Ridge Vent Underperforming


  #1  
Old 02-16-05, 07:13 AM
spspsp
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Ridge Vent Underperforming

Hi All again,

I had a questions regarding our ridge vents performance.

We have had moisture issues in our attic, and there is mold present on the decking.

I don't expect you to read them - but here's some background info -
http://forum.doityourself.com/showth...704#post708704
http://forum.doityourself.com/showth...158#post713158

All bath fans and any "direct" sources are all vented outside through roof vents with hoses. I have checked all the hosing as well.

I recently also added a 6 mil poly sheeting under all the existing unfaced insulation. It had not had a vapor barrier prior. Also, all insulation is out over the top plates of all wall framing.

My next step was to replace all the soffit pannelling down both sides of the house's eaves (40 feet in length each) with perforated panel. There is a single continuous ridge across the peak. You can see plenty of light through all vent panels / ridge.

None of the eaves are blocked at all with insulation - there is approximately 1.5 " of space between the insultaion and roof decking leading down to the eaves in each of the rafter channels.

Down in the eaves, if you're on the joists laying, you can feel the breeze, but up in the attic area, you can not. So it seems to possibly not be drawing from the ridge. How well should you feel any flow ?

It's a baffled (has the side channels to prevent rain blowing in) - Certainteed shinglevent II ridge if that helps anyone.

The ridge is 40' long approx - and each eave is the same - so the ratio should be almost 80 square feet of supply air to the 40 sq foot ridge draw. I thought this should have it with ample push and pull.....

My question is, even with the spacing and clear and definite light showing through every channel, that should allow for plenty breathing, are the hard baffle vents necessary to help "direct" and "channel" the wind more ?

Would they even matter ? I assumed not, as I painfully made sure of the spacing, that was all that was necessary .....

I would say 80 % of the mold is finally drying and or dead, but last night, in another bleaching mission, some of it looked to possibly be fresh again ?!?!?! It could be utter paranoia or a literally bleached-brain at this point, but I just wanted to run by you all the "channeling" aspect of the resepctive supply side rafter chases....

Any help or other ideas / insight is very appreciated. Thank you all
 

Last edited by spspsp; 02-18-05 at 04:24 AM.
  #2  
Old 02-16-05, 07:21 AM
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Could it be the ridge vent is not enough?? You need 1 sq ft for every 150 sq ft of attic space for vents 1/2 in 1/2 out. Are how about a power vent fan. Attic sq ft X0.7=CFM of fan. Some ridge vents have a filter like in them that get full of dust and can let the air out it should.

ED
 
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Old 02-16-05, 02:30 PM
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spspsp wrote:

>>My question is, even with the spacing and clear and definite light showing through every channel, that should allow for plenty breathing, are the hard baffle vents necessary to help "direct" the wind more ?

It sounds like you have far more soffit vent than what is necessary, but that might not be such a bad thing. You do need to keep a proper ratio in order to create convection, but it doesn't sound to me like you are that far out of line. Here's what I imagine is the case:

You feel a draft when laying on the ceiling joists, but that could just as easily be from a slight breeze outside as from anything. It could be going in one side of the house and out the other side, and actually drawing air down thru the ridge. Doing a smoke test with an incense stick would be an easy experiment to see if that's the case. If air is being sucked down through the ridge, you have too much soffit ventilation. Most houses in my area only have 1 out of 4 open, and they usually lead to a roof can vent.

The worst thing you could do is add gable end louvers. If I could just find it, there was a Journal of Light Construction article written on this subject, which showed that gable end vents can end up drawing air down your ridge vent, which isn't a good thing. You use one or the other (ridge vent or gable vent) but not both.

The other thing to consider is the current temperature. Unless it's 75F outside, and 125F in your attic, you probably aren't going to notice any sort of chinmey effect. Heat rises, and that's basically what is going to cause your ridge venting to become effective. If it's 50F outside, and 60Fin your roof, the temperature differential is negligible, and you won't hardly notice the convection- it will be much more likely to just ventilate from one side of the house to the other, depending on the prevailing wind.

The main thing with your mold problem is to ventilate your attic, and keep the humidity down. You seem to be on the right track, and probably already have the problem solved.

As Mr. Imeduc pointed out, a power vent fan is also an option- and since mold seems to be the main concern, it could be set up with a humidistat, instead of a thermostat. (Since mold growth will occur if the humidity is greater then 60%, the power vent fan could be set to turn on if the humidity in the attic rises above 55% or so.) You might have a hard time finding an installer with that sort of technical know how, though. Something to think about, anyway.
 
