Vented Attic Detailed Cross Section

An individual vent for a single appliance shall have a cross sectional area equal to or greater than the area of the connector to the appliance but not less than 7 square inches 4515 mm 2 except where the vent is an integral part of a listed and labeled appliance.

Vented attic detailed cross section.

However spurred by recent claims of energy savings and moisture control unvented attics have become popular in both residential and commercial applications. The building codes and building science for. Theinternational building code 2012 edition ibc 2012 requires enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof framing to have cross ventilation for each separate space. Section 402 2 1 ceilings with attic spaces.

For decades designers of attics and crawl spaces have used cross ventilation to minimize the potential for moisture accumulation and condensation. Vent roofs with steeples towers or cupolas can be found in different buildings from barns to cathedrals. The idea of roof vents existed for hundreds of years with natural vents employed in chinese buildings during the tang dynasty natural ventilation ducts in the buddhist monks caves and wind catchers incorporated in arabian architecture. If there is no vapor barrier double it to one square foot of nfa for every 150 square feet of attic floor space half for intake half for exhaust.

Section r806 4 of the 2009 international residential code irc and section r806 5 of the 2012 irc have requirements for unvented conditioned attic assemblies. If your attic floor has a vapor barrier you will need one square foot of nfa per every 300 square feet of attic floor area half of that will be intake half for exhaust. 2015 iecc irc section r402 1 2 n1102 1 2 insulation criteria. The building thermal envelope must meet the requirements of table r402 1 2 n1102 1 2 based on the climate zone specified in chapter 3 and the building assemblies associated with the unvented attic assemblies that are considered part of the building thermal envelope.

Intake vents located at the lowest part of the roof under the eaves allow cool. Blocking and bridging shall be arranged so as not to interfere with the movement of air. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof framing members shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain and snow. Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents.

2015 iecc irc section r402 1 3 n1102 1 3 or 2012 iecc irc.