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Showing papers in "Center for the Built Environment in 1998"


Journal Article
TL;DR: In this paper, the adaptive hypothesis predicts that contextual factors and past thermal history modify building occupants' thermal expectations and preferences, which is contrary to static assumptions underlying the current ASHRAE comfort standard 55-92.
Abstract: The adaptive hypothesis predicts that contextual factors and past thermal history modify building occupants' thermal expectations and preferences. One of the predictions of the adaptive hypothesis is that people in warm climate zones prefer warmer indoor temperatures than people living in cold climate zones. This is contrary to the static assumptions underlying the current ASHRAE comfort standard 55-92. To examine the adaptive hypothesis and its implications for Standard 55-92, the ASHRAE RP-884 project assembled a quality-controlled database from thermal comfort field experiments worldwide (circa 21,000 observations from 160 buildings). Our statistical analysis examined the semantics of thermal comfort in terms of thermal sensation,

1,455 citations


Journal Article
TL;DR: In this paper, a field study was carried out to assess the impact of installing a desktop task/ambient conditioning (TAC) system at 42 selected workstations within three San Francisco office buildings occupied by a large financial institution.
Abstract: A field study was carried out to assess the impact of installing a desktop task/ambient conditioning (TAC) system at 42 selected workstations within three San Francisco office buildings occupied by a large financial institution. In this study, field measurements, including subjective surveys and physical monitoring, were performed both before and after the TAC system installation to evaluate the impact of the TAC system on occupant satisfaction and thermal comfort, as well as the thermal environments within the office buildings. For comparative purposes within each building, a control group, consisting of workers who did not receive a desktop TAC unit, was studied concurrently. During the follow-up field tests, performed three months after the TAC system installation, measurements were repeated under three different room temperature setpoint conditions (normal, set-up, and set-down) to investigate the ability of the occupants to use the desktop TAC units to control their local environment in response to a wider range of ambient temperatures. Survey results show that among the six building assessment categories investigated, installation of the desktop TAC system provided the largest increases in overall occupant satisfaction for thermal quality, acoustical quality, and air quality. In terms of specific environmental factors, increased occupant satisfaction levels among the TAC group were strongly significant in comparison to changes within the control group for both temperature and temperature control. A large majority of the workers in the control group indicated a preference for higher air movement at operative temperatures of 73°F (23°C) and above. The percentage preferring higher air movement within the TAC group was significantly lower. Workers in the TAC group had the ability to use their TAC units to adjust the air movement in their workstations in response to changes in the ambient temperature. Over the range of operative temperatures covered by this field study, air movement preference and thermal sensation votes by workers in the control group indicated that they were more than twice as sensitive to changes in temperature as those in the TAC group.

138 citations


Journal Article
TL;DR: Sharag-Eldin et al. as discussed by the authors developed a mathematical model for predicting exterior surface pressures and indoor air velocities for small-scale buildings in urban settings, using a set of geometric variables that describe urban surroundings in terms of obstruction blocks and the gaps between them.
Abstract: Author(s): Sharag-Eldin, A. | Abstract: The objective of this dissertation was to develop, through systematic research and experimentation, a mathematical model for predicting exterior surface pressures and indoor air velocities for small-scale buildings in urban settings. The resulting model is a step-by-step series of functions that produce these results while accounting for various possible geometric relationships between the building and the urban surroundings.This study was conducted in two phases. The first phase developed an empirical Pressure Prediction Model (PPM) for shielded surfaces using a sequence of wind tunnel tests. The model produces a non-dimensional Pressure Modification Coefficient (Cpm) using a set of geometric variables that describe urban surroundings in terms of obstruction blocks and the gaps between them. A number of empirical corrections account for horizontal displacement of obstructions and for wind direction effects. Cpm is then used to calculate the average pressure coefficient on shielded surfaces. The wind tunnel tests show that the shielding effect of an obstruction block is significant within a ±70° arc around the wind direction, and that it is possible to predict the shielding effect of multiple obstruction blocks within this arc by averaging the shielding effects of individual obstruction blocks and summing the effects of all the gaps.The second phase concentrated on the development of an Indoor Velocity Prediction Model (IVM). The IVM uses the PPM-predicted surface pressures on shielded walls as input to a model developed by Ernest (1991) to determine the Indoor Velocity Coefficients (IVC). The IVM model also adopts a procedure developed by Arens et al (1986) to convert remote weather station data into site-specific wind speeds. Arens’ procedure corrects for the differences in height between the weather station and the site, the differences in terrain roughness characteristics between the two locations, and wind acceleration due to site topography.The PPM was verified against Wiren’s (1984) tests of an instrumented model in different arrays of similarly configured obstruction blocks, and against an instrumented model in a more complex layout. The predicted and the measured pressure values showed a reasonably good fit in both cases. The successes and limitation of the model are discussed.The IVM predictions of interior airflow were not validated here. Ernest has validated his model in both unobstructed and simply-obstructed conditions, and the PPM is not expected to change the nature of the interior flows predicted by Ernest’s model.

12 citations