March 12, 2003—Simple steps to remove mold in small commercial and residential buildings by decreasing humidity were presented at the public session held recently in Chicago during ASHRAE’s 2003 Winter Meeting.
There needs be a shift in designing buildings in different climates as well as greater attention paid to the rule that water moves from warm temperatures to cold, according to Joe Lstiburek, Ph.D., P.Eng., Building Science Corp., Westford, Mass.
“We are designing buildings the same way regardless if the building is in Las Vegas or Miami,” Lstiburek said. “In addition, buildings and HVAC systems are being designed for cold months but not for summer months.”
He attributes standardization of building codes to uniform construction practices. These practices allow moisture to stay in the buildings longer and to attack construction materials, such as particleboard, fiberboard and paper, which provide food for the growth of mold.
“We need to design for drying buildings for wetness,” he said. He also stressed that those in the HVAC industry need to design for local conditions. One major hindrance to removing moisture from buildings is oversized systems. “Rules of thumb” applied to determining the heating and cooling loads in buildings have led to a dramatic oversizing of installed equipment, according to Glenn Hourahan, P.E., Air Conditioning Contractors of America, Arlington, Va.
“Oversizing equipment degrades systems’ ability to control moisture load,” he said.
Hourahan recommended that accepted load calculation references and programs be used and that special conditions related to geographic locations and part load operation be considered.
If engineers have to make a choice on the size of the system based on load calculations, it is better to go with slightly undersizing the system, he said.
