Flood Vents

There is an outfit that sends a free catalog of nearly every standard air vent out there. It has the net opening. It's at the office right now but I'll be there Tuesday if you can wait.

That looks like Figure 12 in the http://smartvent.com/documents/NEOG_vol2.pdf&apos ;">Non-Engineered Opening Guide:

Tyler Parsons, post: 406646, member: 139 wrote: I keep running into the situation where the installer of a manufactured home on piers has installed rigid skirting with louvered under eve air vents to comply with both air venting and flood venting. In the past, I have calculated the open area of each louver and multiplied by the number of louvers to get the net area of each vent. Twice in the past, I've insisted on additional vents to comply with the 1sq in per 1sq ft of enclosure. Same this time, but the installer sent me a photo of the vent box showing a NFA (Net Free Area) of 56 sq in, for a 16"x8" vent vs the 30.2 sq in (3.6"x0.2"x42 louvers) per vent I'd calculated.

There are currently 34 of these vents in the skirting. By my calculations, there should be 10 more to make up the required vent area. The installer says that at 56 sq in per vent, there are adequate vents. I've asked for more information, but I believe these are probably Air Vent Inc., under eve vents as shown in http://www.airvent.com/index.php/products/intake-vents/undereave-vents . I've attached a picture which looks exactly like what is installed.

I may shoot this up to my State Flood Coordinator, but before I do. Has anyone else encountered this, and what did you do?

You measure the minimum opening area, which would appear to be horizontal to the vertical face, count the number of openings and report your findings. You are the expert measurer. Based on what I see, I would say the 30 sq.in is more realistic.

While FEMA may accept air vents, their open area space calculation method remains the same.

Paul in PA

That, and if those have insect screen behind them like the ones in my house, it may not comply with the free-flowing water requirement.

As Paul above said we are measurers. FEMA Elevation Certificate Instructions say to measure the openings. On the form check if the opening is engineered or not and the total square inches of the openings you measure. It is the responsibility of the home owner, the insurance agent, builder, or property manager to attach to the Elevation Certificate paper work that says whatever is in the opening equals x amount of square inches.

My area of practice is the western end of the Hamptons, NY. In the flood plain small houses are $2 mil. and it goes up to 12,000 sq. ft. summer cottages. I do 50-75 Elevation Certificates a year. Been there done that, about vents with the insurance companies.

Thank God for digital cameras. Besides FEMA's outside pictures, I take pictures of all of the mechanical equipment, electrical switch boxes, outlet boxes, light boxes, and vents below the BFE. Never ever take pictures of anything else in the house.

Floyd Carrington, post: 406726, member: 474 wrote: On the form check if the opening is engineered or not and the total square inches of the openings you measure. It is the responsibility of the home owner, the insurance agent, builder, or property manager to attach to the Elevation Certificate paper work that says whatever is in the opening equals x amount of square inches.

This interpretation doesn't comport with current requirements. From the 7/15 EC instructions:

Items A8.b ... Estimate the total net area of all such permanent flood openings in square inches, excluding any bars, louvers, or other covers of the permanent flood openings, and enter the total in Item A8.c. If the net area cannot be reasonably estimated, provide the size of the flood openings without consideration of any covers and indicate in the Comments area the type of cover that exists in the flood openings.

It's the surveyor's job to provide a reasonable estimate of the effective opening area, but if he can't do so it's his responsibility to note the type of cover in the comments so that a more competent person can do so.

Thanks all for the information.

I obtained the manufacturer of the vent from the installer. It was Air Vent. Fortunately, they obtained theirs from Lowe's, so I purchased one and did a better job of measuring the area available for water entry, about 31 sq in.. I was just a little short from my original field measurement.

Lowes has a similar sized vent without louvers and a crosswise 1/4" mesh that would provide considerable more open area , about 94 sq in for the same size outside of 16"x14" and negligible (in my opinion) screen obstruction. it would also be much easier to clean of debris.

Anyway, they'll have to add more vents to make the area requirement

I queried my State Flood Hazard Manager - a very nice lady who gives FEMA seminars at our annual conferences - about the installed vents. She indicated that air vents used as flood vents should be used at the manufacturer's vent rating for air and quoted FEMA TB_1 dated August 2008. Apparently I was looking at an outdated document.

"Non-Engineered Openings" on Page 20 starts by showing how to calculate the net opening area, with a diagram. Then it sneaks in a couple of sentences
...
"Manufacturers of devices intended for use as standard air vents typically indicate the number of square inches that each device provides for air ?ow (either stamped into the metal frame or noted on the packaging). The same number should be used for the net open area calculation when these devices are installed as non-engineered openings...."

So, with the manufacturer's rating of 56 sq in, the manufactured home meets the venting requirement. By my original calculation they would have had to install 24 more similar vents in addition to the 34 already in the skirting.

Tyler Parsons, post: 408303, member: 139 wrote: By my original calculation they would have had to install 24 more similar vents

So if the Mfr number is wrong, FEMA is ok with that?

That does appear to be the case. Pitiful. Just pitiful.

Those manufacturers are reminiscent of insecure males who insist on claiming THIS MUCH is twelve inches.