Volume 7, Issue 1 (January 2010)
Experimental Assessment of Hygrothermal Properties of Wood-Frame Wall Assemblies—Moisture Content Calibration Curve for OSB Using Moisture Pins
As part of a research program to establish the hygrothermal response of wood-frame wall assemblies to varying climate conditions, a series of drying experiments was performed in a programmable environmental chamber used to replicate exterior climatic conditions. In these experiments, bulk moisture content of the assembly was measured using a weighing system, and as well, measurements of local moisture content of oriented strand board (OSB) sheathing were taken with the use of electrical resistance moisture pin pairs. The local moisture content of the OSB was based on the relationship between moisture content and electrical resistance determined from a series of controlled laboratory experiments on OSB specimens of the same type and thickness. This paper reports on the results from experimental tests on seven small-size OSB specimens to establish the correlation between electrical resistance and the moisture content of the OSB. The process required the installation of several moisture pin pairs at different locations on and depths in the OSB. The weights of specimens together with resistance measurements taken across each pair of moisture pins were continuously monitored and results captured on a data acquisition unit. Details are provided in regard to electrical resistance measurements, the data acquisition unit, and method of weighing specimens. The results of the tests provided a simple equation to correlate moisture content of OSB to electrical resistance measurements using moisture pins pairs and as well correlation to moisture measurements using commercially available moisture metre. Given that moisture reading results obtained from commercially available moisture metres typically correlate to a specific wood species, the work completed in these experimental tests can be used to determine moisture contents in OSB from moisture metre readings.