Existing Lighting Conditions

Transcription

1 Casey Schardt Lighting/Electrical Option Howard County General Hospital, Columbia, MD Primary Faculty Consultant: Dr. Mistrick Technical Assignment #1. October 9, 2003 Existing Lighting Conditions The overall lighting system for Howard County General Hospital is almost exclusively fluorescent, except for some specialized medical situations, such as surgical task lighting. Some metal halide fixtures are also used in the parking areas. The hospital has a very functional design. Aesthetically, it is relatively simple. It is easy to maintain with many of the same few fixtures found throughout and with consistent lamping. There are three types of lamps used in almost all fixtures: F32T8 and F17T8 linear fluorescent, and F26DBX compact fluorescent. The lighting system is designed with other maintenance issues in mind as well. For example, it is important that the fixtures be easy to clean, especially in spaces where airborne dirt and dust particles are a specific concern. All of the lighting operates at 277 volts. The standard correlated color temperature for all lamps in the hospital 4100 Kelvin. The lighting power densities in the hospital seem a little high because the system delivers a fair bit more light than is required. This is beneficial, especially considering that a large percentage of their patrons are elderly people, many of whom may be visually impaired. Even those who do not a visual medical condition, they require more light to see properly simply due to the aging of the eye. The lighting system is direct in most spaces. This increases the efficiency of the system but can create dark ceilings and convey a dismal appearance. High surface reflectances help to combat this problem. Adding some direct light components would also remedy this problem, and would increase the uniformity of light distribution throughout the space providing a more pleasant and more comfortable atmosphere. Many of the spaces have relatively plain surfaces. Objects could be added to the walls with accent lighting to increase visual interest in many areas, particularly in waiting rooms and other areas where people may be long periods of times, with little else to occupy them. For any institution such as this one, money is always an issue as they are likely operating on a strict budget and will be looking to reduce expenses wherever possible without sacrificing their functionality. With the high light levels that are provided, it seems that there could be areas where the efficiency of the lighting system could be increased to help cushion the excess power usage. For example, 1 x4 parabolic fixtures are used in most of the corridor spaces. These fixtures are considerably less efficient than 2 x4 and 2 x2 fixtures. A certain downlight is used extensively throughout the hospital. The lamping for this downlight is 2-F26DBX compact fluorescent lamps oriented horizontally. This is also considerably less efficient than the same downlight with one vertical lamp, which could be of a higher wattage. Using more efficient fixtures would

2 not only reduce the energy consumption of the building, but could also reduce the construction costs because fewer fixtures may be needed to obtain the same light levels. The controls found throughout the hospital are primarily simply toggle switches with some dimming applications in a few areas where the task specifically requires it. This is another area where energy costs could be cut down by providing dimming in a variety of other spaces where the occupants could determine how much light they need. Adding dimming controls to a variety of other spaces would definitely increase the initial construction costs of the building, but in the long run, could cut down on the energy consumption and therefore reduce their electric bills. The actual finishes for many of the spaces were not available, so reflectances and other information was assumed based on what could be gathered from the drawings and from pictures of different areas in the building. The illuminance calculations were acquired from building relatively simple models of each space in AGI-32 and using the photometric reports for the light sources as specified in the lighting fixture schedule. The individual ballasts used were not specified, but the performance criteria were given in the electrical specifications. To determine the performance of the ballasts, the performance data for a ballast matching this criteria was used. These criteria include A sound rating, high power factor (>95 %), rapid start, maximum total harmonic distortion of 10%, and a minimum ballast factor of 85 %. Light loss factors were determined using the calculations from the IESNA Lighting Handbook. The downlights and parabolic louvered fixtures were considered type III. The environment was considered very clean and the light was direct. The ballast factors for the linear fluorescent fixtures is 0.88, and for the compact fluorescent fixtures, it is The lamp lumen depreciation was 0.9 for linear fluorescent and 0.85 for the compact fluorescent. The luminaire dirt depreciation is 0.9. The room surface dirt depreciation was determined using the room cavity ratio for each individual space. For the indirect/direct pendants, the luminaire dirt depreciation was 0.93 for a type VI fixture in a very clean environment. For a semi-indirect distribution the room surface dirt depreciation was All of the light loss factors were multiplied together to obtain the total light loss factor. For example, for the 2 x4 louvered fixture in the nurse station corridor: LDD=0.9, LLD=0.9, RSDD=0.96 (RCR=8.5), BF=0.88, therefore the total LLF=0.68.

