Hygric Redistribution in Insulated Assemblies: Retrofitting Residential Envelopes Without Creating Moisture Issues
- Building Science Corporation, Somerville, MA (United States)
This research report was prepared by the Building Science Corporation Building America Research Team as part of the Energy Efficient Housing Research Partnerships project. The project title is Hygric Redistribution in Insulated Assemblies. The exterior retrofit of frame assemblies can be risky when impermeable insulating sheathings of relatively low thermal resistance are used. For example, basic hygrothermal analysis demonstrates that removing the existing cladding and installing a board foam insulation with low vapor permeance (such as ½-in. foil faced rigid insulation) directly over the sheathing membrane under a replacement cladding (such as vinyl siding) is likely to cause moisture problems in cold climates. One such problem is known as a “cold sided vapor barrier.” Tens of thousands of such retrofit and renovation projects have been completed, however, without apparent problems. There is also a perception that when water is intentionally drained in a drainage cavity between exterior insulation and the existing structure following an energy retrofit, moisture-related durability concerns exist for the sheathing and wood structure. This experimental program includes a literature review of previous research, laboratory testing programs, and an analysis of full-scale test wall performance in the U.S. Department of Energy’s climate zone 4C.
- Research Organization:
- National Renewable Energy Laboratory (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Building Technologies Office
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1067936
- Report Number(s):
- NREL/SR--5500-55877; DOE/GO--102013-3720; KNDJ-0-40337-00
- Country of Publication:
- United States
- Language:
- English
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