September 2003
Background
In 1999, the Manufactured Housing Research Alliance (MHRA) conducted a study to identify moisture problems for the manufactured home industry. The common problems were described in the publication Moisture Problems in Manufactured Homes – Understanding Their Causes and
Finding Solutions (MHRA 2000). From those common problems a set of three checklists were developed for the various stakeholders: manufacturers, home installers, mechanical equipment designers, contractors and homeowners. That work prompted discussion of moisture-related problems currently plaguing the entire building industry. A consensus developed that moisture problems were most acute among homes in the hot and humid Gulf Coast region. In 2001, MHRA's moisture research was directed towards tackling problems common to homes built in this region.
While this report focuses on manufactured housing, moisture problems are in no way unique to this
type of construction. Extensive problems have been reported in site-built housing, and other
residential and commercial buildings. The physical forces that drive moisture dynamics and cause
moisture to accumulate where it may cause damage are the same for all types of buildings.
Excess moisture infiltration and accumulation is a damaging agent affecting housing durability and
potentially reducing its service life. Moisture is readily absorbed by many building materials, and
when present at critical levels can cause these materials to fail to perform as designed, deteriorate,
and develop odors or stains.
Moisture infiltration problems are particularly difficult to diagnose and address because of the
complex mechanisms by which moisture migrates through building materials and assemblies. Many
individual building components influence moisture dynamics through their thermal performance and
through their capability to store moisture and/or to allow vapor diffusion. In some instances the
design of the structure can contribute to the problem, while in others the material selection is the
culprit. Furthermore, homes designed properly to control moisture flow may still have moisture
problems as a result of homeowner activities and operation and maintenance of the home.
Prepared for:
U.S. Department of Housing and Urban Development
Affordable Housing Research and Technology Division
52 pages