Floodproofing Non-Residential Buildings

Safety, cost and liability in flood hazard areas

Layne Evans

Almost everyone lives in a potential flood zone. In addition to the hurricanes and catastrophic floods that make national headlines, a damaging flood is happening somewhere in the U.S. every day, even in desert regions, caused by local heavy rainfall, dam failures, land development runoff, drainage problems, inland remnants of tropical storms and many other conditions. Nationwide, flooding is the leading cause of deaths related to severe weather, and it wipes out businesses, too. According to the National Flood Insurance Program (NFIP), almost 40 percent of small businesses never reopen their doors after a flood disaster, because just a few inches of water can cause tens of thousands of dollars in damage.

In an increasing number of areas around the country, the risk of flood is even more acute. Over 178 million acres have been designated as floodplains by FEMA. These areas are growing steadily, and more people are finding themselves within a floodplain as flood maps are redrawn. The new maps reflect changes in conditions and new development, and also improvements in scanning technology, additional years of climate, flood and topographic data, and more advanced prediction models.

Building in floodplains, or Special Flood Hazard Areas (SFHA) designated by FEMA, is strictly regulated by the NFIP, the International Building Code, ASCE national reference standards, and by local community codes, all of which are discussed in this course. Deciding on a non-residential building's floodproofing strategy will have a direct connection to the project's cost, to the safety of the building's occupants and the survivability of the building itself, and to the risk of liability for the designer and builder in case of flood damage.

National Flood Insurance Program

Standard insurance policies do not cover floods. The NFIP was created to provide flood insurance, but also to prevent flood damage in the first place by encouraging effective management and use of floodplains. Community participation in NFIP is voluntary, but flood insurance and many types of disaster assistance are only available in communities that participate by adopting and enforcing floodplain management and construction ordinances that meet or exceed NFIP guidelines. Over 20,000 communities participate in the NFIP, in an effort to avoid the skyrocketing costs of disaster assistance, repair and rebuilding.

NFIP insurance is available to anyone within the participating community, and FEMA encourages homeowners, business owners and renters even in low-risk areas to purchase flood insurance, since at least 25 percent of flood insurance claims every year come from low- and moderate-risk flood areas. In designated Special Flood Hazard Areas, however, flood insurance is mandatory. Premiums are based on the specific measures taken in the building, and can vary widely depending on what floodproofing options are used.

Photo by Anton Grassl/Esto At the new James E. Clyburn Research Center, Charleston, South Carolina, foundation flood vents meet functional as well as aesthetic requirements.

With luck, most of the buildings built to NFIP standards will never face a catastrophic flood, but effective floodproofing measures also result in more durable structures that require less maintenance and suffer an estimated 80 percent less damage every year. If the worst case does occur, the right floodproofing option will increase a building's “sustainability” in a fundamental way, often determining whether or not the building will survive at all.

Photo by Smart Vent Products, Inc. Unless hydrostatic pressure acting on structures during floods is equalized or relieved, walls can be damaged or even fail.

Special Flood Hazard Areas

Special Flood Hazard Areas are designated on Flood Insurance Rate Maps prepared by the NFIP. These are areas subject to flooding during what is called the base flood: a flood that has a 1-percent chance or greater of being equaled or exceeded in any given year.

The base flood is also commonly referred to as a “100-year” flood, but it's important to note that this is not a flood event that is expected to happen only once every 100 years. The base flood has a 1-percent chance of happening every year. This translates to a 26-percent chance of happening once over a 30-year mortgage. In fact, in some areas 100-year floods have happened in consecutive years.

The Special Flood Hazard Areas are divided into zones beginning with the letter A or the letter V. There are also numerous subdivisions, such as AO, AE, VE, etc., based on varying types of risk for the exact topography and other characteristics of the area. “V” zones are in coastal floodplains where high velocity wave action could occur during the base flood, so building designs have to take hydrodynamic forces into account. “A” zones can be on coastal floodplains, but they can also be in inland areas. High-velocity waves are not expected in “A” zones, so most damage results from hydrostatic forces, as will be discussed in more detail below.

