Secondary Author(s)

Withers Jr., Charles; Parker, Danny; Colon, Carlos

Report Number




Utilities; Buildings; Energy Consumption; Electrical Loads


The Vacant Home Space Conditioning Study was sponsored by Florida Power & Light (FPL) as part of its Conservation R&D Program and carried out by the Florida Solar Energy Center (FSEC). In the US, about one in four retiree "snowbirds" make Florida their destination to escape the northern cold. Snowbird residents number more than 900,000 in Florida during the winter. In some counties of FPL's territory these seasonal residents compose up to 15% of the population (Shih, 1981). This pattern of seasonal occupancy creates a need for space conditioning guidelines for vacant homes to avoid mold problems while minimizing both customer energy usage and electrical load during utility peak hours. In 2004, a Phase I Snowbird project was carried out. Three homes on Florida's east coast in Brevard County were equipped with monitoring equipment for the experiments. The first was a 45-year-old 1100 ft2 single-story, painted concrete block home on a concrete slab with a low pitch tar and gravel roof. The second house was a 40-year-old 1950 ft2 split-level home, with block and frame construction. The third home was a 900 ft2 single-wide mobile home manufactured in 1984. All three test-homes had 2.5-ton central air conditioning (AC) systems with heat pump, gas, and electric strip heating, respectively. Five space conditioning strategies for vacant homes were assessed during hot, humid summer conditions and/or warm, humid fall weather conditions. The aim was to control relative humidity (RH), minimize energy use, and limit peak electrical demand. The five approaches were: 1) no space conditioning as the baseline, 2) AC thermostat set at 85°F or 83°F, 3) morning AC operation at 74°F, 4) dehumidifier alone, and 5) space heating. An important observation was that some homes require more aggressive action to control RH than others. Air infiltration was found to be an important factor in the struggle against high indoor RH. Air infiltration, usually measured in air changes per hour (ach), is the rate at which outside air enters the house. Homes that have higher infiltration rates require greater moisture removal rates to achieve RH control.

Date Published



Original Publication: Cummings, J., Withers, C., Parker, D., Colon, C., "Executive Summary: Evaluation of the Impact of Vacant Home Space Conditioning Strategies on Summer Relative Humidity, Energy, and Peak Load: Phase II", Submitted to: Craig V. Muccio, General Office of Florida Power & Light, FPL PO# 4500292934; C # 4600002848, FSEC Project # 20128099, December 18, 2006

Local Subjects

Buildings - Electrical Loads; Buildings - Energy Consumption; Utilities


FSEC Energy Research Center® Collection



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