Building Science Corp.'s Dr. Joe lists vented crawlspaces as one of the top ten dumb things to do in the South--and the North. However, before attempting any changes he advises: "Be sure to consult local experts and code officials before attempting unvented attics or crawl spaces on your own."

Sardonic but not what I was looking for. I had a guy from the cleanspace company come out and spec what was needed and what it would cost. After inspecting my crawlspace, he showed me pictures of a floor beam that had some powder post beetle damage as well as some piers wicking water from the soil, rat urine and feces, rodent holes dug under the footing. He told me I would need to clean out all the debris, close the vents, install a drainage mat under neath a 20 mil vapor barrier, install a dehumidifier with a condensation pump and a new crawlspace door. I asked if I needed to replace the insulation in the crawlspace and he said you don't need it because the encapsulation would keep the air at a constant temperature as well as the dehumidifier maintaining any moisture issues. I wouldn't have to worry about spiders, rats, mold, mildew, beetles or anything and I would be able to store items underneath the house and they would smell as clean as they were before they were put in. All for the total price of 14k.

love this forum that you can do a little diy advising! ok the mold in the supply boxes and on the grills probably isn't from the duct takeoffs @ the plenum. it takes a long time for mold to travel that far..and if there isn't moisture & food source it won't spread to that area. it isn't always mold..sometimes it is just dust. so mold/dust buildup at the ducts @ plenum is lack of proper air seal. mold in supply boxes & on grills is lack of proper air seal at the cut in the sheetrock ceiling where supply grill is attached to the box. nine times out of ten..you can solve the issue by sealing supply boxes to sheetrock. see attached picture. hardcast brand #1402 mastic tape is used to seal supply box to sheetrock. this tape is 3" wide. I split the 3" into 1 1/2" lengths. stick to sheetrock and fold into supply box. as the tape adheres to many surfaces you need to be careful to keep it within the area covered by the supply grill. once it sticks to the sheetrock..you'll lose paper if you try to move it. surfaces have to be clean & dry for tape to adhere. and once in place you'll want to press it in place as it is somewhat pressure sensitive. the tape is strong enough to keep the box tight to attic floor on the attic side when installing the supply grill. wash the dust off the grills, wipe inside the supply box & into the duct. reinstall the supply grill. oh and when you remove the supply grills..take a sharpie and mark what direction they faced (throw to window..dirveway side whatever note you need to put them back in same position) this way you'll put them back as they were. I've tried several other brands of mastic tape. hardcast 1402 is the best. the others are 2" width and mastic is thinner, resulting in less strength and useful life. why would I chose spray foam for my floors? I've sealed floors several ways, foam is the easiest albeit more costly, once prep work is done. there isn't enough room to physically install foam sheathing to the bottom of the floor joists. I'll seal any big holes..like under tub then do 3" foam. I've looked at froth packs like tiger foam..but having worked with so many foam companies locally, will just have them do my floor when they are in my area. the software is pricy. we lease it yearly. once upon a time we bought the cd..but too many people abused it. so now it is a download & upgrades to original install. a lot of mastic isn't always an indication of a good seal. it doesn't take a lot if you put it in the actual leaks. you can feel around the duct take offs on the plenum while unit is running and feel some of the leakage. also checking plenum connections to the equipment at the same time. I use mastic tape to connect plenums (after screwing them in place) much easier to seal under the plenum to equipment with tape than painting mastic upside down.

The side that isn't blocked should be used to ventilate the space. Open two areas,as far apart as possible and install an exhaust fan set up to a humidistat. The other opening will be the intake as well as an additional vent into the living space. In the winter, close off the openings. Ron