Mold in Attic


Old 04-30-05, 02:51 PM
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Mold in Attic

I have recently discovered mold in my unfinished attic. I pretty much know that it was my whole-house humidifier that caused it and am planning on installing an attic fan. BUT, what do I do about the mold?

Can I just use a bleach solution on the wood up there? Does everything have to be replaced? Do I need to call in some sort of professional?

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Old 04-30-05, 02:59 PM
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Depending on the type of mold there are different problems. To be safe, wear a respirator and use a 1 to 4 bleach to water solution to clean up the mold. Make sure you clean it all up and let it dry. No need to replace the wood if it isn't rotted out. You will have to use your judgement on this. Good luck with your project.
Old 05-06-05, 02:52 PM
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After spraying mold with bleach/water solution, inspect attic for adequate ventilation. Inadequate ventilation is one of the major contributing factors to mold in attics. Warm, moist air rises to ceiling and if attic is well ventilated it passes on to outside. If poorly ventilated, the moisture will condense on cool/cold attic surfaces and provides a breeding ground for mold. On very cold days, icicles may be found growing in the attic.

Local building codes specify attic ventilation requirements. New homes tend to be ventilated with both ridge vents and soffit vents. Some homes have vents installed in the roof. Some have motorized vent fans. Older structures tend to have gable end vents. 1 sq. ft. of free vent area per 300 sq. ft. above floor area is recommended. When no vapor retarder is used, 1 sq. ft. of free vent area for every 150 sq. ft. of attic floor is recommended.

The degree of mold in attics due to poor ventilation and condensation varies considerably. Mold can be found on roof rafters and on sites where moist air passes through ceiling. In severe cases, roof rafters and insulation may be moldy.

Because air tends to move upward and out of the attic the mold places you at little risk. About the only time air would travel downward is if your home should develop a negative pressure such as when burning fireplace or if you have a continuous running vent.

Installing sufficient attic ventilation tends to solve most attic mold issues. If you have heavy infestation of mold (on rafters & in wet cellulose insulation), you can have it tested. Lift some samples with transparent tape and have them tested.

Check to see if there is a vapor retarder beneath insulation. Batt insulation should have been installed with the vapor retarder side downward toward ceiling below. If cellulose or blown in insulation, a vapor retarder is also recommended. Check to see that all bathroom, kitchen, and dryer vents are vented to outdoors and not into attic.

To monitor humidity levels in the home, you will need a hygrometer (sold where they sell thermometers). Humidity should be maintained between 35-55%. Below 35% humidify. Above 55% dehumidify. Many people run humidifiers and dehumidifiers and don't know what the humidity level is.
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