Thermal Behaviour of an External Residential Wall Panel

NASH-NZ-Report-Study on Thermal Behaviour of an External Residential Wall Panel – 21-July2013

NASH NZ commissioned the Smart Structure Laboratory (SSL) of Swinburne University of Technology to undertake thermal tests on a steel framed residential wall panel to examine the potential for condensation due to thermal gradient across the thickness of the wall. The testing and evaluation of results are preliminary in nature and the scale of work was quite limited to developing basic understanding of the performance of this wall panel.

The wall panel measured approximately 1.9mx1.6m and was made of full scale components. The test panel included building wrap, 10mm XPS thermal break, R2.6 pink batts and 10mm plasterboard. The framing members were made of 0.75mm thick G550 steel 90mmx40mm lipped C sections. The test wall did not have a cladding material.

A number of tests were conducted on the test wall which attempted to form condensation and also to examine the drying potential of the wall due to artificial wetting within the wall construction.

These preliminary findings suggest that condensation is unlikely to occur for this type of construction when the outside temperature is as low as 2°C and the humidity is as high as 70%RH if indoor conditions are 20°C with relative humidity of 50%. The test specimen did not visually show any condensation on the XPS thermal break or on the flanges of the studs.

Due to lack of condensation, the inside face of the XPS thermal break and pink batts were sprayed with approximately 200ml of water over a wall area of about 0.6m2 between two studs. The Hot Room was maintained at 20°C and 50%RH while the Cold Room was maintained at 10°C and 70%RH. At these conditions, it took eight days for the sprayed water to completely dry.

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