Florida Exterior Wall Insulation Field Test: Final Report

The Florida Solar Energy Center (FSEC) and Oak Ridge National Laboratory (ORNL) have conducted a field test of exterior insulation applied to Florida masonry residences. Approximately 50% of Florida\u27s six million existing residences are of concrete block construction. Many of these homes, particularly those 15 years or older, have uninsulated walls. Within the project, two single-family homes in Central Florida were extensively monitored to measure the energy savings of the technology. The primary objective was to examine the effect exterior insulation has on air conditioning (AC) energy use and peak electrical demand for two typical residences. A secondary objective was to gain practical experience with the system costs and application technique. A before/after test protocol was followed with the exterior insulation retrofit of the homes occurring in mid summer of 1994. Instrumentation was calibrated and setup at these sites in March. Electrical power use and meteorological data were collected for the spring and first half of summer while the homes were in their base configuration. Data collection continued after exterior insulation had been retrofit for the balance of the summer. Two data analysis methods (matched days and long-term periods) and a simulation model were used to determine the savings in AC power use. The data showed good agreement between the methods for estimation of the insulation\u27s impact on air conditioning use at both sites. The indicated summer season savings were from 9% - 14% (3 to 5 kWh/Day) of AC use at Site 1 and savings were estimated to be -1% (-1 kWh/Day) at Site 2. Peak AC reductions between 4 and 5 PM were approximately 7% (154 Wh) at Site 1 and 1% (17 Wh) at Site 2. Analysis of individual matched days indicated that the differing savings at the two sites may be largely explained by the thermostat settings maintained inside the two homes. Site 1, which maintained an average interior temperature of 73° F realized a savings, while Site 2 with a 79° F set point did not. A fundamental conclusion of the study was that exterior wall insulation will produce savings in Florida homes only if a low cooling thermostat setting is desirable. Simulation analysis of a prototype home was performed using the DOE-2.1D computer program. These results confirmed the important role that the gradient between interior and exterior air temperature plays in the effectiveness of insulation on exterior masonry walls in reducing cooling needs. Secondary interactions with insulation performance were seen from wall solar absorptance and house ventilation schedule