequency of

occurrence were computed. Overall, we found that the

reflections caused by this development are typical of what

would be seen from any contemporary building. The shape

of the building does not act to concentrate the reflections in

a particular area, thus we do not anticipate heat gain related

issues.

The reflections which do occur are generally infrequent

occurring at most 10% of the daytime hours in the

pedestrian realm, with Nicola Street seeing the most

frequent reflections. The upper floors of the 1487 West

Pender Street tower will also experience frequent

reflections, though again these reflections are unlikely to

lead to significant thermal impacts.


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1. INTRODUCTION

This report provides the computer modelling results of

reflected sunlight from the proposed 1445+1455 West

Georgia St. development, which will consist of a 46 story

tower located at the intersection of West Georgia and West

Pender Streets in Vancouver, BC. It is our understanding

that the development will be surrounded by typical urban

spaces such as busy roadways and other buildings.

RWDI has been retained to investigate the thermal impact

that solar reflections emanating from the proposed

development will have on the surrounding urban realm.

This report outlines the results of a screening level of

analysis which predicts the peak intensities and frequencies

of the reflections for this tower, which is used as an

indicator for potential thermal issues reflected to reflected

light.

Figure 1 – Aerial photograph of existing site and surroundings - project site

indicated. (Courtesy of Google earth™)

Proposed

Project Site


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2. BACKGROUND – URBAN REFLECTIONS

It is a common experience in urban areas to occasionally experience

reflected light from glass and metallic surfaces. The interactions

between a building and the sun can lead to numerous visual and

thermal issues.

Visual glare can:

• impair the vision of motorists and others who cannot simply look

away from the source because of an important activity;

• cause nuisance to pedestrians or occupants of nearby buildings;

and,

• create undesirable patterns of light throughout the urban fabric.

Heat gain can:

• affect human thermal comfort;

• be a safety concern for people and materials, particularly if insolation

levels are high as a result of focusing of multiple reflections to a

single point; and,

• alter heating and cooling loads of conditioned spaces affected by the

reflections.

The most significant safety concerns with solar reflections

occur with concave facades which act to focus the reflected

light in a single area. In contrast, convex facades act to scatter

reflections in a “pinwheel” pattern. RWDI does not expect

issues with solar focusing to be present in this case because all

the glazed surfaces on the towers are planar.

To quantify the impact of solar reflections from the

development, it is important to understand four critical

characteristics:

1. Frequency (how often glare events occur);

2. Duration (how long each instance of glare lasts);

3. Intensity (how “bright” the events are based on a

combination of solar intensity, surface size and orientation,

and the distance from the point of interest); and,

4. Location (does the reflection fall on a sensitive location)


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3. METHODOLOGY

RWDI assessed the potential reflection issues using computer

modelling based on RWDI’s proprietary software called Eclipse, as

per the steps outlined below:

• A 3D model of the area of interest (as shown in Figure 2) was

developed and subdivided into many smaller triangular patches

(see Figure 3). The reflective properties of the various surfaces

were defined using the data presented in Appendix A.

• For each hour in a year, the expected solar position was

determined, and “virtual rays” were drawn from the sun to each

triangular patch of the 3D model. Each ray that was considered to

be “unobstructed” was reflected from the building surface onto a

the surrounding airspace. A radius of 500m around the

development was assessed in this analysis.

• This analysis used “clear sky” solar data at the location of

Vancouver International Airport. That is to say, a data set where it

is assumed that no cloud cover ever occurs, which provides a

“worst case” scenario showing the full extent of when and where

glare could occur.

• Finally, a statistical analysis was performed to assess the

frequency, and maximum intensity of the glare events.

Figure 2: 3D Computer Model of the Proposed

Development Along with the Surrounding Area

Figure 3: Close-up View of the Model, Showing Surface Subdivisions

on the Proposed Building


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4. ASSUMPTIONS AND LIMITATIONS

Key assumptions and simplifications of the modelling process included:

Model

• The analysis was conducted based on the geometry provided by James KM

Cheng Architects to RWDI on September 19, 2016. It should be noted that this

study is highly dependent on building geometry, and any significant changes to

the buildings’ geometry are likely to require a new analysis.

• Potential reductions of solar reflections due to the presence of vegetation, or

other non-architectural obstructions, were not included.

• Only a single reflection from the development is included in the analysis. That

is to say, light that has reflected off several surfaces is assumed to have a

negligible impact.

• Only the proposed building was considered as potentially reflective in the

current model. Existing structures were included for shading purposes but were

not considered reflective.

Material Properties of Reflective Elements

• It is RWDI’s understanding that the primary reflective element on the facade of

this building will be glazing and that the exact type of glazing unit has not been

selected yet.

• As such RWDI has assumed that the glazing will reflect 40% of incoming solar

energy. This is a typical level of solar reflectivity for high performance glazings

which employ low-emissivity coatings.

• Metal elements were also noted in the provided drawings. As the final finishing

of the metal has not been decided upon, we have assumed a relatively matte

finish, typical of contemporary architecture with a specular reflectance of 10%.

