- What is the definition of a flood?
How FEMA / National Flood Insurance Program defines a flood:
In simple terms, a flood is an excess of water on land that is normally dry. The official definition used by the National Flood Insurance Program is, “a general and temporary condition of partial or complete inundation of two or more acres of normally dry land area or of two or more properties (at least one of which is your property) from:
- Overflow of inland or tidal waters;
- Unusual and rapid accumulation or runoff of surface waters from any source;
- Mudflow*; or
- Collapse or subsidence of land along the shore of a lake or similar body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels that result in a flood as defined above.”
*Mudflow is defined as, “A river of liquid and flowing mud on the surfaces of normally dry land areas, as when earth is carried by a current of water…”
- What / Who is FEMA?
FEMA stands for Federal Emergency Management Association. In 1979, the Federal Emergency Management Agency (FEMA) was established by an executive order, which merged many of the separate disaster-related responsibilities into a single agency.
Since then, FEMA has dedicated itself to the mission of helping communities nationwide prepare for, respond to and recover from natural and manmade disasters – a mission strengthened when the agency became part of the Department of Homeland Security (DHS) in 2003. To learn more, download FEMA’s brochure.
- What/WHO is NFIP?
NFIP stands for the National Flood Insurance Program.
The Flood Insurance and Mitigation Administration (FIMA), a component of FEMA, manages the NFIP. The three components of the NFIP are:
- Flood Insurance
- Floodplain Management
- Flood Hazard Mapping
Nearly 20,000 communities across the United States and its territories participate in the NFIP by adopting and enforcing floodplain management ordinances to reduce future flood damage. In exchange, the NFIP makes federally backed flood insurance available to homeowners, renters, and business owners in these communities. Community participation in the NFIP is voluntary.
Flood insurance is designed to provide an alternative to disaster assistance to reduce the escalating costs of repairing damage to buildings and their contents caused by floods. Flood damage is reduced by nearly $1 billion a year through communities implementing sound floodplain management requirements and property owners purchasing flood insurance. Additionally, buildings constructed in compliance with NFIP building standards suffer approximately 80 percent less damage annually than those not built in compliance.
In addition to providing flood insurance and reducing flood damages through floodplain management regulations, the NFIP identifies and maps the Nation’s floodplains. Mapping flood hazards creates broad-based awareness of the flood hazards and provides the data needed for floodplain management programs and to actuarially rate new construction for flood insurance.
- What is a flood vent?
A flood vent or “flood port” is a permanent opening in a wall designed to allow the unobstructed passage of water automatically in both directions in to or out of the building interior. Flood vents are intended to reduce the risk of structural damage (from the forces of floods or flood waters) for buildings located in special flood hazard areas [or “flood plains”] in accordance with the National Flood Insurance Program (NFIP).
Flood vents may be solid hinged covers intended for use on occupied space (or a garage) or vented hinged covers for dual use as a crawl space foundation vent (for un-conditioned crawl spaces) and as a flood relief opening.
- What is the purpose of a flood vent?
Flood vents relieve hydrostatic pressure on the foundation walls to help prevent/minimize structural damage to the building.
- Why install flood vents?
Many homes meeting certain criteria require flood vents to be installed. In many instances you cannot obtain a mortgage without flood insurance.
Flood vents may substantially reduce the destruction and damage to your home during certain flood events. You may even quality for a discount or reduced premium on your current flood insurance policy by installing flood vents. The “lowest floor” used for calculations by the NFIP may be raised by installing proper openings and thereby lowering your insurance rates. You may want to check with your insurance agent to determine if you qualify for a discount on your existing flood insurance policy by adding flood vents.
Non-Engineered and Engineered Openings
- What is the difference between non-engineered and engineered openings?
A non-engineered opening is one that is simply measured by calculating the opening in the vent itself. It’s the amount of air/water flow or net open area that is used to meet FEMA requirements for Flood Vents. You will require 1 square inch of free area for each square foot of enclosed space to meet the FEMA requirements. You may use a non-engineered opening in any state without the requirement of an engineered certificate or ICC Certification.
An engineered opening is one that is designed and certified by a registered engineer or architect as meeting certain performance characteristics describes in FEMA Technical Bulletin 1/Aug 08.
If using an engineered vent then additional data must be provided. The “engineered openings must be certified by a design professional as having been designed to provide automatic equalization of hydrostatic flood forces by allowing for the entry and exit of flood waters.” Design requirements and specifications for certification statements are outlined in FEMA Technical Bulletin 1-08.
- Are Flood Solutions flood vents engineered or non-engineered openings?
All flood vents that Flood Solutions, LLC manufactures and sells are non-engineered openings.
You do NOT NEED a certification if the vent is a non-engineered opening.
All Flood Solutions vents are non-engineered openings and are acceptable in ALL 50 STATES. You would simply need the amount of free area for the vent from the manufacturer in writing to submit. Flood Solutions includes this information with all orders that are shipped. See pages 18 – 23 in the FEMA Technical Bulletin 1/08.
If you are using an engineered vent, then it isa requirement that you have an engineered certificate from the manufacturer of the vent in order to be able to use the engineered calculations to determine how many vents you will require.
- Do I need certification that my flood vents have engineered openings?
YES, it is a requirement that you have an engineered certificate from the manufacturer of the vent in order to be able to use the engineered calculations to determine how many vents you will require.
This certificate must be from the state in which your building is located, unless the vent is ICC-ES certified and has an ICC-ES evaluation report. If the vent has neither an engineered certificate from the state in which your building is located or does not have an ICC-ES evaluation report than you may not use the engineered calculations for the vent to determine how many vents you will require. You would then have to use the ACTUAL net free air of the vent to determine how many vents you will require. This would require far more vents to meet the requirements.
