Seal cracks and gaps around windows, floor/ceiling connections, piping and electrical penetrations, interior and exterior walls and hallways
Weatherize doors, windows, and plumbing and electrical penetrations in building corridors. Sealing cracks and gaps will conserve heat during the winter, and reduce air conditioning use during the summer.
http://www.energystar.gov/index.cfm?c=home_sealing.hm_improvement_sealing