OR-20-015 -- Potential Building Reheat Energy Saving Determination in Hot and Humid Climates

According to the U.S. Energy Information Administration(EIA), in 2017, about 39%, about 38 Quads, of USA totalenergy consumption was consumed by the residential andcommercial buildings. Some portion of that energy use hasbeen wasted because one, or a combination of, defective buildingdesign, low-efficiency systems or their improper operation.For the cases related to the building operation, there are stillquestions as to how adequately evaluate building performanceand how to identify potential energy saving. This paper dealswith the determination of potential building energy saving onlyfrom re-heat operation using the measured monthly energyconsumption data. The study focuses on systems analysis operationof hot and humid climates conditions, where duringsummers the outside air temperature monthly average could beas high as around 80.0°F (26.7°C). Under these weatherconditions, it is expected the heating/reheat loads duringsummer would usually be small for most buildings, except forbuildings that need large ventilation or special cleanliness/safety requirements, such as health care facility or laboratories.Therefore, the evaluation of the building energy savingpotential is derived from a reheat ratio, the ratio between thereheat to the cooling energy use, calculated from measuredconsumption data. The reheat ratio by itself is a good index ofthe building performance operation, but does not provide away to generalize the potential savings determination. For thispurpose, a reheat density chart is proposed that relates thethermal energy consumption to the reheat ratio. Based on thestatistical analysis of the thermal energy consumption andreheat ratio data from over one hundred buildings, the reheatdensity chart is divided into four categories that clearly identifythe potential energy savings. The function of the buildingsanalyzed includes offices, classrooms, dining rooms, sportfacilities, dorms or residence halls, and laboratories. From theapplication of this methodology it was found that, most buildingsanalyzed, 60%, fall in the category of buildings that operatereheat in a fair-efficient range. Approximately 15% of thebuildings could have more saving potential for cooling energyuse and 21% could have more saving potential for heating hotwater use. Finally, it was found that five buildings have a highpotential saving opportunity, from both cooling and heatingenergy use perspective, and should be considered to becommissioned.