Food Lion Perishable Warehouse Conversion to New SSC Office Building Salisbury, North Carolina
35.7°N 80.5°W
Index 5-12
Initial Daylighting and Solar Analysis
13-20 ReďŹ ned Analysis 21-25 Final Assessment and Recommendations
Lab Director Dale Brentrup - Professor of Architecture Lab Assistants Brian Ficker Ben Futrell Rhonda Lowe Andrew Nagle Sarah Weiser
The initial analysis looked at the entire building in order to assess the location of problem areas. The building’s facades, ceiling with skylights, and mezzanine were modeled. A simulation of the annual solar penetration was run, and revealed that each facade of the building allowed an undesirable amount of sunlight in depending on the time of day and year. The western window wall was the most problematic. Year round, this wall allowed low angle sun to penetrate the building from approximately 3 PM until sunset. Morning sunlight was of major concern on the northern facade during summer months. In the winter, low angle sun would pass under the shading devices on the south and west facades. Direct sunlight entered the building year-round through the eleven horizontal skylights. This resulted in visual ‘hot spots’ directly beneath the skylights. Direct sunlight penetration results in large contrast ratios within the interior spaces that adversely affect the visual and thermal comfort of occupants. Three strategies were recommended to counteract these issues. They were: 1) tilt the existing horizontal shading devices downward, 2) utilize automated, sensor controlled shade screens on the interior windows, and 3) reshape the ceiling panel configuration and mezzanine floor to achieve greater daylight distribution. The base case (with exterior shading devices), provided only 45.8% of the space with a daylighting factor of 3 or greater (assuming an average visual light transmittance of 60% for all glazing). It was concluded that further refinement of shading and glazing strategies would more comprehensively address the critical issues of sun control and daylighting.
Initial Daylighting and Solar Analysis
Summary
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image 1 first floor 8am
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image 2 first floor 12pm
summer solstice [dst]
sun patch
equinoxes
sun patch
winter solstice
sun patch
- Concerning direct solar penetration; the western window wall is by far the most problematic. Through all seasons of the year direct low angle evening sun (roughly 3:00 pm to sunset) will pass under the designed horizontal shading deceives and reach deep into the interior, thirty feet in the summer to seventy feet in the winter (image 3).
- During the summer months direct morning sunlight will enter through the northern facade (image 1).
- During the winter months low angle sunlight will pass under the designed horizontal shading devices on the south and west facades and enter the building. The shading devices on the south sufďŹ ciently shade the south facade during the late spring, summer and early fall (image 1, 2 and 3).
- As modeled a signiďŹ cant amount of direct sunlight enters the building year-round through the eleven horizontal skylights. This analysis did not account for diffusive properties of glass or detailed geometry of roof and ceiling design, which will have an impact on the solar load (image 2, 3, 4 and 5). image 3 first floor 4pm
summer solstice [dst]
sun patch
equinoxes
sun patch
winter solstice
sun patch
/ direct solar 7
image 4 second floor 12pm
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image 5 second floor 4pm
summer solstice [dst]
sun patch
equinoxes
sun patch
winter solstice
sun patch
Direct sunlight penetration will result in large contrast ratios on interior surfaces that will adversely affect the visual comfort of occupants. Direct sunlight in work areas will also adversely affect the thermal comfort of employees. As designed the west facade will be the main source of these liabilities. This facade must be more effectively shaded to improve visual and thermal performance. Two recommended strategies are: 1) tilt the existing horizontal shading devices down and 2) place operable shading screens on the interior of windows (images 6, 7 and 8). Although tilting the existing shading devices down will improve their performance, a vertical shading strategy would add ef effectiveness. The above concerns point to the need for further analysis of sun control and daylight performance. sun incident on west facade at 20º altitude above horizon horizontal shading devices (as designed)
shading devices tilted 20º downward
shading devices tilted 40º downward sun can “see” west facade
image 6 28.0% of incident sun shaded
image 7 46.8% of incident sun shaded
image 8 63.2% of incident sun shaded
sun altitude equals 20º above horizon
image 9 sunpath diagram
/ direct solar 9
without shading devices
daylighting factors* 21-24 18-21 15-18 12-15 9-12 6-9 3-6 0-3 image 10 first floor west bays
* a visual light transmittance of 60% was asumed for all glazing
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image 11 second floor west bays
with shading devices daylighting factors* 6.0 - 7.2 4.8 - 6.0 3.6 - 4.8 2.4 - 3.6 1.2 - 2.4 0.0 - 1.2
image 12 first floor west bays
image 13 second floor west bays
-Images 10 and 11 show the analyzed area without shading devices to be over illuminated, resulting in high contrast ratios that cause glare. -Image 12 shows the designed shading devices are effective light diffusers, providing a more uniform distribution of light to space. In image 13 the horizontal skylights provide significant amounts of daylight to the second floor. However, this light is not evenly distributed; resulting in visual “hot spots” directly under the skylights. -As design (with shading devices) approximately 45.8% of the analyzed space has a daylighting factor of 3 or greater. -Further refinement of shading and glazing strategies will more comprehensively address the critical issues of sun control and daylighting.
