Worthy, would you please clarify your response above: "The Building America series shows a conditioned crawl in mixed-humid climates and unconditioned crawls are advised against..." Does that mean that in a mixed-humid climate, conditioned and unconditioned crawls are both advised against? I'm seeking to warm up a bedroom. I live in Anne Arundel County, Maryland, climate zone 4A, in an 1800 SF house, built in 1968, and heated with forced air oil furnace and a/c. It is a rancher with a developed lower level on a concrete slab, built with concrete block foundation walls about 8' high. A bedroom was added on a separate foundation with foundation walls 4'4" high. The crawl space under the add-on bedroom has fiberglass insulation between the joist. has 2 small openings that I close in winter; dirt floor. It is very dry and shows no issues with moisture, bugs or mice/snakes/etc. The add-on bedroom is really cold in winter. I will increase attic insulation. What are the options for improving the bedroom's winter temperature by improving the crawl space? Can the crawl space's cement brick walls have foam panels or should I add more insulation in the crawl space's ceiling? A 6 mil plastic sheet over the dirt floor? There are two insulated duct pipes in the crawl space. Is it advisable to seal the crawl space's two little openings and condition the crawl space? However, if it is infeasible to install a return, is a conditioned crawl space not an option? Thank you.

thanks, i finally found one youtube from "this old house" that showed i can put fiberglass right on top of it. But thanks for your time, always appreciated.

Use expansion foam behind the pipe and run the rigid insulation to it.

I just helped my friend who owns a cabin in the mountains which has a basement that one wall is at 50% undergrade and the other exposed wall, cinder block. Since mold comes from dirt 100% vapor barrier is crucially important to slowing down mold spores in the air. Though mold is everywhere exposed ground that does not receive mold killing UV sunlight grows uncontrolled. I would suggest never to put wood on top of the plastic because it will wick moisture considerably and rot. I reccomend slab pavers and float them next to each other. https://www.google.com/search?q=4+x4+ft+cement+pavers&sxsrf=ALeKk02V51mbSbLGF1xq4pOhQ9u3cpq95A:1599487146944&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjqnt35mdfrAhWnlXIEHUgkBq4Q_AUoAnoECA0QBA&biw=1366&bih=657#imgrc=dIckdvbXW2X8QM Better choice pour a 4 inch floor but thats usually too costly. Get www.SensorPush.com ($50) Humidity device with gateway ($100) which will always show you your rooms humidity level. If not conditioning with AC that pushes 50% humidity air to keep air dry you would want fans that evaporate moisture. The biggest concern are critters...mice..chewing electric wires, in furniture...etc. Get www.MouseX.com to drive them away but not kill them so there dying in the walls of your home. I would REALLY stray away from spun insulation above head. Mice nest in this CONSIDERABLY then snakes hunt them as the snakes push and pull your insulation as seen in your pictures. Mice can chew through steel, concrete block and wood easily and any plastic...so the goal is to not give them a easy nesting place. Mice have really made some thouroughfairs in the header joists to previously get into the room. But no mold means no camel crickets or cockroaches which mice eat, no mice means no snakes. So lower humidity so wood beams are under 16% wood moisture content and they wont grow mold and shuts down thebentire food chain. Snakes enter the space from digging under the foundation and coming up right next to the foundation so sealing the plastic to the walls slows the critters down. Sealing the plastic is done best with pin nails shot from a .23 caliber pin nail gun NO MORE than 16 inches apart that keeps the plastic tight enough to keep out snakes. Keep the mice out keeps the snakes out. On top of the 3x3ft or 4x4 ft cement pavers you could put interlocking 3/4 in foam boards and cover with carpet or throw rugs. My friends neighbor works at Trane and got a DEEEAL on central air system system. : )