ATLANTA - The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) notes that there are multiple heating and cooling load calculation methods to determine system and equipment sizes for buildings of varying size, materials, and complexity. A proposed standard from ASHRAE aims to establish minimum requirements for the methods used to determine peak heating and cooling loads and the input of data into methods, according to Chris Wilkins, chair of the committee writing the standard.

ASHRAE Standard 183P, "Methods and Procedures for Performing Peak Heating and Cooling Load Calculations in Buildings Except Low-Rise Residential Buildings," is open for public comment. It opened for comment on May 6.

"The biggest challenge is allowing for enough flexibility that an engineer can choose the appropriate tool (method) for calculating the load while at the same time being strict enough that an appropriate level of accuracy is attained for all methods," Wilkins said.

Wilkins further explained that "Standard 183P does not dictate a particular method or program but does establish a minimum level of care that would apply to any method. The standard draws information from the Society's handbook and publications, and assigned criteria is based on accepted practices for determining peak loads."

ASHRAE Standard 183P primarily addresses methods for determining the peak cooling load, both manual and otherwise. It requires that calculations for cooling load be performed for appropriate months and times of the day and sets criteria for the use of weather data, external heat gains from fenestration, opaque building envelope and infiltration, and internal heat gains.

"The ultimate goal of the standard is establish the criteria of an appropriate calculation process that will result in an accurate estimate of the air conditioning and heating load in a building," he said. "This load is ultimately the basis of the selection and sizing of the systems and equipment that are required to accomplish inherent psychrometric processes, such as conditioning for outside air, reheat, dehumidification, and humidification.

Wilkins said the standard will have a significant impact on ASHRAE members and the HVAC industry as a whole.

He noted that the membership on the committee includes design engineers, manufacturers, academia, energy efficiency experts, code enforcement engineers, and representatives from other societies.

"The balance on the committee allowed us to fulfill our responsibility to the industry and produce a balanced standard," he said.

Drafts of ASHRAE's proposed standards and guidelines are available only during their public review periods. To obtain an electronic draft version of ASHRAE Standard 183P during the comment period, visit the "Standards for Public Review" shortcut at

Publication date: 05/16/2005