Thread: Attic ventilation and mold

Hi everybody! I am new to this forum, and this is my first post, and I need some help / advise.

I live in the pacific NW and as you guys know, it's very wet here during the winter months.
Just a few weeks ago, I went into my attic to inspect it after winter. To my shock, I discovered mold growth on the plywood sheats, most of it on the north side of the roof. I will try to post a picture later. In addition to the mold, I discovered that insulation baffles have come down, and I think that this is what caused the problem (blocked soffit vents). The main effected area (mold) is around 150sq ft, it starts at the soffits and the mold is up maybe 4 -5 feet over a length of maybe 25-30 feet. It looks like the moisture source is condensation, as I see discolorations higher up only around nails. Right now, everything is as dry as can be, and there is no sign of a leak.

My remediation plan is as follows:
- install power attic vent (at the ridge) to increase ventilation. I plan on using a 1,600CFM fan. The sum of my vents adds up to 5.8 sq.ft, and the manufacturer specs 5.3 sq.ft. miminum for intake vents
- clean up the visible mold with bleach / water
- correctly re-install the insulation baffles.

Here are a few more facts:
- 1850 sq.ft. one story home, built in 2002
- a total of 123 round soffit vents, 2" diameter each = 386 sq inches
- a total of 9 square ridge vents, 50sq. inches each = 450 sq. inches
- every vent vents outside (2 bathroom vents, one in utility room, one more over range, plus the vent from the gas water heater). There are no leaks.

What do you guys think about my plan? Do you have anything to add that I should / should not do?
Thanks a lot for all replies!

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To get it all under control you may want to replace to plywood roofing materials and replace the insulation in the attic. infections like mold cling to the insulation. Once you have this stuff its like an all or nothing job. the mold will keep on infesting the attic area. now that it has a foot hold. the insulation is a big part of the job. get it all clear then paint with a baby pink or light blue. add some strips of yellow. L.O.L. if you plan on selling the home some day. I would Employ a mold company/contractor after you complete every thing. give it a year and let things settle. then call the mold company to do a test and get an all clear.

Best

Ron
Excellence Exterminating and Thermal Imaging

Ron, thanks a lot for the quick reply!
What you are suggesting was going to be my second step --- if what I have outlined above does not work and the mold keeps on growing and coming back. Since the roof is otherwise in a perfect shape, I was hoping to be able to keep it a few more years. Replacing the roof / plywood / insulation will be $10K+ (my estimate, not sure how accurate that is).

So you think I should go ahead and replace everything right now? I thought giving it a shot with some cleanup, installing a power fan and fixing what I think is the source of the problem (the baffles) might do the trick and costs < $1,000 instead of > &#37;10,000. Not a good idea?

If the infection is in the insulation? then its got to go. you may be in over your head with this stuff. do your home work be for you do anything with this. but dont overlook the insulation. you can paint everything before you start. that will contain the spours. cover all duct systems.

just cutting in some vents and moving the insulation around for the vents is enough to kick up the dust and spours and send them every place in the attic/house.

start with some of your own air test. find a lab and get the Proper ID of this mold then you will knownhow to handle that mold type and if its a health type or not. This may be over kill but you ask.

Best

Ron

Thanks Rob again for the reply!

This is one detail I forgot to mention: I have done a mold test. A swab test in the attic (from the visible mold) and four air samples: three in the house and one outside. There was only one type of mold in the swab test: cladosporum which is a common mold around here (and everywhere I believe). It's not the toxic black mold I believe. And the samples inside the house showed about the same concentration of mold spores as the outside sample (low spore counts).

Holy cow.... don't spend 10K replacing insulation and your roof just yet!!

Get us a picture or two when you can. The situation you describe is pretty common in my area and often requires little or no action at all. Even according to the 'mold police'

There's little or no air exchange between your attic and your house so the threat to the occupants is minimal.

The fan is a good idea but beware that often times they are on thermostats which don't come on for about 6 months out of the year. Which happen to be the six months when most of the damage occurs. Insulation blocking soffit vents and bath fans not routed outside are cause most of the time. In 02 it was still common to just point the fans near a roof vent and hope for the best. Lately, I've been seeing a lot more that vent to and through a gable or to one of the newer roof vents that gets the air completely outside.

IMO until the moisture is so bad it has damaged the roof decking there is no need for replacement.

The all or nothing response was correct, with mold you can't do a hit or miss job, or it will come back. It can be treated with a biocide and application of a biocidal encapsulant. As for the ventilation, you are probably correct as far as a high level of moisture pssibly being the cause. However, for proper ventilation, you need to find the total volume ( cubic feet ) of the area to be ventilated and size the fan for at least tthat amount. Then, you have to determine tthe amount of free space ( vent area ) to make sure you can flow that amount of air through the space.

