April 1979 RAIN Page 13 Gentleness When sunlight enters the house it falls on a wide variety of surfaces. There arc many high and low mass areas which receive direct gain for either long or short periods, heating themselves and the air adjacent to them. The heated air adjacent to the vertical mass wall rises in smooth uniform sheets I call slip streams. Before these streams slip off the wall and become turbulent, they are drawn off sideways to the top of open doorways. This smooth lateral motion seems to be allowcd, in part, by a nearly motionless air mass trapped by the deck or roof structure above the section of wall which blocks the path to the glass and by the fact that the down-draft for the windows is very amply supplied from cooler central greenhouse air. This aspect of alternate supply is among the most crucial factors in attempting to design for air currents. The opportunity is for choosing the coolest of warm air to send to the coldest surface. This allows the cold surface (the glazing) to get colder both by slowing the rate of convection motion and lowering the supply temperature. After the sheet of warm air from the walls has entered a room by the top of a doorway, it is drawn off to replace cooler air anywhere in the room. The cooler air forms a pool, usually one to thrce feet deep, inside the room, which drains through the doorway into the center of the greenhouse. This cooler air is still warmer than the glazing and often serves as the supply for the cold window draft. The cold draft from the windows either turbulently mixes with warmer greenhouse air or falls to the floor of the greenhouse, supplying the updrafts of sunlit objects or the slip streams rising on the lower walls. Th~ energetic slip stream on the walls not only serves to transfer heat preferentially to the rooms but also serves to more rapidly cool the mass wall so that Icss heat is re-radiated to the glass and less convection travels from the wall to the glass when the doors are closed in the evening. The total net cffect of this figure eight cycle is that the rooms are heated more quickly, the glass heated more slowly, and the rapid actions are concentrated near the edges of things giving the hOllse a feeling of gentleness despite the massive energy flows which arc taking place. There are a wide variety of reasons why an impression of gentleness seems to be a measure of quality in passive solar design. It's something which is found in the experience of good passive solar homes and nowhere else. It lIsually means that there are sequences of direct exchanges which keep the faster currents near surfaces and often that there arc few direct exchanges between very warm and very cool surfaccs. It means that convective skin cooling is minimized and makes the positive health and odor effects of lower air temperatures morc comfortable. At night it often means that heat is being transferred largely by radiant means rather than by normally dominant convective flow. In contrast to the dead quiet sensory deprivation of some homes designed on the basis of efficiency alone, gentleness in a passive solar home seems to be an aspect of sure-footed responsiveness to nature and a measurc of its sensual life-giving environment. Conclusion The patterns I've been able to observe reinforce. for mc, the notion that there is a better way to approach the understanding of climate dynamics than the prevalent basket of numbcrs approach. This especially for tbe vast majority of designers. builders and building occupants who really need to undcrstand their own impact on their environment without spending endless hours laboriously stirring a cauldron of fantastic formulas delicately spiced with finagle factors. That method may, with sufficient expertise, tdl what you've done, but it doesn't tell you what to do. All you need is to become a good listener. From my listening I've learned that passivc solar design is still very far from being sophisticated. Not only do most designs fail to work as well as expected, but the ones that work better than expected remain a mystery. When you look into it, you find that many of the formulas we usc arc gcnuindy foolish. One case in point is the controversy around Lce Butler's EKOSE'A houses. I can't tell you how many people have "proved" that people in his houses aren't comfortahk when they say they are. I haven't had a chance to personally observe the dynamics of one of his houses. howev<:r whcn someone tells me they're sweating and my eljuarion re'lls me they are in the later stages of frostbite, there's littk question of whieh to bel ieve. There's a lot of learning to do. That the vcry small handful of people who have developed real skill in neating naturall\' luxurious building climates also are the same vcry small handful of people who have bccn devoted observers of nature is no ~~~~~;;;;;;;;;;;;;;;;;;;;;;;;;;:;;;;;~_eoinCidence. Pbilip /leI/shaw can bl' CONIOCICd at Box 1812J, DCllver, CO 80218. fig. 12 !l sligbtly dij/acilt versioll of "SlIcal,y Invisible Thillgs " is beillg pllblished ill the Pru(cedillg) oft!.>e 1979 11S oflSL'i National Passive Solar CU/lVI'lltiol/. rill' details, contact A'; 1I/ISI:'.'i, c/o !l /'II crican Tecbnical L'/liversily, P.o. Hox 14 J6. J{il/een, TX 7(jS4 J. Next m{JII/!.> Phil wilf {Jlltlille principles and teciJniqlles jiJr u/J.\('rvillg alld designing with £IiI' Cllrn'lIlS ill yuur OWII horne.
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