University of Tasmania, Australia

The general objective of this project was to better understand and quantify the thermal performance of light-frame buildings, particularly forms of construction commonly used in the Australian residential sector. Specifically, this project seeks to compare the thermal performance of three commonly used construction types used in the Australian residential sector; to empirically validate the AccuRate software in cool temperate climates such as in Tasmania; and to build research capabilities and expertise.

It included thermal performance monitoring of three test cells with uncarpeted floor during the free running period from January to December in 2007, and the subsequent comparisons and analysis for the empirical validation.

The test cells were built in the same location, with the same planning and orientation but using different floor construction types. Each test cell was designed to match flooring options referenced from the Building Code of Australia. To further align with the primary building types used for housing in Australia, the cells were designed with brick veneer walls with either an enclosed subfloor or no subfloor. Each cell is briefly described as follows:

• Test Cell 1 – Unenclosed perimeter platform floor with plywood cladding
• Test Cell 2 – Enclosed perimeter platform floor with brick veneer cladding
• Test Cell 3 – Slab-on-ground floor with brick veneer cladding
• Prior to this project, no empirical validation studies on AccuRate were conducted on purpose-built buildings, specifically comparing platform timber-floors and slab-on-ground floors.

Each test cell was fully instrumented with a total of at least 60 sensors installed in the room, roofspace, walls and wall cavities, subfloor space, and the ground. A weather station located on the roof of Test Cell 2 provided external environment data for the AccuRate thermal performance simulation.

Measurement and comparison of the test cells’ thermal performance ensued after verifying the air-tightness of the buildings. Infiltration measurements were conducted by Deakin University’s Mobile Architecture and Built Environment Laboratory (MABEL). The weather station on-site measured wind velocity and direction. It was found that the three test cells were very airtight with air change rates of up to 0.1 ACH. Under the same external wind conditions, airflows measured at the roofs were significantly higher and with a wider variation compared with the airflows in the rooms.

Within the whole year, the simulated room temperature was almost always lower than measured temperature. When thermal comfort bands in Launceston according to the protocol for house energy rating (2006) were considered, the simulated hourly temperatures for a warm and a cool week resulted in an underestimation of overheating degree hours during the warm week, and an overestimation of underheating degree hours during the cool week in all test cells.