Attic Leaks/Attic Mold

An attic can be a breeding ground for mold due to many reasons such as over insulating, poor ventilation, lack of circulation, exhausts from bathrooms being vented into the attic and roof leaks.  Too often when a home owner gets a leak from their roof, they address the leak, but overlook the damage it causes.  Once mold starts to grow in an attic, it can easily spread causing major damage that can be quite costly.  So, if you should have a leak from your roof, don’t forget to have the checked to avoid what could become a major mold remediation job.


Attic Fan Sizing

Attic exhaust vent fans can reduce your air conditioning energy costs in the summer as well as prevent condensation and ice dams from forming during the winter. While most are wired into your home electrical system, solar powered vent fans are available that require no electrical hookup. Attic vent fans are designed either to fit over a hole cut in your roof or to mount to the inside of a gable vent.

To determine what size power vent fan(s) you need for your attic, you first need to know the size of your attic in square feet.

Attic Size
To determine the size of your attic, multiply the width by the length of the attic floor in feet. For a single story house, this is usually the same as the square footage of the house itself, plus any attached garage area.

Example (20’ wide by 50’ long attic): 20’ x 50’ = 1,000 sq. ft. attic space
Vent Fan Size
Next, multiply the square feet of attic space by 0.7 to get the minimum number of cubic feet of air per minute that the fan should be rated to move.

Example: 1,000 sq. ft. attic x 0.7 = 700 CFM minimum fan rating
Add an additional 20% (CFM x 1.20) if you have a steep roof, and 15% (CFM x 1.15) for a dark roof. Attic vent fans are commonly rated from 800 to 1,600 CFM, making one fans suitable for attics of up to around 2,200 square feet.

Vent Fan Location
Locate roof mounted fans on the back of the roof below the ridge (but not so high as to be visible from the front of the house) in the middle of the main part of the attic. Install gable mounted fans on the gable vent at end of the house faces away from the prevailing winds.

Intake Air Vents
It’s also important to have plenty of soffit or gable vents for the fan to draw air into the attic. To find out if you have enough vent space, divide the cubic feet of air per minute that the fan is rated for by 300 to come up with the minimum number of square feet of intake vent space needed for that size fan.

Example: 700 CFM ÷ 300 = 2.33 sq. ft. intake vent area
If you prefer the answer in square inches rather than square feet, multiply the answer by 144 and round to the nearest inch (2.33 x 144 = 336 sq. in. vent area).

Fan Thermostat
Set the thermostat on your attic vent fan so that it cuts on between 100° and 110° F. Humidity sensors are also available that cut the fan on if moisture in the attic becomes too high.

Attic Mold Scams

Here’s a brief example of an ongoing scam that is becoming more redundant.  Attic’s are some of the highest priced forms of remediation in a home because of the longevity and cost it takes to complete the job.  They usually average 4 to 5 days and can cost anywhere from $6,000 to $12,000 depending on size, workability and construction type.  But some so called remediation contractors are pricing out large attics for ridiculously low prices.  Why?  Because they’re just painting it.  All they do is spray them down with anti-microbials, which do not remove mold whatsoever, and then paint them with stain blocking paints.  This isn’t mold remediation, and in time, the mold will grow through the coating and will need to be redone.  But the price will now cost twice as much or more, because any material the previous contractor sprayed on the surface will have to be removed.  So, be sure when pricing out an attic, crawl space, basement joist job or any other remediation project, you look into why some prices are so low, because you’re not getting a deal, you’re getting scammed.