It happens to countless homeowners at the end of the year: You make the annual visit to your attic to pick up the Christmas decorations, and what do you find? Stains and stains covering the underside of the ceiling sheathing.
Worse yet, it turns out to be mold in the attic!
What does energy conservation have to do with mold in the attic? Well, if you take a step back and consider how the house behaves as a system, they are often directly related.
Building science experts have long used the “house as a system” approach to diagnose the cause and origin of building defects.
For example, ice dams. These are often caused by hot air entering the attic, causing the snow and ice on the roof to melt. The water drains to the edge of the roof (which is cooler than the rest of the roof because it’s an overhang and the attic doesn’t heat it), freezes, and creates an ice dam. As this process repeats itself daily, the ice dam grows. Eventually, the water is forced under a tile where it can seep into the house.
Understanding how the house behaves as a system and the various causes and effects is necessary to diagnose most construction-related problems.
But how about that mold in the attic? How did he get there?
Mold requires chronic moisture to form and thrive, so there must be a source(s) of moisture. Possibly the humidity came from outside. The roof is newer and a quick roof check shows no obvious damage or leaks.
Possibly the humidity came from inside. During the heating season, the interior of the house tends to have high levels of humidity, especially bathrooms and kitchens. A quick check shows that all the fans in the bathroom, the vents in the kitchen, etc. are properly channeled completely to the outside and not to the attic. The amount of insulation looks good and the attic is well ventilated.
Don’t give up, you’re almost there! Do you remember the house as a system? You know there is warm, moist air in the house, but how does it get into the attic?
For air leaks! Air leaks are the number one source of energy loss in most homes and a frequent source of chronic dampness that can cause attic mold.
Most homeowners are well aware of air leaks around windows and doors (especially old ones), but many overlook the many spaces that lead directly into the attic!
Take a look around the attic and you can find large spaces around recessed lights and fans, holes where cables or pipes are installed, even large spaces around the fireplace.
And don’t overlook the whole house fan and especially the folding ladder in the attic – a large uninsulated hole in the ceiling that is often overlooked!
These spaces can add up to form a large hole that allows warm, moist air from the house to flow directly into the cold attic. Warm, moist air condenses on the cold roof sheathing, creating chronic damp conditions that can lead to attic mold growth. And the loss of energy – can be like leaving a window
open all winter!
Seal these air leaks and you will stop a major source of moisture. And think of all the energy you can save and the cold drafts you can stop!