A capacitance probe for measurement of moisture content in open pore thermal insulations

Technical Report · Sun Jan 01 04:00:00 EST 1989

OSTI ID:6514889

Motakef, S; Glicksman, L R

Low slope roofs often experience deterioration by moisture condensation and water seepage within the built-up structure. Instrumentation to date for measuring the amount of moisture in roofing has had limited success and has centered on large aerial surveys. This paper documents the design of instrumentation to measure the moisture content by volume of porous building materials. The final configuration includes a fork-like 24 pin capacitance probe and an electronic circuit which outputs a voltage corresponding to the wetness measured. The probe is intrusive yet nondestructive, and gives localized readings which are good for grid surveys. An accompanying electronic circuit allows for real-time capacitance readings with dc voltage output. This instrumentation has been calibrated for board and ceiling fiberglass as well as phenolic insulations. Insertion methods place the probe as deep as six inches into fiberglass with minimal disturbance to the material. Tests within a small-scale roof testing apparatus have shown that moisture movement can be quantitatively followed successfully. The uncertainty of moisture determination is 10%. The method is accurate within the moisture content range of 0 to 30% for fiberglass while a wider, yet undetermined, range exists for phenolic. 17 refs., 33 figs., 1 tab.

• Research Organization: Oak Ridge National Lab., TN (USA); Massachusetts Inst. of Tech., Cambridge (USA). Dept. of Mechanical Engineering
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6514889
• Report Number(s): ORNL/Sub-85-27486/1; ON: DE89007909
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
320107* -- Energy Conservation
Consumption
& Utilization-- Building Systems-- (1987-)
DATA
ELECTRONIC CIRCUITS
EXPERIMENTAL DATA
INFORMATION
MEASURING INSTRUMENTS
MOISTURE
MOISTURE GAGES
NUMERICAL DATA
PERFORMANCE TESTING
ROOFS
TESTING
THERMAL INSULATION