The installations should be airtight, using permanent sealing products such as mastic or date-coded foil type tape. Each supply air duct should have a damper to assist in achieving proper airflow. All ductwork should be fully insulated. Once the system is installed airflow should be checked and properly balanced for each room in the house. Multiple air returns are needed in most new homes.
More returns mean better airflow and greater efficiencies.
Zoning can also eliminate the need for multiple units. Digital or programmable thermostats are a good option to achieve and maintain desired comfort levels and reduce operating costs. Variable speed equipment where the unit's output varies based on the home's heating and cooling requirements should be considered to maximize comfort and efficiency. These units are typically rated at higher efficiencies. Dual fuel systems provide efficiency and economy.