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514 CHAPTER 27 1965 Guide And Data Book Dark-Colored Yam--'D" MediUnvColored ^Light-Colored Yam--"M" Yam--"L" '.Determination of Design Air-Conditioning Load due to Heat Transfer through Glass Closed. Weave. Fabric `nr* nio ' Rg. 3 ...V Classification of Drapery Fabrics. Heat flow through opaque structures does not contribute to the required cooling capacity until the inside surface warms sufficiently to convect heat to the space. Similarly, the solar energy through fenestrations does not contribute to the bad until this energy is in the form of convective heat gain. In commercial buildings where the transmitted solar energy is absorbed by a floor of sufficient heat capacity, the time lag may be significant. The maximum instantaneous heat gain through fenestra tion may occur on any day between the summer solstice (approximately June 21) and the winter solstice (approxi mately December 21). When it will occur depends upon the amount of glass on each orientation and the outdoor air' temperatures for various months.' Every month should be considered, particularly for medium and high-rise buildings.' The proper design day and time on which to base the - choice of air-conditioning equipment depends obviously largely upon the net total heat gain through the fenestration. It also depends upon the contribution made by other sources of heat gain or loss (transfer through opaque walls, artificial illumination, people, infiltration, etc.) and upon the avail ability of outdoor air for cooling in the fall and winter. The interaction between these contributing factors is complex and requires the studied judgment of a qualified air-conditioning engineer. Values calculated from data in Tables 11 through 25 should not be used indiscriminately without considering the structure as a whole. Table 23 .... Properties of Representative Indoor Shading Devices Shown in Tables 20A, 20B, 21A and 21B Indoor Shod* ' Solar Froportio* (Normal focsdancc) Trona- Ro- Abmit- Acet torp- . tonce. ones ' tones" Venetian Blinds* (Ratio of slat width to' slat spacing ** 1.2, slat angle = 45) Lignt Colored Slat Medium Colored Slat .1 1 0.6 0.4 0.4 0.6 Roller Shades (opaque). White Shade . Dark Colored Shade -- 0.80: :0.20-\ 0.12 0.88 Prqparite* Dark'Colored Fabric . -Closed Weave - - Semi-Open Weave Open Weave-.. Open- , 0.04 0.14. 0.35 0.10 0.20 0.40 0.20 0.20 0.15 0.70 0.60 0.45 Medium Colored Fabric Closed Weave; . Semi-Open Weave Open Weave- - 0.04 0.15 0.40 0.45 0.14 0.30 0.35- 0.35 0.35 .0.48, 0.30 0.22. T^ght Colored Fabric -- - .Closed Weave, <. < Semi-Open Weave . Opeo-Weave - .. 0.04. 0.14 0.35 0.30 .0.55 0.40 .0.50 0iS5, 0.35 0.15 , 0.10 0.10 * Tba valae* ahawn in Uti* table and ^. .. Venetian Blind*, However, testa ebow these blinds with food accuracy. 6 SoUr properties ara (os unfolded fabric. INSTANTANEOUS HEAT GAINS VS. . INSTANTANEOUS COOLING LOADS The difference between instantaneous heat gain and in stantaneous cooling load has been mentioned previously; its practical importance is sufficient to warrant further - consideration. Fig. 4 offers a simplified schematic illustration showing how the radiative part of the instantaneous heat gain is first absorbed by solid objects, and is not'encountered by the conditioning equipment as a cooling load until some later time, when it finally appears in the air stream entering the equipment. While it is true that some lag also is inherent in convective heat transfer and the time required to change the air in the conditioned space, this is usually of the order ofa few minutes to perhaps half an hour. Heat storage in the interior furnishings and structure increases according to the proportion of the instantaneous heat gain which is in the form of radiation, and also increases as the thermal capac' itance of the objects and materials involved is increased. Constituents of the total instantaneous heat gain which have appreciable radiation