Air movement is one of the six main variables determirzing human thermal comfort; air temperature, relative humidity, mean radiant temperature, metabolic rate, and clothing insulation are the others. Recently, HVACde sign in;zovations, energy conservation concerns, and new laboratory data on fan cooling and drafts have brought substantial ~tttention to the issue of acceptable levels of air movement in qO’ice environments. Thermal comjort standards for indoor occupancy include air movement limits that are constructed from often conflicting evidence and are frequently difficult to apply. A primary reason is that, while air movement can provide desirable cooling in "warm" conditions, it can also increase the risk of unacceptably cool drafts. The transition zone from desirable cooling to uncomfortable draft is a complicated function of physics, physiology, and human expectation. This work focuses on air movement for cooling in the expected temperature range, 25.5°C to 28..5°C, of this transition zone. Fifty-four human subjects were given control of the air supply velocity from a desk fan (FAN), a floor-mounted diffuser (FMD). and a desk-mounted diffuser (DMD) single ambient air temperature. The subjects were asked to adjust the air movement as they pleased to make themselves comfortable. These tests encompassed the full temperature range of the "transition zone," 25.5°C to 28.5°C. Physical measurements of the environment were made and subjective votes collected, including thermal sensation, thermal preference, wor.’~ area preferences, personal control preferences, and health characteristics. A model that predicts the percentage of satisfied people (the PS model) as a function air temperature and air movement in warm conditions is proposed.

This report describes the results of research completed to date during Phases I and II of the project. The report is organized in terms of the major type of work that have taken place. These are: 1) Laboratory studies of air movement and comfort. 2) Review of the influences of humidity on health, particularly as they impact evaporative cooling and naturally cooled architecture. 3) Development of a computer model of the human body sensitive to localized effects of air movement, localized radiant feilds, and other environmental influences. 4) Assistance with the workshops to create compressor-free house designs.

This study addresses the effectiveness of air movement cooling, an alternative to compressor-based cooling of the air itself. Subjects in an environmental chamber were exposed to a range of warm temperatures and allowed to adjust air movement to suit their individual preferences, while answering a series of questions about their comfort. Air movement was from the subject's side, in two modes of turbulent flow. The air speeds chosen by the subjects, and their subjective responses, are evaluated in the context of existing comfort standards and prediction techniques. Choosing air speeds up to 1.4 m/s, over 80% of subjects at 1.2 met were comfortable up to 29°, and at 1.0 met up to 31°C. The cooling effectiveness was significantly affected by the nature of the turbulence. A zone is proposed within personally controlled air movement provides a likely alternative to mechanical air conditioning.

This final report presents the results of research completed during Phase III of the project, "Localized Thermal Distribution (LTD) for Office Buildings," sponsored by the California Institute for Energy Efficiency. The project team consisted of researchers from the University of California, Lawrence Berkeley Laboratory, and Humboldt State University. Work was performed in three task areas: (1)Whole-Building Energy Simulations, (2)Field Studies, and (3)LTD Engineering and Applications Guide Outline. Following this Executive Summary, the final report is presented in four separate parts, each addressing one of the above task areas with two describing work on the two separate field studies.

Background/objectives

Subjects/methods

Results

Conclusions