EDRA: Envelope Drying Rates Analysis Experiment

Several associations form the Building Envelope Research Consortium (BERC), initiated by CMHC. BERC outlines four major research projects: a Field Survey to determine why buildings leak, a Best Practices Guide (BPG) to inform how to build a better performing building, a Quality Assurance Protocol (QAProtocol) to inform how to maintain quality as a criteria through all phases of design, construction, completion, and maintenance; and a Model Buildings Initiative to test the performance of buildings built using the BPG and QAProtocol. Later two other projects were added, the Building Envelope Education Program (BEEP) to certify professional architects and engineers as Building Envelope Specialists, and Envelope Drying Rates Analysis (EDRA), a series of laboratory performance tests of different wall designs and construction.

A summary(also see related references) of EDRA: objective: evaluate the effect of wall design on the drying capacity of wood-frame test wall panels in a controlled laboratory environment. Setup: 12 samples (1.22 m by 2.44 m), 10 stucco cladding and 2 cedar siding. Procedure: prior wetting by immersion to 25%-29%MC; testing 3 month under 5C/70%-20C/40% steady-statel; weight of assemble before and after; weighing components after. Test repeated for no light and with solar lamps (15C solar temperature). Results: all designs dry to below 19%MC. Sheathing (OSB, plywood) get wet by moisture redistribution from wet wood studs, and its MC stays quite constant through testing. OSB has over 30% MC in lower areas of panels. Larger cavity width dry faster.



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CMHC- Canada Mortgage and Housing Corporation

"the federal government's housing agency, is responsible for administering the National Housing", formerly the Central Mortgage and Housing Corporation