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1、建筑遮阳和日光照明 Building shading and daylighting control,许鹏 教授 博士 博导 机械工程学院 Peng Xu Professor, PhD, PE, MBA College of Mechanical Engineering,Contents 内容纲要,Importance of shading control and daylighting 遮阳和自然采光的重要性 Shading strategies 常见遮阳策略 Day lighting and building envelope 日光照明与建筑立面 Sample projects and s
2、uccessful stories 成功案例 Software 计算软件,2,Windows, architecture love them, occupants love them. They are modern, stylish, provide better view, easy to build, easy to maintain,What is the pain?,Public buildings,Office,Residential,Small commercials,3,But engineers hate them, regulators do not want them,
3、because they are wasting energy,What is the pain?,Building codes all over the world are using description or energy budget method to regulate the window to wall ratio,In summer, direct solar heat gain accounts for more than 50% of cooling load,In winter, wall insulation value is about 10 times highe
4、r than that of conventional windows. Therefore, buildings in cold climate can only have small windows,Windows are more important than any other building components in term of energy impact In cold climate, more than 50% heat loss are through windows In hot climate, direct solar heat gain is about 1/
5、3 of cooling load Lighting energy consumption is more than heating and cooling combined in commercial buildings,Low-energy intensity design and windows,Low-energy intensity design and windows,Air conditioning peak load analysis in summer 50% of building envelope load are caused by windows Window sha
6、ding in summer and window insulation in winter are two critical issues,Year of Built, Government office building built at different years,Energy survey results,Worst energy intensity buildings get worse and worse,Energy survey results,Background,Misunderstanding of windows The smaller the better, co
7、ntrol Window to Wall Ratio East and West facades are same Small north facing windows Size matters, height does not Window is fixed Blinds are interior design jobs, nothing to do with energy,Low energy intensity buildings,Mis-concept today,Contents 内容纲要,Importance of shading control and daylighting 遮
8、阳和自然采光的重要性 Shading strategies 常见遮阳策略 Day lighting and building envelope 日光照明与建筑立面 Sample projects and successful stories 成功案例,The major flux is direct solar beam in summer In winter, heat loss is the biggest problem Second transfer is important Tint glass is not very useful,Heat flux through the win
9、dow,Window and shading design principles Use exterior shading, or shading in between glasses, internal shading is useless Design the building to shade itself Use a horizontal form for south windows Maximizing windows in north Recessed windows, somewhat useful on the east Use a vertical form on east
10、and west windows. Give west and south windows shading priority. East is not important The shades color modifies light and heat. Movable shading is better than fixed shade. Use movable devices if budget is allowed,West shading is hardest, vertical louvers sometimes not working,Ways to reduce overhang
11、 size,Reducing the size of overhang furthermore,Allow lighting to come in,Design shading for glare relief as well. Use exterior shading to reduce glare by partially blocking occupants view of the too-bright sky.,Dirt accumulation on blades, negative effects on building appearance Poor reliability. A
12、ctuators and mechanical systems are prone to failure due to exposure to wind, sun and rain. Difficult to repair. Visually unattractive. To avoid glare, blades are typically shut off in winter and useful solar heat is blocked too,From thermal point of view, exterior shading systems are perhaps one go
13、od solution, because direct solar radiation is completely blocked outside of buildings. However, it has the following shortcomings:,Practical problems,Interior shading system,Need to be cleaned and maintained regularly Prone to damage. Furniture moving, indoor activities will inevitably damage the s
14、hutter. No automatic adjustment. Interior blinds are left open or closed as they were, till someone feels discomfort with the glare.,Interior shading systems overcome the shortcomings of exterior shading systems, but on the thermal side, they are not as effectively as exterior shading. Although sola
15、r radiation is blocked, solar heat are retained indoor in summer. Beyond that, other shortcomings include:,Double facades with ventilation,Ventilated faade still have dirt problem. Dirt accumulated in-between the faade is hard to clean Interior recycling ventilated double faades are useless thermal
16、dynamically, because all the heat is still trapped indoor. High cost. Need two layers of window systems. Double the building cost.,Ventilated double facades with shading in between are better than interior and exterior shading system. However, they have several drawbacks:,Shading in between the glas
17、ses, dynamic facade,Contents 内容纲要,Importance of shading control and daylighting 遮阳和自然采光的重要性 Shading strategies 常见遮阳策略 Day lighting and building envelope 日光照明与建筑立面 Sample projects and successful stories 成功案例,Day lighting is untapped energy source in buildings,Natural lighting is free Natural lighting
18、 release less heat than artificial lighting, even with ventilated fixtures Lighting is on all four seasons,Day lighting saving potentials,Adding photo-controls 0.62 kWh/sf-yr of office SF 14.6% of 4.24 kWh/sf-yr (average interior lighting energy use) 2.11 kWh/sf-yr in primary daylit zone 53.5% of 4.