Codes and regulations specify floodproofing measures in relation to the “base flood elevation” (BFE), the water surface elevation associated with the 100-year flood. The BFE is the basic standard for floodplain development, used to determine the required elevation of the lowest floor of any new or substantially improved structure.

In “A” zones, a non-residential structure is allowed to have an enclosed space below the BFE provided that the building has been designed, constructed and certified to be floodproofed and to meet established criteria, as explained in this course. In “V” zones, construction or substantial improvement of buildings with lowest floor elevations below the BFE is not allowed, regardless of floodproofing techniques.

Purchase of flood insurance is mandatory in both “A” and “V” areas.

Photo by Smart Vent Products, Inc. Flood vents provide wet floodproofing, automatically equalizing the hydrostatic pressure acting upon the structure.

Floodproofing Basics

As mentioned above, local communities adopt and enforce their own ordinances, and many exceed the minimum standards discussed here, as the NFIP encourages them to do. But a number of basic concepts apply to all floodplain building ordinances, and they are important to understand when planning a new non-residential building in a Special Flood Hazard Area.

Wet vs Dry Floodproofing

NFIP regulations require flood openings in all enclosures below the BFE of buildings in flood hazard zones. This is referred to as “wet floodproofing,” where water is expected to move in and out of the lower, uninhabited portions of the building. It is required in all residential buildings, but in non-residential buildings an exception is allowed for what is referred to as “dry” floodproofing, essentially attempting to make the building watertight. This course will analyze the costs and benefits of each approach.

Elevation Certificate

The FEMA Elevation Certificate (EC) or FEMA Form 81-31 is the official form the community uses to document compliance with the community's floodplain management ordinance.

Insurance agents also typically use the information from the EC to determine flood insurance eligibility and rates. The current EC form includes a check-box if the project is using pre-certified engineered flood vents. With certain types of other measures, additional documentation will be required. For instance, if using dry floodproofing methods, the design professional on the project is required to certify that the structure is floodproofed to a certain elevation (the BFE plus 1 foot, and higher in many communities). Certification methods are described in detail in the online version of this article.

Enclosure Types

Some of the types of enclosed areas under elevated buildings that will require flood openings or other floodproofing measures include:

• Parking areas or attached garages
• Building access areas such as stairwells, foyers, elevators
• Storage (for low-value items)
• Under-floor spaces like crawlspaces providing access to utilities

Photo by Smart Vent Products, Inc. Hydrostatic pressures are extremely strong under flood conditions, and can shift, separate and even destroy foundations if not properly floodproofed.

Freeboard

The term for extended floodproofed space above the BFE, added for additional safety, functional reasons and often to decrease insurance premiums. (See sidebar “Design Solution: Add Freeboard” on page 5.)

Active vs Passive Floodproofing

“Active” floodproofing measures require human intervention, such as opening and closing flood gates, etc. “Passive” floodproofing measures are built into the building and operate automatically without any human activity necessary. In residential buildings, wet floodproofing must operate automatically, without any human intervention. However, in non-residential buildings, many dry floodproofing systems require human intervention in order to function effectively. Again, these are subject to strict rules and must be individually certified by the design professional in charge of the project.

“Dry” Floodproofing

The only exception to the requirement for flood openings is for non-residential buildings that are designed and engineered to be floodproofed by meeting stringent requirements to be watertight.

Using dry floodproofing essentially means making the building, and all its utility systems, completely watertight and impermeable to the passage of water below the BFE. (Dry floodproofing is not permitted in V zones, where breakaway walls are required below the BFE.)

Dry floodproofing can include passive measures such as waterproof sealants and coatings on walls and floors, water barriers, and automatic backflow prevention valves and sump pumps. But it also may include active measures, for instance, flood gates, shields or doors, which must be manually activated when high water is expected. The design has to take into account important planning considerations such as how much warning time is likely to be available, how people will enter and exit the building, what the flood frequency in the area is, and what floodwater velocities, flood depths and debris impact can be expected.

