Poor attic ventilation can lead to mold growth. If you combine moisture with restricted air circulation you will create a humid and moist environment, the ideal environment for mold to grow and thrive.
Ventilation of the home attic is important for two reasons. During the summer, excess heat that builds up in the attic during the day results in high energy costs for cooling. Also, moisture produced within the home may move into the attic. If this moisture is not exhausted from the attic it can condense and cause insulation and construction materials to deteriorate. Thus, temperature and moisture control are the major reasons for providing attic ventilation.
The two common forms of ventilation used to vent an attic properly is the soffit vent and ridge vent. The soffit and ridge vent work together as a team to allow hot moist air to exit the attic.
Soffit Vent & Ridge Vent
A soffit vent is simply a vent installed on the underside of the eaves. The term used to describe the underside of the eaves is the soffit. The soffit vent permits fresh outside air to be drawn up into the attic. Think about attic ventilation as a two step process. Fresh air enters the attic through the soffit vents and exits through the ridge vent.
STEP 1 - Soffit vent - Air flow through the soffit vent.
Here is an up close image of the soffit on a home. The traditional soffit vents contain small holes that allow to enter. The small holes on a soffit vent looks similar to a cheese grater. Fresh air enters the soffit vent and makes its way into the attic.
The soffit runs around the perimeter of the home. If there is not a proper soffit vent installed then the ridge vent won't function. The soffit and ridge vents work together to move air from the bottom of the attic up through the peak.
STEP 2 - Ridge vent - Hot air rising through the ridge vent pulls more fresh air through the soffit vent.
Hot air naturally rises and exits out the ridge vent, pulling in fresh air from the soffit vents.
The ridge vent looks like a cap where the roof peaks. The cap allows air to exit the attic while still preventing rain or snow from entering the attic.
Here is an image of a ridge vent up close.
This diagram reflects how air begins to flow through the soffit vent (blue arrow) and exits through the ridge vent (red arrow).
An attic becomes a conducive environment for mold growth when a soffit vent and or a ridge vent are not present. Both vents need to be present to allow for proper attic ventilation.
What if soffit vent and ridge vents are present and there is mold in the attic?
Soffit vents may become clogged with insulation and therefore become useless. Insulation restricts the air flow from entering the attic and contributes to hot moist air to build up within the attic.
Ridge vents may collapse over time and or were not properly installed to begin with. Sometimes when a roof is replaced the ridge vent is removed therefore eliminating the second form of ventilation. This hinders the airflow from exiting the attic and contributes to hot moist air to build up within the attic.
Additional problems caused by poor ventilation
Rust: Rust can begin to form on metal components like nails or other critical fasteners. Overtime it can rust the heads off of nails or cause plumbing or venting straps to fail.
Sagging or Spongy Decking: When excessive moisture begins seep into the roof decking it can begin to dissolve the adhesives which hold them together and cause it to warp, sag between rafters or feel spongy when walked on.
Roofing System Deterioration: Not only can excessive heat and moisture ruin roof decking, it can also reduce the life of the underlayment and shingles themselves. Cracking shingles or premature loss of granules can be signs of improper roof ventilation.
Air Conditioner Replacement & Expenses: As heat builds in the attic, air conditioners must work extra hard to keep the air inside the home cool. This undue stress on the unit can reduce its life and increase energy costs.
Frost: Similar to how sitting in a cold car on a winter day will cause frost to form on the windows, the same can occur in a poorly vented attic. As the attic cools and warms with the day, frost formed inside the attic can melt and drip onto the ceiling.
Ice Dams: Ice dams can form at the edge of a roof where trapped warm air can melt snow on the roof that then freezes as it cools. As the snow continues to freeze, melt and refreeze it creates a barrier, or dam preventing water from running off the roof. Once dammed, water and ice can creep back up under the shingles and underlayment resulting in leaks. Proper ventilation and the use of added insulation can help mitigate this melting and freezing process and eliminate ice dams.
If you have questions regarding attic ventilation you should reach out to a reputable home inspection business. Shield Guard Home Inspections LLC and our sister company Albany Mold LLC specializes in performing home inspections and mold assessments as it relates to attic ventilation and mold. Shield Guard home Inspections performs full home inspections supplemented with a detailed report. Additionally we offer walk through inspections at a discounted rate throughout the Albany NY area. Call your local #1 local home inspection company today!
The Author Adam Clark is the owner and operator of Shield Guard Home Inspections. Adam Clark is a local Home Inspector located in Albany NY that has performed over 6000 Inspections.
Phone: (518) 720-7152