百葉角度主要可以分成兩種，其中遮光百葉的角度是市面上廣泛被使用的百葉角度，其主要用來阻擋大部分的自然光以控制進入室內的光通量。導光百葉能將自然光反射至室內深處增加深處的自然採光，但利用此種方法雖然增加室內深處的採光，但卻有可能有眩光發生，且經常伴隨著增加過多熱負荷的風險。

本研究為了評估兩種百葉對於室內環境的影響，必須對光與熱環境同時進行評估。對使用者來說，室內光環境的舒適度為最重要的目標，隨後則追求室內採光效率。採光效率直接影響了人工光源的耗能及空調耗能，因此為了對兩種百葉作較全面的評估及優缺點比較，不只是要評估百葉對於室內光與熱環境的影響，也必須對受到影響的人工光源與空調耗能進行評估。

研究結果顯示導光百葉遮光效率與照度分佈都不及遮光百葉，因此導光百葉容易產生眩光。因為容易產生眩光的關係，導光百葉必須時常關閉百葉開度以達到室內光環境舒適標準。遮光百葉擁有較好的遮光效率，室內照度分布也較為平均，因此在以光環境舒適為前提下，遮光百葉有較好的採光量。

另外從熱環境方面來看，遮光百葉雖然使用了較多的自然光，但其增加的輻射量並沒有減少的人工光源熱負荷還多，因此如果適當地使用自然光源並不會增加室內熱負荷。而從能源使用情況來看，自然光的輻射熱在適當地使用下並不會劇烈影響到空調耗電量，反而人工光源的耗能可以節省較多的電量。

There are mainly two kinds of louver angles, Blocking angle and Redirecting angle. Blocking angle is mostly used blind angle, blocking most of daylight to control indoor illuminance level. Redirect angle can re-direct daylight into deeper place to increase the illuminance level. However, Redirecting angle might make indoor visual environment increase the possibility of Glare appearance because of uneven daylight distribution. Besides, excessive spare daylight is one of reasons causing higher cooling consumption.

In order to evaluate the effect of two kinds of blind for indoor environment, the evaluation for both thermal and lighting environment is in great need to be carried out. While indoor visual environment is first priority factor for occupant, daylight efficiency is more important than before. Daylight efficiency affects the artificial light and HVAC consumption directly. Therefore, in order to evaluate two kinds of blinds comprehensively, this research would evaluate not only thermal and daylight effects of blind application, but also artificial light and HVAC energy consumption with those effects.

This research shows that Redirecting angle has worse daylight distribution and daylight efficiency when compared to Blocking angle. Therefore, Redirecting angle is easier to cause Glare, and need to be decreased for visual comfort. On the premise of visual comfort as a first priority, due to Blocking angle has better daylight blocking efficiency and daylight distribution, it can use more daylight.

From the perspective of thermal environment, the space with blocking blinds uses more daylight. But cooling load would not increase obviously because increasing solar radiance is not higher than artificial light used to make up insufficient daylight. Overall, application of daylight would not increase the cooling load dramatically. Instead, the artificial light consumption saving can make up increasing HVAC consumption.

[1] Christoph F. Reinhart*, John Mardaljevic, Zack Rogers, Dynamic Daylight Performance Metrics for Sustainable Building Design, LEUKOS (3) (2006) 7–31.
[2] Ying-Chieh Chan, Athanasios Tzempelikos, Efficient venetian blind control strategies considering daylight utilization and glare protection, Solar Energy,98(2013)241-254.
[3] Svetlana Olbina, Jia Hu, Daylighting and thermal performance of automated split-controlled blinds, Building and Environment, 56 (2012) 127-138.
[4] David Appelfeld,Svend Svendsen,Performance of a daylight-redirecting glass-shading system, Energy and Buildings,64(2013)309–316.
[5] Toke Rammer Nielsen, Simple tool to evaluate energy demand and indoor environment in the early stages of building design, Solar Energy 78 (2005) 73–83.
[6] E. B1LGEN, EXPERIMENTAL STUDY OF THERMAL PERFORMANCE OF AUTOMATED VENETIAN BLIND WINDOW SYSTEMS, Solar Energy 52(1994) 3-7.
[7] S. RHEAULT and E. BILGEN, EXPERIMENTAL STUDY OF FULL-SIZE AUTOMATED
VENETIAN BLIND WINDOWS, Solar Energy 44(1990) 157-160.
[8] Ming-Chin Ho , Che-Ming Chiang , Po-Cheng Chou , Kuei-Feng Chang , Chia-Yen Lee, Optimal sun-shading design for enhanced daylight illumination of subtropical classrooms,Energy and Buildings 40 (2008) 1844–1855.
[9] D. Saelens, W. Parys, J. Roofthooft, A. Tablada de la Torre, Reprint of “Assessment of approaches for modeling louver shading devices in building energy simulation programs”, Energy and Buildings 68 (2014) 799–810.
[10] Danny H.W. Li, Gary H.W. Cheung, Chris C.S. Lau, A simplified procedure for determining indoor daylight illuminance using daylight coefficient concept, Building and Environment 41 (2006) 578–589.
[11] Athanassios Tzempelikos, Andreas K. Athienitis, The impact of shading design and control on building cooling and lighting demand, Solar Energy 81 (2007) 369–382.
[12] Saadia Barbhuiya, Salim Barbhuiya, Thermal comfort and energy consumption in a UK educational Building, Building and Environment 68 (2013) 1-11.

[13] Anca D. Galasiu , Morad R. Atif, Robert A. MacDonald, Impact of window blinds on daylight-linked dimming and automatic on/off lighting controls, Solar Energy 76 (2004) 523–544.
[14] Viswanathan Kumaragurubaran and Mehlika Inanici, HDRSCOPE: HIGH DYNAMIC RANGE IMAGE PROCESSING TOOLKIT FOR LIGHTING SIMULATIONS AND ANALYSIS, 13th Conference of International Building Performance Simulation Association, Chambéry, France, August 26-28.
[15] J. Wienold, Dynamic daylight glare evaluation, in: Building Simulation 2009,11th International IBPSA Conference, 27–30 July 2009, Glasgow, Scotland, 2009,pp. 944–951.
[16] J. Wienold, J. Christoffersen, Evaluation methods and development of a new glare prediction method for daylight environments with the use of CCD cameras, Energy and Buildings 38 (7) (2006) 743–757.
[17] Velds M, Christoffersen J. ,Monitoring procedures for the assessment of daylighting performance in buildings. In: Daylighting in buildings: a source book on daylighting systems and components; 2001.
[18] E.S. Lee , D.L. DiBartolomeo, S.E. Selkowitz, Thermal and daylighting performance of an automated Venetian blind and lighting system in a full-scale private office, Energy and Buildings 29(1998)47-63.
[19] Ahmed H. Sherif , Hanan M. Sabry, Mahmoud I. Gadelhak, The impact of changing solar screen rotation angle and its opening aspect ratios on Daylight Availability in residential desert buildings, Solar Energy 86 (2012) 3353–3363
[20] S. Rheault, E. Bilgen, Heat transfer analysis in an automated venetian blind window system, Sol. Energy Eng 111(1) (1989) 89-95 .