Simplified Space Conditioning in Low-Load Homes

TO3 2.1.6: Simplified Space Conditioning

IBACOS anticipates that houses achieving 50% whole-house source energy savings with respect to the Building America 2010 Benchmark (Hendron and Engebrecht 2010a) will be considered "low load." Low load is defined by IBACOS as a house with a thermal enclosure that yields a maximum space heating and cooling load of less than 10 Btu/h/ft2 of conditioned floor area (31.5 W/m2 [1,200 ft2 /ton]). These small loads can be met by systems other than today's typical ducted forced-air systems. For example, distributed fan coils with minimized ducts, terminal fan coil units, or point source units with buoyant force or ventilation-driven distribution may provide sufficient occupant comfort in a low-load home. These systems, which can have lower total installed costs than traditional ducted forced-air systems (Stecher 2011), allow the thermal enclosure characteristics of low-load houses to provide first-cost savings in addition to operational cost savings.

The purpose of this study is to help determine cost-effective solutions for heating and cooling houses that are designed to be energy efficient. This is done by testing the occupant comfort performance of some concepts that may already exist on the market but are not in use by production homebuilders. In some cases, the products are market available, but their use in housing may be a new application. The standards used to assess the performance of the systems in this study are Air Conditioning Contractors of America (ACCA) Manual RS (Rutkowski 1997) and ASHRAE Standard 55-2010 (ASHRAE 2010a).