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• i ' i <br /> �� � <br /> I <br /> F R A N K ��� -_ r�.�, ��,�n�� F—�::��.� -___ <br /> J �. <br /> =�:�-�; .�, F,,x��z:�8�-..,���� <br /> ENGINEERING � , -„��,-.�:� ,-� ;_.,,. <br /> P�fEC`,'�MIC:AL :O�SUIT:'1G <br /> U-value Calculation for "Vented" T-bar Ceiling with Light rixtures <br /> R-19 Batts R-25 Batts <br /> U-value Area UA U-value Area UA <br /> Venl Gap 1.73 02916 0.330 Vent Gap 1.13 U.2S16 0.330 <br /> In,ulation H-19 0.05 93.0084 4.650 Insulation R-25 0.04 93.0084 3.720 <br /> Total UA 4.980 Total UA 4.050 <br /> Average U-value = Ua= UA/A U,= 0.053 Average U-value = Ua= UAlA U,= 0.043 <br /> R-19 batts R-25 batts <br /> R-30 Batts R-38 Batts <br /> I <br /> U-value Area UA U-value Area UA <br /> Vent Gap 1.13 0.2916 0.330 Vent Gap 1.13 0.2916 0.330 <br /> Insulation R-30 0.034 93.0084 3.162 Insulation R-38 0.026 93.0084 2.418 <br /> Total UA 3.492 Total UA 2.748 <br /> Average U-value = U,= UAlA U,- 0.037 Average U-value= Ua= UA/A U.= 0.029 <br /> R-30 batts R-38 batts <br /> Background Calculations <br /> Vent Gap <br /> Size: 7/8"wide by 48" long U-value of vent gap: <br /> Are2 = 7/8 x 48 =42 in2 Assume R=0.88, 1/R=U=1.13 <br /> 42 in2/144 inZ = 0.2916 ft2 <br /> Vent Ga Area = 0.2916 HZ U-value of Vent Ga = 1.13 <br /> Light Fixtures Insulation <br /> Assume: Area of insulation <br /> 112 watts/fixture 2 = area of Light Fixtures-area of Vent Gap <br /> 1.2 watls/ft <br /> Z = 93.3 ft Area of insulation = 93.3 - 0.29 i 6 <br /> �Light Fixture per 93.3 ttZ insulation Area =93.0084 tt <br />