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Description
This report summarizes research comparing the energy use of 29 concrete homes built using insulating concrete forms (ICFs), and 29 wood-frame homes. The study estimates ICF construction can reduce energy consumption for heating by approximately 44% and for cooling by 32% compared to wood-frame construction.
Abstract
Statistical comparison indicates that constructing the exterior walls of a house with insulating concrete forms (ICFs) instead of conventional wood frame will reduce the amount of energy consumed for space heating by approximately 44%, and for space cooling (where applicable) by approximately 32%. All figures are averages for houses constructed across the U.S. and Canada. All ICF homes were constructed with a system made of pure foam (no foam-cement composites).The statistics derive from analysis of 58 homes, 29 ICF and 29 frame. The investigators undertook several steps to get an "apples-to-apples" comparison. They solicited participation so each ICF house would be paired and compared with one frame house that was (1) nearby, (2) of similar square footage, and (3) of new construction (less than 6 years old). They then adjusted the energy consumption of each house to control for differences in size, design, foundation, and number of occupants, thermostat settings, and HVAC equipment. The corresponding estimated dollar savings averaged approximately $221 per year for heating energy and (where applicable) $89 for cooling energy. The energy savings rates (44% for heating, 32% for cooling) showed no discernible relationship to local climate. That is, it was impossible to detect that savings rates for either heating or cooling went up or down appreciably in warmer (or cooler) climates. The appropriate tentative conclusion therefore is that these rates of savings should be fairly constant regardless of location. An important implication of this result is that absolute savings will be higher in extreme climates, where total bills are higher. Projected savings on heating are several times greater in cold climates (Minneapolis: $342 per year for a 2000 SF home) than in warm ones (Dallas: $100). Projected cooling savings are higher in warmer climates ($108 in Dallas, versus $34 in Minneapolis).Responses to open-ended questions showed that the vast majority of owners of new homes had positive feelings toward their homes regardless of the composition of their exterior walls. However, the reasons those ICF owners liked their homes contrasted sharply with the reasons cited by frame owners. The ICF owners most often cited functional advantages resulting from ICF walls: comfort (including evenness of temperature and low air infiltration), sound reduction, energy efficiency, and solidity/strength. Frame owners most often cited advantages that accrue to new home regardless of their construction: locations, floor plan, and inclusion of the owner's preferred features. These differences in qualitative responses suggest that frame homeowners saw little advantage to their new houses beyond the features one might expect in any new house. Mention of benefits attributable to superior construction of their new houses was conspicuously infrequent. In contrast, ICF owners were impressed by advantages of their new houses attributable to the superior construction of the walls. Interviews uncovered some possible impacts of ICF construction that have important energy implications not picked up by the energy analysis. Several ICF owners with unheated basements commented that their basements were about as warm in winter as their conditioned living space upstairs. They therefore felt that when they finished their basements they could avoid enlarging their heating systems or consuming more fuel to condition them. The data sizes and statistical tests indicate that the numerical estimates of this study are reliable. However, there are limitations to the research methods of surveys of actual houses such as this. Refinement of the estimates and additional information on the sources of the savings could come from detailed energy modeling or careful metering of specially constructed test modules.
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