3 Nurse Station Courtesy of Leach Wallace Associates The existing lighting for the nurse station includes both direct and indirect components. There are 8-inch compact fluorescent downlights recessed in a bulkhead above the desks, with indirect-direct circular pendant fixtures hanging over the center of the spaces. All of the downlights are on the critical power branch so that the nurse station can remain operational in the event of an interruption of the normal power service. The nurse station is open on all four sides to the surrounding corridor which features compact fluorescent downlights on three sides, with 2 x4 parabolic fluorescent fixtures on the fourth side. About a third of these fixtures are on emergency power. All luminaires in the space are controlled by several toggle switches located on the column adjacent to the

4 nurse station. Each type of luminaire is controlled by a different switch allowing for various levels of light to be achieved. There is no daylight available in this space. The existing power density for the corridor space is 0.96 watts per square foot. For the actual nurses work space, the power density 2.24 watts per square foot. Refer to the lighting plan above for further details on the layout of the lighting system. See the luminaire schedule below for details on luminaires such as fixture names and lamping information. Courtesy of Leach Wallace Associates A5 B1 D1 Courtesy of Courtesy of Courtesy of The ceiling of the corridor is a 2 x2 suspended ceiling tile grid with an 80 percent reflectance. The grid is suspended nine feet above the floor. A gypsum wall board bulkhead with an 80 percent reflectance surrounds the nurse station at 7-2. Inside of this bulkhead, where the work spaces are, is another 2 x2 ceiling tile grid at nine feet above the floor. The walls will be painted a neutral light cream color with a reflectance of about 65 percent. The work surface of the nurses desks is a light colored matte solid polymer with a reflectance of about 40 percent, and is at 30 inches above the floor. The surface of the part of the desk shared by the nurses and the patients is a dark colored semi-specular wood finish with a reflectance of about 15 percent, and the work surface is at 36 inches above the floor. Design Criteria The tasks performed in this space include both paper tasks as well as VDT use. The IES recommends a general horizontal illuminance level of 30 footcandles and a local illuminance of 50 footcandles on the desk surface, which should be fairly uniform. A

5 vertical illuminance level of five to ten footcandles is also recommended. Direct glare is an important issue, as well as reflected glare from both the work surface and the VDT screens. With the nurse station be open to the surrounding corridor, the source-task-eye geometry must be considered both within the nurse station and from the sources in the corridor. Uniformity of the room surfaces is also important as they can also create veiling reflections in the VDT screens. Color and modeling of faces are also important for interaction between nurses and patients. The central charting area is surrounded by walls, and the tasks here are similar, but feature more extensive VDT use. For this reason, the illuminance levels are slightly less important, but the VDT criteria such as uniformity of surface luminances are even more important than the rest of the nurse station. For the surrounding corridor area, the recommended illuminances are only three to five footcandles. While little vertical illuminance is required for the corridor space, brighter surfaces will make the space appear less confined and less dreary. As with any space in a hospital, a pleasant overall appearance is important to make a potentially depressing place as comfortable as possible. Controls for this space are also an issue as energy can be saved when the nurse station is not fully staffed, and at night, when the corridor is not continuously occupied. According to ASHRAE/IESNA Standard , the maximum allowable power density for the nurse station is 1.8 watts per square foot with a possible 0.35 watts per square foot additional allowed if the system complies with VDT criteria. The corridor space is allowed 1.6 watts per square foot. Existing Light Analysis Overall View Illuminances in the surrounding corridor space

