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<br /> <br /> <br /> Page 4 of 8 <br /> <br /> <br /> vent area for each 300 square feet of roof area. No less than 30 percent of the total vent area <br /> shall be in either the ridge vent or the lower half of the ventilated space. <br /> 4.2. A solar-powered exhaust fan that provides at least one cubic foot per minute of airflow <br /> 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 for each <br /> 150 square feet of roof area. At least 30 percent of the total vent area shall be in the upper <br /> half of the ventilated space and at least 30 percent of the total vent area shall be in the lower <br /> half of the ventilated space. <br /> 5. For compliance with Subsections 1.3 or 1.4, a radiant barrier shall have an emissivity of no greater <br /> than 0.05 as tested in accordance with ASTM E-408 The radiant barrier shall be installed with the <br /> shiny side facing down and with a minimum air gap thickness of 1/4 inch below. The radiant barrier <br /> may be securely attached to the roof framing or may be laminated to the bottom of the roof <br /> sheathing. A radiant barrier is a sheet of material with a low emissivity on at least one side that is <br /> used to reduce radiant heat transfer. Radiant 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 more than <br /> 0.75 when tested in accordance with ASTM E-408 and a high solar reflectance The manufacturer's <br /> test results shall be acceptable for compliance. A cool roof has both a light color (high solar <br /> reflectance) and a high emittance (can reject heat back to the environment). White painted surfaces <br /> and other smooth white coatings typically meet these requirements. Surfaces that do not meet the <br /> requirements include unpainted metal 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) shall be <br /> calculated as described in Equation 8-1. <br /> Equation 8-1 <br /> RHGF= U, _X a x RB <br /> Where: <br /> RHGF = Roof Heat Gain Factor FBtU/ft2 -h-'Fl <br /> = overall thermal transmittance value for the gross area of opaque roof surfaces [Btu/ft2 -h- <br /> 7j <br /> a = roof surface absorptivity. Between 0.3 and 1.0 funitless] <br /> RB = Radiant Barrier credit. Equals 0.33 if a radiant barrier is installed and 1.00 otherwise <br /> funitless]. Radiant barrier installation must comply with subsection 8.1 to qualify for Radiant <br /> Barrier credit. <br /> 8.1. To qualify for the radiant barrier credit (RB) described in Subsection 8, the installation of the <br /> 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 must <br /> provide test data or documentation of the emissivity as tested in accordance with ASTM E- <br /> 408. <br /> 8.1.2. The radiant barrier must be securely installed in a permanent manner using one of the <br /> following installation methods: <br /> 8.1.2.1. The radiant barrier shall be draped with the shiny side facing down over the <br /> top cord of the truss before the roof deck is installed A minimum air gap of/4 inch <br /> must be provided between the radiant barrier and the roof deck above at the center of <br />