Daylighting in Schools and related case-studies

Transcription

1 Daylighting in Schools and related case-studies DSC 558 Daylighting Submitted by: Supriya Goel, Kavish Munshi

2 CONTENTS INTRODUCTION 3 DAYLIGHTING AND HUMAN PERFORMANCE.4 DAYLIGHTING AND BUILDING ENERGY PERFORMANCE....5 DAYLIGHT CHARACTERISTICS....6 DESIGN STRATEGIES FOR IMPROVED DAYLIGHTING WHOLE BUILDING ENERGY SIMULATION AND DAYLIGHTING....7 CASE STUDY: NORTHERN GUILFORD MIDDLE SCHOOL- NORTH CAROLINA.. 8 REFERENCES 9 2 P age

3 INTRODUCTION The controlled admission of natural light into a space through windows to reduce or eliminate electric lighting Daylighting helps create a visually stimulating and productive environment for building occupants, while reducing as much as one-third of total building energy costs. The purpose of this study is to observe the change in the performance of building and humans by introducing daylighting. A remarkable change is seen in building system and human environment. General observation shows the increase the human efficiency; in terms of quality and quantity of work. Building system all shows drastic difference in building energy, this can be observed by the difference between the peak loads of system of building having daylighting. Introduction of daylighting in a building shows improvement in student s performance in terms of grade and even in health. We chose to study elementary schools since children at that age spend most of their school time in one physical environment their assigned classroom. Whereas students in middle schools and high schools tend to move from classroom to classroom throughout the day, in elementary schools children are usually assigned to one teacher in whose classroom they spend the majority of the school year. We reasoned that if the physical environment affects learning, it should be easier to identify any effects at the elementary level where we could characterize a given student s environment with some certainty. DESCRIPTION Appropriate design strategies need to be used for effective daylight design- Provided wide, diffuse distribution of light- Use of diffuse lenses or diffusing louvers. Prevented direct penetration of sunlight into classroom Allowed manual control of amount of illumination through the use of louvers and blinds. 3 P age

4 DAYLIGHTING AND HUMAN PERFORMANCE The study shows the clear relationship between human performances in buildings and the presence of daylight. This daylight could come from windows or skylights. This daylight could come from windows and skylights. Recent studies show that daylighting in schools may significantly increase students test scores and promote better health and physical development and can be attained without an increase in school construction or maintenance costs. Three different school districts were studied and all daylighting strategies were analyzed. Strategies which this study defined to be most effective have been discussed in detail later. Daylight provided from skylights is more uniform as compared to windows. Windows- include aspects of visual disturbance and depending on the kind of view available, is might be visually appealing or distracting. These are profound results, which have been carried out under rigorous statistical controls. In one school district, students with the most daylighting in their classrooms progressed 20% faster on math tests and 26% faster on reading tests when compared to students in the least daylit classrooms. In the other two school districts,.students in classrooms with the most daylighting were found to have 7%.18% higher scores than those in the least. Another study compared test scores for students in three daylit schools in North Carolina to scores in the county school system as whole and other new schools within the county. Test scores for over 1,200 students in daylit schools were compared to scores for the students in the county. The study showed that students who attended daylit schools outperformed the students in non-daylit schools by 5%.14%. Two studies suggest that daylighting in classrooms can promote overall health and physical development. In a study of 90 Swedish elementary school students, researchers tracked behavior, health, and cortisol (a stress hormone) levels over the course of a year in four classrooms with varying daylighting levels..the results indicate work in classrooms without daylight may upset the basic hormone pattern, and this in turn may influence the children s ability to concentrate or cooperate, and also eventually have an impact on annual body growth and absenteeism. Daylighting allowed for the heating, ventilation, and air conditioning (HVAC) system to be downsized, which in turn reduced the noise levels in both the classrooms and library, thus enhancing the learning environment. Thus fresh and natural ventilated environment is proved to be more favorable for study and academically. 4 P age

