Error Analysis

There are several methods for measuring air tightness that may result in different values and sometimes quite different uncertainties. The two main approaches trade off bias and precision errors and thus result indifferent outcomes for accuracy and repeatability.  To interpret results from the two approaches, various questions need to be addressed, such as the need to measure the flow exponent, the need to make both pressurization and depressurization measurements and the role of wind in determining the accuracy and precision of the results.

The Universal Thermal Climate Index UTCI assesses the interaction of ambient temperature, wind, humidity and radiant fluxes on human physiology in outdoor environments on an equivalent temperature scale. It is based on the UTCI-Fiala model of human thermoregulation and thus also allows for thermal comfort prediction.

Air tightness is an important property of building envelopes.  It is a key factor in determining infiltration and related wall-performance properties such as indoor air quality, maintainability and moisture balance.  Air leakage in U.S. houses consumes roughly 1/3 of the HVAC energy but provides most of the ventilation used to control IAQ.  There are several methods for measuring air tightness that may result in different values and sometimes quite different uncertainties.

Conventional multiple types of perfluorocarbon tracers use the number of gases equal to the number of zones (n). The possible n×n+n airflows are solved from the mass balance of the gas and the airflow balance. However, some airflows may not occur because