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.
Required ventilation in attic.
Most building codes require a ratio of 1 150 ventilation space to attic floor space.
Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents.
30 lineal feet required.
Calculate or enter the square footage of the attic or area to be vented.
Furthermore nrca also rec ommends the amount of ventila.
Intake vents located at the lowest part of the roof under the eaves.
A discussion on attic ventilation isn t complete without going over the calculations to determine the minimum required net free ventilating area nfva.
The following is an example shown in the irc commentary for a simple gable roof using the 1 300 ratio.
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.
For large volume attics such as where roof slopes are greater than 8 12 designers also should consider increasing the amount of attic ventilation to account for the additional volume of attic space.
Of attic space 1 150 ventilation ratio measured at the attic floor level ceiling.