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Old 02-16-05, 02:43 PM
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Like said on the fan dont need a tech for it. Just tie a humidistat right there by the tstat that way you are covered winter mold or hot summers. Ridge vents down here are going by by code. The wind would blow the rain water up the roof and in to the attic.

ED
 
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Old 02-17-05, 04:53 AM
spspsp
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Thanks

Hi Ed and XSleeper,

Thank you very much for your insight

I'll try to hit a few of the points.

The ridge to soffit ratio - the attic is 1500 sq ft. As mentioned I have opened the soffits entirely - which would equate to 40 sq ft down each side - so 80 sq ft there of venting - then the ridge is approx 40' long - with on the sides of the main peak rafter about 1.5" cut away - this then would be 40 x 3" (2@1.5") = 120" = 10 sq ft ?

I had written prior to see if too much soffit venting could harm or disrupt the ridge's pull - everyone had thought and said not - http://forum.doityourself.com/showth...158#post713158

I have seen the 1:150 ratio - but in many places I also saw 1:150 (or more) so it seemed to not hurt having more soffit supply air below - as it'd give the ridge access to any / all rafter channels to pull from.

After your comments - I am now worried if this could hurt the ridge's performance by "flooding it"

I am aware of the ridge and any gable or other cross venting and would never add those - as the ridge would pull only from it's closest and least resistant supply source.

The ridge simply just does not seem to pull at all. I've looked at the meshing, and it is clear of debris and dust. Also as mentioned, I have LOTS of light from all venting showing clear.

A humidi/thremo-stat fans only run 100.00 - so if and when I do get the roofer involved again - I would insist he add that if not 2 - one to each end of the place where the mold seems worse. I'd easily buy them but let him install them, as I don't want to mess with the shingles due to the warranty from him....

I simply just don't feel a flow up there.... I'll try the smoke test. I had meant to, but forgot a stogie in the basement last time. And once I go up there I try to only come down 1x as to not get any of the mold spores etc into the house as we have an infant.

Tonight 2/17 is time for my every 2 day check-up up there, so I'll have an up to date idea as to status. Hopefully I'll get up there and all will be cool - we have had a huge temp swing in the past 2 days - 60 F one day - 20 F the next - so I think it'd be a good detereminant scenario as to "progress".

I'll keep you all posted - or if anyone has any other ideas, feel free to shout. Thanks again very much !!!!

=====================================================

Update 2/18/2005

Went up through the attic again on another checkup.

Now that the weather has turned cold again, it definately was chilly up there. Which I was glad for, meaning the ventialtion is getting any heat and or humidity out of there. Also, another new development is from the outside, you NOW could see the ridge line -which you previously couldn't in the snow - leads me to think adding / opening all the soffit supply vents was good and the roofer had not had enough ventialtion for the ridge prior.

I did a test with a cigar for my smoke visuals. It definately cleared the smoke fairly fast throughout the entire attic. I huff'd and puff'd that bad boy back, and it took only a minute or so each time to clear my test clouds.

There was not a defined visual draw, but it definately had a flow going.

Mold-wise - It seems to be much much better. In the very "bad" spots I had bleached, there is no re-growth. So I then examined each rafter spacing of decking top to bottom - Intermittently I would find darker spots (the size of an emoticon every now and then, but I am nto sure if they were simply missed before in all my bleaching, and hopefully not developing / fresh.

A very promising tell tale sign is the smell is also gone. Hopefully meaning anything and everything up there is dieing or dead.

That funky mildew mold smell is no longer there. I found some partial decking (small section between last rafters and facia) that I had missed / not hit with the bleach, which had a funk, but I hit it last night.

That being said, I believe I have now thoroughly sprayed down all the existing mold, so IF, and I hope not obviously, but if I see it anywhere now, then it would lead me to think the problem is still on going.

I'll give it another look in a few days or so to test. Hopefully though, I am in the home stretch !!!!

Thank you again very much Ed and XSleeper !!!!!!! The next Stogie I'll have for you guys in celebration
 

Last edited by spspsp; 02-18-05 at 04:27 AM.
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Old 02-20-05, 06:47 AM
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Everyone is basically correct in saying you can't have too much ventilation. What I meant to say was merely that excess ventilation turns into exhaust, which decreases the exhaust at the ridge. Not that it's a bad thing, but it explains why you don't have as much draw at the ridge.

Here's a quote from http://www.professionalroofing.net/a....aspx?A_ID=218 that basically supports this idea.

