Attic Ventilation Requirements Texas

Residents of southern and central texas should insulate their attics to at least r 30 or about 9 5 inches of conventional fiberglass batt insulation.

Attic ventilation requirements texas.

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. A 30 inch minimum clear headroom in the attic space shall be provided at or above the access. Mechanical ventilation shall be provided by a method of supply air and return or exhaust air except that mechanical ventilation air requirements for group r 2 r 3 and r 4 occupancies three stories and less in height above grade plane shall be provided by an exhaust system supply system or combination thereof. Generally speaking you need a ratio of 1 300 where for every 300 square feet of ceiling space you need 1 square foot of attic ventilation.

If you live in the texas panhandle consider increasing your insulation level to at least r 38. For a 200 amp service the nominal size shall be no. Of vent for every 300 sq. Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the national roofing contractors association nrca.

Building codes vary. Calculations indicate that on a july day in texas a ventilation rate of one air change per minute for a typical attic using 95 degree f air will lower the peak attic temperature to about 101 degrees f. You can also contact your local municipality to check on building code in your area. The nominal size of wire used with a 100 amp service shall be no.

For large volume attics such as where roof slopes are greater than 8 12 designers also should consider increasing. An opening not less than 20 inches by 30 inches shall be provided to any attic area having a clear height of over 30 inches. Most building codes require a ratio of 1 150 ventilation space to attic floor space. The minimum service entrance shall be 100 amperes with a 3 wire 120 240 volt single phase service with a grounded neutral.

General requirements the building code section 1209 for any attic space even if no mech equipment. That said air resistance and interference such as vent grates reduces the area of true ventilation. Uninsulated attic spaces are responsible for significant heat loss since heat rises in a building. In other words the entire vent opening doesn t count as vented space.