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Condensation Potential in High Thermal Performance Walls - Cold Winter Climate.

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Forest Service research paper,

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As a result of steadily rising energy costs, construction practice for light-frame wood structure has changed over the past few years. The use of 6-inch-thick walls and application of high-R-value, low-permeance sheathings to 4-inch walls has caused concern for the changing moisture patterns that may occur in walls. To observe actual moisture patterns and the potential for condensation, a test structure was constructed near Madison, Wis., for exposure of eight types of insulated wall panels at controlled indoor conditions and typical outdoor weather conditions. Panels were instrumented with moisture sensors and tested without Phase 1 and with Phase 2 penetrations electrical outlets in the indoor surface. Continuous vapor retarders effectively prevented condensation asphalted paper stapled between studs was inadequate. The installation of an electrical outlet changed the moisture profile and resulted in some condensation in most panels. Moisture levels on the back of siding in most Phase 2 panels have been known to produce buckling in long sections of hardboard siding. Although streaking occurred on the siding of two types of Phase 1 panels and three Phase 2 types, and some condensation occurred in all types of Phase 2 panels, there was no long-term accumulation of free water in the structure. The moisture content of framing remained below 12 percent throughout the 2-year study. There was no apparent increase in condensation potential with the addition of low-permeance foam sheathing in this study with controlled indoor conditions.

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  • Air Conditioning, Heating, Lighting and Ventilating
  • Civil Engineering
  • Construction Equipment, Materials and Supplies

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