Leave it alone. It sounds like you have the proper amount of ventilation.
Mold is everywhere. You are breathing it while you are reading this. Especially mold in an attic - so what? Do you want to remove it from your yard too? The summer heat in the attic will probably make whatever you can see disappear - I don't know how hot it gets in your attic. - then it will recycle again every year. If there is no water intrusion into the area, other than humidity, forget about it.

Mike
Hydrogen peroxide is the only sure fire killer for the mold........ and fix the baffles.
Rick

Thanks everybody for the replies!
About the fan I am planning on installing: yes, it's on a thermostat. But I will install a digital timer in parallel to that and plan on setting the timer to turn the fan on 4 times per day (every 6 hours) for one hour each time. I don't really care about the thermostat and will either set that to the highest temp setting or maybe even completely disconnect it. The main purpose of the fan in my case is to ventilate and remove any possible condensation, not attic temperature control.

Jim, as for sizing the fan: I have done a lot of research on that topic, and I believe that one can make two major mistakes here:
(1) is undersizing the fan with regards to the open intake area. In this case, it becomes pretty much useless, as it will suck the air in mainly through the other ridge vents that are close to the fan, and there will be little to no added benefit in the lower soffit areas.
(2) is oversizing the fan with regards to the open intake area. That would have two negative effects: it would create a negative pressure in the attic, possibly causing air to be pulled out of the living space. That would increase the heating bill unnecessarily. Another negative side effect of this would be that the fan would be running overloaded all the time, and that could drastically shorten its life.

As I said, Broan recommends an open intake area of > 5.3 sq. ft for their 1,600 CFM model. My open intake area sums up to 5.8 sq. ft so that's probably the closest I can get to an optimum sizing. So I'd expect a significant amount of air to be sucked in through the soffit vents, without too much negative pressure build up. Yes, I am an engineer, and I have been up there and measured it out ....
As for the volume, that fan is theoretically capable of exchanging the entire attic air volume every 7.5 minutes.
Am I missing something important with regards to the fan?

IMO, an additional benefit to the fan is that spores in the attic air will be sucked out instead of having the chance of somehow entering the home. But I am really not too concerned about that, because the mold tests have shown that (a) it's not the toxic stuff and (b) it appears that none of it has been coming into the living area at this point.


So I hope to be fine with my solution. Another thing about replacing everything right away: that could back-fire badly IMO. For it to be a long term solution, the source of the moisture needs to be removed. I suspect condensation is causing the moisture, combined with the lack of proper ventilation (blocked vents). But there is no way to be 100&#37; sure. Doing some mold clean up now and fixing the ventilation will show me if the mold continues to spread and/or comes back. Maybe there is another issue in addition that I have not discovered yet? Imagine I spend $10-$15K now for the all or nothing approach and then next spring the mold is back? That would not be good. Fixing what appears to be the source now and then monitor the situation seems like the more feasible approach to me.

But as I said, I am just and engineer and first time home owner, and by no means an experienced home inspector or mold expert. That's why I am here asking my questions. And thanks a lot again to everybody who has replied / will reply. Any additional input is highly appreciated!

- Mike.

Oh, and here is a picture. I had posted this before, then edited the post and somehow managed to delete the pictures.

Searching the net I have found a solution called "Concrobium", sold at Home Depot. Does anybody here have any experience with this stuff, good or bad?

Mike,
I think it's important not to put the cart in front of the horse.
B y the way, what were the air quality results?
A mold remediation expert to get in there and resolve the condition will cost you a chunk of coin.

I think we all tend to get prematurely exited when we hear the M word......and no....not Marriage!
The sky isn't necessarily falling because of the M.
If it is Cladospoium, it is black mold, but not considered toxic black....however, avoidance should be mandatory if you have any respiratory weakness.

I'm afraid I couldn't glean much from that photo, but what I did see didn't APPEAR to be frightening. Looked to me like a very common sight in poorly ventilated attics, but it won't go away by itself. Mildew formation on the north sides of attic roof sheathing is common and particularly so closer to the soffits, if ventilation is being impeded.

Sprayed on Hydrogen Peroxide, according to mold experts I've spoken with is the sure fire cure. They have claimed that it is the most effective of all the mold disinfectants available and the least harmful to the human body. From what I've been told, it's the only product that will kill the sub-surface mold spores. Bleach is a complete waste of energy, looks like its doing something but NOT!. I encourage you do research the product more.

The thing is, this mold must be eliminated or encapsulated before any ventilation improvements are attempted.

The two most important things of course to be vigilant about, are personal respiratory protection and preventing any contaminated materials from entering your living space. I would be darn clear that you wear an appropriate respirator for this type of work.

The soffit venting you described is very commonly a sign that there will be attic ventilation issues. The 2 in. discs, do not provide enough airflow. What you've descibed equates to about 7 ft of strip soffit venting and even then I doubt that they would provide as much air. I think finding a way to get more air in from the soffits will be the big one for you and then maintaining a route for the air movement (baffles).

