In the Pacific Northwest, we have lots of precipitation and moisture. Since those of us who live here realize that, you would think that houses would be built in a manner that makes them resistant to moisture problems. It is amazing to me how many houses in our climate have roofs with poor to no drainage and poor or missing gutters or downspouts that empty next to the house.
Another problem, maybe not as intuitive to understand, is the case of the under ventilated attic. General guidelines for building state that attics should be ventilated. Around here that venting, usually, consists of ridge vents, box vents, gable vents or soffit vents. Venting should, ideally, be low (under eaves) or high on the roof, such as ridge or box vents. And putting more and different types of vents, for the sake of more vents, is not the right plan. Doing so can, in fact, lead to impeding ventilation and airflow. The system has to be designed right.
Since people never go in the attic, attic problems are often hidden: Out of sight and out of mind. But what happens when the vents are not functioning properly? Here is a photo.
This attic is under ventilated, hence the abundance of fungus. There may be too few vents; however, that is hard to determine since those vents that were present at the soffit were completely blocked by insulation.
This is a good example, and a lesson -- homeowners should not take for granted that every system is working just fine in the attic or in a crawl space. If the homeowner does not want to check, or traverse, such areas on an annual basis, then he or she should hire someone else who is knowledgable, to take a look. It is much easier to resolve problems prior to their becoming significant cleanup issues.