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.
A building's envelope is the product of the choice of framing materials and quality of craftsmanship. Exposed to weather, it may 1101 provide the same airtight conditions in which its insulation material had been tested. Air permeable insulation offers little resistance to pressure driven, or convective, heat loss. Air impermeable insulators can additionally reduce convective, as well as conductive, heat loss by being sprayed into and sealing up sources of infiltration normally addressed by caulks and sealants.
The purpose of this project was to devise a simple, experimentally validated method for quantifying the energy impacts of exterior envelope air leakage. Four full-size exterior envelope test specimens, two opaque wall systems and two fenestration systems, were built for determining simultaneous conductive and convective heat loss. The two opaque clear wall sections were metal-faced sandwich panel and cold formed steel frame.
Air leakage and duct wall conduction in forced air distribution systems often waste 20% to 40% of the energy used to condition residences in hot, humid climates. The simulation of these forced air distribution system leakages, their attendant uncontrolled airflows within the building system, and their consequential energy uses may be achieved by treating building spaces as pressure vessels (nodes) that are interconnected with the forced air distribution system, the outdoors, and each other through the basic laws of pressure and airflow.
The methodology of risk analysis and assessment is reviewed and applied to study the reliability of condensation control measures in lightweight building envelopes. It is generally recognized that airtight construction is an essential part of condensation control. Nowadays, different air barrier systems are developed and documented to prevent air leakage and moisture accumulation in the envelope. But does this mean that the condensation risk is sufficiently minimized and that the protective system is reliable?
A field measurement study of the airtightness of 73 - less than 5 year old - French dwellingswas led between 1999 and 2000. Buildings have been selected and classified according to theconstruction structure, the thermal insulation and the occupancy mode. Using a fandepressurizationtechnique, we assessed the air leakage rate of each dwelling with twodepressurization tests. Meanwhile quantifying air leakage rates, we observed qualitatively themost frequent locations of air leakage paths using a smoke detection method and infraredthermography.
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