Before any of the negative conditions can be addressed properly the crawl space environment has to be controlled. We know moisture is a major problem with crawl spaces so let’s start there. When it comes to controlling any environment one has to know where the problems are coming from. So far we know the foundation vents, the open earth, the foundation walls and the cracks around the rim joist and foundation are the main source causing the negative conditions and high crawl space moisture. Some franchise companies will want to sell what is called a vent cover to seal the open vents. On paper, this product looks like it will work, and it does to some degree but it does not work as well as the alternative which is less expensive, a permanent solution and fairly easy to do. Most foundation vents are an 8” x 16” metal vent. A cement block is the same size and will fit into the opening once the vent and the excess mortar have been removed. To seal the block you have two choices; use a concrete sealant (caulk) around the block on the inside and outside of the crawl space or mix up some new mortar and fill the gaps around the block. Either way, the vent will be permanently closed and is in the same condition or better than the rest of the foundation. How you choose to close the vents will directly impact how much of a saving you will receive on your heating bills. The open vents are the number one vehicle for energy loss in the crawl space so be diligent here and don’t cut corners.