my father did his new house last year and wow what a difference. the air was completely clean, no mold, mildew or insects once the humidifier was installed, stays around 50%. I think he used 1" foam board on the block walls and heavy plastic on the floor.
Have You Sealed Your Crawlspace?
Our summer place has a crawlspace. Years ago the pipes and beams had a lot of condensation. We laid plastic sheets on the dirt and added ventilation which stopped the condensation but the first floor of the house is still damp most of the time. The thin plastic is beginning to decompose and some of it has been moved around over the years. I believe that most of the dampness is coming up from the crawlspace. From what I've read, the new theory is not to ventilate but to seal it off completely. They do this by laying a 20 mil vinyl fabric on the dirt, sealing the pieces together. They also run it up the block walls and seal it at the top and around the footings. Then they close off all the vents and place removable covers on the access points. Sealing drains and dehumidifiers are also available if necessary. The job is fairly costly. I could get the materials and do it myself but I hate going down there anymore because some areas have only 1 foot of clearance. 
Has anyone sealed their crawlspace with "Clean Space"?
Has anyone sealed their crawlspace with "Clean Space"? 
