(2/5) Impact of Skylights on Indoor Thermal Comfort and Energy Performance in a Non-Residential Building
Collecting data for the project
Figure 1 Arpico Super Center, Wattala.
As stated earlier, the influence of skylights is highly dependent on the geographical location. Since the majority of the found information and conclusions are based on European and American countries, it was required to first examine an actual case from a local building prior to commencing more research. I could arrange a site visit by contacting a representative of the specific supermarket chain. After revealing the purpose of the study, the manager agreed to share some non-confidential information that was readily available.
* All information published here in my personal blog are freely available to anyone visiting the supermarket premises, and do not include any confidential information.
According to the management, the building is a 50,000 square-feet steel structure that was originally constructed as a storage facility for another organization and then acquired by Arpico in 2010. A contractor later installed a set of skylights at the supermarket chain's request, as they wished to experiment with a similar system for the first time. According to the management, the skylights had been leaking water for years, negatively impacting the supermarket's operations. However, they had observed a significant reduction in energy consumption due to the skylights, as artificial lighting systems are rarely used during daylight hours. In addition, the average daily occupancy of the building was determined to be 1,500 on weekdays, around 2,000 on weekends, and more than 3,000 during the April and December holiday seasons. The supermarket is open every day from 08:00 to 23:00, including holidays. The building is equipped with eight air conditioning units. This information was kept confidential by the management. However, according to their understanding, sixty to seventy percent of the building's energy use is accounted for by air conditioning and refrigerators that run continuously. According to the building manager, this building consists of an automated daylight control system that automatically dims artificial lighting when adequate daylight is available during the day. However, due to the system's high sensitivity and the administration's lack of technical expertise in operating it, the system was eventually disconnected. Therefore, the maintenance team manually turns on the lights if daylight is insufficient, or else after 18:00 every day. The management did not provide the monthly power use invoices or any other maintenance-related documentation owing to organizational regulations. Therefore, authorization was granted to visit the building and collect further information and photographs if necessary.
Figure 2 Skylight fixture as seen from inside
The facility is placed in the center of a massive parking lot, with no trees or buildings nearby to provide external shade. The front façade of the building is comprised of glass walls and an automated entrance door; however, the building's other sides are composed of solid walls with no windows. Each glass window is fitted with awning window blinds, as seen in the picture. Even though the site inspection took place on a partly cloudy day, the interior of the building was well-lit without the use of artificial lighting. However, spotlights were employed to illuminate the vegetable and fruit racks, meat and flesh displays, and some of the furniture. The artificial lighting system of the building consists of luminaires with two 2-foot, 18-watt LED batten bulbs each. These luminaires are mounted in a series of cable trays 8 feet above the floor and positioned throughout the building's width. There were approximately 475 luminaires within the building. In addition, air ducts were positioned parallel to the luminaires throughout the building.
As for the skylights, they were installed in a zigzag pattern and were randomly distributed across the roof. There were fifty skylights in all throughout the building. By measuring the distance between the threaded rods used to hang the luminaires and air ducts from the roof, the approximate dimension of a skylight was determined to be 8' x 4'. It should be noted that the skylights were perfectly dispersed, preventing any visual discomfort or shadows within the building. Roofing insulation and a ventilation system were utilized to restrict the amount of heat entering through the roof. In addition, the chosen building contains a small bank branch, a café, and an office area. As they occupy such a minor portion of the building's interior compared to the total floor area, these parts can be disregarded while expanding the studies.
Developing available data to model the building
Since much of the important information required for an accurate study was not exposed due to confidentiality, I had to find them using alternative approaches in order to continue the study. Getting measurements inside the building was not permitted by the administration. Therefore, I used google maps to identify the size of the building. Using satellite view and the distance measurement tool provided by Google, a rough sketch (Figure 4) of the building could be generated with dimensions and coordinates. The total floor area of the building could be calculated as approximately 50,000 square-feet, which agrees with the information provided by the manager. With the assistance of a senior civil engineer in the field and the previously discovered dimensions, the floor to ceiling height of the building could be approximated as 7.5 meters with a roof pitch of 5.7°.
Figure 3 Satellite view of the building
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