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Certification of Engineered Flood Openings
In accordance with NFIP, FEMA TB 1-08, and ASCE/SEI 24-05
I hereby certify that the Crawl Space Door Systems flood vents 816CS, 1220CS,1232CS, 1616CS, 1624CS, 1632CS, 2032CS, 2424CS,
and 2436CS are designed in accordance with the requirements of the NFIP "Flood Insurance Manual' (2011) to provide: automatic
equalization of hydrostatic flood forces by allowing for the entry and exit of floodwaters, when properly installed and sized as set
forth below. This certification follows the design requirements and specifications established in FEMA Technical Bulletin 1-08,
"Openings in Foundation Walls and Walls of Enclosures Below Elevated Buildings in Special Flood Hazard Areas", and the ASCE
Standard for "Flood Resistant Design and Construction" (ASCE/SEI 24-05). The actual vent opening measurements were determined
and certified by Mr. Christopher Mark Loney, Virginia PE No. 029000. Calculations are based on the spreadsheet formulas, and
"Review of certification of Engineered Flood Openings, dated January 16, 2012" prepared by Dr. Georg Reichard, Associate Professor
of Building Construction, Virginia Tech.
Design Characteristics
Section 2.6.2.2 of ASCE 24 provides an equation to determine the required net area of engineered openings (A.) for a given enclosed
area (A.). This equation is based on the hydraulic formula for the flow rate across sharp edged orifices. I have utilized this equation
to calculate 1) the respected flow rate through the individual openings between louvers; 2) the flow rate through the main frame
opening in case the louver is blown out during a flood event; and 3) the flow rate of water flowing through louver blades following
hydraulic short tube theory. The ultimate maximum total enclosed area (Ae) that can be serviced by a single vent has then been
determined by utilizing the lowest flow rate of the three assessed scenarios for each vent and is listed in Table 1.
These values are based on the following assumptions:
• In absence of reliable data, the rates of rise and fall have been
assumed with 5 feet/hour;
• The (maximum) difference between the exterior and interior
floodwater levels has been assumed with 1 foot during base
flood conditions;
• A factor of safety of 5 has been assumed, which is consistent
with design practices related to protection of life and property;
• The net area of openings (AJ as provided by the manufacturer.
Installation Requirements and Limitations
This certification will be voided if the following installation
re airements and limitations are not enforced•
*)
Model
H x W
[in]
A,,
[in']
Ae
(ftZ]
❑
816CS
8 x 16
106
205
❑
1220CS _
12 x 20
237
Soo
KA
-As306
645
❑
1616GS v..
16 x 16
184
395
❑
1624CS
16 x 24
312
670
❑
1632CS
16 x 32
408
835
❑
2032CS
20 x 32
630
1240
❑
2424CS
24 x 24
570
1230
❑
2436CS
24 x 36
852
1 1765
q Table 1 Maximum total enclosed area (Ae) that can be
• There shall be a minimum of two openings on different sides of served by each individual model based on the
each enclosed area; given net area of engineered openings (A.)
• The bottom of each required opening shall be no more than 1ft
above the adjacent ground level;
• No temporary (e.g. during cold weather) or permanent solid cover may be placed into or over the flood vent that would block
the automatic entry or exit of floodwaters at any time;
• Where analysis indicates rates of rise and fall greater than 5 ft/hr, the total enclosed area as given in Table 1 shall be reduced
accordingly to account for the higher rates of rise and fall.
Certifvim Design Professional .U10111//,1,,
Name, Title Steve A. Geci, President, Geci & Associates Engineers, Inc. ;1�0
Address 2950 N 12`h Avenue, Pensacola, FL 32503 G:'V� s � �i
F •.
• � r
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License Florida Professional Engineer, Lice se o. 33658 No. 33656 •
Signature �-p • ;
�. STATE OF •% ��
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Identification of the Building and Installed Flood Vents '(By Others) i2 ONAL
The flood vent models marked in Table 1*) are being installed at the following building:
Building Address