6 Nurses Work Area Charting Area Critique of existing conditions The nurse station features a variety of fixtures that allows the lighting system to serve the function of the space very well by delivering different layers of light. The direct and indirect components allow for a pleasant atmosphere with the pendants

7 providing ambient light and brightening the space, the downlights deliver the most light where it is needed most, to the work surfaces. This also provides uniformity of the surfaces which is important aesthetically and especially to prevent veiling reflections in VDT monitors. It might help to provide controls with dimming capabilities so that the users can control the amount of light being delivered. There is a generous amount of light that may be altered to make the space more comfortable, while conserving energy at the same time. Another improvement that could be made is to add some indirect light to the corridor spaces to prevent a dark ceiling and tops of walls which conveys a dreary appearance. The power consumption for this space does fall within the requirements. The work space is high, but the corridor space is considerably lower than the maximum allowable. The entire space is compliant as a whole and there is some spill light between these spaces which balances the power densities out.

8 Lobby/Reception/Waiting Area Courtesy of Leach Wallace Associates The lobby area for the emergency department includes several different types of spaces that are integrated together. All luminaires in this space are direct fluorescent fixtures. The reception area includes two 2 x4 parabolic fixtures above the space, with 8-inch compact fluorescent downlights mounted in the bulkhead above the desk area. All of these fixtures are on the critical power branch to allow the reception area to operate at all times. The adjacent waiting area and café areas have 8-inch compact fluorescent downlights overhead providing the ambient light, with a few owner-furnished table lamps placed on the tables in the waiting area to give the space a more comfortable residential feel, and provide additional reading light. A few of the downlights are on emergency power. The corridor running through the space is also illuminated by the same downlights, with some on emergency power. The lights at the reception desk are all controlled by a toggle switch at the door behind the desk. The downlights in the waiting area are controlled by a toggle switch near the building entrance. Those in the corridor are controlled by three-way toggle switches at each end of the waiting area. The power density for the reception area is 3.04 watts per square foot. The waiting area has a power density of 1.75 watts per square foot, excluding the table lamps. Assuming 60-watt

9 incandescent bulbs in the table lamps, it brings the lighting power density to 2.24 watts per square foot. The café space has a power density of 1.93 watts per square foot, and the corridor space in between along with the entry area has a power density of 1.48 watts per square foot. Courtesy of Leach Wallace Associates Courtesy of A6 Courtesy of The majority of the ceiling is a 2 x2 suspended ceiling tile grid at 10 feet above the floor. The tile has a reflectance of about 80 percent. There is a gypsum wallboard bulkhead running around much of the perimeter of the space at 9 feet above the floor. Another gypsum wallboard bulkhead will be above the receptionist s desk at 7-2 above the floor. The walls will be of a light cream color with a reflectance of about 65 percent. The work surface of the receptionist s desk is a light colored matte solid polymer with a reflectance of about 40 percent, and is at 30 inches above the floor. The surface of the part of the desk shared by the receptionists and the patients is a dark colored semispecular wood finish with a reflectance of about 15 percent, and the work surface is at 36 inches above the floor. There will be framed artwork hanging on the walls in the waiting area which will require adequate vertical illuminance, and will need to be considered for specular reflections from the light sources. Below is photograph serving as an example showing the typical finishes in the building for a reception desk. B1