I am in agreement that the insulation adjacent to the affected area may require removal. Use lots of big garbage bags, and protect your living area.

Rick

I would not get too concerned with mold in the attic based on that picture. It is pretty common when eave vents are missing or are blocked .....or if there is inadequate ventilation. I would ensure there is adequate ventilation (1 net sq. ft. per 150 sq. ft. with 50% at the ridge and 50% at the eaves). I don't even recommend installing the fan-- I don't think it is necessary and have read that the fan can cause other problems in the home.

Just my take.

Your picture is on the very minor side compared to what I see regularly. It's good to be concerned and you're ahead of most people by just identifying it.

For comparison, here's a picture from my house that was built in 89. The installers of the insulation got a little excited and blocked off all of the soffit vents. 15 years later when I bought the house this is what I uncovered. The only real view of the side facing the attic is the scrap lying on the roof to the left side of the picture.

Again, it's good you found it but don't lose any sleep. I've seen cases MUCH more severe where the mold remediation folks only recommended washing with a bleach solution and adding better ventilation. And they are pretty well known for bordering on the side of overkill.

Add ventilation and keep an eye on it.

Mike, fix the roof leak as it apears in your photo add ventallation if needed, as far as the insulation your ok it appears to be fiberglass once it dryes out the mold or fungus cant grow.
As far as Matts situation it appears the insulation is a cellulouse type of which in my opinion should never be used.

Originally Posted by Randy Clayton

Mike, fix the roof leak as it apears in your photo add ventallation if needed, as far as the insulation your ok it appears to be fiberglass once it dryes out the mold or fungus cant grow.

Randy, where do you see a roof leak? I am not aware of one. The last time I checked the attic (a couple days ago), we had heavy rain and all was bone dry.
Matt, what did you end up doing? Replace all the plywood & insulation?

Again, thanks everybody for replying!

I ended up doing 30 sheets of new plywood which was a pretty good portion of the entire house. I left the insulation and it's been fine ever since.

Originally Posted by Matt Fellman

I ended up doing 30 sheets of new plywood which was a pretty good portion of the entire house. I left the insulation and it's been fine ever since.

Can these effected sheets be replaced without replacing the whole roof? If so, how would the cost compare?

Generally, you'd need to replace the roofing above the sheets of plywood that are replaced. Make sure you have a good roofer who can properly 'blend' the new materials with the old. Basically, when you're doing the roof you start at the bottom so it's somewhat un-natural to remove this lower roofing without removing what's above it. Not that it can't be done. It's just not as easy as some other roof repairs.

IMO the risk you run cutting into the roof to replace the plywood isn't worth it to replace what's on that picture.

Thanks Matt!

Compiling all the replies I got here, and what I have seen myself, I believe I will stick to the plan outlined in my OP:
- treat the area with a bleach / water / detergent solution.
- have a power vent installed
- correctly re-install the insulation baffles.

Then, I will watch the whole scenario until next spring, and if the mold comes back, I will have the roof / sheets and insulation replaced. It's worth the $1K that I spent right now IMO.
One good thing: the insulation company will come out and install new baffles for free next week. They are going to replace the cardboard ones that have fallen down with fiberglass baffles, or so I was told. Is that a better solution?
I have also talked to the builder. They are still building many homes with the exact same floorplan, and an attic fan is standard since 2004. There has to be a reason for that, so I think I can't go too wrong with that. The fan will go in this Friday.
Besides that, I will watch the attic on a weekly basis from now on until next spring, probably with a series of pictures every time (to be better able to spot any new mold growth). And I will take serious action next spring if there is no improvement. Does this make sense?
BTW: I did a little test today: I sprayed a small 1 sq ft area with:
(1) Concrobium (the stuff from home depot), got a spray bottle for $10
(2) a 3&#37; Hydrogen Peroxide solution as suggested here
(3) with a 1:3:10 solution of detergent / bleach / water

The results looking at this 3 hours later (after it was dried, we had a lot of sun today):
(1) the area looked discolored, worse than before IMO. Dark spots have become a little lighter maybe, but the whole area in general looks worse.Weird.
(2) no difference with the Hydrogen Peroxide. It looks exactly the same as before. Does this stuff take longer?
(3) the bleach solution resulted in a clean area. Mold is gone there. The wood looks very clean and kind of white(-ish) at spots, but definately the best result.

So I will go with (3) most likely, unless somebody can convince me otherwise. When doing it, I will wear protective gear and have the attic vented with the new fan.

Let me know what you all think!

Thanks,
- Mike.

Got the attic fan in today: seems to work very well. Now I can check from the outside if any of the soffit vents are blocked: turn on the fan and hold a small piece of paper infront of each soffit vent. It gets sucked tight with the fan on, and falls off when I turn off the fan. I could tell the areas that are still blocked.
On Tuesday the new baffles will be installed. I am looking forward to getting this issue resolved .....

Thanks everybody for the help and support!