Commercial Attic Ventilation Requirements

The intended purpose was to allow warm air and moisture to escape.

Commercial attic ventilation requirements.

However in pursuit of attic ventilation some people choose to install attic power ventilators. It s essential for reducing moisture and preventing excessive heat. Regarding attic ventilation nrca recommends designers provide at least 1 square foot of nfva for every 150 square feet of attic space 1 150 ventilation ratio measured at the attic floor level ceiling. The thermal resistance thickness of the rigid insulation is climate dependent and moisture load dependent.

Traditionally building codes have required attic ventilation. The colder the climate the higher the thermal resistance required for the rigid insulation. These are significant challenges. Hence you would need two square feet 600 300 of attic ventilation.

Ibc 1203 2 requires 1 150 th of the attic area to be ventilated but there is an exception that is commonly used instead. According to the fha federal housing administration us for every 300 square feet of attic floor area you should have at minimum one square foot ventilation. Intake vents located at the lowest part of the roof under. In theory these are excellent tools for circulating air in the attic and keeping the attic temperature low.

The higher the interior moisture load the higher the thermal resistance required for the rigid. The same goes for attic ventilation. Measure the length and width of the attic floor space to be ventilated. Exception 1 allows you to only ventilate 1 300 th of the attic area if 50 to 80 of the ventilation occurs at least 3 above eave or cornice vents.

As an example in an attic that is 30 feet by 20 feet you would have 600 square feet of floor area.