10 There is a limited amount of daylight available in the space. The waiting area has windows down its length on one side. This glass is tinted however, faces a northern exposure, and is shielded by the overhang in front of the entrance to the emergency department. The glazing is tinted polished plate glass with a transmittance of about 50 % and a reflectance of about 5 %. Some light may also come in through the vestibule that serves as the entrance to the building. Design Criteria With this space being the first thing that many people see when arriving at the hospital, this should be a very welcoming and impressive space. People coming to the hospital could be worried, intimidated, depressed, or under a lot of stress. Therefore these spaces should be as uplifting as possible to soothe these emotions and make their visit as pleasant as it possibly can be. The critical tasks at the reception desk are similar to that of the nurse station including both paper and VDT tasks. The IES recommends a general illuminance level of 30 footcandles and a local illuminance of 50 footcandles on the desk surface, which should be fairly uniform. A vertical illuminance level of five to ten footcandles is also recommended. Direct glare is an important issue, as well as reflected glare from both the work surface and the VDT screens. With the reception desk open to the waiting area on the other side, the source-task-eye geometry must be considered both from luminaires within the reception area, and from the sources in the opposing part of the corridor. Uniformity of the room surfaces behind the receptionists is also important as they can

11 also create veiling reflections in the VDT screens. Color and modeling of faces are also important for interaction between receptionists and the patients. The waiting area and café areas involve tasks such as light reading and conversation. These spaces require a general illuminance of ten footcandles, with a local level of 30 footcandles available for reading. Color and modeling of faces is important for interaction between people in the space. Controls can be used to provide these differing levels as desired by the users and therefore conserve energy when the 30 footcandles is not necessary. The waiting room is a place where people may have to wait for long periods of time if the emergency room is particularly busy, therefore the space should be as interesting as possible to occupy the minds of those waiting to make the time pass more quickly and to calm their potentially anxious emotions about being at the hospital. For the corridor, only an illuminance of 5 footcandles is required, but this may be increased to maintain some degree of uniformity throughout this continuous space. For this same reason, the light quality considerations for the reception area and waiting area will also carry over into the corridor. The amount of daylight available for these spaces is not very significant, and since the hospital is in operational 24 hours a day, the spaces must be designed to adequately light the space with no daylight, but control flexibility could allow some energy savings for when daylight is contributing to the space. According to ASHRAE/IESNA Standard , the maximum allowable power density for the lobby/entrance area is 1.8 watts per square foot. Considering the receptionist area an office space, the maximum lighting power density is 1.5 watts per square foot. Considering the waiting area and café as lounges, the allowable density is 1.4 watts per square foot. The corridor space is allowed a density of 1.6 watts per square foot.

12 Existing Light Analysis Overall Waiting Area Receptionist s Desk

13 Entry/Lobby Area Café Area Critique of existing conditions Waiting Room and adjacent corridor The waiting area has a relatively simple lighting system, but it serves the function well, and is easy to maintain. The lighting system does an excellent job of drawing those entering the emergency department directly to the receptionist, with that area of the space being illuminated much brighter than the rest of the space. The power density for the space is exceeding the allowance given by ASHRAE/IESNA The illumination of the space is high compared to what the IES recommends. This is not necessarily bad because, being a hospital, a large percentage of their occupants are older people who require higher light levels. Even with this excess light, it seems that this could be achieved with more efficient fixtures. For example, the downlights use two horizontal compact fluorescent lamps each. If one more powerful vertical lamp were

14 used instead, the luminaires would be more energy efficient, and would reduce maintenance costs. All of the light is direct, but with the high ceiling in most of the space, a wider horizontal light distribution allows for fairly uniform illumination, so the light quality seems good. exceeds the recommended values, but again this may be more desirable by the occupants, and therefore would justify the additional energy expense. The system does put a generous amount of light where it is needed on the work surface.

15 Conference Room Courtesy of Leach Wallace Associates The conference room is simply illuminated by two 2 x4 parabolic fluorescent luminaires with four 32 watt T-8 lamps. For details on the fixture, see luminaire A6 in the above lighting fixture schedule for the waiting room. They are controlled by a toggle switch at the door. There is no daylight available in this space. The walls will be of a light cream color with a reflectance of about 65 percent. The surface of the table is a dark colored semi-specular wood finish with a reflectance of about 15 percent. There will also small dark wood tables in two corners of the room, one with a television on top of it, the other with a personal computer monitor for use in video conferencing. The camera will be mounted on top of the monitor. A four foot by five foot projection screen hangs from one wall. When in use, the projector will sit on the table. There is also a white four foot square marker board on another wall. The ceiling is a 2 x2 suspended ceiling grid hung at 8-6 above the floor. The lighting power density in the space 1.48 watts per square foot.

