Proper Attic Ventilation - Utilizing Baffles or Vent Chutes
A common defect found in my inspections would be inadequate or insufficient attic ventilation. An improperly vented attic can cause many adverse results including formation of condensation, mold growth, and even structural damage.
Idealy an attic will have a system of air intake and air exhaust. Keeping in mind that a general rule of thumb for venting is that there should be 1 sq. ft. of free vent space for every 300 sq. ft. of floor area. A proven system for venting is the use of soffit venting and top venting. Continuous soffit vents, continuous ridge vents, or an adequate number of mushroom style top vents should be in place. Airflow can then enter at the soffit, and exhaust at or near the top of the roof.
Problems occur when the airflow is blocked or restricted, such as in this Gurnee home.
As you can see, the fiberglass insulation has been installed in such a way that it completely blocks the soffit areas. This attic is getting little to no air intake from the eves. Insulation is a good thing. We do not want to remove the insulation completely. The insulation should be installed all the way to the top plate, but space needs to be provided for air flow. This can be achieved by using attic baffles, rafter vents, or vent chutes as they are sometimes called. Below is an example of a foam or polystyrene rafter vent.
These are available at most local home improvement retailers and can be installed by most somewhat handy homeowners if you are willing to get a little dirty and swear a bit. Try installing them at a time of year when your attic is cool, and cut some plywood scraps to use for support so you do not come through your nicely drywalled ceiling! Wear a Tyvek suit or coveralls, goggles, a quality mask or respirator, and gloves. The fiberglass will irritate your skin, lungs, and eyes if proper precautions are not taken.
Here is a home in Mundelein where inadequate attic venting and blocked soffits had some time to create problems. You can see from the photo that continued condensation from poor ventilation has created a layer of black mold on the underside of the roof decking.
If not rectified, this attic will cost thousands of dollars to repair. Mold remediation, replacement of roof decking and insulation, etc. Proper venting is key to remaining mold free and to prevent ice dams as well.
Bee Sure Home Inspection Svcs.
Grayslake, IL 60030