"One of the most common questions roofing contractors ask at Air Vent seminars is, "Can you have too much intake ventilation?" It's nearly impossible to have too much. If, for example, more intake net free area is installed than there is exhaust net free area, the excess intake will become exhaust on the house's leeward side because the intake vents on the windward side of the house will have pressurized the attic. As a result, the intake vents on the house's leeward side will work with the exhaust vents to release air. In general, it's more likely houses will have too little intake than too much. "

I'm glad to hear that things are looking up in your attic. It sounds like you've got it whipped!
 
  #7  
Old 02-20-05, 07:00 PM
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mold

Something to take into account is how hard it is to kill mold in a porous

surface like plywood or osb. Bleach works well on a countertop or some other

smooth, non-porous surface, but has limitations when used on roof decking.

Any mold imbedded in the decking that escapes the bleach, can come back.

Having sat through hours of mold seminars in the past, apparently mold

doesn't need a lot of excuses to grow, it finds just about any temperature/

humidity level on this planet to be just fine. It's easier in most cases to

prevent mold than to get rid of it. A professional abatement contractor will

usually use a fungicide to kill mold and some kind of sealer to keep the

miniscule amount of surviving spores from making a ''comeback''.

If your best efforts fail to keep the mold away, you may need a professional.
 
  #8  
Old 02-22-05, 01:28 PM
spspsp
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Thank you very much Michiganguy & XSleeper,

I believe things are still coming along well. There is still minimal condensation up there (not on the decking, but if I touched the top of the insulation, your hand would come off of it moist). Would you all think this to be a sign to add insulation I am guessing ?

I get the moisture though on both the r50 areas, as well as the areas with only r30.... So it may also simply be unavoidable due to the outside frigid weather / convection process ????....

No new mold has been progressing or restarting on the decking - that is obviously my biggest worry.

I do have the roofer coming on Thursday to take a look at it. He wants to see what I have done, as well as I obviously want to talk to him as the roof was only 14 months old when the mold began (again, as we had had him tear off the old decking 14 months ago, as the old owner had tons of mold up there).

I will give a furhter update after our visit then. Thank you again both very much !!!!!!
 
  #9  
Old 02-23-05, 06:06 PM
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moist insul.

Moisture on the surface of the insulation doesn't sound normal, I've been in

lots of attics and the only times I've seen moisture on the insul., other than a

roof leak, was when condensation was dripping off the roofing nails. The

answer to this one may be '' above my pay-grade''. I hope you can get some

answers soon.
 
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Old 02-24-05, 11:44 AM
spspsp
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update - 2/24 - following roofer's visit

update - 2/24 - following roofer's visit

Had the roofer over today. Everything is clearing up nicely, with a few spots here and there. Some do seem new, or re-forming which is troubling, but the bulk - I'd say 90 % - seem to be adios'd.

He thinks 2 things -

First, what is reforming or starting is seemingly do to the moisture in the wood from the previous lack of the vapor barrier - which is what he blames for the initial onset of the problem.

Secondly, he still insists I up the r value from the existing r30 to the recommended r48 - for northern Ohio.

He feels what condensation is getting up there now, is due to the low r value letting the heat up there which is then condensing.... It does make sense, but I still stressed had his ventilation been working better, it's simply a question of efficiency......

Also I said, that prior to me opening up those soffit panesl around the entire perimeter - his lack of ventilation seemingly got the mold started...... He didn't agree - so obviously I am not thinking he's going to be receptive towards reimbursing me for the soffit panelling, etc.

Oh well life goes on - he did mention to put a fan or something up in the attic to really circulate the air - or I mentioned a dehumidifier to hopefully suck the moisture out of the wood. Otherwise, I am thinking I'd have to wait for June or so, until the heat starts drying it out totally up there.

He was not open to adding a roof fan as he said it'd pull from the ridge rather than the soffits as the ridge was the closest source of least resistance..

Any other info regarding to the "low" r value or how to "dry" it out would be very appreciated.

Thanks Guys !!!!!!!!
 
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Old 02-24-05, 12:13 PM
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No way doest the R of the insulation have anyhing to do with the moisture up there that is controled by the V/B you have on the ceiling.


ED
 
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Old 02-24-05, 12:45 PM
spspsp
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Hi Ed

Do you believe then that now since a v/b is in place, I should simply keep vigilant on the spraying and then following the wood drying out over Spring / Summer with the hotter temps, all should then be solved ?

I'd love to not drop more $$$ on insulation, and do feel NOW, with the ventilation totally opened up, maybe all that needs to be done is get what may have soaked up some moisture dried out once and for all.

