SPLIT CONTROLLED BLINDS AS A THERMAL AND DAYLIGHTING ENVIRONMENTAL CONTROL SYSTEM

Transcription

1 SPLIT CONTROLLED BLINDS AS A THERMAL AND DAYLIGHTING ENVIRONMENTAL CONTROL SYSTEM Svetlana OLBINA Ph.D. 1 Keywords: automated blinds, illuminance, energy savings, computer simulations Abstract Commercially available blinds are occasionally part of the building s thermal and daylighting environmental control systems. Inappropriate application of blinds increases the use of electrical lighting, heating/cooling loads for a building and thus, the total energy consumption. Manually controlled blinds rarely meet thermal and daylighting performance requirements. With the conventional, automated blinds control, the slats tilt angle is always the same at a particular point in time. This research looked to improve the thermal and daylighting performance of blinds as an integral part of the other building systems by developing a framework for a new, automated split control of the blinds. The proposed split control adjusts the slats position at different angles at a particular point in time, depending on the position of the slats within the height of a window. This paper describes: 1) development of a framework for split control of blinds 2) validation of a split control system, and 3) analysis of energy savings as a result of the application of the split controlled blinds. A case study for two automated blind control systems (conventional and split) was conducted to validate the split control system and determine performance of the split controlled blinds. Computer simulations were performed to calculate the illuminance levels in a building and energy consumption as a result of the application of these two blind systems. The simulation results were compared for two blind systems to determine benefits of using the split controlled blinds. This research sought to enhance the knowledge in the area of innovative applications of shading devices in buildings. The main contribution is an automated, split control system for blind adjustment that selects the most appropriate slat tilt angles to accomplish the required thermal and daylighting performance of the blinds. 1. Introduction Windows as building components are multifunctional systems. Windows affect air quality and provide thermal, lighting, visual, and acoustic comfort. The thermal requirements for windows are to protect the building from heat loss in winter and heat gain in summer, and to collect solar energy in winter. The lighting requirements for windows are to provide daylight and protection from glare in the space. The visual requirements include providing a view to the outside or privacy for the occupants. A shading device as a component of a window system contributes to meeting these requirements by providing protection from direct sun and overheating in summer, thus reducing the cooling loads for the building, by providing protection from glare, and by providing privacy or view to the outside. A shading device is not often used as part of a daylighting system. A shading device can redirect daylight to spaces where daylight is needed, for example, to spaces at a large distance from the window. The benefits to using daylight in buildings include: an increase in the well-being of the occupants, an increase in the productivity of the employees in an office building, an accelerated recovery time of patients in hospitals, and an increase in student test scores. Use of daylight decreases the use of electrical lighting, resulting in a decrease in an internal heat gain from lighting and in a decrease in cooling loads, leading to energy savings for the building. Another important function of the window is providing a view to the outside. The shading device slats are usually made of nontransparent materials. If these slats are in a closed or nearly closed position, the direct view to the outside can be partly obstructed (Vine et al., 1998, Kuhn et al., 2001, Ruck et al., 2000), and consequently visual transparency of the façade is more difficult to achieve. A well-designed and properly used shading device contributes to creating thermal, lighting and visual comfort for the occupants and to decreasing the energy consumption and cost. 1 Rinker School of Building Construction, University of Florida, Gainesville, Florida, USA, solbina@ufl.edu

2 1.1 Problem Statement Commercially available windows cause energy loss for buildings and are usually not integrated with the other building systems. Blinds installed in these windows are occasionally part of the thermal and lighting systems. Inappropriate use of blinds increases the use of electrical lighting, cooling and heating loads for the building and therefore, the energy consumption and operational cost of the building are increased. Manually controlled blinds often do not meet thermal, lighting and visual performance requirements. Automatically controlled blinds: 1) are not commonly available in the U.S.A., 2) are not cost effective, and 3) always have the same tilt angle in all the parts of the window at the particular point in time regardless of the function they need to accomplish and the blinds position within the height of the window. Because different parts of a window need to accomplish different functions, various shading device systems and control strategies need to be used in different parts of a window system. This solution creates a complex window system with a complex control strategy. 