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Tri State homes: a case study of extensive decay in the walls of older manufactured homes with exterior vapor retarder

Tsongas, G. and Olson, J.
1995
Proceedings of the DOE/ORNL/ASHRAE/BETEC Conference, Thermal Performance of the Exterior Envelopes of Buildings VI, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Orlando, Florida, pp. 207-218
fungi decay, exterior vapor retard, plywood, manufactured home


Tsongas, G. and Olson, J., (1995), "Tri State homes: a case study of extensive decay in the walls of older manufactured homes with exterior vapor retarder", Proceedings of the DOE/ORNL/ASHRAE/BETEC Conference, TThermal Performance of the Exterior Envelopes of Buildings VI, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Orlando, Florida, pp. 207-218.
Abstract:
The first known cases of extensive decay in the wall ftaming members of hundreds, if not thousands, of nwm~actured homes involve the Tii State Homes in Wisconsin, Minnesota, and Mich-igan (the company has gone bankrupt). About 6,000 such homes were built in the 1970s. The decay has been attributed to high levlels of indoor moisture, but recentfield test and computer modeling results indicate that the primary cause is the presence of an exterior vapor retarder (EVR) that trapped moisture within the wall cavity. The low-permeability retarder (building paper) was on the outside of the plywood sheathing behind hardboard lap siding. The presence of the zvpor retarder caused the plyuvod to get much wetter than normal during the winter and spring, and it reduced the rate ofdrying of the plywood. Thus the wood zaas still quite wet in the late spring and early summer, when temperatures were high enough to promote the growth of decay fiingi. The result was severe and extensive rotting of the plywood sheathing that occurred aver the last 20 years. But the decay progressed slowly, such that it was first noticed only about eight years ago. Moreover, the wet wall conditions led to the growth of substantial mold that seriously impacted the health of many of the occupants.

An inspection of 15 Tri State homes in Wisconsin that had siding removed (completely rewtoved in 11 of the cases) revealed that 14 had plywood decay and 12 of the cases were sewre enough that the plywood could be torn apart by hand. Ten of tlw 11 homes with siding completely removed had decay present. In addition, decay was noted infive of six houses with siding removed only in two localized areas, those homes urre not inspected by the

Thus, overall, 19 of 21 homes inspected had plywood decay. It is conjectured that most, ~ not all, of the Tri State homes either already hazle experienced or eventually will experience severe plywood decay. Plywood delamination also ztas observed in 8 of 10 of the cases.

Many of the walls were unusually wet during winter and early spring, and plywood moisture contents above 60% (the meter limit) zww measured during late June and early July, when the plywood in a conventionally constructed wall is considerably drier. The plywood moisture contents measured in the Tri State homes during that early summer, as well as during the previous winter and early spring, um higher Own the highest values mea- sured in any of three Pacific Northwest wall moisturefield stud- ies. While it has long been noted that the outside layers of a wall should be less permeable than the inside layers, these results dra- matically emphasize the catastrophic results that can occur when the rule is notfollowed.

A comparison of sheathing and siding moisture levels for walls with and without an EVR also was undertaken using the MOIST computer model developed at a national laboratory. The modeling resultsfurther reinforce thefield inspectionfinding that the EVR is the cause of the structural damage.

Details of thefield tests and the computer modeling are pre-sented, along with conclusions and recommendations. Practical lessons learnedfrom this case study are presented to avoid similar problems in thefuture with presently available building products that act as an exterior vapor retarder.

Anderson, L.O., andGE. Sherwood. 1974. Condensation prob-lems in your house: Prevention and solution. Forest Prod-ucts Laboratory, Forest Service, U.S.D.A. Agriculture Information Bulletin No. 373. Based on 1972 U.S.D.A. Forest Service Research Paper FPL 132 and numerous reports published in the 1940s.

ASHRAE. 1993. 1993 ASHRAE lwndbook-Ftindanientals. At-lanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.

Burch, D.M., and A. TenWolde. 1993. A computer analysis of moisture accumulation in the walls of manufactured hous-ing. ASHRAE T?-atisactions 99(2).

Burch, D.M., and W.C. Thornas. 1992. An analysis of moisture accumulation in a wood-frame wall subjected to winter cli-mate. Proceedings, Thermal Performance of the Exterior Enve-lopes of Buildings V, ASHRAE/DOE/BTECC Conference, December 7-10, Clearwater Beach, Fla.

Burch, D.M., W.C. Thomas, and A.H. Fanney. 1992. Water vapor permeability measurements of common building materi-als. ASHRAE Transactions 98(2).

Merrill, J.L., and A. TenWolde. 1989. Overview of moisture-related damage in one group of Wisconsin manufactured homes. ASHRAE Transactions 95(l):405-414.

