Measured Space-Conditioning Energy and Humidity in a Mechanically-Ventilated House Lab with Fixed and Variable-Capacity Cooling Systems Located in a Hot and Humid Climate

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Humidity; Buildings; Energy Efficiency; Ventilation


Residential whole-house mechanical ventilation has become more important as air tightness requirements have increased under certain building programs and codes. Generally, homes mechanically ventilated during warm and humid weather will have elevated indoor relative humidity (RH) during low cooling load periods. Supplemental dehumidification has been relied upon to control RH. Herein lies a challenge to balance acceptable RH with minimal energy use. Three specific types of space cooling equipment configurations were tested in a controlled research lab home. The central Florida 3 bedroom, 2-bathroom lab home was furnished, had automated internal sensible and latent loads, and was ventilated in accordance with ASHRAE 62.2-2013. The focus of the testing was to evaluate space cooling and dehumidifier energy use as well as the resulting indoor RH throughout the home. The three primary test configurations covered in this paper involved: 1) a central ducted fixed-capacity SEER 13 rated system 2) a central ducted variable-capacity SEER 22 rated system, and 3) a SEER 21.5 ductless variable-capacity minisplit. The minisplit was operated as the primary cooling system with central system used for cooling backup during near peak cooling load periods. The project found that the SEER 22 central system configuration used 20% less energy than the SEER 13 central system, and the minisplit configuration used 25% less energy than the SEER 13 system under typical seasonal conditions. Limited supplemental dehumidification was needed to maintain indoor RH below 60% during some low cooling load periods. When needed, dehumidifier use was typically only 1-3 cycles per day. This paper will share greater details on the variability of indoor RH among the test configurations, factors that resulted in the very limited need for supplemental dehumidification, and recommendations to improve latent performance of variable capacity cooling systems.Presented at the 2016 IAQ Conference.

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Buildings - Energy Efficiency; Humidity; Buildings - Ventilation

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