Published in Mathias, J. A., & Mathias, D. M. (2009). Energy efficient, cost effective, passive solar house. ASHRAE Transactions, 115(1), 419-426. ©2009 ASHRAE (


A house was constructed in Carbondale, IL, in the mixed humid climate region, using the best current construction methods with commonly available materials. Good passive solar characteristics were obtained by properly orientating the house to have many south-facing windows with proper overhangs which provided 23% of the energy needed for heating. The house also included 15 cm (6 in) thick insulated walls, insulated concrete forms for foundation walls, insulated rim joist, a ground-source heat pump, Energy-Star windows, clothes washer, refrigerator, and compact fluorescent bulbs (CFLs).

Electrical usage data was metered separately for heating, air conditioning, hot water, lights and appliances. The energy used by the actual house was compared to the same sized house built to the International Energy Code Council 2004 Residential Energy Code. The actual house used 7809 kWh (50%) less than the code house for an annual cost savings of $826. The annual on-site electricity used by the house was 19.8 kWh/m2. Cost of the energy-efficient improvements in the actual house was $7,990. The house was very cost-effective by using commercially available materials and employing an on-site general contractor knowledgeable in maintaining the high energy-efficiency standards designed into the house, coordinating the work, and allowing the homeowners to perform manual tasks. This method resulted in a price of $1,062/m2 ($99/ft2) of finished floor area, noticeably less than a comparable house in the region.