Examples of features of dry floodproofing systems include the following (and additional examples of system design are given in the Cost Analysis PDF in the online version of this course):

• Sealants, coatings and membranes to reduce seepage of floodwater through walls and wall penetrations
• Installation of watertight closures for doors and windows
• Reinforcement of walls to withstand floodwater and floating debris
• Anchoring of the building to resist flotation, collapse and lateral movement
• Installation of pumps to control interior water levels
• Installation of check valves to prevent the entrance of floodwater or sewage flows through utilities
• Location of electrical, mechanical, utility and other valuable damageable equipment and contents above the expected flood level

The choice to use dry floodproofing triggers a requirement for a floodproofing certification: Floodproofing Certificate for Non-Residential Structures (FEMA Form 81-65). Among other requirements, the certificate must state: 1) the elevation to which the building has been dry-floodproofed, 2) that the building, together with utilities and sanitary facilities, is watertight to the floodproofed elevation, with walls that are substantially impermeable to the passage of water, and 3) that the structure is capable of resisting hydrostatic, hydrodynamic and debris impact forces, including the effects of buoyancy.

Every building floodproofed in this way within the Special Flood Hazard Area must also be certified by a design professional, as stipulated in NFIP regulations: “Provide that where a non-residential structure is intended to be made watertight below the base flood level, a registered professional engineer or architect shall develop and/or review structural design, specifications, and plans for the construction, and shall certify that the design and methods of construction are in accordance with the accepted standards of practice for meeting the applicable provisions of … this section.” Note: Detailed information on dry floodproofing is found in FEMA's Technical Bulletin 3, Non-Residential Floodproofing – Requirements and Certification.

“Wet” Floodproofing

As mentioned above, NFIP regulations require wet floodproofing in residential buildings, and it is also an option in non-residential buildings. Costs are lower (see the Cost Analysis PDF in the online portion of this course for more detailed cost and design discussion), and human activity is not needed, a definite plus under emergency conditions where warning is short and travel is difficult or impossible. In addition, in the case of engineered automatic flood vents which have been pre-certified under the International Code Council Evaluation Service (ICC-ES), the certification process is substantially streamlined, and liability for the performance of the product during a flood is the responsibility of the product manufacturer rather than the certifying design professional.

Photo by Smart Vent Products, Inc. For commercial, industrial and other non-residential applications, pre-tested and certified engineered flood vents are available in large frame sizes and custom configurations.

Wet floodproofing measures allow water to flow in and out of the lower, uninhabited portions of the building such as parking garages, building access areas and crawlspaces. Installation of flood openings—most commonly flood vents—in the walls allows for the automatic equalization of flood levels on both sides of the walls, preventing the catastrophic damage that can be caused by unbalanced hydrostatic forces created during floods.

When flood water rises against the building enclosure and is unable to flow into the space, or recedes much more quickly than it entered, unequal pressure is created on opposite sides of the walls. The magnitude of hydrostatic pressure increases linearly with water depth. Unless the pressure is equalized or relieved, walls can be damaged or even fail (see figure at top of page 143). If they are load bearing walls the building will collapse. Lateral pressure pushes against exterior walls, while vertical force can shift and separate the foundation or walls, and even in some cases literally lift the structure. When significant floodwaters are present, forces of buoyancy can float the entire structure away.

Flood vents equalize the pressure of the forces acting upon the structure, by letting the water flow evenly in and out.

Code-Compliant Flood Vents

Requirements for flood opening sizes, location, number and other characteristics are primarily governed by NFIP regulations. The major requirements are outlined below, but the FEMA document that provides extensive details about meeting flood opening regulations is Technical Bulletin 1-2008, Openings in Foundation Walls and Walls of Enclosures. The American Society of Civil Engineers (ASCE) has developed the standard Flood Resistant Design and Construction (ASCE 24). This standard applies to buildings and site developments proposed in flood hazard areas. It is also referenced by the International Building Code. ASCE 24 Section 2.6.2.2 contains installation and design criteria for engineered openings. Local ordinances also refer to these three documents as a basis of their own floodproofing ordinances.

