Commercial Attic Ventilation Requirements

The colder the climate the higher the thermal resistance required for the rigid insulation.

Commercial attic ventilation requirements.

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. However in pursuit of attic ventilation some people choose to install attic power ventilators. Intake vents located at the lowest part of the roof under. The intended purpose was to allow warm air and moisture to escape.

Ibc 1203 2 requires 1 150 th of the attic area to be ventilated but there is an exception that is commonly used instead. The higher the interior moisture load the higher the thermal resistance required for the rigid. Hence you would need two square feet 600 300 of attic ventilation. The thermal resistance thickness of the rigid insulation is climate dependent and moisture load dependent.

In theory these are excellent tools for circulating air in the attic and keeping the attic temperature low. Cool air in hot air out attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents. For large volume attics such as where roof slopes are greater than 8 12 designers also should consider increasing. These are significant challenges.

As an example in an attic that is 30 feet by 20 feet you would have 600 square feet of floor area. The same goes for attic ventilation. Traditionally building codes have required attic ventilation. Vented attics can be effective as long as hvac ducts are not located in them and the ceiling deck is well air sealed and insulated.

It s essential for reducing moisture and preventing excessive heat.