Hello, I am considering encapsulating my crawl space and I had several contractors give me estimates. One estimate was for creating an un-vented, semi-conditioned crawlspace where they would treat the the walls and floor of the crawl space and rely on the gaps or spaces (can't remember the exact wording) between the house and the crawl space to keep the air in the air in the crawl space from going bad. I live in the Washington DC area. Is this approach sufficient or do I need a grill, HVAC ducts, or humidifier for air quality in the crawl space. I do not have moisture issues in the crawl space. Thank you.