How widespread is the moisture problem in buildings? In 2011, NIOSH (National Institute for Occupational Safety and Health) reported that up to 50% of U.S. buildings have some degree of water damage that make them uninhabitable by folks with biotoxin Illness. Scientific opinion refects a higher incidence in newer homes.
There is no national database on the prevalence of dampness and mold in U.S. houses. The table below compiles data from studies that reported prevalence of various moisture-related conditions in U.S. houses. For the "any dampness or mold category", four of the studies report the prevalence to be 50% or more, while three report prevalence values below 50%. The largest study (Spengler, 1994) reports prevalence of dampness and mold in 50% of the homes. Excluding the Freeman study because it only included bathrooms, the population weighted average prevalence of dampness or mold from these studies is 47% in the U.S.
Reported prevalence of dampness and mold in U.S. houses
In addition to the association between dampness and mold, it is also well known that relative humidity affects the rate of VOC emmissions. For example, field studies have shown formaldehyde emissions doubled when relative humidity rose from 30% to 70%. Research in 2014 showed Total VOC (TVOC) concentrations rose over 300% when humidity rose from 40% to 85%.