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CHAPTER 12 tor INTERIOR ENVIRONMENT SECTION 1201 located in the upper portion of the attic or rafter GENERAL space. Upper ventilators shall be located not more 1201.1 Scope. The provisions of this chapter shall govern than 3 feet (914 nun) below the ridge or highest ventilation, temperature control, lighting, yards and courts, point of the space,measured vertically,with the bal- sound transmission,room dimensions, surrounding materials once of the ventilation provided by eave or cornice ?' and mdentproofng associated with the interior spaces of vents. Where the location of wall or roof framing . buildings. members conflicts with the installation of upper �.'I; ventilators, installation more than 3 feet (914 min) I: below the ridge or highest point of the space shall be SECTION 1202 permitted. • DEFINITIONS 1203.2.1 Openings into attic. Exterior openings into the } 1202.1 General.The following tends are defined in Chapter 2: attic space of any building intended for human occupancy i SUNROOM. shall be protected to prevent the entry of birds, squirrels, ); rodents, snakes and other similar creatures. Opening • s for THERMAL ISOLATION. ventilation having a least dimension of not less than 7,s • inch(1.6 mm)and not more than 4,inch(6.4 mm)shall be permitted. Openings for ventilation having a least dimen- r SECTION 1203 sion larger than 44 inch (6.4 mm) shall be provided with VENTILATION corrosion-resistant wire cloth screening, hardware cloth, 1203.1 General. Buildings shall be provided with natural perforated vinyl or similar material with openings having a r' ventilation in accordance with Section International,or mechanical least dimension of not less than /,s inch(1.6 nun) and not • • ventilation in accordance with the Mechanical more than Y4 inch (6.4 mm). Where combustion air is �fe. obtained from an attic area,it shall be in accordance with 1i Chapter 7 of the International Mechanical Code. ., 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 1203.3 Unvented attic and unvented enclosed rafter O. pressure 0.2 inch w.e. (50 Pa) in accordance with Section assemblies. Unvented attics and unvented enclosed roof 402.4.1.2 of the International Energy Conservation Code— framing assemblies created by ceilings applied directly to the 1' Residential Provisions, the dwelling unit shall be ventilated underside of the roof framing members/rafters and the strut- , by mechanical means in accordance with Section 403 of the tural roof sheathing at the top of the roof framing members International Mechanical Code. Ambulatory care facilitiesI shall be permitted where all the following conditions are met: and Group 1-2 occupancies shall be ventilated by mechanical 1. The unvented attic space is completely within the means in accordance with Section 407 of the International building thermal envelope. 2. No interior Class I vapor retarders are installed on the ,;� Mechanical Code. 1203.2 Ventilation required. Enclosed attics and enclosed ceiling side(attic floor) of the unvented attic assembly rafter spaces formed where ceilings are applied directly to the or on the ceiling side of the unvented enclosed roof =$' underside of roof framing members shall have cross ventila- framing assembly. Hon for each separate space by ventilation openings protected 3. Where wood shingles or shakes are used,a minimum '/4- against the entrance of rain and snow.Blocking and bridging inch(6.4 mairspace in) vented separates the shingles or shall be arranged so as not to interfere with the movement of shakes and the roofing underlayment above the shoo- air.An airspace of not less than 1 inch(25 mm) shall be pro- tural sheathing. vided between the insulation and the roof sheathing. The net free ventilating area shall be not less than Viso of the area of 4. In Climate Zones 5, 6, 7 and 8, any air-impermeable the space ventilated. Ventilators shall be installed in actorIL insulation shall be a Class II vapor retarder or shall dance with manufacturer's installation instructions. have a Class III vapor retarder coating or covering in Exception: The net free cross-ventilation area shall be direct contact with the underside of the insulation. permitted to be reduced to '/jw provided both of the fol- 5. Insulation shall be located in accordance with the fol- lowing conditions are met lowing: '} 1. In Climate Zones 6, 7 and 8, a Class I or II vapor 5.1. Item 5.1.1, 5.1.2, 5.1.3 or 5.1.4 shall be met, retarder is installed on the warm-in-winter side of depending on the air permeability of the insula- the ceiling. tion directly under the structural roof sheathing. 2. At feast 40 percent and not more than 50 percent of 5.1.1. Where only air-impermeable insula- the required venting area is provided by ventilators tion is provided, it shall be applied 2015 INTERNATIONAL BUILDING CODE° 311