Measured Air Distribution Effectiveness for Residential Mechanical Ventilation

Abstract

The purpose of ventilation is to dilute or remove indoor contaminants that an occupant is exposed to. In a multizone environment, such as a house, there will be different dilution rates and different source strengths in every zone. Most homes in the United States have central HVAC systems, which tend to mix the air, and thus, the indoor conditions between zones. Different types of ventilation systems provide different amounts of exposure depending on the effectiveness of their air distribution systems and the location of sources and occupants. This paper will report on field measurements using a unique multitracer measurement system that has the capacity to measure not only the flow of outdoor air to each zone, but zone-to-zone transport. The paper will derive seven different metrics for the evaluation of air distribution. Measured data from two homes with different levels of natural infiltration will be used to evaluate these metrics for three different ANSI/ASHRAE Standard 62.2-2007, Ventilation for Acceptable Indoor Air Quality in Low-Rise Residential Buildings compliant ventilation systems. Such information can be used to determine the effectiveness of different systems so that appropriate adjustments can be made in residential ventilation standards such as ASHRAE Standard 62.2 (ASHRAE 2007).