Great comments everyone...price ...can be between $2- $3/sf. Anything more is overkill. As to the smell of some companies poly ... there was a run 4+ years ago where a handful of manufacturers that made a poly that was white on one side and black on the other and was reinforced. 1 of 10 after several months to a year started smelling like cat pee and got stronger. I ripped out a handful of these crawl poly's. I wouldn't blame the sealed company's only because we all look for a deal on plastic to pass on to you ... and the odor doesn't start for awhile...that could be 400 crawls in 6 months for a handful of us. That's 40 of them stinking and 30 notice enough. About the DIY'ers ... I have DIY hardwood floors ... brakes... toilets...etc ... It takes me 6 months to get a diligent guy up and going on crawls where I can let him run and inspect his work after. I couldn't imagine the $ lessons learned that a DIY'er gets into. Just know it takes one really experienced crawl space tech and 3 new techs to finish correctly a 2600 sf sealed crawl using 50 labor hours. Know that 50% of your homes air comes from the crawl space so a poorly prepped sealed crawl can trap some pretty nasty mold. Dehu's: to use or not to use??? Tests show that mold has not grown in sealed crawls that use a 4 inch air supply line per 1500sf with average height of 2.5 ft. Though the humidity reduces down in the South (Raleigh Area) to 68%-77% when sealed still leaves high humidity compared to the average homes humidity of 52%. But mold does not grow. Why? I can only guess ... A. Ground, where mold comes from, is sealed off B. Air is slightly circulating from the air supply line on your supply side. And a dehu wholesales $1000 average ... then install and electrical hardwire hookup and gravity fed condensation line. $1600-$1800 should be fair?? And that will take your humidity down to your chosen level ... most, I have found, chose 50%. Now here's the rub ... your dehu is taking up a chunk if not all of your energy efficiency that your conditioned sealed crawl gives to your AC system. So if you don't take the old insulation out and seal in the mold and the defication from the crickets, mice and snakes and you aren't getting any efficiency out of the sealed crawl ... then why invest $ at all??? No savings or better air quality. My recco: pull floor insulation, sanitize entire crawl for SUPERIOR lifetime air quality ... seal crawl and forget the dehu and gain 15.8% energy efficiency on new homes past 2008 ... higher efficiency for older homes. My pet peeve.... if a home has mold on the beams and evidence of cricket poop ... little black pellets all over the joists ... I wont seal it without pulling the insulation and disinfecting the crawl. But 95% of all companies seal the crawl trapping in ALL THAT MESS and that's there standard seal crawl practice. That should be criminal!!! Like all the contractors who knew back in early 1900's that lead based paint was killing children but kept using it because it was cheap ... until 1970's when a law was passed after ??? more than a million baby's past away. I feel mold in the crawl is that same issue that is slow to REAR ITS UGLY HEAD ... buyer beware ... short cuts can hurt you long term. www.SealedSolution.com

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. : )

That may be the case for you but i warn people we had the exact opposite result. We put everything in a air tight bin control and all the different varibles plastic soil, just plastic and just soil and the bin when there is is moisture on the plastic it gives off this smell our soil just smelled like soil it can happen within amonth of testing soil and plastic amonia, just just plastic amonia when it is dry there is no smell sometime even if moisture is under neath and not on top no smell once some moisture gets above the plastic you get this smell. hope this helps.

Above all, the lot needs to be sloped in such a way as to direct water away from the foundation. Your gutter downspouts need to be extended in order channel water away from the edge of the structure or buried drainage pipes need to be installed. The thinking about crawlspaces has changed in the last few years. It used to be that crawl spaces were ventilated. Now, crawlspaces are encapsulated as closed conditioned spaces. Often this is an additional item after you build a home involving a specialty contactor. If this were an entirely custom home, you would consult with your general contractor and get them to order it. My guess is this a production home. You need to discuss your options with the salesmen and construction supervisor and determine the plan for this space. It can involve HVAC elements. You definitely want pay attention to this. It's easy to forget until you have a problem with mold, mildew and air quality in the home. Better to take care of it before it becomes a problem.