Where the air infiltration rate in a dwelling unit is less than 5 air changes per hour when tested with a blower door at a pressure 0.2 inch w.c. (50 Pa) in accordance with Section R402.4.1.2 of the International Energy Conservation Code Georgia State Minimum Standard Energy Code (IECC with Georgia State Supplements and Amendments)—Residential Provisions, the dwelling unit shall be ventilated by mechanical means in accordance with Section 403 of the International Mechanical Code.
- The net free cross-ventilation area shall be permitted to be reduced to 1/300 provided that not less than 50 percent and not more than 80 percent of the required ventilating area provided by ventilators located in the upper portion of the space to be ventilated at least 3 feet (914 mm) above eave or cornice vents with the balance of the required ventilation provided by eave or cornice vents.
- The net free cross-ventilation area shall be permitted to be reduced to 1/300 where a Class I or II vapor barrier is installed on the warm-in-winter side of the ceiling.
- Unvented attic assemblies (spaces between the ceiling joists of the top story and the roof
rafters) and unvented enclosed rafter assemblies (spaces between ceilings that are applied
directly to the underside of roof framing members/rafters and the structural roof sheathing at the
top of the roof framing members/rafters) shall be permitted if all the following conditions are
- The unvented attic space is completely contained within the building thermal envelope.
- No interior Class I vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly or on the ceiling side of the unvented enclosed rafter assembly.
- Where wood shingles or shakes are used, a minimum 1/4-inch (6 mm) vented air space separates the shingles or shakes and the roofing underlayment above the structural sheathing.
- Either Items 3.4.1, 3.4.2 or 3.4.3 shall be met, depending on the air permeability of the
insulation directly under the structural roof sheathing.
- Air-impermeable insulation only. Insulation shall be applied in direct contact with the underside of the structural roof sheathing.
- Air-permeable insulation only. In addition to the air-permeable insulation installed directly below the structural sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing as specified in Table 1203.2 for condensation control.
- Air-impermeable and air-permeable insulation. The air-impermeable insulation shall be applied in direct contact with the underside of the structural roof sheathing as specified in Table 1203.2 for condensation control. The air-permeable insulation shall be installed directly under the air-impermeable insulation.
- Where preformed insulation board is used as the air-impermeable insulation layer, it shall be sealed at the perimeter of each individual sheet’s interior surface to form a continuous layer.
|CLIMATE ZONE||MINIMUM RIGID BOARD ON AIR-
IMPERMEABLE INSULATION R-VALUE
|2A and 3A||R-5|
(Effective January 1, 2014)
Ventilation openings in under-floor spaces shall not be required where:
- Exposed earth is covered with a continuous Class I vapor retarder. Joints of the vapor retarder shall overlap by 6 inches (152 mm) and shall be sealed or taped. The edges of the vapor retarder shall extend at least 6 inches (152 mm) up the stem wall and shall be attached and sealed to the stem wall or insulation; and
- One of the following is provided for the under-floor space:
- Continuously operated mechanical exhaust ventilation at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7 m2 ) of crawlspace floor area, and perimeter walls insulated in accordance with Section 1301.1.1 of this code;
- Conditioned air supply sized to deliver at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7 m2 ) of under-floor area, and perimeter walls insulated in accordance with Section 1301.1.1 of this code.
(Effective January 1, 2014)
Exception: Exterior openings required for ventilation shall be permitted to open into a sunroom with thermal isolation or a patio cover provided that the openable area between the sunroom addition or patio cover and the interior room shall have an area of not less than 8 percent of the floor area of the interior room or space, but not less than 20 square feet (1.86 m2). The openable area of the openings to the outdoors shall be based on the total floor area being ventilated.
Exception: Openings required for natural light shall be permitted to open into a sunroom with thermal isolation or a patio cover where the common wall provides a glazed area of not less than one-tenth of the floor area of the interior room or 20 square feet (1.86 m2), whichever is greater.
Exception: This section does not apply to the following buildings and spaces:
Accessories such as grab bars, towel bars, paper dispensers and soap dishes, provided on or within walls, shall be installed and sealed to protect structural elements from moisture.