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Hotbox Test R-value Database

FSEC - Florida Solar Energy Center



During June 1997, the steady-state thermal performance of five material configurations of the Florida Solar Energy Center (FSEC) wall were measured in the Oak Ridge National Laboratory (ORNL) Buildings Technology Center (BTC) Rotatable Guarded Hot Box.


The structure of the FSEC wall is based on combined wood/metal structural profiles developed by FSEC. As shown in the above figure, FSEC combined wood/metal studs consisting of two metal flanges and connecting web made of OSB or plywood. The FSEC wall cavity can be insulated by R-11 or R-13 fiberglass batts.

FESC Wall Measurements

R-value measurements of the FSEC wall system were carried out by ORNL hotbox apparatus using ASTM C 236, Standard Test Method for "Steady-State Thermal Transmission Properties of Building Assemblies by Means of a Guarded Hot Box". A relatively large (approximately 8 x 8 ft. or larger) cross-section of the clear wall area of the wall system was used to determine its thermal performance. Steady air temperatures (100 deg.F on one side and 55 deg.F on the other) and air velocities were set on both surfaces of the tested wall during the test.

Exterior surface of the wall was originally finished with ½-in. thick layer of gypsum board. Then, several thick layers of XPS foam insulation were installed over gypsum board to analyze thermal performance of FSEC walls with insulating sheathing. This was done to simulate the EIFS (exterior insulated finish system) wall system which generally has the foam insulation installed to the outside surface of the structural sheathing. Two types of the cavity R-11 fiberglass batts and one type of R-13 batts were used during the tests.



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