Measuring Residential Ventilation System Airflows: Part 2 - Field Evaluation of Airflow Meter Devices and System Flow Verification
The 2008 California State Energy Code (Title 24 Part 6) requires that new homes meet ASHRAE 62.2-2007 requirements for mechanical whole-building ventilation and local exhaust. This study evaluates a sample of fifteen new California homes for ASHRAE 62.2-2007 compliance. The flows were measured with six commercially available flow hoods, and the accuracy and usability of these flow hoods were evaluated based on the results of these field measurements. Only two of the fifteen homes tested met all the ASHRAE 62.2 requirements for whole-building ventilation and local exhaust. Because of physical constraints, range hood flows were especially difficult to measure; the flows for only five of the thirteen homes could be evaluated. Consistent with laboratory findings of previous studies, powered flow hoods were found to provide more accurate field measurements than non-powered flow hoods. The errors for the powered flow hood measurements were around 6%, whereas those for the non-powered flow hoods ranged from 11% to 25%. A flow hood measurement standard that takes ‘real world' conditions into account should be developed to ensure that residential buildings receive the intended ventilation flows. In addition, specific guidance should be developed with regard to the acceptable methods and equipment used to measure ventilation flows and to evaluate compliance with ASHRAE 62.2.