1.2 Research Objectives The purpose of this project was to improve thermal and daylighting performance of blinds as part of a window system by developing a new, automated, split control system for adjusting blinds. The proposed split control system adjusts the blinds for different tilt angles at a particular point in time depending on the position of the blinds within the height of the window. These blinds are used both as a thermal and daylighting environmental control system. The objectives of this research were: 1) developing a framework for the automated split control of blinds, 2) validating the split control system, 3) analyzing energy savings obtained by the application of the split controlled blinds. 2. Literature Review The proper design of a building and a window as a building component has the goals of providing comfort for the occupants and energy-efficiency for the building. The use of daylighting helps in achieving these goals. The use of electrical lighting in a building causes a considerably higher cost than the cost of heating and cooling the building (Koster, 2004). The appropriate application of daylighting decreases a building s energy cost by 30%. In addition to the proper use of daylighting, electrical lighting should be used only when the amount of daylight in the space is not sufficient. The use of daylight responsive controls provides adequate quantity and quality of daylight in interior spaces, improves the overall distribution of light when daylight is insufficient, and saves energy. It is possible to conserve cooling energy by increasing the use of daylighting and also using daylighting-responsive lighting controls, provided that solar heat gain is also controlled (Ruck et al., 2000). Energy savings are difficult to achieve in daylit buildings if the electrical lighting is not dimmed or switched off based on the amount of available daylight in the space (Ruck et al., 2000). The appropriate use of a shading device in a window also contributes to energy savings. When designing a window and a shading device for the window, the goal is to achieve a low, total energy transmittance while maintaining a high light transmission and good transparency (Koster, 2004). The proper use of blinds provides lighting energy savings in comparison to cases in which blinds are fully retracted, and electric lighting is fully on (Galasiu et al., 2004). Commercially available blinds are either fixed or moveable. The use of fixed blind systems requires higher energy consumption for lighting compared to moveable blind systems (Galasiu et al., 2004). The position of moveable blinds can be adjusted either manually or automatically. The tilt angle of the blinds needs to be adjusted to meet the following requirements: protection from direct sun and glare, protection from overheating, and the transmittance of a sufficient amount of daylight. 2.1 Manually Controlled Blinds The blinds are usually controlled manually by the occupants of the building based on the occupants personal preferences, which often do not meet requirements for thermal, lighting and visual performance (Lee et al., 1998, Selkowitz and Lee, 1998, Kuhn et al., 2001, Ruck et al., 2000, Gullemin and Morel, 2001, Athienitis and Tzempelikos, 2002). If the control of the blinds adjustment is manual, several problems can occur. The occupants can be absent from the room when the blinds need to be adjusted (Lee et al., 1998, Selkowitz and Lee, 2004). The occupants very often close the blinds completely to protect the space from overheating and glare, but at the same time the amount of daylight in the space is reduced; therefore, both the use of electrical lighting and thus cooling loads are increased (IESNA, 1999). The occupants will adjust the blinds to protect the space from direct sunlight, but will rarely adjust the blinds again when the direct sunlight is gone, and daylighting can be admitted (Galasiu et al., 2004). The blinds are lowered completely by the occupant during daylight hours when glare is present and fully opened otherwise (Vartiainen, 2000; Lee and Selkowitz, 1995). The blinds are not often used appropriately: not being raised when there is little sun, and not being lowered when there are high solar gains (Foster and Oreszcyn, 2001). The use of blinds is a response to solar radiation intensity and the sun s angle, and once a blind is lowered, it usually will take a dramatic change before the blind is raised again (Oscar Faber Associates, 1992). The closing criteria for blinds are usually clear, but it is not clear whether occupants re-open their blinds on a daily, weekly, or even seasonal basis (Bullow-Hube, 2000; Rea, 1984; Rubin et al., 1978). Blinds are not adjusted in single offices for weeks or months (Rubin et al., 1978; Foster and Oreszcyn, 2001). Manually controlled blinds are not accurately controlled in response to changes in solar radiation. If the blinds are open when a large amount of solar radiation enters, excessive energy is consumed for air-conditioning When the blinds are closed on days without solar radiation, the advantage of the view from the window is lost (Inoue et al., 1988).

