NA-04-6-1 – Field Observations of Room Air Distribution Performance in a High-Performance Home PDF

The objective of the current investigation was to evaluate the field performance of room air distribution in two rooms of a high-performance (low heating and cooling load) home. The two rooms had similar exterior exposures but had different supply register locations (high sidewall and floor). The impact of normal equipment cycling on the room air distribution performance was also investigated. The performance was evaluated based on room air temperature measurements and the requirements of ASHRAE Standard 55 (ASHRAE 1992). Measurements were made in a test home in Pittsburgh, Pennsylvania (cold climate), during both heating and cooling periods. The room with the high sidewall register (bedroom) had approximately 50% of the design airflow based on load calculations, and the room with the floor register (dining room) had approximately 140% of the design airflow. Acceptable temperature conditions were maintained at most times in the room with high sidewall supply with approximately 50% of the design airflow. Based on this observation, a conclusion of this investigation is that the heating and cooling loads associated with the thermal envelope of a high-performance home create a rather forgiving situation for a space-conditioning system with high sidewall supply. A preliminary conclusion, based on stratification and temperature cycling performance, is that high sidewall supply with a non-spreading register is effective for both heating and cooling operation in a cold climate. This requires further investigation because it is not clear how the low supply airflow impacted the vertical temperature stratification in this room. Another preliminary conclusion from this investigation is that floor supply with a spreading register provides marginal heating operation in a high-performance home, as indicated by higher vertical temperature stratification and unacceptable temperature cycling. All the conclusions from this investigation are limited to the conditions of the room air distribution methods studied and are worthy of further investigation. Future work will include balancing of the test home system and continued investigation of the room air temperatures.

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