Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.
Formula for proper attic ventilation.
See how simple that was.
Ensuring your home has the proper attic ventilation according to these guidelines however can save yourself the stress and hassle of an emergency roof repair.
You can also contact your local municipality to check on building code in your area.
1 100 square inches of intake net free area needed.
Next multiply the 4 square feet into cubic inches.
In order to find the right calculator divide the attic floor space by 300 sq feet.
Most building codes require a ratio of 1 150 ventilation space to attic floor space.
The next step is to select a suitable exhaust vent and intake vent that fits the roof design for best performance and best aesthetics.
Now let s figure out how much ventilation space we need.
It states that for every 150 sq.
According to the national roofing contractors association nrca a power vent with an airflow rate of 1 0 cubic foot per minute per square foot of attic space measured at the attic floor is generally considered to be equivalent to a 1 150 ventilation ratio.
1 500 square feet 300 5 square feet.
So in our example we will divide the 1 500 square feet by 300.
2 200 2.
Proper attic ventilation consists of a balance between air intake at your eaves soffits or fascias and air exhaust at or near your roof ridge.
Remember the minimum area requirement when using a continuous system is a ratio of 1 300.
There is a generally agreed upon formula that you can apply for balanced attic ventilation known as the 1 150 rule.
Cool air in hot air out.
In our case the required 4 vents for the 1200 sq ft house multiply the 144 cubic inches by 4 576 cubic inches.
Tips for assessing your needs.
Of attic space you need 1 sq.
Ok so now we know the square footage of the attic area to be ventilated.
After that find out the vent s nfa as rated by the manufacturer.
Length x width of attic in feet 150 total sq.
Calculate the total vent area needed multiply the length of the attic times the width in feet to find the attic area then divide by 150 to find the total square feet of vent space needed.
Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation evenly split between intake and exhaust for every 300 square feet of attic floor space.
Let owens corning roofing help you calculate exactly how much ventilation you will need for a healthy and balanced attic with our 4 step ventilation calculator.