• The locations of both the metallic and glazed elements are presented in Figure

4 on the following page.

• The results presented here are sensitive to the reflectivity values. Should the

facade materials that are ultimately selected have full spectrum reflectances

which are significantly different from these assumed values, a new analysis

may be needed.

Meteorological Data

• Irradiance levels were computed using “clear sky” solar data at the

location of Vancouver International Airport. This data uses mathematical

algorithms to artificially derive solar intensity values for a given latitude

and altitude, ignoring local effects such as cloud cover.

Radiation Model

• The analysis conducted in this report is only applicable to the thermal

impacts of solar radiation (i.e. ultraviolet, visible and infrared

wavelengths) on people and property in the vicinity of the development.

It does not define the visual impact of solar reflections (i.e. glare) on

pedestrians or motorists, nor does it consider the impact of the building

related to other forms of radiation, such as cellular telephone signals,

RADAR arrays, etc.


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4. ASSUMPTIONS AND LIMITATIONS (CONT’D)

Figure 4: Diagram indicating locations of glazed and metallic facade elements.

View from north east (left) and southwest (right)

Glazing

Metal

Non-

reflective

Glazing

Non-reflective

Stone


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5. CRITERIA – HEAT GAIN

Solar Focusing

Solar focusing is a phenomenon where more than one reflection falls on

the same point. This can occur when reflections from multiple flat surfaces

converge at a single point, but is more common on inward-curving

(concave) facades. Although this feature is not present in this project, care

must be taken to understand the potential solar insolation levels that

reflections from the building may create.

There are currently no existing criteria or standards that define an

“acceptable” level of reflected solar radiation from buildings. RWDI has

conducted a literature review of available scientific sources to determine

levels of solar radiation that could be considered acceptable to an

individual in the urban realm1.

Irradiance Limits – People

The U.S. National Fire Protection Association (NFPA) sets thermal

radiation criteria which define a tenable environment for people exiting a

fire event in a building or tunnel (NFPA 130). They set the upper limit for

thermal radiation at 2,500 W/m². Irradiance levels at or below this value can

be tolerated for at least several minutes without significantly affecting an

individual’s ability to escape from a fire event. That being said, skin

damage (sun burns) and pain can occur at this 2,500 W/m² threshold.

According to British fire standards2, the onset of pain for bare skin can

occur within 30 seconds at an irradiance of 2,500 W/m². This threshold

closely matches the irradiance exposure guidelines published by the U.S.

Federal Emergency Management Agency (FEMA), summarized in Table 2.

This table also includes the length of time required before the onset of a

second degree burn due to thermal radiation. It should be noted that these

numbers are guideline values only, and that in reality many factors (skin

color, age, clothing choice, etc.) influence how a person reacts to thermal

radiation. For our work RWDI have established 2,500 W/m2 as a ceiling

exposure limit.

Due to the public nature of the building, the significant variability in both

how individuals will respond to thermal irradiation exposure, and the fact

that individuals may not fully appreciate the impact of the reflection until

they are exposed, it is RWDI’s opinion that a lower threshold value may

be more appropriate for human thermal comfort.

Thus, we suggest that for ground level areas where the public will be

present, reflected irradiance levels should not exceed 1,500 W/m². This

threshold value is a conservative one, which is based around the

potential for damage to human skin, requiring several minutes of

exposure before damage or discomfort potentially occurs.

For these reasons, we have applied a short-term exposure threshold

of 1,500 W/m² for our work.

1 Danks, R., Good, J., & Sinclair, R. (2016). Assessing reflected sunlight from building facades: A literature review and proposed criteria. Building and Environment, 103, 193-202. 2 The application of fire safety engineering principles to fire safety design of buildings – Part 6: Human Factors’ PD 7974-6:2004, British Standards Institution 2004. 3 Federal Emergency Management Agency, U.S. Department of Transportation, and U.S. Environmental Protection Agency. 1988. Handbook of Chemical Hazard Analysis Procedures. Washington, D.C.: Federal Emergency

Management Agency Publications Office.

Thermal

Irradiance

[W/m²]

Time To Onset

of Pain

[s]

Time To Onset of

Second Degree Burn

[s]

1,000 115 663

2,000 45 187

3,000 27 92

4,000 18 57

5,000 13 40

6,000 11 30

8,000 7 20

10,000 5 14

12,000 4 11

Table 2: Time for Physiological Effects on Bare Skin at Specific

Thermal Radiation Levels3


November 2, 2016 RWDI # 1600058

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4 Building Research Establishment: ‘Fire spread in car parks’ BD2552, Department of Communities and Local Government 2010 5 SFPE Handbook of Fire Protection Engineering 4th Edition NFPA/SPFE 2008 USA 6 V. Babrauskas ‘Ignition Handbook’ Fire Science Publishers + SFP , 2003 7 E Ungar, K Stroud ‘A New Approach to Defining Human Touch Temperature Standards’ National Aeronautics and Space Agency , 2010

5. CRITERIA – HEAT GAIN (cont’d)

Irradiance Limits – Property

The impact of solar irradiance on different materials is primarily based on

the temperature gains to the material which can cause softening,

deformation, melting, or in extreme cases, combustion. These temperature

gains are difficult to predict as they are highly dependent on the convective

heat transfer from air movement around the object and long-wave radiative

heat transfer to the surroundings.