3 2.2 Automatically Controlled Blinds In the case of moveable blind systems, there is a need for appropriate automated control systems used to adjust the blinds tilt angle. Automated control systems help in achieving a balance between a sufficient amount of daylight and maximum overheating protection (Inoue et al., 1988, DiBartolomeo et al., 1996, Klems and Warner, 1997, Lee et al., 1998, Selkowitz and Lee, 1998, Selkowitz and Lee, 2004). Automated blinds provide higher levels of daylight and better protection from overheating and glare in the space compared to manually controlled blinds. The use of automated Venetian blinds decreases the cost of energy by 30% during the winter and by 50% during the summer. The thermal performance of an automated blinds system is much superior (lower by %) to the performance of an ordinary window system without blinds when cooling is needed (Bilgen, 1994). Automated Venetian blinds have better thermal and daylighting performance than static shading devices, and they can achieve savings in both cooling loads and lighting energy (Lee et al., 1998). The advantage of automated blinds is that they close automatically when the indoor temperature and light levels become too high, and re-open later when the temperature and light levels decrease to allow penetration of daylight (Galasiu et al., 2004). The control system adjusts the automated blinds to block the direct sunlight, to provide designed workplane illuminance levels with daylight, and to provide total illuminance from daylight and electrical lighting within the designed illuminance level range. The computer control system sets the position of the blinds according to the presence of direct sunlight. If direct sunlight is not present, the blinds should be set to the horizontal position to maximize the view to the outside. If direct sunlight is present, the control system should set the blinds position to the correct tilt angle, to block the direct sun accordingly (DiBartolomeo et al., 1996). The minimum blind tilt angle should be selected based on two criteria: first, to allow more daylight into the room (the transmittance values are greater for blinds closer to horizontal) and second, to allow a better view to the outside. With the conventional, automated control system, the slats tilt angle is always the same at a particular point in time regardless of the slats position within the height of the window. The position of the blinds can be changed by pulling them up or down and by adjusting the tilt angle. Keeping the tilt angle the same restricts the blinds in meeting various requirements. Advanced window strategies employ a more sophisticated approach of using different blind systems in different parts of the window to fulfill different requirements. Shading device systems can be differentiated according to their position within the window such as upper window area, lower window area, and parapet area. The upper window area provides the transmission of low-angled daylight for increased light levels in the room depth. The lower window area provides daylight and shading to nearby workplaces while providing view to the outside. The parapet area does not need to provide daylight to the room, so it can be used to provide downward views (Koster, 2004). For example, Venetian blinds can be used in the lower window area and the daylighting louvers in the upper window area Daylight Performance Parameters: Daylight Autonomy and Useful Daylight Illuminance Reinhart et al. (2006) recommend use of dynamic daylighting performance metrics, such as daylight autonomy (DA) and useful daylight illuminances (UDI), to evaluate the daylight performance of blinds. Both DA and UDI are based on work plane illuminances (Reinhart et al., 2006). DA is defined as the percentage of the occupied times of the year when the minimum required illuminance level at the sensor point is provided by daylight only (Reinhart and Walkenhorst, 2001). UDI determines when illuminance levels are useful for the occupant, that is, more than 100 lx (not too dark) and less than 2000 lx (not too bright) (Nabil and Mardaljevic, 2006). UDI is expressed in the percentages of the occupied times of the year when the UDI is achieved ( lx), not sufficient (less than 100 lx) or exceeded (more than 2000 lx) (Reinhart et al. 2006). Mardaljevic (2006) suggests dividing achieved UDI into autonomous UDI ( lx) and supplementary UDI ( lx). Supplementary electric lighting may be needed for the daylight illuminance values from lx, while daylight alone is sufficient for the illuminance levels from lx (Mardaljevic, 2006). 