Monitored Energy Use Patterns in Low-Income Housing in a Hot and Humid Climate

The Florida Solar Energy Center (FSEC) is metering energy use in two Habitat for Humanity developments. The objective is to understand how energy is used in low income housing and how it can be effectively reduced. The ten "control homes" come from a conventional housing project built by in 1993 Habitat for Humanity in Homestead, Florida. Another ten "experimental homes" have been recruited from the 190 home Jordan Commons development in the same vicinity. These houses, which are soon to be metered, are designed to be energy efficient with high SEER air conditioners, reflective roofing, solar water heaters and energy efficient lighting and appliances.' The instrumentation was installed in the control homes in July of 1994 with a year of 15-minute data now collected on all sites. Data are obtained on seven electrical end-uses (air conditioning, heating, hot water, dryer, range, refrigerator, washerlfreezer) as well as total. Weather conditions are also monitored as well as interior comfort conditions (temperature and humidity) and hot water consumption and window ventilation status. The field data allow unique insight into how energy is used in low income housing in a hot and humid climate. THE HOMES AND THEIR OCCUPANTS The control group homes for the Jordan Commons study are located 16 krn away in Florida City, just south of Homestead, Florida. There are two similar building models in the project, both with rectangular floor plans. The houses with three bedrooms have a conditioned floor area of 96 m2 (1030 square ' The 190 homes. v-g in conditioned floor ma fmm 90 140 ma (1.000 1.500 f?). will lealure a bawry af energy-efficiency mwrum recommended in a comprehensive study for the Hurricane Andrew relief effon in 1992 (Parker el al.. 1992: 1994). The homes will also strus lighIa1orrd exterior surfaim and exunsive landscaping as pan of EPA's Cool Communities pmgram. feet); the four bedroom models total 1 11 m2 (1 190 ft2). The construction is conventional for South Florida: concrete block on an uninsulated monolithic slab with an exterior light colored stucco finish. The homes generally face north or south with a small porch over the entrance. The roofs are of standard A-frame construction with plywood decking covered by asphalt shingles. The concrete block walls are insulated with RSI-0.5 m2-WUr (R-3 ftZ-hr-OF/Btu) insulation on the interior; the attic has RSI-3.3 (R-19) fiberglass batts over the sheetrock ceiling. The windows are single glazed units with aluminum frames and are single-hung so that about 30% of their gross area can be opened for ventilation. Most of the homes' windows are located on north or south exposures. Several homes in the development are shown in Figure 1. Figure 1. A view of the Habitat homes in the Florida City development. ESL-HH-96-05-38 Proceedings of the Tenth Symposium on Improving Building Systems in Hot and Humid Climates, Fort Worth, TX, May 13-14, 1996 The mechanical cooling system in the houses consists of 7.0 kW,(2.0-ton) air conditioners in the three bedroom homes and 8.8 kW,(2.5-ton) air conditioners in the four bedroom units. The split systems are conventional with an interior evaporator and air handler located in a small utility room. The air-cooled condenser is located outside with the R-22 refrigerant piping from the evaporator insulated to RSI-0.9 (R-5) with foam insulation. The units have a rated seasonal coefficient of performance (SCOP) of 3.5 WJW, (SEER = 12.0 BtulW). Heating is provided by 4.8 kW electric resistance elements (7.1 kW in four bedroom homes) located in the air handling unit. The conditioned air is distributed through a ducted system in the attic to ceiling mounted supply registers. The air distribution system consists of approximately 15 m (50 ft) of RSI-0.9 (R-5) flex duct. A thermostat is located on an interior wall. The slide type control has a set range from 10 32°C (50 90°F) with two toggle switches for mode selection (heating1 off/ cooling). The fan mode selection has two modes: "on" where the fan runs constantly regardless of the compressor operation and "auto" in which the fan operates only when the heat strips or compressor is energized. The major appliances in each home are a 154 L (40 gallon) electric resistance storage water heater, a 510 L (1 8 f?) refrigerator, an electric clothes dryer, range, and a washing machine. Several homeowners have added a chest freezer. Except for the refrigerator, all the appliances are located in a small conditioned utility room. Lighting in the homes is of the conventional incandescent type. Typical minor appliances include a living room ceiling fan, microwave oven, video cassette recorder, television, and stereo. The occupant density is fairly high. Whereas occupants number 2.4 in the average Florida household, the Habitat homes have an average of 4.6 members. The households vary from a maximum of eight occupants per home to a minimum of three and all have one or more children of varying ages. Although income information is not available, Habitat for Humanity's mission is to provide affordable housing for low-income families. Each household has been in residence for a year or more and although the homeowners have an interest free mortgage payment for their homes, they are responsible for payment of their monthly utility bills. During audits, we found the head of household at each house to be very aware of their monthly utility expenses. At least one family (House 4) has only very limited prior experience with air conditioning systems. MONITORING AND DATA SUMMARY In April, of 1994, research engineers visited the ten sites in Florida City. The homeowners were interviewed after which each site was audited and physically measured for instrumentation. Multi-channel data loggers and associated metering equipment was installed in June of 1994 with the site data collection system becoming operational by midJuly. Detailed performance data are being collected at each house, including energy use of all major appliances, meteorological conditions and interior house conditions such as temperatures, water use and window ventilation status. A detailed description of the instrumentation is contained in a source report (Parker et. al., 1994). A unique part of the monitoring process is the ability to detect when the home's windows are opened for natural ventilation. Contact switches were installed on the most commonly opened windows for ventilation. This allows researchers to determine the fraction of each data interval during which the building's windows are opened for natural cooling. Impacts of internal heat gains from appliances and occupants on space cooling energy use is widely acknowledged (Abrarns, 1986). Typically such sensible heat must be removed from the interior to meet the thermostat setting. Another innovative part of the monitoring protocol is that all electrical end uses that take place within the potentially conditioned space are sub-metered so that interior levels of appliance heat gain can be assessed in their impact on air conditioning needs. Miscellaneous electricity use for lighting and other plug loads are obtained by differencing the total recorded site electrical use from the recorded energy use of the various sub-metered major appliances. The data loggers scan the various instruments at 5 second intervals and integrated or totalized values are output to storage every 15 minutes. Data are transferred from the data loggers via modems and dedicated phone lines to a mainframe computer each evening. ESL-HH-96-05-38 Proceedings of the Tenth Symposium on Improving Building Systems in Hot and Humid Climates, Fort Worth, TX, May 13-14, 1996 In December. 1994, the person primarily homes from September 1, 1994 to August 3 1, 1995. responsible for controlling the cooling system, was These data provide insight into the magnitude of AC interviewed at each home. The interview questions electricity consumption relative to other household were designed to provide detailed information about energy end-uses during the cooling season. About how the systems are controlled as well as the occu40% of the daily average electricity use is for air conpant's reasons for operating the systems as they do. ditioning. The next largest end-use, water heating, is much lower at 19% of total consumption. Table 1 and Figure 2 summarize a breakdown of measured daily energy end-use in the ten Table 1 Average Daily Energy-End Use at Habitat Sites: August 31,1994 September 1,1995' kWh/Day