ATLANTA - Interactions between various factors, such as indoor air quality and thermal comfort, can make an apparently acceptable building environment less acceptable to a substantial fraction of the occupants. A proposed guideline from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) calls attention to many interactions that designers might not have previously recognized or understood. These interactions can strongly influence occupant reactions to and perceptions of the quality of the indoor environment, according to Hal Levin, chair of the committee writing the guideline.

Guideline 10P, "Criteria for Achieving Acceptable Indoor Environments," is open for public comment until June 20. It specifies indoor environmental criteria that are acceptable to human occupants and are intended to minimize the potential for adverse health effects.

"Guideline 10 will be most helpful to designers who want to understand the interactions between the thermal conditions and indoor air quality," Levin said. "While the two are addressed separately in ASHRAE Standards 55 and 62, their important interactions are not."

For example, the warmer the air, the poorer and stuffier the air quality is perceived by occupants. This suggests that while the thermal comfort range spans several degrees, the lower end of the range should be preferred when there are known to be sources of pollutants, according to Levin. At the same time, when the thermal conditions are expected to be at the higher end of the comfort range, extra care must be taken to reduce indoor air pollutant sources or increase dilution with outdoor air.

"By carefully selecting the materials that are used in construction and furnishings, designers will be able to reduce the likelihood that occupants will find the air quality unacceptable, even at the upper end of the thermal comfort range," he said.

When pollutant sources are known to be present or are unavoidable, designing buildings to maintain temperatures at the lower end of the thermal comfort range will decrease the likelihood of complaints and reports of sick building symptoms.

Drafts of ASHRAE's proposed standards and guidelines are available only during their public review periods. To obtain an electronic draft version of ASHRAE Guideline 10P during the comment period, visit the "Standards for Public Review" shortcut at

Publication date: 06/13/2005