Once the foundation vents are closed it is time to address the open earth and the foundation walls. There are many different ways to address these two problems. If what you want is to completely eliminate these areas from causing any problems again in your lifetime then I suggest installing a heavy duty vapor barrier. There are some mixed reviews on how to install a vapor barrier in a crawl space and what products are recommended. Some “experts” will tell you that a 6 mil plastic will do just fine and in fact it will. But it will not last as long and is prone to tears and compromises that will get you right back to where you were when you started. Is it a temporary fix? Yes it is. It is also the minimum requirement for a crawl space floor. A better and a more permanent solution is to use a product designed for the problem like the SilverBack™ family of vapor barriers. The main differences between one crawl space vapor barrier to another is going to be it’s durability, the perm rating (rate at which water will pass through) and the quality of the resin that was used to make the polyethylene. It is important to use a polyethylene barrier that is made from virgin resins, this will insure a long life for your investment. Most low cost polyethylene barriers are made from recycled plastic. While recycling is good for most products in the market place it is not good for this application because it puts your barrier closer to breaking down and becoming brittle. Any open seams, cracks or splits in the barrier will render even the highest quality barrier ineffective. Make sure you know what you are buying before you buy or you could end up with an overpriced knock off. Ask the supplier if there is a warranty for the longevity of the barrier they propose to sell you. If they are not confident enough to give a warranty then I would question the quality.