Olson, J., S. Schooler, and M. Mansfield. 1993. Tri State Homes: A case study of liability for defective homes which created unhealthy environments causing personal injuries. Pro-ceedings, International Conference on Building Design, Technol-ogy & Occupant Well-Being in Temperate Climates, Brussels, Belgium, February.

Sherwood, G. 1987. Condensation potential in wood-framed waus. Thermal Insulation: Materials and Systems, ASTM STP

922, F.J. Powell and S.L. Mathews, eds., pp. 405417. Phila-delphia: American Society for Testing and Materials.

Trechsel, H., ed. 1994. Moisture control in buildings, chapter 13. Philadelphia: American Society for Testing and Matefials.

Tsongas, G.A. 1980. A field study of moisture damage in walls insulated without a vapor barrier. Proceedings, 1979 ASH-RAEIDOE-ORNL Conference on the Thermal Performance of the Exterior Envelopes of Buildings, ASHRAE SP 28, pp. 801-815. Also Oak Ridge National Laboratory Report No. ORNL/Sub-78/97726/1,1979.

Tsongas, G.A. 1986. The Spokane wall insulation project: A field study of moisture damage in walls insulated without a vapor barrier. Proceedings, 1985 ASHRAEIDOEIBTECc Conference on Thermal Performance of the Exterior Envelopes of Buildings III, ASHRAE SP 49, pp. 556-569. Also U.S. DOE/ Bonneville Power Administration, DOE/BP-541, Septem-ber 1985.

Tsongas, G.A. 1990. The Northwest wall moisture study: A field study of excess moisture in walls and moisture problems and damage in new Northwest homes. U.S. DOE/Bonne-ville Power Administration, DOE/BP-91489-1, June. The information in this BPA report supersedes that in Tsongas, G.A. 1990. The Northwest wall moisture study: A field study of moisture in the exterior walls of new Northwest energy-efficient homes. In Insulation Materials, Testing, and Applications, STP 1030, D.L. McElroy and J.F. Kimpflen, eds., pp. 464482. Philadelphia: American Society for Test-ing and Materials.

Tsongas, G.A., and G. Nelson. 1991. A field test for correlation of wall air leakage and wall high moisture content sites. ASHRAE Transactions 97(l).

Tsongas, G.A. 1995. Wall wood decay and weatherizing older mobile homes. U.S. DOE/Bonneville Power Administra-tion, RCDP Update: Technical Bulletin, DOE/BP-2545, March.

Tsongas, G.A., D. Burch, C. Roos, and M. Cunningham. 1995. A parametric study of wall moisture contents using a revised variable indoor relative hun-ddity version of the "MOIST" transient heat and moishn-e transfer model. Proceedings, Thermal Performance of the Exterior Envelopes of Buildings VI, Clearwater Beach, Fla., December.

USDA. 1987. Wood ha?idbook.- Wood as an engineering nwterial. USDA Forest Products Laboratory, Agriculture Handbook No. 72. Washington, D.C.: U.S. Department of Agriculture.


Related Resources:
  • This link has not been checked.ANSI-- American National Standards Institute
    "a private, non-profit organization (501(c)3) that administers and coordinates the U.S. voluntary standardization and conformity assessment system. to enhance both the global competitiveness of U.S. business and the U.S. quality of life by promoting and facilitating voluntary consensus standards and conformity assessment systems, and safeguarding their integrity."
  • This link has not been checked.ASHRAE-American Society of Heating, Refrigerating and Air-Conditioning Engineers
    "the sole purpose of advancing the arts and sciences of heating, ventilation, air conditioning and refrigeration for the public's benefit through research, standards writing, continuing education and publications."
  • This link has not been checked.ASTM
    "provides a global forum for the development and publication of voluntary consensus standards for materials, products, systems, and services"
  • This link has not been checked.DOE--Department of Energy
    "The Department of Energy's overarching mission is enhancing national security. Responsibility for accomplishing this mission is shared between four principal program lines."
  • This link has not been checked.Forest Products Lab
    "on pulp and paper products, housing and structural uses of wood, wood preservation, wood and fungi identification, and finishing and restoration of wood products."
  • This link has not been checked.FPL publications
    Large amount of searchable publication database, including This link was broken when checked on Dec. 2006Dividends From Wood Research, This link was broken when checked on Dec. 2006Durability, and more.


Related Concepts


Author Information and Other Publications Notes
Tsongas, G.
  1. A computer analysis of the moisture performance of roof constructins in the U.S. DOE Moisture Control Handbook
  2. A field study of indoor moisture problems and damage in new northwest homes
  3. A prarmeteric study of wall moisture contents using a revised variable indoor relative humidity version of the "MOIST" transient heat and moisture transfer model
  4. Case Studies of Moisture Problems in Residences
  5. Field observations and laboratory tests of water migration in walls with shiplap hardboard siding  
Olson, J.
NRCC-IRC - National Research Council Canada - Institute for Research in Construction M-24 OTTAWA, ON K1A OR6
     



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