遮陽：糾結的藝術

張利/ZHANG Li

可能沒有什么本性上比遮陽更糾結的建筑構件了。

我們都希望建筑的內部空間沐浴在陽光下。畢竟是太陽的光和熱造就了地球的生命。然而，雖然太陽的溫感和明媚令人向往，它的物理溫度和亮度有時卻是讓人避之不及的。所以，我們永遠被建筑最古老的困境之一所籠罩：我們想要陽光，我們又不想要陽光，至少不要太多陽光。

因此，遮陽作為一種解決方案，命中注定是一個妥協。特別是當遮陽與它通常伴隨的構件——窗——形成鮮明對比的時候。窗，透明、開放、純粹、一致，它是內部與外界之間的通道，是我們借此獲得洞察世界的建筑之眼。遮陽的氣質就沒那么明確了。阻隔、遮蔽、混雜、多變，它至多只能是一個快門，在必要時暫時關閉內外的對話。我們不妨拿各種遮陽與存在于我們自己眼睛周邊的視線調節方法作一下比對，給每一種遮陽一個類比。

第一種方法是“眉骨”式的：伸展窗洞的上邊緣，形成遮蔽或反射的表面，同時在建筑立面增加一個富有表現力的水平陰影。這是最傳統但最直接的方法之一。通過與不同高度角的太陽共同作用，這類方法從早期到現代都是許多偉大建筑的形式締造者與日光漫散者。丹麥海澤胡瑟訥DSV總部讓我們看到了來自現代主義鼎盛時期的此類遺風——來自帶形窗上緣的富于表現力的水平性——甚至讓人想起貝聿銘或阿爾瓦羅·西扎。

第二種方法是“眼瞼”式的：使用固定卷簾/百葉形成窗口的屏蔽。它們一般通常有兩種狀態：打開或關閉。我們完全可以認為，幾個世紀以來，各種顏色和材料的百葉窗一直是傳統的城市景觀中最具活力的因素，它們曾是無數街道上空生動肌理的來源。然而，現在的建筑師似乎不再甘心使用它們，可能是出于一種恐懼——一旦使用百葉窗就會立刻讓立面呈現出熟悉與懷舊。于是建筑師們費盡心機，努力嘗試各種“眼瞼”的新化身，并有意用其他含意來淡化百葉窗的意象。在布基納法索隆果的社會福利中心，開合窗似乎主要是為了兒童的頑皮準備的。在奧地利施蒂里亞的基弗技術展廳，外百葉則變身占據了整個建筑表面的皮，其夸張的折疊方式造就了一種建筑變臉的效果。

第三種方法是“簾/傘”式的：使用通常是半透明的全方位外層包被，對整座建筑進行遮蔽。這是一種高風險的作法，因為“簾/傘”體系的完整性極有可能與建筑本身產生沖突。當設計技巧與控制力足夠時，簾或傘可能會形成“第二屋頂”——一層薄如蟬翼的浮于建筑之上水平界面，例如美國德克薩斯州的金貝爾美術館擴建。當設計上不有意對簾/傘進行控制時，它們可能會被誤認為是獨立的附加結構，產生一種體系與意義上的混雜，如在智利的普曼克社區中心。

第四種方法是“太陽鏡”式的：將遮陽構件作為手法化的個性表現工具，甚至是裝飾。這雖是一個相當有爭議的方法，但不出意料的，它在我們這個時代十分流行。21世紀的技術帶來了可移動部件的更高精度與大量的新奇材料，為建筑師進行實驗創作提供了更多自由。然而，我們在其中一些實驗里看到的不全是精妙的物理原理所帶來的大眾健康與神祉，而更多的是復雜的形狀與圖案所營造的視覺愉悅或游戲。德國埃森蒂森克虜伯樓的立面，其經過計算的精細遮陽構件的對稱性確實達到了一定程度的優雅，但其實際的熱工性能卻沒有得到必要的證明。中國天津天友綠色設計中心是熱情溢出的見證：它在每個立面上都有一種手法化明顯的遮陽設計，并且在頂部還橫亙了第五種。在塞浦路斯尼科西亞的“白墻”，我們則看到了又一個來自垂直綠化學派的演示——蔓延于整個立面高度的植物栽培，其密度與造價都相當可觀——它們恐怕首先是在城市里產生視覺注意力的中心，其次才是調節居住空間的內部微氣候。

特別感謝林波榮教授，他的幫助使這一期的出版成為可能。

There is hardly another building component whose nature is as schizophrenic as that of sunshading.

