DAYLIGHT | MODELLING ABDM EVALUATION OF AN APARTMENT 3.2m 1.5m 1.5m Sky lm 1.5m 1.5m 8260 4576 5300 2118 Obstruction lm 0 0 6692 4962 8260 3835 4532 1331 No context / No obstruction Context / No obstruction No context / Obstruction Context & Obstruction Figure 2: Lumens received at the glazing aperture of the apartment in four cases 24 24 24 24 24 20 20 20 20 20 22222 22222 Stot = mm ==8.26 m (Snorm = 1928 hours) S =15928 =15928 15928 hrs hrs AA =8.26 8.26 m [[ [S ==1928 1928 hrs hrs glaz SSS 15928 mm mhours hrs hrs ::::: AA A 8.26 mm m [SSS 1928 hrs hrs]] ]] tot tot glaz glaz norm norm tot tot==15928 glaz glaz==8.26 norm norm==1928 180 180 GBR_London 180 180GBR_London GBR_London GBR_London apart00/glaz01 apart00/glaz01 apart00/glaz01 apart00/glaz01 24 24 24 24 24 (a) (a) (a) 1.50 1.50 1.50 1.50 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 888 N NN N 88 4 44 44 N NN N 444440.500.50 0.50 0.50 1 1111 2 222 2 3 333 3 4 444 4 5 555 5 6 7 666 6 777 7 Month Month Month Month Month 8 888 8 9 999 9 10 10 10 10 10 11 11 11 11 11 12 12 12 12 12 2222 2222norm = 1292 hours) Stot = 10674 m2 m hours : A AA=Aglaz 8.26 m2mm (S S 10674 m hrs hrs 8.26 [[ [S 1292 hrs SSS ===10674 10674 10674m m hrs hrs :: ::glazA ===8.26 8.26 8.26m m [SSS ===1292 1292 1292hrs hrs hrs]] ]] tottot= glaz= norm norm= tottot glaz glaz 180 180 GBR_London 180 180GBR_London GBR_London GBR_London 24 24 24 24 24 (c) (c) (c) 0.50 0.50 0.50 0.50 0.00 0.00 0.00 000000.00 1 1111 apart00-gobs-g000/glaz01 apart00-gobs-g000/glaz01 apart00-gobs-g000/glaz01 apart00-gobs-g000/glaz01 norm norm 0.00 0.00 0.00 0.00 2 2 222 3 3 333 4 444 4 5 555 5 6 7 6 7 666Month 777 Month Month Month Month 8 888 8 9 9 999 10 10 10 10 10 11 11 11 11 11 12 12 12 12 12 2222 2222norm = 530 hours) Stot S= 4381 m2 m hours : A AA= 8.26 m2mm (S 4381 m hrs hrs 8.26 [[ [S 530 hrs SSS ===4381 4381 4381m m hrs hrs :: ::glazA A ===8.26 8.26 8.26m m [SSS ===530 530 530hrs hrs hrs]] ]] tottot= glaz glaz= norm norm= tottot glaz glaz 180 180 GBR_London 180 180GBR_London GBR_London GBR_London apart01-gobs-g000/glaz01 apart01-gobs-g000/glaz01 apart01-gobs-g000/glaz01 apart01-gobs-g000/glaz01 norm norm (d) (d) (d) 22 2 hrs] 2hrs] S [m [m SSS [m [m hrs] hrs] 20 20 2.00 2.00 20 20 16 16 16 16 16 12 12 12 12 12 22 2 hrs] 2hrs] S [m [m SSS [m [m hrs] hrs] 20 2.002.00 2.00 2.00 2.00 2.00 16 16 16 16 16 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 12 12 12 12 12 8 88 88 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 888 N NN N 88 4 44 44 0 00 00 22 2 hrs] 2hrs] S [m [m SSS [m [m hrs] hrs] 2.00 2.00 2.00 2.00 12 12 12 12 12 8 88 88 20 20 20 20 20 (b) (b) (b) 16 16 16 16 16 1.50 1.50 1.50 1.50 Hour 12 12 12 12 12 24 24 24 24 24 180 180 GBR_London 180 180GBR_London GBR_London GBR_London apart01/glaz01 apart01/glaz01 apart01/glaz01 apart01/glaz01 20 20 2.00 20 202.00 20 2.00 2.00 Hour Hour Hour Hour 16 16 16 16 16 0 00 00 2 2222 2 2222 StotSS=SStot 8609 mm hours = 8.26 mm =norm 1042 hours) ==8609 8609 hrs hrs A ==8.26 8.26 [[ [S ==1042 1042 hrs hrs 8609 mm m hrs hrs ::: :A : glaz AAA 8.26 mm m(Snorm [SSS 1042 hrs hrs]] ]] tot glaz glaz norm tot tot==8609 glaz glaz==8.26 norm norm==1042 22 2 hrs] 2hrs] S [m [m SSS [m [m hrs] hrs] Hour Hour Hour Hour Hour The lumens received at the glazing aperture from each of the three layers of view for all four cases is annotated on each image of the apertures in the respective row/column position. For case (a), the glazing receives the maximum possible lumens from both the sky and the ground that is 8.26 x 1,000 = 8,260lm. In other words, from any