Low-Cost HVAC For Green Buildings According to the R.S. Means Square Foot Costs, 25th Edition, the HVAC cost for a single-story office building 7,000 to 20,000 square feet in size will be $13 to $17 per square foot. This cost range is for a typical HVAC system that meets minimum building code requirements, but can not meet ASHRAE Standards 62 or 55. Our intent was to provide an HVAC system that met ASHRAE Standards 62 and 55 and used less energy while costing at least 20% less than a standard system. Our design approach combined air-to-air energy recovery with furnace/air conditioning units. The air-to-air energy recovery units deliver 1,648 cubic feet per minute (cfm) of outdoor air at constant volume or 38 cfm for each building occupant. This ventilation rate is almost twice the rate required by ASHRAE Standard 62. In addition, the air-to-air energy recovery units allow moisture transfer between the exhaust and outdoor air streams, helping to meet ASHRAE Standard 55 for comfort all year long. The total cost of the HVAC system is just $99,120 or $8.30 per square foot which includes all overhead and profit. This cost is 35% less than the lowest figure published by R.S. Means. Furthermore, the system uses 30% less cooling energy and 10% less heating energy than a system that just complies with ASHRAE Standard 90, and the system uses non-chlorinated refrigerant. This system is green and very cost effective.