We want the inside of our buildings to bath in sunlight. It is the warmth of the sun that makes life on earth after all. Yet while the sensual warmth and brightness of the sun is so desirable, from time to time its physical heat and flare is not. Thus we are perpetually blessed by one of the oldest dilemma in architecture: we want sunlight and we do not want sunlight, at least not too much of it.

Therefore the solution, sun-shading, has a fate of being eventually a compromise. Particularly so when a sun-shading is put in contrast with the formidable component it usually accompanies: a window. Being transparent, open, pure and consistent, a window is a portal between the inside and the outside world,an eye of the building through which we gain the capacity of seeing. A sun-shading, however, is much less distinct. Being opaque, blocking, hybrid and volatile, it is at best a shutter that temporarily shuts down the inside-outside dialog when necessary. We may compare different approaches of sun-shadings with the different means we use to temporarily block or modulate our eye sight, and give each of these approaches an analogy.

The first one is the "brow ridge" approach:extending the upper edge of the window's opening,forming a shading/reflecting surface while adding an expressive horizontal shade in the building fa?ade.It is one of most traditional yet most intuitive approach. By working with different altitude of the sun, it is both the form-giver and day-light diffuser for many great buildings, from early times to the modern era. In DSV headquarters in Hedehusene,Denmark, we see a legacy of the clean and expressive horizontality of high modern times, something reminiscent of I. M. Pei or Alvaro Siza.

The second approach is the "eyelids" approach:using fixed shutters/blinds to form a shield of the windows. Usually there are two operating modes: open or closed. One may safely argue that blinds of various colours and materials have been adding vibrancy to traditional urban landscapes for centuries. They used to be some of the most vivid elements above our streets. Yet it seems that architects nowadays no longer use them, possibly fearing the instant nostalgia they would bring.New incarnations of the "eyelids" do exist, albeit designed with other connotations. In the Social Welfare Centre of Laongo, Burkina Faso, the blinds serve the playfulness of children. In Kiefer Technic Showroom, Styria, Austria, the blinds are folded in the most conspicuous way possible and occupy the entire surface of the building, giving the impression of a fa?ade that is forever changing.

The third approach is the "curtain/umbrella"approach: using an outer layer/shell, usually of translucent nature, to shade the entire building. When implemented with skill and care, the curtain or umbrella may form a second roof that is both dematerialised and floating, such as the Kimbell Art Museum Expansion in Texas, USA. When used less carefully, the curtain(s)/umbrella(s) can be mistaken for some standalone structures and produce some sense of hybridity, such as the Pumanque Community Centre in Chile.

The fourth approach is the "sun-glass" approach:using the sun-shade as an vehicle to idiosyncratic expressions. This is a truly controversial approach but not surprisingly, a popular one in our time. 21st century technology has certainly ensured higher precisions of moveable parts and the intensive use of exotic materials, giving the architects more freedom to experiment. Yet what we see in some of these experiments is less about the sophisticated physics working for the general good, but more about complex shapes/forms working to please/tease the eye. In the fa?ade of Thyssenkrupp Quarter Essen in Germany, the calculated symmetry of the subtle sun-shadings does achieve some elegance without necessarily proving the actual thermal performance. In the Tenio Green Design Centre,Tianjin, China, things are becoming overkills: there is one shading idiosyncrasy in each fa?ade, added by a fifth one sitting on top. In the White Walls of Nicosia, Cyprus, we witness another demonstration of the vertical green school: extensive use of plants along the height of the fa?ade, arguably more to generate an urban visual impact than to regulate the micro climate.

Our special thanks to Professor LIN Borong,whose generous help makes this publication possible.