Generally, irradiance levels at or above 10,000 W/m² for more than 10

minutes are required to ignite common building and automotive materials in

the presence of a pilot flame. That value increases to 25,000 W/m² when

no pilot flame is present4,5,6. However, some materials like plastics and

even some asphalts may begin to soften and deform at lower

temperatures. For example, some plastics can deform at a temperature of

140°F (60°C), or lower if force is applied. The applied force typically comes

from the thermal expansion of the material, the force of gravity acting on

the material or an external mechanical force (i.e. someone or something

pushing or pulling on it).

NASA7 defines an upper limit of 111°F (44°C) for surfaces that require

extended contact time with bare skin. Surface temperatures below this limit

can be handled for any length of time without causing pain.

Because of the difficult nature of determining material temperatures,

RWDI takes a conservative approach and uses a threshold value of

1,000 W/m² which is approximately the peak intensity of natural sunlight

that could be expected to occur over the course of a year. Intensities

beyond this value exceed the levels of irradiance that common exterior

building materials are presumably designed for, and depending on the

duration, may lead to deformation or damage. Though, as noted this

would depend heavily on environmental conditions and the material

properties of the exposed object or assembly.


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6. RESULTS

The following plots are presented in this section:

• Peak Annual Reflected Irradiance

These plots display the annual peak intensity of the reflections

emanating from the development within the surrounding airspace.

It is important to note that these plots show the peak intensities of

all reflections that occur over the entire year. In order to attain a

better understanding of the impact of the solar reflections on the

development, other factors must be considered such as the

frequency and duration of the reflections.

For full spectrum reflectance, RWDI considers 1500 W/m² as a

short term thermal comfort threshold and reflections above 2500

W/m² as a human safety threshold (as defined in Section 5 – Heat

Gain Criteria). 800 W/m² is a typical peak intensity from direct

sunlight which one would expect to experience on a given day.

The results are presented in plan view at pedestrian height (i.e.

1.5 m above local grade) and well as in a volumetric format. The

plan view results are presented as coloured contours based on

predicted peak intensity and the volumetric views are used to

highlight areas which exceed RWDI’s threshold values.

• Percentage of Daylit Hours (or Frequency) of Reflected Light

This plot identifies the locations most frequently impacted by reflections

of any intensity. Like the peak annual reflected irradiance plots, the

results are presented both in plan view at pedestrian height (i.e. 1.5 m

above local grade) and well as in a volumetric format. The plan view

results are coloured based on frequency and the volumetric views are

used to highlight areas which experience particularly frequent reflection

impacts


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Peak Annual Reflected Irradiance (Plan view – 1.5m above local grade)

Peak Annual Reflected Irradiance [W/m²] Peak Annual Reflected Irradiance [W/m²]

500 0 250 750 >1000 1000

1000 W/m² represents a typical

intensity for direct sunlight.


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Reflection Frequency (Plan view – 1.5m above local grade)

Percentage of Daytime Hours With Reflection

0.0 7.5 15.0 22.5 30.0


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Peak Annual Reflected Irradiance (Volumetric)

Peak Annual Reflected Irradiance [W/m²] Peak Annual Reflected Irradiance [W/m²]

400 0 200 600 >800 800 700 500 300 100

No areas were found which exceed

RWDI’s short-term or safety thresholds.


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Reflection Frequency (Volumetric)

Areas Which Experience Reflections More than 10% of Daytime Hours


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7. OBSERVATIONS & CONCLUSIONS

1. Like any contemporary building, the reflective surfaces of the 1445-1545

West Georgia Street development are naturally causing solar reflections

in the surrounding neighborhood.

2. The planar nature of the facades prevent reflections emanating from the

development from focusing (concentrating) in any particular area. No

areas in the surrounding neighbourhood were found to exceed RWDI’s

reflection intensity criteria

3. The overall frequency of reflections is generally low. The most frequent

impacts at grade level are along Nicola Street, however as noted above

the intensity of the reflections does not pose a risk of thermal impacts and

the reflections occur at most 10% of the daytime hours.

4. Some adjacent buildings, particularly 1487 West Pender Street, will also

be impacted by reflections relatively frequently, though again this does

not represent a risk of thermal impacts to people or property.

5. RWDI does not anticipate any heat gain issues on people or property due

the reflections from this development.

The results presented in this report are dependent on both the form of

the facade and the reflective properties of the materials with which it is

clad. Should changes to the form or materiality of the facade occur, a

reanalysis may be required. It is the responsibility of others to contact

RWDI to initiate this process.

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