TABLE OF CONTENTS This chapter presents weather data for the United States, Canada, and other countries and recommended interior and exterior design conditions. The data come from the 1997 ASHRAE Handbook-Fundamentals and are based on long-term hourly observations. The major change from data presented in previous editions is that the summer percentile frequency categories have been changed from 1, 2.5, and 5 to 0.4, 1, and 2. The winter percentile frequency categories of 99 and 97.5 have been replaced by 99.6 and 99. The change was made to provide design conditions that have the same probability of occurrence at all locations. The new outdoor design conditions tables are presented in Section 5.2.
The primary purpose of the heating and air-conditioning system is to maintain the space in a comfortable and healthy condition. To do this the system must generally maintain the dry-bulb temperature and the relative humidity within an acceptable range.
ANSI/ASHRAE Standard 55-1992 gives thermal comfort values at selected conditions in the building environment. Physiological principles, comfort, and health are addressed in the Fundamentals volume of the ASHRAE Handbook. The Systems and Applications volume gives specific recommendations for indoor design conditions for such applications as hospitals and other special cases.
ANSI/ASHRAE/IESNA Standard 90.1, Energy Efficient Design of New Buildings, recommends that indoor design temperature and humidity conditions be in accordance with criteria established in ANSI/ASHRAE Standard 55. This gives considerable latitude in selecting design conditions. Experience has shown that, except in critical...
