The Devastation “Down the Shore.”
A Conditioned Crawl Space is one that has one or more heating/ac supply ducts in it. The underlying idea is to keep the crawl space at a slightly positive pressure. This means that the crawl space, which by nature of its position at the bottom of a building or house, in its natural state, is usually under a negative pressure. What does that mean? It means in common terms– it is always sucking in moisture and air. Crawl spaces have been verified to have sucked in moisture from 40′ away. A crawl space under a negative pressure, naturally sucks in outside air and moisture, and this is what we want to prevent, the sucking, along with keeping the temperature of the crawl space somewhat moderate in temperature and relative humidity. Now to do this we put in a one or more HVAC supply vents, to keep the positive pressure and prevent the sucking in of contaminants, etc.
Well now some group of highly intelligent people of a nether world have made it code to now include a return duct in this crawl space. So now we are back to the negative pressure crawl space. We put air in, we take it out and we suck more in from outside. This means radon, other contaminants, moisture, is now brought into our duct system purposely.
This is a prime example of Green Stupid. Wait until someone proves that the return, because a leak occurred in a gas furnace, put in a conditioned crawl space, caused death by spreading carbon monoxide gas or bringing excessive radon into a home, there will be hell to pay. Dumb, dumb, and dumber.