English

The low-slope roofs of ten cold storage buildings in the Dallas area were examined visually and thermo graphically (Tobiasson and Korhonen 1985) from above and below. Two inch (51 mm) diameter cores were taken to verify infrared findings and to determine moisture contents for estimating wet thermal resistances (Tobiasson et al. 1991 ). Twelve inch (0.3 m) square specimens of many of the insulations were removed for laboratory studies of their thermal properties and structure.

The National Building Code of Canada (NBC) requires that an "effective" air barrier system be incorporated within the building envelope. Although the NBC addresses the performance characteristics to be considered to demonstrate that an effective air barrier system has been achieved, the NBC does not prescribe any specific test protocols with acceptance criteria to verify compliance of proprietary air barrier systems.

This paper summarizes the most recent results from an ongoing, multi-year research program to monitor the long-term performance of residential air barrier systems. Airtightness tests were conducted on I 7 houses, located in Winnipeg, Canada, ranging in age from 8 to I I years, for which there was extensive historical data. Eight of the houses used polyethylene air barrier systems and nine used an early version of the airtight drywall approach (ADA). The latest tests were conducted in 1997.

In insulated structures, air voids and cracks allow for airflows driven by temperature differences, i.e., natural convection. The airflow paths often exist in structures built with bad workmanship, but sometimes even with the best workmanship they are difficult to avoid. Air paths within new types of loose-fill insulation may also occur. For horizontal structures, critical channel flow Rayleigh numbers can be identified for the onset of convection.

This paper presents a numerical model to investigate the foundation heat transfer from conditioned basements when the ground is composed of multilayered strata with different thermal properties. The model is used to determine the thermal performance of several basement insulation configurations under both steady-state and transient conditions. It is found that the nonhomogeneity of the soil significantly affects the heat transfer from uninsulated basement walls rather than the basement floor or insulated basement walls.