If possible, try to avoid putting the washer and dryer in spaces that are heated or air-conditioned. There are a couple of reasons: 1) both the dryer and washer would make your air conditioner work harder because of the heat and moisture produced during use, and 2) dryer vents lacking dampers allow warm, humid outside air to enter the home in summer and cold air to enter in the winter even when the dryer is not in use.

If the laundry room is in conditioned space, install a closeable fresh-air intake vent to the dryer, along with a closeable dryer exhaust vent. These will effectively keep unconditioned outdoor air from coming in and keep conditioned air from going out when the dryer is off.

Source: Wendell A. Porter, Hyun-Jeong Lee, and Kathleen C. Ruppert, Energy Efficient Homes: Laundry Area UF/IFAS FCS3260, 2008

Additional Resources
EnergyStar®  - http://www.energystar.gov/

Progress Energy  Home Energy Check-  http://progress-energy.com/

UF IFAS Energy Efficient Homes: Laundry Area - http://edis.ifas.ufl.edu/FY1030