This paper examines certain workmanship requirements applying to insulants in cavities. It presents previously reported measured values for the effects of edge gaps, and compares these results with new laboratory measured results for the heat transfer across insulated wall and ceiling cavities, in configurations which permit natural convection to flow around the insulant. The results show the ex istence of a threshold edge gap width of a few mm for the onset of convection in upward heat flow, but no threshold gap width of detectable size for horizontal heat flow. The loss of thermal performance from convection, as expected, outweighs that previously reported for non-convecting gaps.
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