I have a problem with mold growth in my attic, both on the sheathing and the trusses (especially the trusses). An 'environmental consultant' recommended that I have it professionally cleaned, new insulation installed and extra venting/baffling put in to improve air flow. I expect I can get a new roof (and new sheathing material) for about the same as the cost of remediation, but my roof is only about 11 years old and is in otherwise fine condition.

Mold remediation will not qualify for the tax credit and who knows whether the stuff will grow back or not! You must see mold in attics all the time. Any thoughts on this? I had one roofer tell me the whole mold thing was a scam and he would not worry about it. With children in the house, I want to be sure. Thank you! Chris

Craig’s response – no simple answers, but don’t spend “good money after bad”

Indeed, the whole subject has become a "sexy" topic in the media and is highly discussed on TV renovation programs, etc. In my experience, there are not many homes built in the last hundred years that do not have some issue of mold somewhere (basements, showers, plumbing issues, etc.). However, it is certainly not an ideal scene to have any major issues regarding mold. Some people are highly impacted, such as people with respiratory issues, children etc.

It is certainly an issue, as well, for someone buying or selling a home.

Your letter does not identify what your remediation expert noted as the specific cause of the mold issue. What I can gather from reading your letter is that excessive humid, moist air in the attic space may be the cause. During winter months, hot air inside the attic rises to the under-surface of the plywood sheeting and when it contacts the cold exterior temperature, condensation can form on the interior plywood surface and on the roofing nails protruding through the sheeting. (I have been in attics in the winter where it literally looks like it is raining.)

During the warmer months the plywood dries out. This cycle can repeat for many years and the result is a black residue which appears on the underside of the sheeting and eventually the plywood rots and/or will begin to cup. Other contributing factors can be uninsulated pot lights, which can radiate excessive heat into the attic space.

Also, bathroom vents which are exhausted into the attic instead of out through the roof or wall can contribute to the issue. Other items to potentially correct include plumbing vent stacks which protrude through too large an opening in the roof (foam sealing is recommended), allowing cold exterior & warm attic air to mix.

Proper correction involves insuring adequate ventilation at roof eaves areas (intake venting) and through the roof (exhaust venting). Ideally, 50% of your ventilation should be intake and 50% exhaust. In a traditional attic, you would require one vent for every 300 sq. ft. of attic space. In a vaulted ceiling configuration or interrupted attic space (would exist if there is a room in the attic) you would require ridge venting at the peak of the roof, venting trays installed between each rafter space and continuous soffit ventilation.

Correct venting is only part of the story. Proper insulation is the other. When addressing insulation, make sure that all areas of air leakage are addressed. This includes large penetrations through the roof and gable walls, at the top plates of framed perimeter walls, and the area around pot/can lights.

Make sure correct insulation levels are present. You may need to upgrade this if old insulation has been water damaged for example. Check that insulation is not blocking your soffit's as this will impede proper ventilation.

Regarding the roof: Unless you installed premium laminate shingles eleven years ago, your current shingles are realistically half to 3/4 of the way through their lifespan. If the current plywood is warped or severely blackened, or if you hear a "crunch" sound when walking over the roof surface, you are wasting your money to clean it.

What I suggest you do in this event is replace the sheeting when you replace the roof. If the rafters are solid, then you may engage in cleaning the mold if it is severe. Don't spend good money after bad. Ensure there are no roof leaks, which are the actual cause of the mold, before you invest in cleaning the interior attic.

If your abatement professional has proper credentials and references; you may have little reason to doubt their advice.

As always, my comments are for information purposes only. I have not had the opportunity to observe your specific situation personally, but I hope my information is helpful. If you still have any doubts, get a second or third opinion (as carpenters say: measure twice, cut once). If you require any more help, please do not hesitate to contact us.

Chris responds to Craig’s response – Thank you for the prompt and comprehensive advice

Thank you for the prompt and comprehensive advice. I appreciate your input. You described the situation accurately. The cause of the mould is inadequate ventilation and insulation. I don't think there are any leaks.

I am scheduled to see someone from Avenue Road Roofing today who will give me an estimate and some suggestions and what could or should be done. I definitely don't want to spend big money on remediation ($10,000 and $14,000 have been my two quotes so far!) if the roof needs to be replaced in a few years anyway.

I suspect I would be better off getting a new roof now. Anyway, I will wait for suggestions from your people and the estimate before deciding.

Again, thank you!