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<br /> <br /> <br /> <br /> <br /> <br /> than 30 percent of the total vent area shall be in either the ridge vent or the lower <br /> half of the ventilated space. <br /> 4.2. A solar-powered exhaust fan that provides at least one cubic foot per minute <br /> of airflow for each square foot of roof area. <br /> 4.3. Upper and lower vents with total net free vent area of at least one square foot <br /> for each 150 square feet of roof area. At least 30 percent of the total vent area shall <br /> be in the upper half of the ventilated space and at least 30 percent of the total vent <br /> area shall be in the lower half of the ventilated space. <br /> 5. For compliance with Subsections 1.3 or 1.4, a radiant barrier shall have an emissivity of <br /> no greater than 0.05 as tested in accordance with ASTM E-408. The radiant barrier shall <br /> be installed with the shiny side facing down and with a minimum air gap thickness of/o <br /> inch below. The radiant barrier may be securely attached to the roof framing or may be <br /> laminated to the bottom of the roof sheathing. A radiant barrier is a sheet of material with <br /> a low emissivity on at least one side that is used to reduce radiant heat transfer. Radiant <br /> barriers typically have a shiny metallic appearance. <br /> 6. For compliance with Subsection 1.4, a cool roof shall have an infrared emittance of no <br /> more than 0.75 when tested in accordance with ASTM E-408 and a high solar reflectance. <br /> The manufacturer's test results shall be acceptable for compliance. A cool roof has both a <br /> light color (high solar reflectance) and a high emittance (can reject heat back to the <br /> environment). White painted surfaces and other smooth white coatings typically meet <br /> these requirements. Surfaces that do not meet the requirements include unpainted metal <br /> and metalized roof coatings (silver appearance). <br /> 7. At building sites higher than a 2,400-foot elevation, only Subsections 1.1 or 1.2 shall be <br /> acceptable for compliance. <br /> 8. For purposes of compliance with Subsection 1.5, the Roof Heat Gain Factor (RHGF) <br /> shall be calculated as described in Equation 8-1. <br /> Equation 8-1 <br /> RHGF=U,xaxRB <br /> Where: <br /> RHGF = Roof Heat Gain Factor [Btu/ft2-h-°F] <br /> U, = overall thermal transmittance value for the gross area of opaque roof surfaces <br /> [Btu/ft2-h-°F] <br /> a = roof surface absorptivity. Between 0.3 and 1.0 [unitless] <br /> RB = Radiant Barrier credit. Equals 0.33 if a radiant barrier is installed and 1.00 <br /> otherwise [unitless]. Radiant barrier installation must comply with subsection 8.1 <br /> to qualify for Radiant Barrier credit. <br /> 8.1. To qualify for the radiant barrier credit (RB) described in Subsection 8, the <br /> installation of the radiant barrier must meet the following criteria: <br /> 8.1.1. The emissivity of the radiant barrier must be 0.10 or less. The manufacturer <br /> must provide test data or documentation of the emissivity as tested in accordance <br /> with ASTM E-408. <br /> 8.1.2. The radiant barrier must be securely installed in a permanent manner using <br /> one of the following installation methods: <br /> 8.1.2.1. The radiant barrier shall be draped with the shiny side facing down <br /> over the top cord of the truss before the roof deck is installed. A minimum <br /> <br /> <br /> <br /> 4 <br />