the invention provides blower housings for air handlers and hot air furnaces which are made from molding compounds that allow for wide flexibility in molding complex configurations so as to improve blower efficiency , which improve manufacturing efficiency and safety and provide suitable mechanical properties , safety in use , and sound dampening . these compounds are generally liquid thermosetting molding resins which comprise a thermoset resin matrix such as a isophthalate polyester having a specific loading of glass reinforcing fibers . the compositions also include flame retardant additives . they are further formulated to meet the desired molding characteristics ; to withstand the operating temperatures to which they will be exposed ; and to have a predetermined strength and a desirable user interface including appearance , and odor . typically , the compounds will have a glass transition temperature from about 160 ° c . to about 185 ° c . .