Here in the southeast where moisture is a big issue, plenum crawls are not common. Typically an encapsulated crawl has a dehumidifier to condition the space. In an dry climate, a properly ventilated crawl could perform very well. In fact, down here some vented crawls do pretty well with a proper vapor barrier.
It definetly should have been sealed, yes. Vented carwlspaces shouldn’t have rodents getting into them either. However that is usually not the case. It can be a difficult task, and not exactly practical in my opinion.
Keith R Henry
Certified Professional Inspector
General Liability Insurance
Online Scheduler and Other Information:
Vapor barrier on the ground, spray foam applied to the perimeter walls overlapping the vapor barrier on the ground by a few inches, going up the wall and rim joist, and overlapping the sub-floor slightly. For airflow, you either add a supply and return duct, or not quite as good, you cut a few open registers from the crawlspace into the conditioned area above. Access to the crawlspace is from the interior of the home. This is how I would do it if it were my home.
Personally, I prefer conditioned crawlspaces. My biggest concern is for termite access. With insulation on the foundation, it provides a hidden access up the wall. Have heard the same thing from pest folks.
For this reason a few inches of exposed foundation is to be left at the top.