Any species wood will do with a vapor barrier at block/wood on the wall only, #7: http://publicecodes.citation.com/ico...9_3_sec017.htm
Or, without the v.b.:
NATURALLY DURABLE WOOD.
The heartwood of the following species with the exception that an occasional piece with corner sapwood is permitted if 90 percent or more of the width of each side on which it occurs is heartwood. Decay resistant.
Redwood, cedar, black locust and black walnut.Termite resistant.
Alaska yellow cedar, redwood, Eastern red cedar and Western red cedar including all sapwood of Western red cedar.
P.t. still lets water through to your drywall unless you add a poly plastic or shield like Grace (or sill-sealer); http://www.greenbuildingadvisor.com/...-building-code
Clothes taking longer to dry?
Clean the dryer screen in HOT water if using fabric softener sheets.
They leave a residue that impedes air-flow, costing you money.
Clean the ducting in the last six months? 17,000 dryer fires annually!