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' ( j <br /> I � � <br /> � <br /> F R A N K L I N ��5:����Yzh .���n�e F��25��;-»�_ <br /> ENGINEERING ����� ��� �������`�-����� <br /> Y-i:lan�;6";A S��U�J �v,C����orelrerg.ccm <br /> MEC�—PdJICAL CONSUL71N6 <br /> U-value Calculation for "Vented" T-bar Ceiling with Light Fixtures <br /> R-19 Batts R-25 Batts <br /> U•value Area UA U-value Area UA <br /> Vent Gap 1.13 02916 0.330 Vent Gap 1.13 02916 0.330 <br /> Insulation R-19 0.05 93.0084 ,.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 betts <br /> R-30 Batts R-38 Batts <br /> U-value Area UA U-value Area UA <br /> Vent Gap 1.13 0.2916 0.330 Vent aap 1.13 02916 0.330 <br /> Insulation R30 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, = UA/A U,= 0.037 Average U•value = U�= 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 o(vent gap: <br /> Area = 7/8 x 48 =42 inZ Assume R=0.88, 1/R=U=7.13 <br /> 42 in2/144 inZ = 0.2916 tt2 <br /> Vent Ga Area- 0.2916 tt U-value of Vent Ga = 1.13 <br /> Light Fixtures Insulation <br /> Assume: Area o( insulation <br /> 112 watis/fixt2 re _ 93.3 ft2 = area of Light Fixtures- area ot Vent Gap <br /> 1.2 watts/ft Area of insulation =93.3 -02916 <br /> 1 Li ht Fixture er 93.3 tt2 Insulation Area=93.0084 tt �`� <br /> �f-b <br />