CLOQUET RESIDENTIAL RESEARCH FACILITY:
WALL SYSTEMS HYGROTHERMAL PERFORMANCE EXPERIMENTAL EVALUATION
2007 - 2008

ACKNOWLEDGEMENTS AND DISCLAIMER

The research described herein has been performed with funding provided by the CertainTeed Corporation and the Minnesota Lath and Plaster Bureau with additional contributions by Brian Peterson Stucco, Inc. and Moisture Magangement, LLC.

While this support is gratefully acknowledged, the Principal Investigators assume complete responsibility for the contents herein.

SYNOPSIS

In partnership with the CertainTeed Corporation and the Minnesota Lath and Plaster Bureau, the University of Minnesota (Building Physics and Foundations Research and Cold Climate Housing Programs) is experimentally investigating the hygrothermal performance of a range of above-grade wall systems over the 2008 calendar year.  Some of these systems conform to the proposed universal building envelope hygrothermal performance standard that is a generalization of the foundation standard included in the draft building foundation rule developed for the State of Minnesota, while others are compliant with existing building code prescriptive rules.  This research has a strong focus on understanding the basic heat and mass transport physics for both standard and innovative systems in absolute terms and as a means of validating simulation codes, rather than as a residential application emulation exercise.  Hence, for example, some of the imposed boundary conditions are severe and not likely to be encountered in market applications.

In terms of particular components, the research systems are focused on:

• comparing the efficacy of 2-mil PA-6 (polyamide 6) membrane as a warm-side vapor retarder to standard 4-mil PE (polyethylene); and,

• clarifying the hygrothermal interactions between stucco cladding and various wall systems as they relate to biotic failure mechanisms.

• an exterior water separation plane (WSP) in combination with an interior PA-6 warm side vapor retarder
• a comparison of Kraft paper and PA-6 as a warm side vapor retarder in combination with 2 layers of 60-minute grade D as an external water resistive barrier (WRB)
• open-cell polyurethane foam without any interior vapor retarder
• closed-cell polyurethane foam adjacent to the sheathing combined with fiberglass batts
• the efficacy of wood fiberboard sheathing as a moisture sequestration system in combination with an external WSP
• the efficacy of a dedicated moisture sequestration system in combination with OSB sheathing
• a comparison of the relative impact of stucco and lapped fiber cement board cladding on the wall system hygrothermal performance
• a performance comparison of PA-6 faced fiberglass batts that are friction fit into the stud pockets (without sealing to the stud faces), to that of unfaced batts with interior PA-6 sealed to the stud faces.

The experiment will be run for a period of a full calendar year.  Since the start in December 2007, the experiment has focused on measuring the response of the wall systems to internal vapor pressure.  To this end, the internal relative humidities ranged from about 35% or less (no interior humidification) to 60% in increments of 5% through January and February, 2008.  Internal humidification was terminated in early March allowing the drying behavior of the wall systems to be captured during the spring and early summer.  During the summer, it is planned to externally wet the exterior cladding in order that the hygrothermal impacts of high cladding vapor pressures on the wall systems may be studied. 

Publication of the final report is expected in the first quarter of 2009.

Southern exposure view of test bays – stucco clad systems are orange, cement fiberboard is brown.

 

Comparison of 2-mil PA-6 and 4-mil PE with wood fiberboard sheathing and an external
water separation plane (WSP) in bay 1.
 

Bay 2 configuration:
PA-6/unfaced batts/moisture sequestration layer/OSB/2-layers Grade D-60/stucco in left hand pocket
Open cell urethane/OSB/2-layers Grade D-60/stucco in center pocket
R-13 batt/closed cell polyurethane/OSB/2-layers Grade D-60/stucco in right hand pocket

Bay 3 configuration:
Kraft-faced batts/ OSB/2-layers Grade D-60/stucco in left hand pocket
PA-6-faced batts/OSB/2-layers Grade D-60/stucco in center pocket
4-mil PE/unfaced R-19 batt/OSB/2-layers Grade D-60/stucco in right hand pocket

Bay 4 exterior configuration:
Water separation plane (modified bitumen coated plastic) on left hand pocket
Water resistive barrier (spun, bonded polyolefin) on center and right hand pockets.

Interior boundary conditions

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Revision date: 4/2/08