Design Solution: Add Freeboard

Adding an extra one or more feet above the BFE to a building space can significantly reduce insurance premiums in a flood hazard zone while providing additional space and functionality for the life of the building. For example, making a 4- or 5-foot-high crawlspace into a 10-foot enclosure might reduce insurance premiums by as much as 48 percent. Even adding one foot of freeboard might reduce premiums by over 35 percent. The additional space can add low-value storage areas, parking, better access or even just much improved headroom, and typically has a very quick payback of 2-3 years, since the cost in extra materials and labor is often minimal. Elevating a building a few feet above legally mandated heights has very little effect on its overall look, but it has significant benefits, including: Increased protection from floods and storms. Stormwaters can and do rise higher than shown on Flood Insurance Rate Maps (FIRMs). Freeboard helps protect buildings from storms larger than those that FIRMs are based on, and provides an added margin of safety to address the flood modeling and mapping uncertainties associated with FIRMs. Better preparation for ongoing sea level rise. For example, Massachusetts has experienced a relative sea level rise of approximately 1 foot over the past 100 years. Since elevations on FIRMs do not include sea level rise, freeboard will help keep structures above floodwaters as storm surge elevations increase. Greatly reduced flood insurance premiums. Recognizing that freeboard reduces flood risk, FEMA and NFIP provide substantial (sometimes more than 50 percent) reductions in flood insurance premiums for structures incorporating freeboard. These savings can rapidly accumulate, especially over the life of a normal mortgage.

The major requirements are as follows:

Openings must be in multiple walls. In order to allow water to flow freely in and out of the building, each enclosed area is required to have a minimum of two openings on exterior walls, located below the BFE. They should be installed on at least two sides of the enclosed area to allow for more even filling and draining of floodwater. If possible the openings should be reasonably distributed around the perimeter, unless there is a special justification for putting them on just two sides, e.g. in townhouses or buildings set into sloping sites.

The International Building Code (by reference to ASCE 24) requires a “minimum of two openings on different sides of each enclosed area.”

Wall location. The NFIP's definition of an enclosure is any portion below an elevated building that is fully shut in by four rigid walls. Basements are not allowed in Special Flood Hazard Areas. To avoid having an enclosure classified as a basement, the entire length of one wall must have its inside grade higher than or equal to the outside grade for that wall. This would qualify the enclosure as a walkout basement.

Opening location. The bottom of the opening must be no more than one foot above the grade that is immediately under the opening, either the adjacent ground level, or the interior grade, whichever is higher. The lower wall will experience hydrostatic pressure first, so most of the openings should be there. This alleviates the initial force of the water and then provides quick drainage when water begins to recede.

In practice, most communities require additional height, or “freeboard,” and insurance premiums will be substantially reduced by additional freeboard. (See sidebar.)

Materials. All materials below the BFE must be made of flood resistant material such as stainless steel or specially treated flood resistant lumber.

Opening size. ASCE 24 is referenced in all regulations, and it requires that a 3-inch sphere should be able to pass through the flood opening. This is to ensure that grills and louvers don't interfere with the passage of debris, or become so blocked that they are ineffective. It is well known that no flood water is crystal clear. Debris is a fact of flood, and can be devastating in itself.

Photo by Smart Vent Products, Inc. Debris is a fact of flood. Flood openings that are not sized properly, such as this air vent, can become blocked with debris and rendered ineffective.

Screening. ICC building codes require that openings be screened to prevent the entry of insects, rodents, birds, etc. Commercially available grates, louvers and grills are available for this function. However, as just mentioned, the louvers and screens can't interfere with the equalization of the water levels, and they must be selected to minimize potential blockage by debris. Any opening that includes a cover is an unacceptable measure according to FEMA TB-1.

Screens also affect the calculation of the required net opening area, discussed next.

Net open area. The NFIP's standard for non-engineered openings requires one (1) square inch of net open area for every square foot of enclosed area. Any part of a screen, grate or louver that impedes entry will be subtracted from the net opening area. Non-engineered openings also do not meet the standards if they are likely to be closed during the winter, as many air vents are. In fact, any air vent intended to be used as a flood opening is required to be disabled in the open position, so that it physically cannot be closed. Other commonly used air vent devices will not qualify as acceptable flood openings, such as devices with detachable covers, or temperature-controlled vents that will shut automatically when waters rise around the foundation.

Windows will not qualify as flood vents. Often window glass will remain in place even when a wall is dislodged from its foundation. Garage doors do not qualify in themselves, as they could be disabled in a power outage and would require human intervention even if useable. However, some code-compliant automatic flood vents can be installed in garage doors.

