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attic mold


jiml
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I have mold covering the roof sheathing over the bedroom (whitch is a very tight area of the attic) and over the bathroom (in the main (open) part of attic next to the bedroom). the insulation in these areas are damp. The roof was new about 4 years ago and installed soffit ridge vents. At that time I had some moisture issues in the attic but thaught I solved it by increasing ventalation and sealing any air leaks i could find.

bath vents to outside.

how do I kill mold and should I lift batt insulation and put down a continuas plastic vapor barrier? should I also add a powered vent?

thanks

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Originally posted by jiml

I have mold covering the roof sheathing over the bedroom (whitch is a very tight area of the attic) and over the bathroom (in the main (open) part of attic next to the bedroom). the insulation in these areas are damp. The roof was new about 4 years ago and installed soffit ridge vents. At that time I had some moisture issues in the attic but thaught I solved it by increasing ventalation and sealing any air leaks i could find.

bath vents to outside.

how do I kill mold and should I lift batt insulation and put down a continuas plastic vapor barrier? should I also add a powered vent?

thanks

* Make sure that the bath fan exhaust goes out through a vent that's high on the roof. If it goes out through a soffit vent, then there's a good chance that the moist, humid air is just being drawn back into the attic.

* If the insulation in your attic is damp, you have a condensation problem. Nothing else that you do will help in any way until you solve the condensation problem.

* Power vents often make condensation issues worse. The vent depressurized the attic. This causes more indoor air to flow into the attic and condense on the cold surfaces there.

* If you put down a continuous plastic vapor barrier properly, it will help. If you do it wrong, it will make things worse. You'll probably do it wrong.

* There's no need to kill the mold on the underside of your roof sheathing unless you're phobic about mold. If you're phobic about mold, you can have a pest contractor spray it with either Timbor or Boracare. Both are borate solutions that are harmless to people.

- Jim Katen, Oregon

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* Make sure that the bath fan exhaust goes out through a vent that's high on the roof. If it goes out through a soffit vent, then there's a good chance that the moist, humid air is just being drawn back into the attic.>>>>

Its vented through a wall at the end of the house w no soffit.

* If the insulation in your attic is damp, you have a condensation problem. Nothing else that you do will help in any way until you solve the condensation problem. >>>>>

what is the best way to find where the indoor air is getting up there. I thaught I found it years ago when I found and closed a gaping hole around the chimney. I havn't found any others.

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Originally posted by Chad Fabry

Ill try to get some pics. Its an L shaped ranch about 1400 sq ft, only other venting is very thin gable vents

Hi Jim,

If you have ridge vents and small gable vents and no intakes at the eaves then your attic is essentially unvented.

Chad, hit the nail on the head. Need those soffit vents for the ridge vents to work properly.

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Need those soffit vents for the ridge vents to work properly.

>>>>

when they put in the ridge vents In 4 yrs ago i took off the perforated alluminum soffit covers to find no actual vents so I did cut 2X4 holes every couple of feet and then recovered w the perforated aluminum covers.

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I did cut 2X4 holes every couple of feet and then recovered w the perforated aluminum covers.

Most perforated aluminum soffit has very little net free vent area and most would only provided adequate volume if it was continuous. That is, if all the soffit were perforated. 2x4 holes would need to be in each rafter bay to come close to being adequate and 4x4 holes would be better.

You'll need around 9 square inches per linear foot of eave intake on all of the eaves(except gable ends) to balance the 18 square inches per foot of ridge vent. Make sure the insulation in the attic isn't blocking the intakes.

Once you've provided adequate intake, block off the gable vents with some old trade show banners or plywood.

A power vent will use your ridge vent as an intake location and your attic will still be essentially unvented, or worse, it will be depressurized and draw even more conditioned air from the moist interior of your home.

Either seal and separate the attic space from the interior space or ventilate the attic with adequate intake and exhaust vents.

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Check above the basement stair hole. It is not uncommon to find no draft stopping in this area.

Do you have recessed cans or ceiling fixtures? They need to be sealed up.

Check anywhere plumbing,HVAC or electrical are coming up threw the walls. Tradesmen are not to paticular on how they cut through framing.

Check the basement for holes going up into the partition walls.

Weather strip the scuttle hole cover and lock it down.

This is just a small list of common sources moisture. None of these may be the one bullet but a combination of all the above may be what is happening.

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the smaller wing which is above the master bedroom (and also very tight in relation to the rest of the attic. and adjasent to it over the bathroom. The rest of the attic is much better w no mold. However I did see water in the pan under the air handler (in the unefected area of the attic) indicating some condensation.

Originally posted by Chris Bernhardt

What wing is the area with the problem in? (in relation to the prevailing winds)

Is the other wing doing OK?

I have seen a number of L shaped buildings where one wing is clear and the other is black with mildew.

