Proper Roof Ventillation

When I see something like this, the first thing I think is ventillation. Or lack there of I  should say. For your shingles to last the normal lifespan, the roofing system needs to be properly ventillated. This is usually done through some type of roof vent, gable vent, or soffit and ridge vent.
Below, we will take a look at soffit and ridge venting. The two go together hand in hand. You can't  have one without the other, as it will be of no use, and will not provide proper airflow. For the ridge vent, an opening is cut open along the ridge of the roof. This is then enclosed with a ridge vent and covered with ridge cap. This will allow warm air to exit the building envelope.

The other part of this equation is the soffit venting. These are spaced throughout your soffit, the ones with the small holes in it. Go outside and look at yours. If you have aluminum soffit, they will be evenly spaced. If you have wood, you may have openings covered by screens for this type of system.

One problem with this system is that it  can become blocked by insulation in the attic. Foam baffles need to be installed in between the trusses up against the roof sheathing. These will hold the insulation back from the sheathing and allow air to flow to the roof peak. Without these, the insulation can and will end up over the soffit vent and block the airflow.

With this system, the air is allowed to enter at the bottom, and exit at the top. the air moves through the area, but is allowed to exit, thus maintaining a steady temperature, and not allowing it to become an oven in your attic. Without the proper ventillation, it becomes very hot in your homes' attic, and will basically cook your shingles. This will greatly reduce the lifespan of your shingles.

When purchasing your home, your  home inspector will identify which type of ventillation system is installed on the homes roof, and make a determination of adequacy for the system.