Measuring Airflow and Capture Efficiency of Over-the-Range Microwave Exhaust Fans

The Challenge

Determine if over-the-range microwave exhaust fans commonly meet the code required airflow performance for kitchen ventilation in California homes.

The California residential building code requires kitchen exhaust ventilation for indoor air quality protection. The code has requirements for minimum airflow and maximum sound level to be certified with standardized test methods. For years, over-the-range microwaves (OTRs) have been installed in new California homes despite limited certification data and uncertainty about their performance.

The Solution

In a project funded by the California Energy Commission, Berkeley Lab researchers used the U.S. Department of Energy’s FLEXLAB® facility to measure the performance of several OTR models observed in a study of recently built California homes, and compared them to conventional range hoods that met minimum code requirements at similar cost. The study measured airflow and capture efficiency (CE), the fraction of cooktop-generated air pollutants captured and removed by exhaust devices. The study in FLEXLAB also evaluated the accuracy of the method used to measure OTRs in homes in the California study.

The Bottom Line

OTRs performed similarly to comparably priced range hoods and confirmed that they could meet the code requirement for airflow.

Download the full case study here: Measuring Airflow and Capture Efficiency of Over-the-Range Microwave Exhaust Fans

"Tests of range hoods and over-the-range microwaves in FLEXLAB have offered unique insights in the assessment of airflows and capture efficiency for kitchen ventilation, a critical element in high-performance homes."

Nicholas Hurst, Indoor airPLUS Program, U.S. Environmental Protection Agency