Automatic Operation. Wet floodproofing measures that satisfy NFIP requirements must be automatic. That means that the system must be strictly passive, operating with no human interaction required (e.g., opening or closing of vents).

Engineered and Non-Engineered Flood Vents

Products used to meet the flood opening requirements outlined above fall into two broad categories. Non-engineered flood openings need to meet the NFIP's requirement of 1 square inch of net open area for every square foot of enclosed area. This category includes mostly air vents if they have been rigged in the open position to meet the requirements.

Engineered flood vents can either be designed individually as site-specific solutions to meet specific performance criteria, or they can be pre-tested and certified products. However, just as with dry floodproofing, if a unique, project-specific engineered flood vent is being specially designed for the project, it will trigger a requirement for additional documentation, in this case a Flood Opening Certification signed by a registered design professional stating that the engineered vents will meet ASCE 24 standards and have all other required design performance characteristics. A pre-tested product certified through the ICC-ES process, will already have the required documentation. ICC-ES certified flood vents are certified to provide floodproofing for a specified amount of square feet, as described in the Certification Methods section below.

If openings are found not to be compliant, the floor of the crawlspace or the floor of the enclosure becomes the “lowest floor.” In those cases, the result will be significantly higher flood insurance premiums, especially if the floor of the crawlspace or enclosure is more than a foot or two below the BFE.

(As noted above, all these requirements are discussed in more detail in Technical Bulletin 1-2008, Openings in Foundation Walls and Walls of Enclosures.)

Certification Methods

As has been discussed, there are two certification methods available under FEMA/NFIP and local community ordinances.

For dry floodproofing methods, a Floodproofing Certificate for Non-Residential Structures (FEMA Form 81-65) is required. For unique project specific engineered flood openings designed to provide wet floodproofing, an Engineered Opening Certification is required. Both of these require information about the location of the property, the license of the design professional making the statements, with the original raised seal (all documents for these certificates must be original, not photo-copied), documented square footage of openings and number of vents, and other detailed information about the design of the system. These must be submitted to the surveyor and local building official in addition to being attached to the Elevation Certificate required by FEMA.

The second engineered opening certification method is for products for which an Evaluation Report has been issued by the International Code Council Evaluation Service, Inc. (ICC-ES), a subsidiary of the International Code Council, Inc. (ICC).

The ICC-ES issues such reports for a variety of building products, methods, and materials. Evaluation Reports are issued only after the ICC-ES performs technical evaluations of documentation submitted by a manufacturer, including technical design reports, certifications, and testing that demonstrates code compliance and performance.

For pre-tested engineered flood vents that have been certified by ICC-ES, their provided Evaluation Report document is all that is required for submittal with the plans and the Elevation Certificate.

Photo by Smart Vent Products, Inc. Pre-tested and certified engineered flood vents in custom configurations were used to meet all flood venting and air ventilation code requirements in the new James E. Clyburn Research Center at the Medical University of South Carolina (see Case Study on the next page).

The ICC-ES report lists the name of the manufacturer, different models that are offered, and the square feet that each model is certified for (for instance, the report might require a minimum of one unit per 200 square feet for a certain model and certain applications, or one per 400 square feet, etc.). Installation requirements are also included. The responsibility for the performance of the flood vents rests with the product manufacturer, not the project designer.

Common experience indicates that building officials favor the simplicity of the ICC-ES as a method of evaluating products, and a 2006 national survey substantiates this. Eighty (80) percent of the building officials surveyed preferred ICC-ES to other methods of evaluating products such as reviewing product listings, test laboratory reports, manufacturers information, reports from local engineers and other information. Probably the most important element for code officials is their judgement in the field, but ICC-ES certification means the product has already been thoroughly tested and its performance can be reliably predicted. Insurance agents also use the certification to generate premiums. When certified engineered flood openings are installed it guarantees the lowest possible flood insurance premium for the property owner.

