This is the time of year that defines what spring and summertime will bring to your roof. We enter many attics and one thing we see and get asked about on a regular basis is “what is the black stuff on the inside of my roof?”. The answer is not that cut and dry, it could be from something as simple as an un-vented bathroom vent fan. Bathroom fans and dryer vents can generate a lot of moisture. They should always be vented directly up and out through the roof. Often times builders or do it your-selfer’s will discharge fans or dryer discharges directly into the attic, greatly increasing the overall humidity. Do-it-your-selfer’s often try to connect more than one fan into a discharge and will commonly run the discharge out to the eves or soffit rather than straight up and out through the roof. The remedy is simple, one fan, one roof vent, vertically up through the roof overhead. On the outside the vent has a hat and is not a risk for water leaks. Remember, the soffit vents are air intakes. Venting a bathroom or dryer through a soffit vent will allow some of the moist air to get drawn right back into the attic.
Other times, it can just be from a large amount of heated, warm air reaching the attic. During the winter months when we heat our homes, some of the heat is inevitably lost into the un-heated attic space. This warm heated air should move upward towards the attic ridge vent and harmlessly dissipate outside the attic, but only if the attic is properly vented. If however, the attic is poorly vented, the warm trapped air will start to condense on the cold surface of the underside of the roofing boards or sheathing. This warm air meeting a very cold surface results in a dew-point being achieved. This dew-point created condensation is often more noticeable on the roofing nails as the nails are more efficient at conducting the cold temperature from outside. The condensation on the roofing nails then forms water droplets which can drip onto the floor of the attic. When the night-time temperature is cold enough the nail heads will start to frost up.
Perhaps your home has a network of ducts supplying heat, running through the attic space. If those ducts are under-insulated or un-sealed, moisture production can be a problem inside of the network. If left un-checked, the ducts can start to leak at their seams and water damage is likely to happen in both the ducts and the heating system.
The skinny of this is, water is the most destructive substance known to man, we have to work and come up with systems to remove the potential moisture from our homes before its too late! One of the best ways to eliminate the convective process is to have the attic professionally air sealed and insulated properly. We provided FREE Home Assessments and would love to take a look at your attic and come up with the best plan to correct or prevent warm air infiltration of your attic!