- --- -- Page 10 RAIN April 1979 ,1/ ,1/ -O~ -0 /1' / 1" \\\\\ \\\\\ (cool. ( o,() C".(IT1« O«) --------~~~----- ~'--" K\\\\S\\\\\SSS'&S1 ~~ (l) Tht ~fKl::lb tht "'-'r~, tilt .~ A.. ~lf-arnpll~(n9 (6tatL"9 :;tJI'fOce hc>t.. l~a.-r' Tht w:nmu19 rnclioI1 ~'!> 9lVU1/j .....,r11'\t!... aif 0<.(' O<-ptlnd6 cr1!.at,"9 Or] i.nd.,lqnce. "11 Upwort! rTlo<TltnLum. -(tK M>~ -rn~ utltblQrtce £,<lcI1.Uy t>tCO ~~ wm ~'«-':> ~ " ' I::u~' upon wnodt u"5~ble. rnor't. rapid motio" devdOf"" : f he"" ~;pt"',} ~tch~~-"'< '; J product cl q.J l<k. t.~~ nnd Q ..)cf'\:>~ o~ r Q~t " l t ::,,--, not ttl<)" ~~cd 'pho~ I')9t"np~~ ~ The Air Currents of Two Classic Passive Solar Homes Natural climatic behavior, while increasingly recognized as both highly ordered processes and a powerful tool for building climate conditioning, is so complex, silent, invisible and foreign to our traditional awareness that quality understanding might secm beyond reach. In my view, high quality undertanding of the intricate cyclic interactions of conduction, radiation, convection and material properties, in response to the daily sun cycle, is available through direct observation of these natural cycles. The highly energetic yet well protected indoor climates of passive solar homes create air currents which tend to be highly distinct and individualistic. In this, passive solar homes seem to be a new feature on earth and provide a first opportunity to observe protected yet uninhibited natural climate behavior. Two solar homes I've observed, Karen Terry's house and First Village Unit No.1, display individual current patterns of such beauty, clarity and consistent order as to suggest some traight-forward means by which the repetitive patterns of discrete currents can be engineered. They also can serve as a measurable expression of the t-hermal harmonies between the building and the environment. The drawings which follow show reasonable first order approximations of air currents and current patterns. The true behaviors in these homes, though sometimes several orders more complex, are generally as distinct and individual. In Karen Terry's house I not only found beautiful patterns, I also found a natural pumping process which pulls cold air uphill and warm air down. In First Village Unit No.1 I found a much more complex order \vhich, among other things, neatly drew the hottest individual currents away from the coldest surfacc (contrary to the normal direction of hottest to coldest) by involving them in a figure eight convection loop. A Discrete Air Current One critical aspect seems to be how currents invent themselves without any obvious suggestion, i.e. turn themselves on at a time when they don't exist. This concept has a variety of very interesting spin-orfs. The following sketches show major stages " 1 / -0 /1" f I ~. ")\' ~t I t ~""~~~~\."J @ 11t~ t1Joh 01' VlQr'm a'" "'l'~ tht. coole.. ,,0-' <I r>:l ~p ulknq the Y'ot1~",t lltr t r'" in a dletart.:e 'Pmtir19 a plume U1 -tho:: Ct:rl~. I~.,al c ULulatLort 'n f.nt>: rtJSI1. .,,"kl '" 0 5 tht >111(11) - = 1 I~XJn:Jaty ~rech~. in the self-invention of an air current (1 through 6). A second crucial aspect is the way air currents travel by means of n continuous unfolding of a central core which rushes to the front, splits itself and the air mass and remains relatively stationery on the outside 'surface' as the rest of the current passes by. This and other sorts of similar orderly behaviors are generally characteristic of passive thermal air currents as con tasted with the familiar disorderly qehavior of forced non·thermal air currents. The easiest place to observe simplified versions of these orderly flows is in doorways and along floors of any building where there is very commonly found a smooth and well defined river of cool air flowing steadily in one direction or another. Such observation is necessary for those who wish to attempt design with air currents. Karen Terry's House (Santa Fe, NM, designed by David Wright, Fig. 7) Karen Terry's house is a direct gain solar house. It is composed of two parallel north-south insulated adobe walls which step up a south facing slope, spanned on top by alternating flat roof and tilted glazing and joined below by three floor le\'els. The floors and the bankos between floor levels are high thermal mass elements. The house works quite well, being comfortable throughout at most times and requiring use of the heating stove on only ten to fifteen days a ycar. No operable insulation is used. The first hint that something unusual is happening in the climate of the house is that the top to bottom temperature stratification is much lower than might be expected in a twenty-five foot high room with lots of windows, even considering the thermal mass. The second hint 'comes from notic.. ing that in winter, both day and night, the cool air streams along the floor are gentle and tend to go northward, effectively up-hill. The keys to discovering the overall pattern of flows lies in the interaction of cool rushes which descend from the overhead glazing with the warm rushes which rise from warm mass below, the effect of the strong warm sheet of air which rushes up the broad smooth back wall of the house and then in that these current patterns operate COIl tinuously, both day and night, so long as thc mass surface are warmer than the air and th~ air is warmer than the windows.
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