/ daylighting * a visual light transmittance of 60% was asumed for all glazing
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Based on the initial base case analysis, shading and glazing strategies were further refined to address the issues of sun control and performance. Parametric assessments were run to test how light levels would be affected through reshaping of the acoustical ceiling and repositioning the skylights. In these assessments, a weighted average of 50% visual light transmittance was assumed for all glazing. The objective to maximize area of daylight distribution was evaluated utilizing the LEED threshold daylighting factor of 2. Daylit space percentages in this analysis are more realistic than in the previous analysis, based on the assumed weighted average glass transmittance. The second floor acoustical ceiling obstructs daylight from illuminating portions of occupied space. By reshaping the acoustical ceiling as illustrated on pages 13 and 14, the space can be more uniformly illuminated, eliminating areas of great contrast.
Refined Daylighting Analysis
Summary
In an effort to increase the daylit area, it was necessary to assess the skylights. Skylights allow direct sunlight to penetrate the space, and create visual ‘hot spots’ on the second floor. Changing the orientation and position of skylights was found to more uniformly illuminate the east end of the second floor. Although this increases the illuminance on the mezzanine floor, the skylights are ineffective at securing more daylighting floor area on the first floor.
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Base Case Design location of adjacent view
acoustical ceiling shading occupied zone below 8-9 7-8 6-7 5-6 4-5 3-4
proposed design of acoustical ceiling and skylights
(LEED threshold)
2-3 1-2 0-1
daylighting factors*
* a visual light transmittance of 50% was used for all glazing - all surfaces were assigned a 50% reflective matte finish
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daylight section curve (readings taken 2’6” above floor)
-the second floor acoustical ceiling obstructs daylight from illuminating portions of occupied space, resulting in areas of great contrast
first floor isolux diagram
38.2% of tested space above a daylight factor of 2
7-8 6-7 5-6 4-5 3-4 2-3 1-2 second floor isolux diagram
0-1
daylighting factors*
(LEED threshold)
* a visual light transmittance of 50% was used for all glazing - all surfaces were assigned a 50% reflective matte finish
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Reshaped Acoustical Ceiling location of adjacent view
acoustical ceiling designed to let daylight pass 8-9 7-8 6-7 5-6 4-5
analyzed redesign of acoustical ceiling
3-4 (LEED threshold)
2-3 1-2 0-1
daylighting factors*
* a visual light transmittance of 50% was used for all glazing - all surfaces were assigned a 50% reflective matte finish
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daylight section curve (readings taken 2’6” above floor)
-reshaping of second floor acoustical ceiling creates more uniformly illuminated space
first floor isolux diagram
42.3% of tested space above a daylight factor of 2
7-8 6-7 5-6 4-5 3-4 2-3 1-2 second floor isolux diagram
0-1
daylighting factors*
(LEED threshold)
* a visual light transmittance of 50% was used for all glazing - all surfaces were assigned a 50% reflective matte finish
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Repositioned Skylights
8-9 7-8 6-7 5-6 4-5
analyzed repositioning of skylights
3-4 (LEED threshold)
2-3 1-2 0-1
daylighting factors*
* a visual light transmittance of 50% was used for all glazing - all surfaces were assigned a 50% reflective matte finish
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daylight section curve (readings taken 2’6” above floor)
-changing the orientation and position of certain skylights more uniformly illuminates east end of second floor
first floor isolux diagram
42.9% of tested space above a daylight factor of 2
7-8 6-7 5-6 4-5 3-4 2-3 1-2 second floor isolux diagram
0-1
daylighting factors*
(LEED threshold)
* a visual light transmittance of 50% was used for all glazing - all surfaces were assigned a 50% reflective matte finish
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Using the methods demonstrated in previous analysis, the final window wall and shading device configuration were tested to assess how effectively they performed. Direct solar analysis was performed on two facade designs based on previous evaluation. From the incident sun assessment it was observed that the configurations performed equally well, but it also brought attention to the need to differentiate between the ‘Daylight Window’ and the ‘View Window’ because of the difference in the amount of sunlight that penetrates each part. Tests were performed to determine the best method of reducing glare from the window wall. The previous studies conducted on light levels through the building were reproduced with 36% visual light transmittance for all glazing. While skylights are able to effectively daylight the mezzanine, the mezzanine prevents a large portion of the third floor from receiving light. Where the mezzanine is not blocking the light, the first floor is able to be daylit effectively. A final glare analysis was conducted using High Dynamic Range Photography to evaluate the effective use of interior screening shades on the interior of the window wall. This comparative analysis was done to demonstrate that a dark black/brown shade with a 5% open weave facing toward the interior will perform better than a lighter screen in both reducing glare and providing the greatest field of vision, allowing for a greater occupant comfort probability.
