Venting bathroom exhaust fans into attics is something we see quite often. Let’s look at why this is a mistake. Mold needs four things in order for you to suffer the problems associated with it, they are; mold spores, a food source, the right temperature and moisture. The mold spores come from outside. Their role is to digest dead organic materials, without them every blade of grass and tree that died would not decompose. Nutrients (food source) for mold growth are abundant in your attic, mold prefers cellulose. Wood is mostly cellulose and lignin and I don’t have to tell you that your house is built with wood framing members mostly. Believe it or not, some builders use paper baffles rather than styrofoam to keep the soffits open. We have different types of insulation and one of them is blown in cellulose. So, as you can see everything is in place for a mold remediation project when you add the fourth element - moisture.
Don’t forget that this applies to clothes dryers as well. You must evacuate moisture from your home and when it comes to exhaust fans and attics - get it to the outside. Translation, vent through the roof insuring that a proper boot and flashing integrated under the shingles around the vent stack are in place.
Another good practice, but often unseen even on exhaust fans that are vented through the roof is insulation. Keep in mind you’re sending hot moist air through metal exhaust pipe through a cold attic in winter. You can and will get condensation and consequently mold growth, so wrap that pipe with fiberglass insulation.

If you’re not sure or not comfortable checking for yourself whether you have proper ventilation and whether or not you have a mold problem in your attic. Call Advanced Mold Diagnostics at 610-328-4350 and we will provide you a free telephone consultation to see if we can help.

This entry was posted on Thursday, April 29th, 2010 at 11:56 pm and is filed under Attic Ventilation & Mold. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.