point across the apertures, the hemispherical view is equally divided between the sky and the ground. For case (b), the presence of the balcony, overhang and sides signicantly reduces the lumens received across the apertures from the two visible view layers. The sky lumens lost are 8,260 4,576 = 3,684lm, whereas the lost ground lumens are 8,260 3,835 = 4,425lm. The lumen loss is not the same for the sky and the ground because the glazing does not occupy the full height of the balcony opening. Also, as noted previously, the actual lumen loss is always greater than that which seems apparent from the hemispherical image because the viewpoint for the image (the centre of the apertures) is invariably the point from which peripheral features balcony, overhang, and so on have the smallest apparent obstruction. This highlights the importance of considering the entire aperture in any daylight/sunlight evaluation. The effect of the obstruction alone is determined for case (c). Here, the view lumens for the obstruction equal 6,692lm, indicating that the overall view of the obstruction that 3.2m Figure 1: Urban apartment with balcony and external obstruction 2.7m Ground lm Connection to the three layers of view 5.2m 2.7m Hour Hour Hour Hour Hour Case (a) presents an idealised scenario in other words the maximum possible view of the sky and the ground, and the maximum possible cross-sectional area of sunlight beam that could pass through those glazed apertures. The colour convention used is red, green, blue for respectively the sky, the external obstruction and the ground. 5.2m Hour Hour Hour Hour Hour An apartment featuring two glazed doors opening onto a balcony enclosed on all sides has been used in this practical application of an ABDM evaluation (Figure 1). The windows face due south and the building is located in London. The apartment faces an external obstruction (the dimensions are not important for this illustration). The rst row of images in Figure 2 show hemispherical sheye views from the centre of the glazed doors and normal to the plane of the glazing for four cases: (a) No context/no obstruction no balcony, no external obstruction (b) Context/no obstruction with balcony, no external obstruction (c) No context/obstruction no balcony, with external obstruction (d) Context/obstruction with balcony, with external obstruction. N NN N 0.50 0.50 0.50 444440.50 1 11 11 2 22 22 3 33 33 4 44 44 5 55 55 6 7 66 77 66 77 Month Month Month Month Month 8 88 88 9 999 9 10 10 10 10 10 11 11 11 11 11 12 12 12 12 12 0.00 000000.00 0.00 0.00 11111 0.50 0.50 0.50 0.50 22222 33333 4 444 4 55555 6 7 666 777 6 7 Month Month Month Month Month 8 888 8 9 9 999 10 10 10 10 10 11 11 11 11 11 12 12 12 12 12 0.00 0.00 0.00 0.00 Figure 3: Temporal maps showing annual sunlight beam index across the apertures (at 15-min timesteps) for all four cases is, across the apertures is almost comparable to the completely unobstructed view (8,260lm) of the sky (or, equally, the ground). Finally, case (d) has all the elements in place: balcony, overhang, external obstruction, and so on. Here, it is evident that the combined effect of immediate context (the balcony, overhang) and the external obstruction reduces the sky lumens to 2,118lm and the ground lumens to 1,331lm. The obstruction lumens now equal 4,962lm still signicant, but the actual effect is more faithfully quantied because it now excludes those view lumens already lost to the context. 44 December 2020 www.cibsejournal.com CIBSE Dec20 pp42-44 Daylight modelling 2.indd 44 20/11/2020 16:25