3. Research Methods The following research tasks were performed to accomplish the research objectives 1-3. Objective 1: Developing a framework for the automated split control of blinds. A split control system was defined. The performance parameters that affect the split control system and that were used to evaluate the performance of the split controlled blinds, and variables that affect the performance parameters and the split control system were determined. The interactions and relationships between the variables and the performance parameters were determined. A framework for the automated split control of blinds was developed. The framework development included: 1) developing a diagram that shows the variables, the performance parameters, the control system, and the relationships and interactions between them, 2) defining the input and output parameters for the split control system. Objective 2: Validating the split control system. A case study was conducted to analyze the performance of the split controlled blinds. The proposed office building used in the case study was located in Gainesville, Florida, USA (latitude 30, longitude 81.6 ) which has a hot humid climate. A simple office space, 3.6 m wide, 5 m deep, and 3 m high was simulated. A 1.8 m by 1.8 m window with an aluminum frame and double insulated low-e glass was simulated for the south façade orientation. The window sill was 0.9 m high. Commercially available 12.5 mm white aluminum Venetian blinds were installed inside the window, that is, in the interior space. The blinds were dynamic, automatically controlled. The slats were not retractable and only the slats tilt angle was adjustable. The two automated blind control systems were tested: conventional and split. A dimmable electric lighting system was used. The software Energy Plus (US Department of Energy, 2008) for simulation of thermal and lighting performance of the buildings was used. The simulations were

4 performed for each occupied hour (9:00 to 17:00) of one day per season (March 21, June 21, and December 21). Illuminance levels were measured at the two sensor positions: 1) in the front of the room at a distance of 0.75 m from the window, and 2) in the back of the room at a distance of 3.5 m from the window. The output results of the simulation were the values of: 1) the illuminance levels, 2) the energy consumption of the building for electrical lighting, heating or cooling (HVAC), and total energy. Objective 3: Analyzing energy savings obtained by the application of the split controlled blinds. The results of thermal (energy) and lighting simulation for the two automated blind control strategies were compared to understand the performance and advantages of the split controlled blinds. 4. Results 4.1 Split Controlled System The automated split controlled system for the blinds adjustment utilizes the window in three subsections: a) the upper third, b) the middle third, and c) the bottom third (Figures 1 and 2). If the slats are titled downward to the exterior, the blind tilt angle is assigned a positive value. If the slats are titled downward to the interior the blind tilt angle is assigned a negative value. The zero tilt angle means that blinds are completely open or horizontal. In the uppermost third portion of the window, the blinds are tilted downward to the interior (tilt angle -12º), providing a view of the sky (Fig. 2.a). The blinds set at this particular angle also redirect daylight to the ceiling and into the depth of the room, providing better illumination. In the middle third portion of the window, the blinds are set at the horizontal position (tilt angle 0º) to provide a direct view to the outside (Fig. 2.b). As the major function of blinds just below eye-level is to provide protection from overheating, the blinds in the lower third portion are tilted downwards to the exterior (tilt angle 45º) (Fig. 2.c). In all three parts of the window, blinds have to block the direct sun and protect the interior space from overheating and glare. 4. Framework for the Automated Split Control of Blinds SPLIT CONTROL CONVENTIONAL CONTROL BLINDS FUNCTIONS SLAT TILT ANGLE a) b) BLINDS FUNCTIONS TRASMISSION OF LOW ANGLED DAYLIGHT VIEW TO OUTSIDE, PROTECTION FROM GLARE SLAT TILT ANGLE 12 deg. 0 deg. SLAT TILT ANGLE Figure c) PROTECTION 1 FROM Split and conventional automated control OVERHEATING systems for the blinds. a) TRASMISSION OF 12 deg. LOW ANGLED DAYLIGHT b) VIEW TO OUTSIDE, 0 deg. PROTECTION FROM GLARE OUTSIDE INSIDE Figure 2 Three conditions of usage for the split controlled blinds. c) PROTECTION FROM OVERHEATING

5 A framework for the automated split control of blinds (Figure 3) defines the possible variables and performance parameters, and the relationships and interactions between them that are relevant for developing the split control system for the adjustment of the blinds. The major components of the framework are: 1) independent, dependent, and shading device variables, 2) the required and actual performance of the blinds, 3) control system. Variables and performance parameters influence the control system. Independent variables are assigned to the user of the framework, and the user cannot change these variables. The Figure 3 A framework for the automated split control of blinds. dependent variables are selected by the user of the framework. Shading device variables such as blinds material and geometry are independent because they are defined by the manufacturer of the blinds and cannot be changed. Shading device variables such as tilt angle and occlusion of the blinds are dependent variables because they are affected by the user s decision (i.e. the user s input to the control system), independent