b"Reference velocity pressure - NBC table C-2Exposure factor -NBC clause 4.1.7.3.(5)(b))Topographic factor (NBC sentence 4.1.7.4.(1))Importance factor (normal, NBC table 4.1.7.3)Step 3: Calculate the tributary area of the array normalized by the building size The equation represents it: A N= normalized tributary, A = dimensional tributary area,for the array component under consideration, and penalize the lower-rise buildings L b= normalized building length = min[0.4(hW L )0.5,h,Ws], where relativetothehigher-risebuild-W L= width of the building on its longest side, and ings. This effect is not currently W S= width of the building on its shortest side.solar L paddressedinNBCcomponentspanel (C C )The pressure-gust coefficients (CgCp) n , in Figure 1, are developed from wind tunnel test data.W Land cladding figures. p g2h 2hThis data applies to all building heights. The concept of normalized area is used to not over- nStep 4: Determine the2h 3 2 3 roofpenalize the lower-rise buildings relative to the higher-rise buildings. This effect is not currently(!)Net Pressure-gusthCoefficient (C g C p )net2addressed in NBC components and cladding figures.By Sudhakar Molleti and Mauricio Chavez The net pressure-gust () netW s 2 1 2 L p h 1coefficient Step 4: Determine the net-gust pressure coefficientfor the applicable tributary is cal-culated as follows:The net pressure-gust coefficient for the applicable tributary is calculated as follows: () net=2h 3 2 3 h pt H groundRoof zones (plan view)WhereWhere: p= min (1.2,0.9 + h pt /h) (h ptbeing the height of the parapet above the roofs surface),6.4= min (1.2,0.9 + h /h) (hbeing4.4 p pt pt c= max (0.6 + 0.2L p ,0.8),height of the parapet above the6the roofs surface), 4L p =solar panel length (chord length)3 5.6 3E = edge factor,c= max (0.6 + 0.2L p ,0.8), 3.6 5.2(C g C p ) n= normalized area-averaged pressure-gust coefficients, as defined in Figure 1 L=solar panel lengthp4.8(chord length), 3.2The pressure-gust coefficients values shown in Figure 1 cover the range of solar panel tilt angles4.4E = edge factor, and 2.8 2 2from 0 degrees to 35 degrees. These angles represent the practical range of inclination for solar4(C C )= normalized area-averagedarray installations on commercial buildings. It should be noted that the pressure-gust coefficients g p n pressure-gustcoefficients,2.4 3.6are for both positive and negative values. The wind tunnel data has shown that the wind loading as defined in Figure 1. ) C (C n g p 1 ) n g p 3.2on the interior panels in the array layout (sheltered panels) has different loading conditions thanC (C2Thepressure-gustcoefficient2.8 1the perimeter edge panels in large arrays. Parape1 ' presence worsens the wind loads on solar valuesshowninFiguretscover1.6the range of solar panel tilt angles2.4panels as they tend to lift the vortices higher above the roof surface and push them inward from from0degreesto35degrees.1.2 2the edges. Similarly, the wind tunnel data also revealed that increase the panel chord length has These angles represent the practi-cal range of inclination for solar0.8 1.6array installations on commercial1.2buildings. It should be noted that0.4the pressure-gust coefficients are0.8forbothpositiveandnegative0 0.4values. The wind tunnel data has1 10 100 1000 1 10 100 1000shown that the wind loading onNormalized tributary area, A Normalized tributary area, Atheinteriorpanelsinthearray0 (!) 5 N 15 (!) 35 Nlayout (sheltered panels) has dif-ferentloadingconditionsthan1 ,2 ,3= roof zones (!)= panel tilt angle relative to roof surfacethe perimeter edge panels in large arrays. Parapets presence worsens thewindloadsonsolarpanels astheytendtoliftthevorticesFigure 1: Normalized area-averaged pressure-gust coefficients, (CgCp)n, for solar arrays mounted on low-sloped roofs (NBC User Guide)higherabovetheroofsurface +Build SolutionsTotal Design F architek.com | 1 888 317 9226or Your Green Roof Projects.ORN THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ONTARIO ROOFING NEWSISSUE 2 202125"