19、24 kWh/sf-yr (average interior lighting energy use） 35% of office space sf in daylit area,Market size Office spaces with windows, 67%- 3,578 day lit office spaces Net window-to-wall ratios, 38% average for office buildings,Day lighting and building envelope,Day lighting and building envelope,Adding
20、a light shelf increase savings About 5% increase in savings Reducing furniture partition heights increase savings About 10-14% depending on partition heights Increase interior reflectance About 15% depending on interior reflectance,Day lighting and building envelope,Day lighting and building envelop
21、e,Day lighting and building envelope,Day lighting and building envelope,Day lighting and building envelope,Building Form and Skin Increase exposure to daylight. High skin-to-volume-ratio, the greater percentage of floor space available for daylighting Shape building for self-shading Take a deep faca
22、de approach Balance daylight admittance Keep private offices somewhat shallow,Day lighting and building envelope,Windows The higher the window, the deeper the daylighting zone. The practical depth of a daylighted zone is typically limited to 1.5 times the window head height. With a reflective light
23、shelf, this zone may be extended up to 2.5 times the head height Strip windows provide more uniform daylight. Large windows require more control. Size the windows and select glazing at the same time. Keep occupants away from large areas of single-pane glass. Use separate apertures for view and dayli
24、ght. Position windows to direct light onto the ceiling. Introduce more light-colored surfaces for good distribution.,Window design to maximize daylighting,Incorporate shading elements with windows Use horizontal window shapes Place view windows wisely. Locate windows near room surfaces (beams, walls
25、) for good distributionthese surfaces help reflect and redistribute daylight. Windows on every orientation - North: High quality consistent daylight with minimal heat gains, but thermal loss during heating conditions and associated comfort problems. - South: Good access to strong illumination (the o
26、riginal source), although varies through the day. Shading is “easy”. - East and West: Shading is difficult. Shading is critical for comfort on both sides and heat gain too, especially on the west. Windows facing generally north and south create the fewest problems. Dont waste glazing area where it c
27、ant be seen,Blinds matters!,90% of buildings have operable fenestration controls, blinds, shades, louvers, curtains,Daylighting simulation examples,Blinds day lighting simulation,Automated blinds control,Raised for hours when there is no direct sun, lowered for hours when there is direct sun Blinds
28、are at 45 deg angle to block direct sun Representative of a fully automated system,Blinds control is an energy saving gold mine,Blinds retrofits They are easy to improve Scope of design and product improvement Daylighting optimized blinds Blinds manufacturers dont know the potential of their product
29、 for daylighting savings Everyone is focus on HVAC savings Just like glass/windows forget they are making a daylighting products Low cost retrofit item,Split blinds, no cost ideas,Separate the window functions with different operation schedules Daylight windows provide: Seasonal adjustment for solar
30、 redirection View windows provide: Occupant daily or hourly control for glare,Reflective louvers acts as light shelf,Automated blinds retrofit options,Successful examples,Genzyme Building Automated reflective blinds All facades operated to produce uniform daylighting Archiving persistent savings,Time,% savings,方位：东,Real picture of daylighting control,