If you listen to David Debian of Central City Air in Houston, it would appear that few HVAC companies in the Houston area know how to properly deal with their humid climate. I don't think he's off the mark. Last week I attended a heat pump seminar and RSES conference in Ft. Worth, and spoke with other techs and contractors in the field. The overall consensus would indicate that it's possible up to 80% of residential HVAC service technicians in the DFW area are not adequately trained to do the work.
P.S. I read Shophound's idea and I must point out ERVs are practically unheard of in this region. Not saying that's the way it should be... rhetorically, are we ignorant rubes or do we know something the other guys in the country don't? In the interests of what's more familiar I would prefer to endorse Teddy Bear's concept of a ventilating dehumidifier in its place. Not exactly the same function but I believe it's what we need in the Houston area (I am in Fulshear about 30 miles west).