components include those due to glass areas, exposed walls and roofs, lighting, appliances and people. A large difference in the time-incidence of the peaks be tween various spaces or parte of the same space indicates the necessity for zoning. In a building having an east and west exposure, where solar heat gains form a fair share of .the cooling load,-tire times of individual zone peaks arc apt to 'be some hours apart, and the peak load.of one plus the off-peak load of the other will be substantially less than their combined peak loads. Proper zoning will permit operation to take full advantage of this condition or of. similar con ditions of nonsimultaneous peaks, and will result in a lower total load and in savings in equipment A factor similar in effect and closely related to the nonsimultaneous occurrence of peak loads, is diversity. .Typical of this is the case of a large department'store' where the air- Air-Conditioning Cooling Load 515 Table 24 Shading-Coefficients for Hollow dass'Block'WaD Panels*. Type of Cte Wodt* Description of Clou Block rjn Shodiag Coefficient* PoneJj^io the Sun Pan*/** in fho Shad* IN, NW, W, SW) Type1 Glass Colorless or Aqua Smooth Face ' A, D: Smooth ,, B, C: Smooth or wide ribs, or flutes horizontal or vertical, or shallow . configuration. E: None Type IA Same as Type I except A: Ceramic Enamel on exterior face. ,, Type?? - Same as Type I except E: Glass fiber screen. . Type m Glass colorless or Aqua 1 A, D: Narrow vertical ribs or flutes. B, C: Horizontal light-diffusing prisms, or horizontal lightr-directiog piituua. . * E: Glass fiber screen. _ .; Type IIIA - Same as Type III except -'*5 E: Glass fiber screen with green ceramic spray coating, or glass fiber screen ana gray gtaa3, or glass fiber screen with light-selecting prisma. . 0.65 v. ' `0.40 0.27 0.44 01*33 .0.20 ' 0.34 .0.27 0.25 ' 0.18 For that block used in hbrisastel akytighte see Tables 28 sod 29, Chapter 28 of Urn 1963'ASHRAE Gotti An Data Book. AD sabies are for 7} X 7f X 3i in. block, act in tight-eotored mortar. For 1X| X 111 X 3J in. block in.blocks redoes coefficients by IS percent. , coefficient* by 13 and (or 3} X 5| Sbadmt coefficients as* to be applied to Heat Gain Factors for one hour nattier than the tiTM (nr -which the load MteUtiwi made to allow (or heat at * coefficient* are for peak load condition, but provide a eloee approximation for other conditions Form precise value* (or other conditions, an For HE, E, and SB panele in the shade add SO percent to the valaee Hated (or pane)* in 1 Table 25 .... Length of Horizontal Projection Required for Shading Windows and Walls (For dtadtag'IO:ff down faoa prajocftoA for Aprf.f! through September I) tatijodo; Sun Time AM-* ' 1 6 a.m. ' 24 Deg North 8 9- 10 11 -'-,12N 6 a.m. 32 Deg North - 89 10 . 'll 12 N . k ,N ' NE 17.3" --, -- --... --- -- > --- "15.8 . -- ---- . -- : -- `' 10.8 5.3. ' '2.3" . --. - --,-:t ; w 10.0 i 4.6-v: ; .. 1.4 -- , 6 a.m. 40 Deg North' ' 8 ' 9 10 . 11. 12 N 48 Deg North 6ajnr ,_7;' : 8 9::- 10- ., 12 N ` ; . -I, u.- ; , 12.0/ . -- .. --- , -- . -- - ... * 9.7 4.7 1.3 -- .. -- J , ; -7.3' ' .--. -- -- 1 : -- -- - ' . *' 9.3 ' 3:3 ' -- . . . -- -- -- .,, , ''? N M . NW -v * Projection create* then 30 ft required. t Profocf/on In Foot ' SE S SW Sun Ho*. 16.5 10.0:- 5.8 2.8 -- . 15.8 10.7 - 7.5 . 3.8 .2.2 _ -1.6 2.3 2.7 2.7 2.8 __ " __ __ __ .. ___ -- 2.2 . 6 p.m. 3 - 2 1 . 12 N 17.3 . 10.3 6:0 2.8 . ' -- .14.2 ` 10.0' ' 7 .3 5:1 .3.0 __ 1.7 3.0 3.8 - 4.2 4.2 4.2 ' __ 6 p.m. __ 5 . __ __ '__ - 1:2 3 -'2 1 -. ; .,3.0 = ;12 N - - .. i' 1819 11.2, 6.5 3.1 V . 16.1 11.6 , 9.1 6.5 - 4.3 -Jl' *' ' - 1.8 ' ' ' -5.4. . . 5.8 , 6.1 - *6.3 -- ! . __ .. __ " '2.2 ' '4.3. 1 5- '* , 3,. ,2 1' 12N .. 19.6 12.0 7.3 3.2 . ... ;. ... _ . .___ . 3.6 ' __ 18.7 ' ' 13.7- -'< 7.5 ..... .-__ . . .- 10.8 -8.4 : .. . __ ) ,, * .. 8.4 - .> 8.4,, . 3.2 . 6.0 . , 8.4 .. 6.0 ; .5 3- .. 2-.` b)-..-' ,,1 12.N- _ W-- . - sw -> S , .-hse-,-;/.. /-Vt?*?}*]