Anoka County Public Safety Campus Energy & Daylight Analysis
Abraham & Associates completed a series of Energy and Daylighting Studies for the Proposed Anoka County Public Safety Campus Project in Andover, Minnesota. Daylighting Illumination simulations of overcast sky conditions and an irradiance study using a heliodon device coupled with video capture equipment were conducted at the University of Minnesota - College of Design Daylighting Lab in Minneapolis. The areas studied were those that are of key importance in implementing successful daylighting strategies.
The proposed design performed satisfactorily having ample daylight in all of the high ceiling spaces on a year round basis under varying sky conditions. The portions of the building which do not benefit from perimeter windows and which are restricted to ceiling heights of 10’ or lower enjoy only a marginal daylight level and will not have the same visual quality except for the locations with clerestories. Light Shelves significantly improved the illumination uniformity and visual quality of the SE Library area where they are planned. Studies of the design both with and without lightselves were performed using the methods described below. A summary of the benefits studied are listed below.
Conclusions & Recommendations
• Light shelves are effective and should be incorporated in the design as proposed.
• Clerestories are critical to the interior areas of the North Library and Mainstreet.
• Skylights added to the existing low ceiling area of the library would provide a good daylighting solution to an area that will otherwise not benefit from any significant amount of daylight.
• Light controls in addition to light shelves will be necessary at most of the curtainwall perimeter glazing due to excessive brightness and contrast ratios.
• The glazing selected for this design is optimal for a day-lighting application of this type.
This Daylighting Studies conducted for the Anoka County Public Safety Campus in Andover, Minnesota were performed using the methods outlined below. Daylighting Illumination simulations were performed under an overcast sky (using an artificial sky box) and a solar beam irradiance study using a heliodon device and video capture equipment at the University of Minnesota - College of Design Daylighting Lab in Minneapolis.
The diffuse (overcast) sky illuminance study was conducted at the University of Minnesota Daylighting Lab using a calibrated and certified 8 ft. x 8 ft. Mirrorbox type artificial sky designed by daylighting expert Susan Ubbelohde, Professor of Architecture, University of California Berkeley campus. This Mirror Box Artificial Sky simulates a C.I.E. overcast sky approximately 3 times brighter at the zenith than at the horizon.
This work also utilized a Campbell Scientific eight-channel data logger in combination with seven 1” diameter Li-cor flat plane corrected photo sensors. A digital camera was used to capture still shots of the building interior at various vantage points during the simulation. The Illumination studies were conducted using the Daylight Factor Method (also referred to as the C.I.E. or B.R.S. method). The physical model used accurately represented all daylit portions of the proposed design, excluding the garage, at 3/16” = l’-O” scale. The interior floor and exterior ground reflectance was simulated using museum board of approximately 25-30% surface reflectance.
Certain variations of the design were studied including with and without light shelves and the skylights being considered for the existing low-ceiling portion of the library space. In addition readings were taken at floor level in the stacks areas at several locations.
Methodology for Heliodon Direct Beam (Irradiance) Study
A direct beam (clear sky) daylight analysis was conducted at the University of Minnesota Daylighting Lab in Minneapolis to ascertain patterns of direct sunlight penetration into the space which could cause visual disability or discomfort. This work utilized a heliodon, or daylong solar simulation table, a direct beam artificial light source, and including an AV Computer system and miniature video camera. After positioning the model to correct solar orientation on the Heliodon, the multiple axes of rotation capability of the heliodon allowed simulation of the movement of our stationary “sun” relative to the model. The miniature video camera was positioned in ten different locations both interior and exterior while simulations were performed for the complete solar day on June 21, March/September 21, and December 21. These simulations were recorded with voice overlay noting the day and signaling the passage of each hour. Each day was then analyzed for times of potential problems and these were generally recorded as digital still shots recording the appropriate date and time.