How Do Flood Vents Work?

Flood Vents protect houses and buildings during floods by preventing hydrostatic pressure buildup that can destroy walls and foundations. This mitigation technique, referred to as Wet Floodproofing, allows floodwater to freely flow through an enclosure such as a crawlspace or garage.
hydrostatic pressure

Hydrostatic Pressure: The pressure exerted by gravity at a given point within a fluid that is at equilibrium, increasing in proportion to depth from the surface.


When Are Flood Vents Required?

The NFIP Regulations and Building Codes require that any residential building constructed in Flood Zone Type A have the lowest floor, including basements, elevated to or above the Base Flood Elevation (BFE).

Enclosed areas are permitted under elevated buildings provided that they meet certain use restrictions and construction requirements such as the installation of flood vents to allow for the automatic entry and exit of flood waters.

This wet floodproofing technique is required for residential buildings.

With commercial buildings, elevation and the use of wet floodproofing techniques is the suggested form of mitigation. This technique can be a more cost-effective solution, and reduces the impacts the building has on surrounding floodplain in comparison to dry floodproofing techniques.


Where Are Flood Vents Used?

In A Crawlspace Enclosure

photo credit: FEMA TB-1

In A Garage Door

photo credit: FEMA TB-1

To view examples of other areas where Flood Vents can be utilized in your home.


How Do I Know If Flood Vents Are Required In My Home?

• Determine your Flood Zone by viewing FEMA’s Flood Map Service Center (DFIRM) or Flood Risk can also be determined using the free services provided by Flood Risk Evaluator (FRE).

• Determine whether or not your home has either enclosure pictured above. If it does, you could definitely benefit from flood vents.