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Dave from Powell writes :

Dear inspector Ken, 

I peaked into my attic recently and discovered a dark stain on the underside of my roofing boards. Upon further review, a flexible hose was directly below the stains. Could this be harmful mold? Can I move this hose or should I? Also it was very hot, over 100 degrees in there, while the outside temperature was a mere sunny 80. Should I be concerned? Does this have an effect on my utility bill in the summer?

Dear Dave,

Kudos to you for peaking into the attic. 

Most homeowners never think to inspect their attics at all during the lifetime of their stay in the home, or until it is too late and issues have developed. 

First of all, I suspect that flexible vent is coming from a bathroom vent fan. The fan is designed to remove warm, moist air out of the bath/shower area and should vent to the outside of the home, either through the roof which is ideal, or to a gable or other attic vent, less desirable but a whole lot better than what you have. The vent fan is doing its job of removing the moisture from the bathroom area, however, by dumping the air into the attic, the added moisture has caused the staining on the sheathing. This condition along with poor ventilation could lead to deterioration of the sheathing, shortened lifespan of your shingles, and cause an increase in your utility bills during the summer months. 

You mentioned the previous owner added insulation into the attic. Perhaps some of the perimeter vents in the soffits were blocked. Think of your attic as a person that must inhale and exhale to breath. Airflow comes into the lower soffit or gable vents (inhales) and escapes through the upper vents (exhales), and since hot air rises, takes the hot air with it. Recommended ventilation for the upper vent area is 1 sq. ft. for every 600 sq. ft. of attic area. Recommended ventilation for the lower vent area is also 1 sq. ft. for every 600 sq. ft. of attic area.  If the soffit vents were blocked by the new insulation, the attic is unable to breathe, similar to you or I having a stuffy nose with a cold. The less air movement, the hotter the attic becomes, which indeed will have a negative effect on your energy bill in the summer months. 

It is impossible for anyone to tell if molds are toxic without having a sample analyzed by a professional lab. In my opinion from the digitals you provided, if you re-route the vent to the outside of the home and unclog the soffit vents this will help dry out the area and reduce the conditions conducive to mold. Different types of attic ventilation devices are ridge or gable vents, soffit vents, attic fans or attic roof vents. Conditions may exist in other areas of your home that you can check to cut down on the amount of moisture transfer into the attic. If you have a humidifier on your furnace, make sure it is in the “off” position during the summer. Check to make sure you have a proper vapor barrier in your crawlspace. At least a 6 mil plastic is recommended as a bare crawl space can dump gallons of moisture into the atmosphere daily.  Make sure everyone is using the vent fans in the bathrooms when showering and kitchen when cooking. Also, make sure the duct vent is open in the basement. When normal condensation occurs on the inside basement walls, simple “air flow” will help it to evaporate and will keep it to a minimum and keep the basement dry. 

For additional information you may contact the Home Ventilation Institute at http://www.hvi.org/benefits/ or the Broan Manufacturing Company at http://www.broan.com.