variables (e.g. climate, sun angle) and dependent variables (e.g. heat transfer conditions). Required performance parameters include the values required by the active standards, codes, and recommendations. Actual performance parameters include the values obtained by the application of the particular blinds, the control system, and the actual conditions inside and outside the building (i.e., the values of the independent and dependent variables). In this framework, both the required and actual performance include the values of thermal and lighting performance parameters. These performance parameters were selected because the performance of the blinds is measured by how much heat is blocked/rejected in the summer, how much heat is redirected to a space in the winter (thermal aspect) and what illuminance levels are provided in the space, resulting in lower electrical lighting consumption (lighting aspect). Actual performance also includes energy consumption from electrical lighting, and cooling or heating. The actual performance is influenced by independent, dependent, and shading device variables. Input for a control system consists of: the independent, dependent, and shading device variables; and a difference between the required and actual performance of the blinds. If such a difference occurs, the control system will adjust the tilt angle and occlusion of the blinds in each window section to meet the required performance. The control system generates output for the adjustment of the blinds tilt angle. By changing the blinds tilt angle, the values of the actual performance of the blinds also change Results of Case Study The split control system was validated by performing a case study (see description of the case study, i.e. an office space, and the design of computer testing, in section 3. Research Methods, Objective 3: Validating the split control system). Simulations were performed for each occupied hour of a day, for three days (March 21, June 21 and December 21). Tables 1-5 show the simulation results obtained by Energy Plus TM software. Table 1. shows the simulation results for illuminance obtained for two automated control strategies (conventional and split) and for the various slat tilt angles obtained on December 21. These results show that both blind systems provided sufficient illuminance levels (i.e. > 500 lx) by daylighitng in the front of the room for all the occupied hours (Table 1). The split control blinds provided higher illuminance levels in the back of the room from 10:00 to 16:00 by % and in the front of the room from 11:00 to 15:00 by 10-22% compared to conventionally controlled blinds. At 11:00 and 15:00, the split blinds provided minimum designed illuminance (i.e. > 500 lx) by daylighting in the back of the room. Also, split blinds were more open

6 throughout the day than conventionally controlled blinds, and thus, provided better view to outside. Tables similar to Table 1 were created for the simulation results obtained for March 21 and June 21. Table 1 Illuminance Values (lx) obtained by daylighting on December 21 Conventional control Split control Difference in illuminance Time (h) Illuminance Slat angle Illuminance (split conventional) in % Slat angle Front Back top middle bottom Front Back Front Back 9: : : : : : : : : The obtained values of illuminance recorded in these tables were used to calculate the values of daylight autonomy (DA) and useful daylight illuminance (UDI) for each occupied hour. The optimized tilt angles of the blinds, that is, the angles that provided the designed illuminance levels ( lx) at the two sensor positions, were used for the calculations of DA and UDI. The blind systems were compared for these optimized slat tilt angles rather than the identical angles. Values of the DAs were calculated by using the following method. Any hour that exceeded minimum required illuminance (500 lx) counted as 100% daylight, while any hour that did not provide a minimum illuminance (500 lx) counted as 0%. UDI was calculated by using the following method. Any hour that fell in one of the following categories: insufficient (UDI < 100 lx), achieved-supplementary (UDI = 100 lx lx), achieved-autonomous (UDI = 500 lx lx), exceeded (UDI > 2000 lx), accounted for 100% daylight for that particular category. For the remaining three categories the hour accounted for 0% daylight. The hourly values of DA and UDIs were then used to calculate average daily DAs and UDIs for each of three analyzed dates (Table 2). The same values of DA and UDI indicate that the split blinds and conventionally controlled blinds had the equal performance on June 21 and March 21. However, in the back of the room on December 21, the split blinds provided minimum designed DA and UDI lx for 22% of the time Table 3 Values of the annual daylighting performance parameters (in %) while conventional blinds did not provide the minimum required values of DA and UDI (i.e., DA =0, and UDI lx =0). Back of the room usually does not receive sufficient daylight, so these results show the benefits of using split controlled blinds. In the front of the room, split blinds provided sufficient amount of