Final Assessment and Recommendations
Summary
Recommendations 1. Reshape the second floor acoustical ceiling to uniformly illuminate the space. 2. Reposition the skylights to increase performance in the mezzanine. 3. Use automated, sensor controlled, dark colored shade screens to reduce glare. 4. Use separate automated shade screens operated by an open loop radiometer sensor.
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������������������� Direct Solar Analysis
Daylighting Window
Two analyses were run based on previous discus�������������������������������������� sions of the facade. The first facade was comprised ���������������������������������������������� of three - 3’-0” louvers and one - 2’-0” louvre sloped ������������������������������������������ at 30°. The second was comprised of two - 3’-0” ����������������������������������������� louvers and three - 2’-0” louvers sloped at 30°. The ����������������������������������������� second alternative was selected.
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The difference in light transmittance between the two analyses was 5%. This amount is negligible, �������������������������������������� considering the time period that penetration oc��������������������������������������� curs (reference page 5). From a light transmittance ��������������������������������������� standpoint, the results of both designs are fundamentally the same. �����������������������������������������
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Due to the window’s configuration, interior screening is recommended for both the daylighting window and view window to eliminate glare. Using separate automated shade screens for each window would produce the most desirable results. View Window
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Sunlight ������Direct ������������� Blocked
Sunlight ������Direct ������������� Blocked
Daylighting Factor Previous studies of the daylight analysis were reassessed. Using computer modeling tools, the daylight was measured using a 36% visual light transmittance for all glazing. All wall surfaces for this model were assigned a 50% reflective matte finish. These graphs show the daylighting factors through the space, with the LEED threshold of ‘2’ highlighted in green. 42% of the floor area tested above a daylight factor of 2.
LEED Threshold
Daylighting Factors
9 8 7 6 5 4 3 2 1 0
The repositioned skylights are able to effectively daylight the mezzanine, but do not effect the first floor. The mezzanine prevents a large portion of the first floor from being effectively daylit under any window configuration scenario. Where the mezzanine is not covering the first floor, the first floor is able to be effectively daylit.
Daylight Section Curve (readings taken 2’6” above floor)
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Glare Analysis Contrast Range of Uncontrolled Aperture
Design Objective (within 4:1 ratio)
(Figure 3) (Figure 1)
(Figure 2)
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Contrast and View In general, more light and a lower horizon are visible from a first floor view (Fig. 1). The combination of sunlight and skylight will be experienced at an even higher ratio through the daylighting zone of glazing in the window wall (Fig. 2). High Dynamic Range (HDR) photography was used to produce a glare analysis and measured luminance levels (fl.) that reveal much broader ratios than is desirable from both first floor and mezzanine views (Fig. 3). Automated interior shade screens placed at both the daylighting window and the view window will produce the most efficient increase in visual comfort.
Device Comparison and Performance Analysis Ecoveil 1363 Grey (Figure 4)
Comparison A broad ratio of external hot spots to interior dead spots (darkness), where measured, will create a high contrast and will result in glare and visual discomfort. An ideal maximum ratio is 4:1. The physical model was analyzed for glare through HDR photography . Studies were conducted of two separate interior shade screens with identical light transmittance (5% openness) but having different interior surface colors. The resulting representations illustrate that the darker material will enhance the view while the lighter material is diffusive, and therefore, more restrictive to extending the view through the window. (Fig 4 & 5).
Performance A separate glare analysis was conducted through HDR with each material. The recorded performance in reduced glare and contrast was the same for both materials and lowers the threshold to within the design objective.
While both materials obtained the objective to reduce glare, a darker material on the inside will provide the greatest ďŹ eld of vision (illustrated in Figure 5), which allows for a greater occupant comfort probability. Ecoveil 1354 Black / Brown
(Figure 5)
Material Performance Approx. 6 .
(Figure 6)
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