16 Design Criteria Though this is a relatively small space, tasks will vary for this conference room. This will require a versatile lighting system to accommodate these different activities. It can be used for meetings involving the reading from paper, it may include use of the marker board. Presentations may be projected on the screen. The television can also be used for video presentations. For general meeting situations, the IES recommends a horizontal illuminance of 30 footcandles and a vertical illuminance of 5 footcandles. For video conferences, higher levels are required for quality video renderings. The recommended levels are 50 footcandles of horizontal illuminance and 30 footcandles of vertical illuminance. Other considerations are also important for video conferencing, such as a maximum luminance uniformity ratio of three to one. The vertical illuminance is extremely important to prevent harsh shadows on peoples faces. As with any meeting space, color and modeling of faces is an important design consideration. Glare is also an issue, from direct and reflected components, such as from the somewhat specular table and from the VDT screens. In addition, luminance uniformity of the surfaces will also prevent veiling reflections and will improve the video renderings. With all of these different tasks that may take place in this space on a regular basis, it will be important to have a convenient control system that provides the proper light quality and quantity for each task. This will improve the functionality of the space and can help to conserve energy. According to ASHRAE/IESNA Standard , the maximum allowable power density for a conference room is 1.5 watts per square foot. Existing Light Analysis

17 Conference Room Marker Board Projection Screen Critique of existing conditions The conference room lighting is extremely simple, and does not allow for any versatility. Some indirect components could be introduced to improve facial modeling, and increase the uniformity of the surfaces in the space. Currently the space will have dark ceilings and a strong gradient on the walls. This may cause poor video renderings for video conferencing. Additional layers of light would also allow for controls to aid in providing the proper quantity and quality of light for the different situations. The projection screen and marker board are not illuminate very uniformly. Some indirect light or possibly some accent light would help to remedy this. Increasing uniformity around the room would also minimize the possibility of veiling reflections in the VDT screens. The lighting power density is in compliance with ASHRAE/IESNA Standard Adding additional light layers could cause the power density to be exceeded. This may be justified by adding power to this space by taking it from another, since the lighting is very important for a conference room, especially if video conferencing is involved.

18 North Façade Courtesy of Leach Wallace Associates The North façade is illuminated by three different types of matching compact fluorescent fixtures that are black in color. Several square wall sconces are mounted onto the side of the building at about eight feet above the level of the first floor, as well as being illuminated from within through the tinted glass. The walkway approaching the entrance featured bollards delivering light to the path. Under the canopy at the entrance to the emergency department, there are fixtures mounted to the columns. The exterior of the building is primarily precast concrete, E.I.F.S., and tinted glazing. The adjacent parking lot is illuminated by pole-mounted fixtures with metal halide lamps. Above is an architect s rendering of the building during the day to show the nature of the façade, and a photograph of the entrance to the emergency department during the day. Below is part of the site plan depicting the exterior lighting. Courtesy of Leach Wallace Associates

19 Courtesy of Leach Wallace Associates D4 D5 D6 Courtesy of Courtesy of Courtesy of Critique of existing conditions As might be expected for such an institution, the outdoor lighting is not very flashy. The fixtures are conservative in appearance, but the system works well to guide people from the parking lot into the building by illuminating the path to be followed. With the parking lot lit with metal halide lamps, it may be more aesthetically uniform if the other outdoor fixtures were also metal halide rather than compact fluorescent, but the low wattage of the luminaires probably would not warrant this. If the hospital wanted to make the building more appealing at night, a system could be added to wash the façade with grazing light to show the texture of the exterior wall surface.

20 Leach Wallace Associates Wilmot Sanz, Incorporated Howard County General Hospital IESNA Lighting Handbook AHSRAE/IESNA Standard Sources