daylight for 100% of the time on December 21 and March 21, and 56% of the time on June 21. Table 2 Average daily values of daylighting performance parameters (in %) for three analyzed dates Date 21 Jun 21 Dec 21 Mar Blind control Conventional Split Conventional Split Conventional Split Sensor position Front Back Front Back Front Back Front Back Front Back Front Back DA >500lx UDI <100lx UDI lx UDI lx UDI >2000lx The average daily values of DA and UDI from Table 2 were used to calculate the values of annual DA and UDI (Table 3). The results show that in the back of the room the split blinds provided sufficient amount of achieved-autonomous useful daylight (UDI ) for 7% of the time per year while the conventionally controlled blinds could not provide light levels above the minimum 500 lx at all (i.e., DA =0, and UDI lx=0). In the front of the room, split blinds provided Blind control Conventional Split Sensor position Front Back Front Back DA >500lx UDI <100lx UDI lx UDI lx UDI >2000lx

7 sufficient amount of daylight for 85% of the time per year. Analysis of results of energy consumption for electrical lighting, heating (HVAC) and total energy consumption on, for example, December 21 show that the use of the split blinds caused lower energy consumption for lighting by 37-87% and total energy consumption by % from 10:00 to 16:00 compared to conventionally controlled blinds (Table 4). Table 4 Values of energy consumption (W) on December 21 Conventional control Split control Difference in energy consump Time (h) Energy consumption (W) Slat angle Energy consumption (W) (split conventional) in % Slat angle Lighting HVAC Total top mid botto Lighting HVAC Total Lighting HVAC Total 9: : : : : : : : : Average Tables similar to Table 4 were created for the simulation results obtained for March 21 and June 21. These results were then used to calculate the average daily energy consumption for each analyzed day (Table 5). Average energy consumption for electrical lighting was 45.7% lower for split blinds than for the conventional blinds on December 21. On March 21 the split blinds provided 5.6% lower energy consumption for lighting and 8.4% lower energy consumption for cooling. On June 21, the use of the split blinds caused decrease of the cooling energy consumption by 9.4% compared to conventional blinds. For all three days the total energy consumption was % lower for the split blinds than for the conventional blinds. On average the split blinds caused lower energy consumption for electrical lighting (by 17%), HVAC (by 6%) and total energy consumption (by 5%) when compared to conventional blinds. Table 5 Values of average daily energy consumption (W) for three analyzed dates Conventional control Split control Difference in energy consump Date Energy consumption (W) Energy consumption (W) (split conventional) in % Lighting HVAC Total Lighting HVAC Total Lighting HVAC Total 21 Dec Mar Jun Average Conclusions This research contributes to the area of sustainable design and construction of buildings, particularly the design and production of energy-efficient windows as building components. The main contribution is a framework for the automated split control system for blinds. The blinds with automated split control of their position can become an important component of integrated building systems used to improve the overall performance of buildings. Through the use of split control system for blinds, the most appropriate position of the blinds and the slat tilt angle can be selected to accomplish the required thermal and lighting performance of the blinds. This leads to the increased level of comfort, well-being, and productivity of the building s occupants. Split controlled blinds help reduce cooling loads in the summer by rejecting the warm components of the sunlight and increase heat gain in winter by redirecting sunlight into the space. By using split control, the tilt angle of the blinds can be properly adjusted to block direct sunlight, reject heat, provide the design work plane illluminance, maximize view, minimize lighting energy consumption and minimize cooling load. Split controlled blinds can provide cost savings for the building owner by reducing the energy consumption of a building. The split controlled blinds function as a daylighting system by increasing the levels of daylighting in the space, especially in the spaces that are the farthest from the window. Results of the case study showed that the split blinds provided sufficient daylight:1) in the front of the room for all the time on December 21 and March 21, and for 85% of the time per year, 2) in back of the room for 22% of the time on December 21 and for 7% of the time per year. When compared to conventional blinds, the split blinds caused lower energy consumption for electrical lighting (by 45% on December 21 and by 17% on average), cooling (approx. by

