Post by ogeezer on Apr 28, 2007 6:37:51 GMT -6
For homes not built on concrete, slab foundations that are typically constructed on raised earth footings, at least 12" above known 100-year flood planes, foundation flood vents reduce the chances of a perimeter beam foundation being compromised during flooding.
To be eligible for flood insurance through FEMA's National Flood Insurance Program (NFIP), foundations must be constructed with certain flood damage mitigation features. In coastal areas and riverine zones, where high velocity floodwaters can occur, homes must be elevated on open pile foundations, and enclosures below the living space must be located at an elevation higher than the 100-year base flood elevation and must be designed to break away in a storm surge.
Homes built in floodplains where floodwater velocity levels are lower than coastlines and riverine zones (< 5 feet per second), on perimeter type foundations, should be designed so that exterior walls of the foundation automatically equalize hydrostatic flood forces by allowing for the free flow of floodwater. This minimizes structural flood damage by reducing the horizontal hydrostatic force that unbalanced water levels impose on foundaton walls.
Foundation designs meeting NFIP requirements must include prescribed openings or an engineer's certification that the following minimum criteria have been met:
Any openings that allow the free flow of floodwater into or out of a foundation will meet NFIP requirements, subject to minimum size and location criteria.
Several manufacturers have developed unitized, shuttered products that meet the minimum flood venting requirements of NFIP. Smart Vent, Inc., one of these manufacturers markets several types of vents, including the Smart VENT® that automatically opens and closes as flood waters rise and fall and features temperature-controlled louvers open in warm weather to provide 50 in2. of net free ventilation area, then close in cold weather. Each Smart VENT®, sized 8" x 16" is certified to protect 200 sq ft of foundation area.
Another model, Flood VENT™, is used when flood protection, not ventilation, is needed. This model has a non-vented insulated door that minimizes heat loss, air leakage, and pest intrusion when the door is closed, but swings open during a flood.
INITIAL COST - Smart VENT® retails in the range of $175 per vent. Because of its certified status, an 1800 sq. ft. foundation would only require six units to comply with the NFIP minimum criteria. A small price to pay to help prevent house loss to a flood.
To be eligible for flood insurance through FEMA's National Flood Insurance Program (NFIP), foundations must be constructed with certain flood damage mitigation features. In coastal areas and riverine zones, where high velocity floodwaters can occur, homes must be elevated on open pile foundations, and enclosures below the living space must be located at an elevation higher than the 100-year base flood elevation and must be designed to break away in a storm surge.
Homes built in floodplains where floodwater velocity levels are lower than coastlines and riverine zones (< 5 feet per second), on perimeter type foundations, should be designed so that exterior walls of the foundation automatically equalize hydrostatic flood forces by allowing for the free flow of floodwater. This minimizes structural flood damage by reducing the horizontal hydrostatic force that unbalanced water levels impose on foundaton walls.
Foundation designs meeting NFIP requirements must include prescribed openings or an engineer's certification that the following minimum criteria have been met:
- A minimum of two openings (on different foundation wall elevations) having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided.
- The bottom of all openings shall be no higher than one foot above grade.
- Openings may be equipped with screens, louvers, valves, or other coverings or devices, provided that they permit the automatic entry and exit of floodwaters.
Any openings that allow the free flow of floodwater into or out of a foundation will meet NFIP requirements, subject to minimum size and location criteria.
Several manufacturers have developed unitized, shuttered products that meet the minimum flood venting requirements of NFIP. Smart Vent, Inc., one of these manufacturers markets several types of vents, including the Smart VENT® that automatically opens and closes as flood waters rise and fall and features temperature-controlled louvers open in warm weather to provide 50 in2. of net free ventilation area, then close in cold weather. Each Smart VENT®, sized 8" x 16" is certified to protect 200 sq ft of foundation area.
Another model, Flood VENT™, is used when flood protection, not ventilation, is needed. This model has a non-vented insulated door that minimizes heat loss, air leakage, and pest intrusion when the door is closed, but swings open during a flood.
INITIAL COST - Smart VENT® retails in the range of $175 per vent. Because of its certified status, an 1800 sq. ft. foundation would only require six units to comply with the NFIP minimum criteria. A small price to pay to help prevent house loss to a flood.