Thanks Ed !!!!
 
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Old 02-24-05, 12:57 PM
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Id see how it goes from here .

ED
 
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Old 02-24-05, 08:58 PM
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In my opinion, the moisture is probably coming from the current humidity in the roof. (the moisture content in the wood, any moisture existing in your insulation, and any moisture that has been added by spraying the mold.) Or some of it might be normal condensation- kind of like how you get frost or dew on your car in the morning... or on a pop can that you take out of the refrigerator. It doesn't necessarily mean something is critically wrong- a small measure of that sort of thing would be expected, I would think. When something cold comes into contact with something warm and moist, it sweats. I guess it could also mean that it's getting TOO cold in your attic at night, and then when it warms up a little in the morning, the sudden warm air creates condensation. Perhaps this would indicate that you might have too much ventilation (although as we've been over this before, its hard to have too much). If the condensation occurs in the morning, that would explain it. But if it's throughout the day, or in the evening, that's another story.

It would be interesting to get a meter to measure the humidity of your framing and sheeting. I'm pretty sure that N. Ohio is the same climate as Nebraska. Dry framing here usually is between 7-10%.
 
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Old 03-02-05, 06:34 AM
spspsp
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3/2/2005 update

Hi Ed and XSleeper,

I just wanted to drop in an update

It does appear that things are beginning to right themselves, with a few issues here and there.

There has been some areas of new mold growth, it seems to be more topical and spread out, rather than robust as it was.
I do believe it is as you have said, that it is eating up what's left in there and due to the moisture which had been in the decking, joists, and insulation.

Since the soffits have been completely opened up, the insulation has dried out - there is no more moisture on top of it.
Also, the decking and joists / rafters seem to be SLOWLY beginning too. However, as mentioned there is some new mold on the decking, but I simply keep bleaching it.

Over the course of the evenings I have been running a room fan in the attic itself to assist in circulating air.

Am I correct in saying that now since the vapor barrier is installed, the 6 mil poly will block the vapor - this then should significantly stop the molds food source ? Once the current moisture is depleted up there.

With the increased ventilation - it should simply be a waiting game to get all the previously soaked up moisture out of the wood - which Spring/Summer's heat, and the fan - may assist / remedy.

I do still only have r25 for the insulation - it is recommended r48 by OC for the area as mentioned above.

As Ed said though, he feels the r-value is not the problem, so I am assuming that with the vapor barrier now in place - the lower r value that is installed simply makes the house "less" efficient ?

The lower holding of heat shouldn't contribute to the mold, and should only allow some minute breathing / convection ?

It is cold in the attic (same as outside temp), so you do not notice really any loss of heat at all up into it. None of the decking is no longer moist, nor roofing nails no longer have any ice on them - showing that what/ if any heat is getting up there, is not condensing any longer, significantly.

So again, even in light of the "new" mold in some areas, I am still hoping to be in the home stretch

Thank you again guys very much !!!!!!!!!!!!!!!
 
  #16  
Old 03-29-05, 12:31 PM
spspsp
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3/29 Update

All things still seem to be progressing towards the positive.

Mold growth has slowed and stopped alot - however intermittently there are areas of new growth.

I think these may be due to water still being in the wood - hopefully this will stop once Spring arrives fully.

I do run a fan up there nightly to circulate the air and actively pull in from the soffits - this has helped in drying out the decking and rafters from their feeling that they previously had had - where you could feel some moisture in them.

I just want to look at what Ed and Xsleeper had said - they did not think the "lower" r value was the problem.

I agree - but just to throw it out there to any other opinions as well -

I still have only r25 in some areas (about 70 % of the attic) - am I correct in saying that this "under" insulation could NOT cause mold ? Mold needs humidity which is not venting, right ?

Now that the vapor barrier is in place, as well as the soffits wide open - the insulation only being a 25 (whereas OC recommends r48 in total for our climate) - with the moisture stopped, all this could be is less efficient ?

Now, I am hoping, the attic should dry under the heat of Spring / Summer, and then with the greater airflow, and VB - it should be AOK next year ?

Maybe the low R value transferring heat up into the attic is condensing as now the attic is so cold being totally opened up on the peripheral soffit panels ??? I'd hope not...but at this point, as paranoid as that sounds, could it be possible ? You'd think the heat transfer should convect and draw up quickly then through the greater supply ventilation of the soffits up through the ridge....

Again, thank you all very much for your help and insights into this on-going struggle
 
 

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