Indoor thermal environmental conditions near glazed facades with shading devices e Part I: Experiments and building thermal model M. Bessoudo a , A. Tzempelikos b, * , A.K. Athienitis a , R. Zmeureanu a a Department of Building, Civil and Environmental Engineering, Concordia University, 1455 de Maisonneuve Blvd. W., Montreal, H3G 1M8 QC, Canada b School of Civil Engineering, Purdue University, 550 Stadium Mall Dr., West Lafayette, 47907 IN, USA article info Article history: Received 26 February 2010 Received in revised form 9 May 2010 Accepted 10 May 2010 Keywords: Indoor thermal environment Facades Shading Building simulation abstract This paper presents an experimental study of indoor thermal environment near a full-scale glass facade with different types of shading devices under varying climatic conditions in winter. Interior glazing and shading temperature, operative temperature and radiant temperature asymmetry were measured for façade sections with roller shades and venetian blinds at different positions. Interior glass surface temperatures can be high during sunny days with low outdoor temperature. Shading systems signifi- cantly improved operative temperature and radiant temperature asymmetry during cold sunny days, depending on their properties and tilt angle. During cloudy days the impact was smaller, however the shading layers could still decrease the amount of heat loss through the façade. A transient building thermal model, which also calculates indoor environmental indices under the presence of solar radiation, was developed and compared with the experimental measurements. Part II of this paper uses this validated model with a transient, two-node thermal comfort model (including transmitted solar radia- tion) for assessment of indoor environmental conditions with different building envelope and shading properties, façade location and orientation. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction It is often forgotten that energy related issues in buildings are only secondary factors; the primary objective of buildings is to provide shelter, space, and comfort for the people that live, work, and interact in them. Therefore, in designing for energy efficient buildings, the building’s primary objective should not be neglec- ted. It can be said that the “success” of a building depends on whether a comfortable indoor environment is achieved without increasing energy use. Although the broad definitions given to thermal comfort have been subject to deep inquiry and philo- sophical debate [1], they nevertheless emphasize that the judg- ment of comfort is a cognitive process that is influenced by a combination of physical, psychological, and physiological factors. In general, comfort is attained when body temperature is held within a narrow range, skin moisture is low, and the physiological effort of regulation is minimized [2]. From earlier research [3e5], it is known that thermal comfort is affected by the thermal interaction between the body and surrounding environment. There are six primary factors that affect this thermal interaction: air temperature, mean radiant temperature, air speed, humidity, metabolic rate and clothing insulation. The first four factors define the conditions of the surrounding environment while the latter two represent “personal” variables that can vary between from person to person. Occupants react to any perceived discomfort by taking actions to restore their comfort. Sometimes these actions will come with an energy cost; for example, using a shading device and turning on lights is a costly way to eliminate glare and overheating due to the presence of solar radiation. Similarly, opening a window in the winter due to overheating is also a costly way to alleviate discomfort. Therefore, it is important to recognize that a ‘low energy’ standard that increases occupant discomfort may be no more sustainable than one that encourages energy use [6]. The adaptive approach of describing thermal comfort [7e10] does not rely only on strict descriptions of clothing variables and metabolic rates, but depends on many factors (climate, HVAC systems, and time) and active occupant participation. Adaptive thermal comfort is a function of the possibilities for change as well as the actual temperatures achieved and it has the potential of making the comfort zone wider, with profound effects on the cooling system operation. On this basis, Yao et al. [11] developed the “adaptive predicted mean vote” concept. Toftum et al. [12] applied the adaptive thermal comfort model and predicted energy savings for different climatic regions. * Corresponding author. Tel.: þ1 765 4907010; fax: þ1 765 4940395. E-mail address: ttzempel@purdue.edu (A. Tzempelikos). Contents lists available at ScienceDirect Building and Environment journal homepage: www.elsevier.com/locate/buildenv 0360-1323/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.buildenv.2010.05.013 Building and Environment 45 (2010) 2506e2516