8 9% on March 21 and June 21, and by 6% on average) and total energy consumption (by approx. 7% on March 21 and June 21, and by 5% on average). It can be concluded that the split controlled blinds seemed to indicate better thermal and daylighting performance compared to conventionally controlled blinds because they provided sufficient daylight levels in the back of the room for longer period of time, and lower energy consumption for both electrical lighting and cooling for most of the time. The objective of the future research will be determining cost, benefits and economical scalability of the split controlled blinds. A feasibility study will compare the life-cycle cost of the split controlled blinds with the lifecycle cost of the conventionally controlled blinds to evaluate the cost benefits of using the split controlled blinds. The feasibility study will also investigate the trade-off between the increased initial cost of the split blind system and decreased overall energy consumption due to the split blinds application. References Athienitis, A. K. and Tzempelikos, A. 2002, A methodology for simulation of daylight room illuminance distribution and light dimming for a room with a controlled shading device. Solar Energy, 72(4), pp Bilgen, E. 1994, Experimental study of thermal performance of automated venetian blind window systems. Solar Energy, 52(1), pp Bulow-Hube, H. 2000, Office worker preferences of exterior shading devices: A pilot study. Proceedings for EuroSun. Copenhagen, Denmark. DiBartolomeo, D.L., Lee, E.S., and Rubinstein, F.M., Selkowitz, S.E. 1996, Developing a dynamic envelope/lighting control system with field measurements. The 1996 IESNA Annual Conference. Foster, M., and Oreszczyn, T. 2001, Occupant control of passive systems: The use of Venetian blinds. Building and Environment, 36, pp Galasiu, A. D., Atif, M.R., and MacDonald, R. A. 2004, Impact of window blinds on daylight-linked dimming and automatic on/off lighting controls. Solar Energy, 76, pp Guillemin, A. and Morel, N. 2001, An innovative lighting controller integrated in a self-adaptive building control system. Energy and Buildings, 33(5), Illuminating Engineering Society of North America (IESNA). 1999, Recommended Practice of Daylighting IESNA Rp New York. Inoue, T., Kawase, T., Ibamoto T., Takakusa, S., and Matsuo, Y. 1988, The development of an optimal control system for window shading devices based on investigations in office buildings. ASHRAE Transactions 104, pp Klems J. H. and Warner J. L. 1997, Solar heat gain coefficient of complex fenestrations with a Venetian blind for differing slat tilt angles. In ASHRAE Transactions 1997, 103(1), Paper number PH , pp Koster, H. 2004, Dynamic Daylighting Architecture. Birkhauser. Basel, Boston, Berlin. Kuhn, T. E., Bühler, C., and Platzer, W.J. 2001, Evaluation of overheating protection with sun-shading systems. Solar Energy, 69 (Suppl.6), pp Lee, E. and Selkowitz, S. 1995, The design and evaluation of integrated envelope and lighting control strategies for commercial buildings. ASHARE Transactions 101, pp Lee, E.S., DiBartolomeo, D.L., and Selkowitz, S.E. 1998, Thermal and daylighting performance of an automated Venetian blind and lighting system in a full-scale private office. Energy and Buildings, 29, pp Mardaljevic, J. 2006, Examples of climate-based daylight modeling. In CIBSE National Conference 2006: Engineering the Future. Nabil, A. and Mardaljevic, J. 2006, Useful daylight illuminances: A replacement for daylight factors. Energy and Buildings, 38(7), pp Oscar Faber Associates. 1992, Occupancy data for thermal calculations in non-domestic buildings. Building Research Establishment (BRE). Contract: F3/ Rea, M. S. 1984, Window blind occlusion: A pilot study. Building and Environment, 19(2), pp Reinhart, C. and Walkenhorst, O. 2001, Dynamic RADIANCE-based daylight simulations for a full-scale test office with outer Venetian blinds. Energy and Buildings, 33(7), pp Reinhart, C., Mardaljevic, J., and Rogers, Z. 2006, Dynamic daylight performance metrics for sustainable building design. Leukos, 3(1), pp Rubin, A.I., Collins, B.L., and Tibott, R.L. 1978, Window blinds as a potential energy saver - a case study. NBS Building Science Series 112. National Bureau of Standards. Washington DC. Ruck, N., Aschehoug, Ø., Aydinli, S., et al. 2000, Daylight in Buildings: A Source Book on Daylighting Systems and Components: A Report of IEA SHC Task 21 / ECBCS Annex 29, Lawrence Berkeley National Laboratory.

9 Selkowitz, S. and Lee, E. 1998, Advanced fenestration systems for improved daylight performance. In Daylighting 98 Conference Proceedings, Ottawa, Ontario, Canada May Selkowitz, S., and Lee, E. 2004, Integrating automated shading and smart glazings with daylight controls. International Symposium on Daylighting Buildings (IEA SHC TASK 31). Tokyo, Japan. US Department of Energy. 2008, Energy Plus - Version Copyright the Board of Trustees of the University of Illinois and the Regents of the University of California through the Ernest Orlando Lawrence Berkeley National Laboratory. Energyplus is a trademark of the US Department of Energy. Vine, E., Lee, E., DiBartolomeo, D., and Selkowitz, S. 1998, Office worker response to an automated venetian blind and electric lighting system: A pilot study. Energy and Buildings, 28, pp Vartiainen, E., Peippo, K. and Lund, P. 2000, Daylight optimization of multifunctional solar facades. Solar Energy, 68(3), pp