Photo by Anton Grassl/Esto James E. Clyburn Research Center Medical University of South Carolina, Charleston, SC, Stevens & Wilkinson Architects When Bill Fleming, Associate V.P. and Senior Architect of Stevens & Wilkinson Architects was appointed to design the new James E. Clyburn Research Center at the Medical University of South Carolina located in a flood zone, he had to find a compliant and reliable flood vent system. He determined that, because of its unique location, the medical facility would be elevated above the Base Flood Elevation (BFE) on a crawlspace. The BFE for this construction site was 13 feet with the existing site grade at 7 feet. Building the facility on top of a crawlspace would also provide easy access to utility lines and other services so that maintenance could be performed from under the building instead of inside. For non-residential structures in a floodplain, there are two options to floodproof the enclosed area below the BFE: dry floodproofing, defined as making the building watertight, and flood venting, also referred to as wet floodproofing. Because FEMA discourages dry floodproofing when flood depths are in excess of 3 feet, and because of the cost and liability associated with a dry floodproofed design, flood vents were specified as the floodproofing measure. To make the crawlspace compliant with the building codes and NFIP/FEMA regulations, the flood vents needed to be installed around the perimeter of the foundation to relieve the hydrostatic pressure that occurs during a flood. Flood vents allow the floodwater to flow in and out of the enclosed space during a flood event; this equalization of pressure maintains the structural integrity of the building. After extensive research, a pre-approved foundation flood vent system certified by the International Code Council Evaluation Service (ICC-ES) and accepted by the Federal Emergency Management Agency (FEMA) was selected. A dual-function design was used to provide both flood protection and air ventilation, meeting all flood venting and air ventilation code requirements necessary for the project. The combined square footage for the two crawlspaces was roughly 47,400 square feet. The project utilized nineteen 4x3 custom configuration frames and one 3x3 custom frame. A french drain system was designed around the inside perimeter of the foundation to assist with drainage in the event of a flood. “Because the application was over a crawlspace, the project needed to meet the air ventilation code requirements, along with the flood venting requirements, since the building was being built in a flood zone,” said Bill Fleming, and the products used “allowed us to meet the functional requirements of the crawlspace, as well as providing an aesthetic character that worked well with the exterior building.”

Engineered Automatic Flood Vents: How They Work

Products that have passed the ICC-ES certification process work as follows. A vent frame is inserted in the foundation or wall opening. The flood door is contained within the frame, comprised of an insect screen and air vent louvers or insulation to prevent air ventilation. Stainless steel construction meets the requirements for flood resistant material.

A float system built into the sides of the door locks the door into the frame. As water rises, the flood door automatically pivots open. Since the entire door pivots open, with no obstructing screen or louver, debris can easily flow through the opening. But under normal operation, dual-function vents offer natural ventilation along with flood protection; insulated vents provide a sealed opening for flood protection only. The built-in louvers inside the dual-function flood door are for air circulation only. Even when they are closed, rising water will still activate the opening of the vent. A bi-metal coil requiring no electricity expands and contracts with changing temperature, opening louvers in the summer, and closing them in the winter to prevent cold air from entering the space.

The flood door doesn't bang open and closed like a dog door. The door only opens in response to the buoyancy of the floats caused by flood water.

The door is bi-directional, allowing water to easily flow into and out of the space, with no screens to catch debris or impede water flow.

Flood Vents and LEED®

LEED buildings are being designed and built in Special Flood Hazard Areas. One example is the LEED Platinum house built as part of the Extreme Makeover program, for a firefighter who lost his house due to Hurricane Katrina and his subsequent temporary housing to a tornado. The sealed crawlspace with ICC-ES Certified flood vents contributed to excellent energy efficiency, and adding 1 foot of freeboard saved an estimated 68 percent on the house's insurance premiums.

Major areas where engineered automatic flood vents can contribute to LEED points include:

SS Credit 1 Site Selection

SS Credit 6.1 Stormwater Design - Quality Control: Flood vents can eliminate the need for fill, which can be problematical, sometimes pushing the flood zone into neighboring properties and raising the project's BFE.

EA Prerequisite 2 Minimum Energy Performance: In most non-engineered flood vent situations it is nearly impossible to seal a space sufficiently for good energy efficiency in the building. However, some engineered flood vents are available with insulated options, which offer a solid, weather stripped vent for a sealed crawlspace in a flood zone. The vent includes 2-inch Styrofoam insulation for an 8.34 R-value.

