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Inadequate venting?

Chad Fabry

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The plywood and some of the rafters looked almost burnt in this attic. There are some surfaces that are kind of crumbly. There were four roof vents each about 3/4 of a square foot venting the 1,000 square foot or so attic space.

Before I report that the discoloration is caused by condensation/ dirt accumulation from inadequate ventilation I'd like to hear some other opinions.

The house is just shy of 20 years old.

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I don't know that I'd go so far as to call it mold. When you tell someone it's mold they automatically think "toxic mold" when it's anything but. It makes more sense to call it mildew and Kurt is right - insufficient air movement and that insulation against the underside of the roof is causing it.

Moisture-laden air is migrating up through that loose fill and when it reaches the underside of that cold roof is condenses and feeds the spore. Increase air movement from the perimeter by adjusting the height of the insulation, increase the amount of intake air and it will probably arrest. They could try using some JoMax on that gable end wall to see if it disappears and then, if so, treat the underside of the roof.

Look for additional moisture-laden air sources - open wire holes in plates, no gasket around the access, leaky outlets and switch plates, fans venting directly into the attic. Stop the source of the moisture and it's licked.



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Around here I occasionally run into the older fire retardant plywood which has turned black and chalky from prolonged attic heat due to lack of venting and the chemical treatment. We have more heat and less moisture in AZ but I would hesitate to call it mold or mildew without further checking.

Also, could be the rooftop vents were installed later. The way they build around here, that amount of ventilation is typical. Has anybody actually seen the recommended 1 Sq. Ft. / 150 sq.ft. of venting? I don't think I ever have.

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If there is a large amount of air leakage from conditioned space in the home into the attic adding additional ventilation will not help. Two places I frequently find large bypasses at are around chimneys and in soffits. When I see signs of condensation at the eaves it is frequently from a soffit that was framed prior to drywalling and contains a large bypass.

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here's my two pesos...when i was a fire investigator we would never state that we smelled gasoline. 'an odor resembling gasoline' or some such phrase would be used so that the defense attorneys could not tear us apart on the stand. Whenever i see something that looks like mold/mildew (which are synonyms btw) i feel it is more accurate to say 'a mold-like substance was noted in the attic' As we all know mold or mildew for that matter must be identified in a lab. As a general report writing principal we use language of certainty when we are certain and use somewhat more amorphous terms when we're not 100 per cent positive about something. I don't mind going out on a limb but I hate being proven wrong; especially by lawyers.

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