5 DAYLIGHTING AND BUILDING ENERGY PERFORMANCE Daylighting plays the important role in energy performance of the building. Along with the human performance, energy performance of the building is positive. It helps in increase the natural ventilation and helps the occupants to breathe fresh air. One of case studies of school shows that the reduced cooling load required a 370-ton chiller instead of a 400-ton chiller needed for a similar school, saving initial and energy operation costs. Students in school needs higher flux of light, daylighting acts as a natural source of light, which in turn, discourages artificial lights. High-efficiency lighting equipment and controls are used, including motion sensors and light-level sensors to automatically adjust energy-efficient fluorescent lighting as needed. An energy management system controls the amount of outside air circulation to correspond with the occupancy level of the school, rather than constant operation, which is typical of school buildings. Thus the overall performance of the energy is reduced to 50% by including daylighting features in school building. Daylighting in school is all important as it s a building used twelve months a year which saving a lot of energy annually. These strategies help in reducing the life cycle cost of the building by downsizing mechanical system as well as installing photo sensors and reducing the lighting. 5 P age

6 Daylight Characteristics In electric lighting design for a typical space, the lighting is directed downwards, illuminating the horizontal surface better than the vertical surface. Whereas, natural daylight is a more diffuse source, evenly distributed in all directions, thus luminance in the space is more comfortable. Daylight has a continuous spectrum whereas electric light has a stronger spectrum in some wavelengths. Alternating current source of artificial lights results in an occasional flicker, which is absent in the case of daylight. 6 P age

7 DAYLIGHTING- DESIGN STRATEGIES Orientation of the building is lengthwise on an east/west axis to optimize placement of the north and south facing daylighting monitors and to reduce heat gain. South-facing and north-facing roof monitors provide daylighting to classrooms, cafeteria, gymnasiums, and hallways with a corresponding 30% overall increase in glazing for daylighting and an absence of glazing on the east and west sides. The roof is equipped with a radiant barrier that reflects more than 90% of the radiant heat. There is low-e glazing throughout, including the roof monitors. The reduced cooling load required a 370-ton chiller instead of a 400-ton chiller needed for a similar school, saving initial and energy operation costs. High-efficiency lighting equipment and controls are used, including motion sensors and light-level sensors to automatically adjust energy-efficient fluorescent lighting as needed. An energy management system controls the amount of outside air circulation to correspond with the occupancy level of the school, rather than constant operation, which is typical of school buildings. Designing the skylight is an important strategy in daylighting. It results in the optimal use energy. 7 P age

8 SKYLIGHT A Appropriate design strategies need to be used for effective daylight design-[4] - Provided wide, diffuse distribution of light- Use of diffuse lenses or diffusing louvers. - Prevented direct penetration of sunlight into classroom. - Allowed manual control of amount of illumination through the use of louvers and blinds. - Skylight A performed well and met all required criteria for appropriate daylighting. SKYLIGHT A SKYLIGHT B HMG Study of 3 School Districst Reveals:[4] Certain skylight designs that did not perform well (Skylight B), had a negative impact on student performance had the following characteristics- - Allowed direct sunlight into the classroom. - Relied on automatic controls which were not performing as designed. - They created small areas of high daylight illumination SKYLIGHT B APPROPRIATE GLASS TYPE: APPLICATION EXPOSURE TYPE View Glass (Non Daylight Apertures) S, N E/W Unshaded E/W Shaded Clear, Double Low E Tinted, Double Low E Clear, Double Low E Windows Above Lightshelves S Clear Double Glass Roof Monitor S Clear Double Glass Blinds-Between-Glazing S Clear Double Glass 8 P age

9 DESIGNING OF ROOF MONITORS: [3] Architects integrated south-facing roof monitors into the school s design to provide the majority of daylighting within the building. The monitors allow the electric lighting to remain at a low level most of the day, reducing internal heat gains and the need for additional cooling. Cloth baffles within the monitors help distribute the light uniformly and eliminate glare. Fluorescent lighting installed in the classrooms operates on dimming ballasts with photo sensors and motion sensors to limit unnecessary electric lighting. PRE- 9 P age

