We have a recently-built house about 1.5 years old with 6” of wet spray-applied cellulose insulation(WSACI) in the sidewalls.  There is a sharp odor of vinegar coming from the wall sockets.  Could this be mold from the wet spray applied cellulose insulation?-Phillip, Wisconsin 

            It is not likely that the odor you are experiencing is directly due to mold growth.  Typically when mold species grow on a substrate, they produce volatile compounds that we detect as musty/moldy odors.  Microbially-produced substances (MVOCs) are typically ketones or alcohols. 

            In decomposition processes involving mold, a variety of substances that are not particularly volatile are produced.  These would include organic acids and may include acetic acid (the odor of vinegar).  However, I know of no reports, nor have I experienced detecting the odor of acetic acid associated with mold infestations.

            When WSACI is formulated, manufacturers include additives such as boric acid or ammonium sulfate to serve as fire retardants, polyborates to serve as mold inhibitors and adhesive substances to hold the WSACI in place on drying. 

            Odor complaints (other than mold) associated with WSACI have been reported.  These primarily are associated with WSACI that has been formulated with ammonium sulfate .  Apparently  ammonium sulfate can break down to produce gaseous ammonia inside the wall cavity with the ammonia then emanating out into the building environment.  Barb Epstein, Industrial Hygienist with Air Quality Sciences in Atlanta, has recently reported on two case investigations of ammonia odors in newly-constructed houses with WSACI. 

            She sensed ammonia odor that varied from slight to quite strong.  On conducting air tests, an average concentration of 2 ppmv in room air and 7 ppmv in wall cavities respectively were measured in one house.  In the second case  average room air concentrations of 4 ppmv with wall cavity concentrations of 20 ppmv were observed.  These investigations showed a strong relationship between ammonia concentrations in  wall cavities and  in living space air. 

            Vinegar-like odors are commonly associated with caulking compounds used around windows and doors (as acetic acid is a normal constituent of such products). Generally the vinegar-like odor decreases to non-detectable levels in a matter of a week or so.

 

September 9, 2006