About six years ago I discovered that if your house is located in FEMA designated flood zone "A" (there are a couple of these zones in Ocean Pines and my house is in one of them) FEMA requirements are such that they practically negate encapsulation of a crawl space.

According to the FEMA folks who run the National Flood Insurance Proram (NFIP) that I contacted, the most destructive force in floods is hydrostatic pressure (flood waters) pressing against crawl space walls and eventually collapsing them and the house sitting atop the walls. Thus, FEMA requires holes in foundation walls that allow flood waters to flow through crawl spaces OR the installation of FEMA approved crawl space vents and doors which open via a float mechanism to allow flood waters to enter and exit the crawl space. Allowing flood waters to flow through the crawl space apparently equalizes the hydostatic pressure on both sides of the crawl space walls so the walls will not collapse.

These "approved" vents and doors were (at the time) made only by one manufacurer and were very expensive (at the time a small vent was $200 and a door was about $1,700). As I recall they were made of plastic. I have 12 vents and two doors on my crawl space walls. I visited Mumford's Sheet Metal (?) in Selbyville and they made float controlled, sheet metal vents and doors for extremely reasonable prices, but their products were not FEMA approved then.

None of the encapsulation companies I talked with at the time were aware of FEMA requirements. A neighbor of mine had his crawl space encapsulated without any method to relieve the hydrostsic pressures because the encapsulation company never mentioned it to them. The FEMA/NFIP employee I talked with said FEMA will NOT pay flood damages to a home if a crawl space is encapsulated and there were no "approved" means of relieving the hydrostatic pressure.

One encapusaltion company did tell me they would encapsulate my crawl space except for the wall areas where I had vents or doors. But that is counter productive to the whole concept behind encapsulation.  I just finally gave up on the idea of encapsulation. 

If you do not live a FEMA flood zone, just forget everything I wrote here and count your blessings.

Gene