Chris, Oregon

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Originally posted by jiml

the smaller wing which is above the master bedroom (and also very tight in relation to the rest of the attic. and adjasent to it over the bathroom. The rest of the attic is much better w no mold. However I did see water in the pan under the air handler (in the unefected area of the attic) indicating some condensation.

So there's an air handler up there and you can see water in the secondary pan?

If so, you've got another problem.

- Jim Katen, Oregon

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how do I kill mold and should I lift batt insulation and put down a continuas plastic vapor barrier? should I also add a powered vent?

Well you don't need to kill it per se. It's existence indicates that present or past relative humidity levels in the attic have been high and sustained. If it makes you feel better you can try and clean it off with bleach or QUAT, which is a lot safer than bleach. I've done this my self with bleach water. Yuck! what a messy, stinky, miserable job that was. For ventilation I took out a couple of siding panels in one gable and jury rigged a fan in the attic access and worked towards the fan so that the fumes were blown away from me. To stop it from growing back you can cold fog the attic with Concrobium or apply it directly.

While in theory installing or establishing an air barrier in the attic would be a common sense solution, in practice it's very difficult to do. Read "Issues Related to Venting of Attics and Cathedral Ceilings" by William B. Rose. There's a link somewhere around here on one of Randy's posts.

Rose, if I am understanding him right, advocates trying to control humidity in the house as the primary means to limit moisture in the attic. The traditional method of trying to block high humidity at the ceiling envelope and dilute the leakage with attic ventilation is not guaranteed to work.

If you have already made reasonable attempts at air sealing the ceiling assembly and providing passive ventilation means and it's not working then I would seek to control humidity levels in the house.

The problem is I don't know of any studies evaluating humidty control measures in a home that has been having problematic moisture in the attic so I don't know what to tell you.

Obviously a guy could monitor humidity and then when it gets too high try and dilute and exhaust it out or turn on a dehumidifier but who knows if that will be practical?

Chris, Oregon

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how so. It seems the water is from sweating (frost)on the air handler.

the intake duct was sealed off w plastic. the outlets were just closed w a screw driver. although IM now sealing off them w plastic also.

When I first had this prob originally I did have high humidity levels in the house. I traced the prob to a large open topped fishtank. humidity levels have been more normal since.

Originally posted by Jim Katen

Originally posted by jiml

the smaller wing which is above the master bedroom (and also very tight in relation to the rest of the attic. and adjasent to it over the bathroom. The rest of the attic is much better w no mold. However I did see water in the pan under the air handler (in the unefected area of the attic) indicating some condensation.

So there's an air handler up there and you can see water in the secondary pan?

If so, you've got another problem.

- Jim Katen, Oregon

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Originally posted by jiml

how so. It seems the water is from sweating (frost)on the air handler.

There's a condensate pan under the evaporator coil inside your air handler. During normal, day-to-day operation of the air conditioner or heat pump, water condenses on this evaporator coil and flows into the condensate pan. From there, the water runs out of the house via a drain pipe. Water in this pan is normal. It does not mean that you have high humidity levels in the house.

There's also a secondary, back up, drain under the air handler in the attic. Its function is to catch any water that spills out of the primary condensate pan. During normal, day-to-day operation of the air conditioner or heat pump you should never see water in this secondary pan. If you do, it means that the water is missing the primary pan, the primary pan is leaking or the primary pan is overflowing. It does not mean that you have high humidity levels in the house.

If this is a heat pump, you should never see water on or in the air handler in winter. In heating mode, there should be no condensation happening on the exterior surface of the indoor coil.

the intake duct was sealed off w plastic. the outlets were just closed w a screw driver. although IM now sealing off them w plastic also.

I have no idea what you're talking about. What intake duct? What outlets? Surely you haven't blocked off your return duct with plastic?

When I first had this prob originally I did have high humidity levels in the house. I traced the prob to a large open topped fishtank. humidity levels have been more normal since

When you first had what problem, water in the condensate pan or mold on the attic sheathing?

Covering the fish tank is a good idea, but it probably had nothing to do with water in the secondary condensate pan.

- Jim Katen, Oregon

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Originally posted by jiml

... bath vents to outside ...

Define "outside" if the exhaust pipe is dumped in the soffit area that is NOT "outside" of the building envelope. Soffits are air "intake" for attic circulation.

I get to argue that with here in TX all the time with builders as well as local building officials.

I've seen situations where there is plenty of mold/mildew on the bottom of the roof decking due to the moist air that is 'supposedly' being sent out of the building envelope is actually being driven back into the attic due to the precise purpose of the soffit vents as air "intakes".

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Define "outside" if the exhaust pipe is dumped in the soffit area that is NOT "outside" of the building envelope. Soffits are air "intake" for attic circulation.

I get to argue that with here in TX all the time with builders as well as local building officials.

>>>>

its on an end wall - not near or below a soffit

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