10 SUMMARY : DESIGN STRATEGIES MINIMIZE SIZE by MAXIMIZING TRANSMISSION PASSIVE SOLAR BENEFITS : Overhangs should be optimally sized. Use RIGHT COLORED ROOFING IN FRONT OF MONITORS Use BAFFLES to block direct beam radiation, diffuse light and reduce glare Use translucent baffles to help reduce contrast. Maximize Contrast at wall-to-ceiling intersection o Curved edge or a 45 cut for a better transition from a vertical to horizontal surface. Minimize depth of ceiling cavity Deeper the well more difficult it is for light to reflect into space For a square skywell with 70% reflectance- the loss is effectiveness is over 50% 10 P age

11 INTEGRATED APPROACH TO DAYLIGHTING [2] A well-integrated design approach to daylighting: 1. South facing roof monitors for lighting the central classroom. 2. South facing lightshelves for the remaining spaces. 3. Use of a. Lighting Controller b. Photosensors c. Motion sensors 4. Use of double low-e glass for view windows 5. Use of clear glass for daylighting windows (with lightshelves) 11 P age

12 CASE STUDIES NORTHERN GUILFORD MIDDLE SCHOOL, GREENSBORO, NORTH CROLINA [5] Parametric studies to explore ENERGY PERFORMANCE with DAYLIGHTING STRATEGIES A study of Northern Guilford Middle school to analyze an integration of daylighting strategies with whole building enrgy performance to minimize construction costs and annual energy costs. BASE CASE sq.ft classroom with a 8 ft corridor - Zero Additional Cost. - No Daylighting Strategies - Flat Roof - VAV Mechanical System Design Type Additional Cost ALTERNATIVE 1 - No Daylighting Strategies - Pitched Roof - VAV Mechanical System DAYLIGHTING STRATEGIES UTILIZED MAXIMIZE T VIS Clear double glass the T VIS - 10% to 25% better than low-e glass. SOUTH-FACING GLASS. South glazing requires 25% less glass area to achieve same PASSIVE HEATING as northfacing glazing. CLERESTORIES White, single-ply roofing in front of clerestory glass. This results in needing 10% less glass area for same daylighting results. ROOF MONITORS 50% of light lost due to internal reflections in ceiling cavities of roof monitors. LIGHTSHELVES, SHADING DEVICES Extended beyond opening to account for early morning and afternoon azimuth conditions. Base Case Design $0.00 Design Type Additional Cost Alternative 1 $ P age

13 ALTERNATIVE 2 - SOUTH FACING ROOF MONITORS with translucent fabric baffles in the light wells. - CLEAR, DOUBLE GLAZING - to maximize VT and minimize WWR - OVERHANGS over the monitor windows protect the spaces from DIRECT LIGHT. - VAV Mechanical System Design Type Additional Cost Used in : Gymnasiums, Dining Areas Designed with minimal required ceiling cavity depth for these spaces. Alternative 2 $3.29 ALTERNATIVE 3 - Daylighting Strategies Curved translucent interior lightshelf, in combination with highly reflective ceiling tiles. - 20% T vis level translucent panel of the lightshelf and the design of the aperture, glare is minimized - Indirect Lighting - Underfloor Air Distribution LIGHSHELVES : BETTER SOLUTION 50% of daylight lost internally within ceiling cavity of roof monitors. Design Type Alternative 3 $2.29 Additional Cost 13 P age

14 REFERENCES 1. Accessed February Heschong Mahone Group, Daylighting in Schools, Pacific Gas and Electric Company on behalf of the California Board for Energy Efficiency Third Party Program, August Nicklas,M. and G. Bailey, Energy performance of Daylit Schools in North Carolina,, Nicklas. Michael, Altre.Umesh, Innovative Design Inc, Comparison of Daylighting Strategies for Schools 7. accessed Feb 2011 Images: P age