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We have a SW Florida (Cape Coral) house built in 2005. The house is block construction, high ceilings (10-14'), about 3100 sq ft, and concrete tile steep hip roof (by eye at least 12 in 12). The locality has reasonably strict building inspections, and has also been through a pre-purchase inspection and two insurance inspections. We bought it new.

But it has no attic vents other than soffit vents along the edge. The edge has continuous vents, and the insulation is spaced nicely below them so there is a lot of air that can flow from the soffits all around. But nothing on any ridge. Nothing anywhere above the soffit. The soffit is all at the same level.

I frankly did not notice for a number of years. I have no idea if this meets code; I would expect it to, given the levels of inspection. I am hesitant to ask the city inspector for fear of opening up an enforcement issue of some sort.

We have one (of two) air handlers in the attic, as well as all AC vents.

It is hot down here. Very hot in the attic 10 or so months of the years, and just slightly miserable in the "winter".

My question is whether it is bad. Would a ridge vent(s) help our AC costs significantly, and/or the reliability of systems up there?

I am hesitant to just add vents, because we have had bad luck with roofers - every problem has required 2-3 visits, and no one seems to have a very good reputation for quality work. At present we have a nice dry roof, all leaks fixed. I hate to open a can of worms for no real point, plus there is cost.

Is there any chance the house should NOT have a vent for some reason? (How can I tell?)

Assuming it might benefit from one, is there any practical way to estimate how much benefit we get? For example, how much less cooling cost (% or whatever)? To see if it is worth the trouble at this point?

Does anyone know if it is code?

  • If you have concrete tiles, then additional venting would be a specialist roofer job. Are you sure it is not vented? Could it be that the ridge courses of tiles are installed in such a way that there is venting through the joints? I really don't think you should be reluctant to call the code enforcement. AFIK they don't enforce code on a long existing installation, and if it is not to code then there's a good chance that when you try to sell it this will be a sticking point. Call roofers who do concrete tiles and ask about venting. – Jim Stewart Feb 7 '17 at 17:24
  • See ohagin.com/products_tile.asp – Jim Stewart Feb 7 '17 at 17:26
  • Yes, I am sure; besides me, I asked a roofer while they were fixing a leak. He scouted the whole roof and found none. I asked if it would help on cooling, he said "yes" but had no speculation on how much. He also did not think (yes, he said "think", I would have expected him to know) it was required by code, but he said "most have vents". He is the one who quoted $2000 for 4 vents (his estimate of the right number given the shape and size). What I keep hoping for is something like "in a study vented vs non-vented attics saved 20% in summer cooling" or some such, not just "might help". – Linwood Feb 7 '17 at 18:19
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    Are you sure there isn't a vapor diffusion vent at the ridge? Also, I suspect that venting the attic more aggressively would make your A/C bills worse due to the poor air barrier performance of a typical partition ceiling assembly + duct leaks...so I'd at a minimum run a blower door test on your attic before putting those ridge vents in! – ThreePhaseEel May 16 '17 at 1:58
  • Is converting this situation to an unvented attic + insulated roof an option? – ThreePhaseEel Nov 2 '17 at 11:49
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Ridge vents are about the easiest thing you can install on the outside of your house. You can do a decent size house in a few hours with a circular saw and hammer. So as far as costs/benefits, if you trust yourself to cut a straightish line and have a few hours your cost is maybe $150. Will you get that back in energy savings. Sure. In 1 year or 40 years though? It is really hard to tell.

Dealing with a climate like Florida the main culprit is the sun. Having some sort of shade trees covering parts of the roof during the day would be probably the best thing you could do for the money.

Now as far as a ridge vent how effective it will be will really be correlated to how ineffective the soffit venting was. I doubt it is optimal but like you said it has done the job. To give you a baseline, I live in the Midwest. Our summers are hotter than Florida's. I have huge trees over my house. I have extensive soffit and ridge venting. And my attic is an easy 120F in the summer if not more. So closed spaces get really hot in the summer in hot climates and not much you are going to do about it.

If you think your house is warming due to the attic you can take thermal imaging of your ceiling and see if the difference is dramatic. Or you can just add insulation to the attic which will cost about how much getting thermal pictures of your ceiling. You have to max out insulation in warm climates. It is just as important to have a well insulated attic in Florida as it is in Michigan.

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    I would not be doing the work; the roof is much too high and steep, plus concrete tiles are foreign to me. I have one quote of $2000 for four vents, but have not shopped around. As to soffit vents having done the job, how would I know? They are well done, but I doubt bring in much air as it has nowhere to go. I have been told down here most heat load into the living space is radiative (from the underside of the roof) and not air-conducted, so it is unclear to me how much more ventilation will actually help, but that's from a sales guy. Hoping for someone who knows the engineering. – Linwood Feb 7 '17 at 14:02
  • The soffit vents feed the ridge vent and allows some of the air escape, if no tiles were removed to see if there is a ridge vent you really don't know if you have a ridge vent or not. If you have attic access you might be able to see the vent from the attic, most of the ones I have installed have run almost the entire length of the ridge. All but 1 were a white material , the oddball was black but you should be able to see a slot where the roof sheeting meets. If you don't have attic access ridge tiles will need to be removed to see. – Ed Beal May 16 '18 at 23:27
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I'd up vote @DMoore's answer. I like adding more insulation to isolate the "warm" exterior air from the conditioned "cool" interior air.

Attic ventilation works "in reverse" in Florida compared to attic ventilation in northern areas. In northern areas, the warm moist side of the attic (that needs to be vented) is on the underside of the ROOF structure. In Florida, the "cool" side of the attic is the conditioned space and the warm side (that needs to be vented) is on the CEILING structure. So, the ATTIC side of the CEILING structure needs to be vented (to remove moisture...potential condensation.)

Eave vents work with "cross ventilation ". Where I live, the wind blows "all the time" so we rely mostly on eave vents because they're "protected" in storms and don't leak. However, the code allows us to decrease the amount of ventilation if 50% to 80% of the ventilation is located 3' above the eave vents....because most of the potential condensation is in the upper part of the attic.

Adding roof vents in the upper part of the attic will allow warm moist air out of the attic, but with cross ventilation, the eave vents will remove the warm moist air that contributes most to condensation...the surface "on" the ceiling structure.

I think adding attic vents in the upper part of the attic will reduce the temperature in the attic(and thus your cooling load and expense) but won't aid much in removing potential condensation. However, adding insulation on the ceiling will reduce the potential of condensation AND help the cooling load and expense.

  • You're forgetting that vented attics need to be fully decoupled from the house air-wise to work (i.e. the ceiling needs to be an air barrier plane and there need to be no ducts in the attic leaking conditioned air into it to waste energy) – ThreePhaseEel May 16 '17 at 5:21
  • @ThreePhaseEel Air ducts?? I thought this was about venting? – Lee Sam May 16 '17 at 11:00
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    Air duct leaks into a vented attic are a great way to drive your A/C bill up (like 30% performance penalties for normal, leaky ductwork -- you can get it down to more like a 10% penalty if you mastic the ducts up the ying-yang to get that leakage down to a few %) – ThreePhaseEel May 16 '17 at 12:00
  • I'm not sure how air ducts leaking into a sealed attic is any better. The trivial reduction in attic air temperature is unlikely to impact energy costs. The conditioned air is wasted in either case. – isherwood Sep 29 '17 at 19:23
  • @isherwood The amount of wasted conditioned air would increase though, because the vents would suck air out of the attic, reducing the air pressure in the attic and thus increasing the amount of air flowing into it. – nick012000 Apr 30 at 8:24

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