Opinions on continuous soffit vents & screening?


#1

A brief recap of my situation: I have to do a mid-winter emergency soffit-vent retrofit to try to stop the moisture/condensation/mold that has come after a new roof was put on, with only a Cobra ridge vent (nailable mesh kind).

The carpenter is coming any day now and I’m trying to spec a continuous soffit vent (aluminum) with maximum NFA.

Why maximum? Because (1) I don’t want to take any chances of underventilating my roof, (2) I may upgrade the ridge vent to get more NFA, and (3) I’m considering adding screening to the soffit vents to keep bugs/flies out.

(Note: I nixed using round mini-louvers, even the big 4" ones in every bay, partly because I don’t think I’d be able to get enough air flow)

Q1: Anyone have experience w/ screen being added on top of continous venting?

Q2: Someone from Airvent thought screens would lower NFA by 20% or more. Anyone ever heard any other estimates on this?

Q3: Do you think my chances of clogged venting is A LOT higher with screen than without?

And about aluminum vent manufacturers. I’ve looked at Airvent, Tamlyn, Lomanco. They’re all about 9 SQ.IN per foot or less. I was hoping for something higher, especially if I diminish it by 20-30% due to screens.

Q4: Anyone know of an aluminum product 2-3" wide with NFA of 10-11 SQ.IN per foot?

Q5: Most products seem to have two sets of louvers one pointing out & one pointing in. However some products all point the same way. Is either better than the other for maximizing air flow?

Thanks for your advice!


#2

Hi,

Have you seen the vent? Or just pictures?

You do not need the screening.


#3

Yes I’ve seen samples & pictures both. Typically the louvers are 1/8" wide. I’m concerned small flying bugs, even wasps could pretty easily get in through those.

Wasps have already liked to setup their nests in my unfinished attic in the past so I’m thinking 64 feet of soffit venting might be a big invitation.

I’m happy to debate this and see where people generally come down on this issue, but I still would like to hear what advice I might get on my original questions.


#4

Hi,

Have you heard or seen where wasps have gotton through the vents?


#5

The reason I’m considering screening (but frankly I haven’t decided 100% yet) is…

  1. I’ve seen mention of people putting screening into soffit vents.
  2. I know there are mini-louvers w/ screening built-in and some people use them for soffit venting.
  3. I’ve seen how flies/wasps can crawl through little holes and I figure adding thousands of holes like this in my soffits is like an “open door policy.”

So that’s why I was thinking of screening. But I can sense in your question that you think this is a non-issue. Thanks for challenging me Lefty (honestly). Perhaps I should back up and ask…

Q: Has anyone ever heard/seen problems where insects/wasps got into an attic via soffit vents? (the kind of continuous, louvered, aluminum vents I’m considering)


#6

All the soffit vents I have ever used came with built-in bug screens.


#7

I assume you’re talking about round mini louvers rather than continuous louvered venting.


#8

rectangular…

Anyways, if you install enough soffit ventilation, you can still excced industry standards, keep the screen, and not worry about air flow being dimininshed to less than acceptable levels.

You can make your own vent by cutting a slot and installing a screen and keep the professionally-installed quality.

Hope this helps.


#9

It’s funny how I haven’t found anyone (yet) who’s added screening to continuous although several people have said “sure you can do that”. I wonder if there’s something tricky about it? i.e. getting the screen to stay pinned in place? (I’m going to be using the U-shaped venting w/ legs/flanges on both sides)

On another front, have you ever heard of bugs/flies/wasps being a problem getting into louvered soffit vents that don’t have screens?


#10

well i have not heard of there being problems with insects getting through the louvers, 2nd was the ridge vent instlled properly? Did they cut back the decking to allow air flow?? Also make sure you have equal intake (soffit) and exhaust (ridge) ventilation. An unballanced system is as bad as no system. Cobra ridge vent is actually pretty good stuff.


#11

MOst all of the continuous soffit venting in my area is simply a slot cut out of the soffit board, and a screen sandwiched with a another piece of wood on the inside and screwed together.


#12

Thanks for the feedback re insects.

Ridge vent was apparently done OK. There’s a 1-1.5 inch channel cut on either side of the ridge beam (if that’s what you call it) and the channel ends about 1-1.5 feet from gable end.

As for Cobra ridge vent, I have the basic nailable roll-kind. From looking at specs it has 14.1 NFA per foot, which is pretty much at the bottom… other designs can go up to 18 or 20 NFA. I’m considering a possible upgrade of that if the soffit vents don’t cure it.

My balance between intake/exhaust should be about 60/40 without screening, but maybe 50/50 or even 45/55 with screening. (the latter is based on somewhat vague advice I’ve gotten from various sources)

The main reason I might NOT do screening is because of the air flow impact.


#13

Do you know the guage of the screen generally used? I’m guessing it’s the 1/8" x 1/8" variety, rather than the much finer common window screening, which I’m gathering may cause problems with air flow, cloggage, etc.


#14

nah…more like the window screening. If you install more than is needed in terms of nfva, redduced air flow isnt even an issue.

Never seen one clogged.


#15

I’m planning on using the standard continuous aluminum soffit vent which is typically 2" wide, so in that case I’m stuck w/ about 9 NFA per foot. (with no screening)

However, I did see one, Lomanco 140, which is 3" and 11 NFA per foot. I don’t know if my narrow soffits (7") will accomodate this one. And then there’s the issue of getting them: 12 pieces at pretty short notice. None of my local suppliers deal w/ Lomanco.


#16

Are you cladding the soffit with aluminum or vinyl by any chance?


#17

Nope. It’s an 80 year old wood soffit which we’re planning to keep that way. Why do you ask?


#18

For the record (and as per my other post)…

I ended up going w/ the standard 2" continuous venting (Alcoa NAS70 at 8.8 per foot NFA) That seems to be more than plenty ventilation.

And ventilation has clearly made a huge difference in my case. My symptoms have been gone ever since I increased ventilation!

-Rich