MR Credit 1.1 Building Reuse: Maintain 75 percent Existing Walls, Floor, Roofs: Building can be retrofitted with certified flood vents to use the same foundation on the property.

EA Prerequisite 1 Minimum Indoor Air Quality Performance: Flood vents with dual function air ventilation and flood performance offer ventilation to crawlspaces and other areas to improve the efficiency of the HVAC system and to diminish conditions for mold build-up.

ID Credit 1 1.4 Innovative Design: Engineered flood vents can be used in innovative solutions in floodplain areas. For example, stacked flood vents in large buildings (see figure in section “Code-Compliant Flood Vents”) mitigate against flood damage. Rooftop floodgates offer stormwater flood control if clogged drains need to release water. Flood vents can offer emergency relief of water pressure in facilities that must handle very large quantities of water, such as breweries, pump stations and nuclear plants.

What to Look For in A Manufacturer

In addition to the ICC-ES certification that will assist with project code approval, insurance premiums and designer liability risk, engineered automatic flood vent products for non-residential buildings should be evaluated for other benefits.

Range of sizes and configurations

Frames should be available in custom sizes, as large frames are typically necessary in non-residential applications. Custom solutions should be available to fit into retrofits of existing crawlspaces, parking areas, etc. Some of the configurations that should be available in addition to units which work with standard concrete masonry units are stacked and quad vents for large industrial or commercial spaces, frames that can be used with wood construction, and vents that can be used with poured foundations. (See previous figures in sections “Engineered and Non-Engineered Flood Vents” and “Engineered Automatic Flood Vents: How They Work.”)

Flood vents should also be available that will work in applications requiring fire rated walls. Typically a fire damper utilizing a fusible link is used in conjunction with the flood vent to meet the fire rating.

Dual function or insulated

Where ventilation is required or desired, flood vents should work effectively both as air vents during normal conditions and as flood openings in flood conditions. In conditions where energy efficiency is at a premium, insulated vents with a 2-inch thick Styrofoam core should be available that will provide effective flood protection and energy efficiency. These are especially applicable in spaces that do not require natural ventilation, like walk-out basements, foyers and other areas with conditioned spaces, such as sealed crawlspaces or accessory spaces.

Range of colors

A full range of powder coat paint options allow the flood vents to fit most exterior designs, even in historic districts where floodproofing retrofits are needed.

Design, Code and Regulation Support

The manufacturer should be able to offer informed guidance throughout the design and approval process, including in-depth CAD files for the custom frames so that vents can be incorporated easily into the project design.

Cost Analysis: Comparison of Dry vs Wet Floodproofing Technologies

Attached to this course is a Cost Analysis PDF document detailing four floodproofing scenarios that demonstrate the differences between dry flood proofing solutions that require flood barriers and wet flood proofing that use ICC-ES pre-certified engineered flood vents.

The scenarios are based on a 5,000-square-ft enclosed space where the expected flood elevation is 4 feet above grade and the flood proofing protection elevation is to 5 feet above grade to provide for 1 foot of freeboard to give some margin of safety against overtopping by a flood.

For Additional Information

• National Flood Insurance Program
• Floodsmart (NFIP site)
• Technical Bulletin 1-08: Openings in Foundation Walls and Walls of Enclosures
• Technical Bulletin 3-93, Non-Residential Floodproofing – Requirements and Certification
• ASCE American Society of Civil Engineers, Structural Engineering Institute. 2005. Flood-Resistant Design and Construction, ASCE/SEI 24-05.
• Whole Building Design Guide
• International Code Council – Evaluation Service

Photo by Smart Vent Products, Inc. The chart shows the substantial differences in cost that can be expected with different floodproofing designs. See the attached PDF document Cost Analysis Comparison: Dry vs Wet Floodproofing Technologies for more details about the designs and costs of these scenarios.

Smart Vent Products, Inc. is the worldwide leading manufacturer of foundation flood venting systems and takes pride in having a FEMA-accepted and ICC-ES certified flood vent. The company staff consists of certified floodplain managers and technical field representatives eager to assist you with any part of your floodplain project. www.smartvent.com