You do NOT need a certificate for a non-engineered opening, you would simply need the amount of free area for the vent from the manufacturer in writing to submit.
- What information needs to be included on the certificate?
For non-engineered openings, only a statement from the manufacturer stating the model number and the amount of free area each vent covers is required. Flood Solutions includes this information with all orders that are shipped. (See pages 18 – 23 in the FEMA Technical Bulletin 1/08.)
For engineered openings the following information is required:
The original certification statement must include:
The design professional’s name and title, address, type of license, license number and the state in which the license was issued along with the signature of the design professional and an applied seal of the certifying registered design professional.
In addition, the certification has to identify the building in which the engineered opening will be installed and it needs to include:
- A statement certifying that the openings are designed to automatically equalize hydrostatic flood loads on exterior walls by allowing the automatic entry and exit of floodwaters.
- Description of the range of flood characteristics tested or computed for which the certification is valid, such as rates of rise and fall of floodwaters.
- Description of the installation requirements or limitations that, if not followed, will void the certification.
This data is a certification as having been designed to provide automatic equalization of hydrostatic flood forces by allowing for the entry and exit of flood waters.
- Do all flood vents need to be ICC-ES evaluated?
NO. This is a test for flood vents that automatically allow water to enter and exit a structure during a flood event to be sure that the vent will open and close as required.
ICC-ES evaluation need not be provided for non-engineered vents.
- Does a flood vent need to have a 3″ opening as required by FEMA?
Absolutely not. The requirement refers to only the hole in the wall that the flood vent is to be installed within, excluding any screen, grate, louver or devices that may be placed in or over the opening. The hole must be not less than 3 inches in any direction in the plane of the wall. See FEMA TECHNICAL BULLETIN 1-2008 page 21 AND 26.
- Can a flood vent have a cover over it or a screen in the opening?
Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters.
A vent cover that impedes the automatic entry and exit of floodwaters is not permitted. This would pertain to, for example, a cover over the face of the vent for the winter that would not allow for the automatic entry and exit of floodwaters. If this cover needs to be manually removed before a flood event to allow for the automatic entry and exit of floodwaters, it’s not permitted.
Screens are permitted as they do allow the automatic entry and exit of floodwaters. See page 20 of the FEMA Technical Bulletin 1/08.
- What are the FEMA/NFIP requirements for installation of flood vents?
The following requirements for installation apply regardless of whether engineered openings or non-engineered openings are used to satisfy the NFIP requirements. You’ll find the technical information below, but simply put, FEMA/NFIP requirements include:
- A minimum of one square inch of net open area for each square foot of enclosed area for non-engineered openings OR a minimum of ONE engineered inch for each square foot of enclosed area for an engineered opening.
- A minimum of two vents per enclosed area, and each must be on at least two different sides of the exterior walls.
- The bottom of the flood vent opening must not be higher than 12 inches above the grade.
- The vent must be installed in an opening in the wall that is at least 3” in diameter. This requirement refers to the hole in the wall and NOT the flood vent.
Each enclosed area must have a minimum of two openings; if there are multiple enclosed areas, each area must have openings in its exterior walls, the openings should be installed on at least two sides of each enclosed area to decrease the chances that all openings could be blocked with floating debris and to allow for more even filling by floodwater and draining of the enclosed area.
It is recommended that openings be reasonably distributed around the perimeter of the enclosed area unless there is clear justification for putting all openings on just one or two sides (such as in townhouses or buildings set into sloping sites).
Non-engineered openings are openings that are used to satisfy the prescriptive requirement that calls for one square inch of net open area for each square foot of enclosed area.
Engineered openings are openings that have been designed and certified by a design professional; engineered openings require fewer vents to satisfy the requirements of the NFIP and FEMA.
Number of openings
ASCE 24 provides an equation to determine the total net area of flood openings that are installed in foundation walls or enclosure walls. The equation includes a coefficient that corresponds to a factor of safety of 5, which is consistent with design practices related to protection of life and property. This factor of safety also helps to account for the likelihood that insect screens may clog with flood-borne debris. The ASCE 24 commentary provides additional background on the derivation of the equation.
The bottom of each opening must be no more than 12 inches higher above the interior or exterior grade immediately under the opening, and a minimum of two vents per enclosed area, on at least two different sides of the exterior wall must be provided.
Screens, grates, etc.
Any screens, grates, grilles, fixed louvers, or other covers or devices must not block or impede the automatic flow of floodwaters into and out of the enclosed area.
- What isn’t allowed by FEMA?
It is important to note that FEMA has determined that certain measures are not acceptable as flood openings, including:
- Standard foundation air ventilation devices that are closed manually because they do not allow for the automatic entry and exit of floodwaters unless they’re permanently disabled in the open position.
- Standard foundation air ventilation devices that have detachable solid covers that are intended to be manually installed over the opening in cold weather, because they do not allow for the automatic entry and exit of floodwaters when the cover is in place.
- Standard foundation air ventilation devices that are designed to open and close based on temperature (unless they also are designed to allow for the automatic entry and exit of floodwaters).
- Windows below the BFE because the automatic entry and exit of floodwaters cannot be satisfied by the expectation that windows will break under rising floodwaters.
- Garage doors without openings installed in them, because human intervention is required to open the doors when flooding is expected. Gaps between the garage door and the doorjamb or walls do not count towards the net open area requirement.
- Standard exterior doors without openings installed in them.