低碳建筑的未來(lái)

安迪·福特/Andy Ford

每個(gè)國(guó)家都有其獨(dú)特的氣候、文化和經(jīng)濟(jì)情況，而英國(guó)在全球降低碳排放的推動(dòng)力作用下，做出了特殊的決策，這些決策可以為其他國(guó)家制定降低碳排放的政策提供生動(dòng)有趣的教材。關(guān)注英國(guó)的經(jīng)驗(yàn)可以使其他國(guó)家的決策者、建筑師、工程師和業(yè)主能夠更有效地應(yīng)對(duì)向可持續(xù)發(fā)展轉(zhuǎn)變所帶來(lái)的挑戰(zhàn)。

25年來(lái)，福坤的設(shè)計(jì)團(tuán)隊(duì)一直以綜合環(huán)境工程的知識(shí)設(shè)計(jì)出低能耗建筑。本文回顧了福坤的低能耗示范建筑，考查最近進(jìn)行的此類(lèi)工程，并探討了政府推行“零碳”建筑作為今后10年內(nèi)行業(yè)標(biāo)準(zhǔn)的新干預(yù)政策可能帶來(lái)的影響。

1. 低能耗設(shè)計(jì)和英國(guó)新型“零碳”建筑的推動(dòng)作用

兩座具有重大意義的創(chuàng)新建筑：

1.1伊麗莎白教學(xué)樓（圖1）

在1990年代發(fā)生的經(jīng)濟(jì)衰退期間，按照我們的工程設(shè)計(jì)理念在東安格利亞大學(xué)（University of East Anglia，UEA）修建了一系列的低能耗建筑，其中的伊麗莎白教學(xué)樓是最新的一座，業(yè)主是一所擁有現(xiàn)代化校園的大學(xué)，該大學(xué)計(jì)劃進(jìn)行擴(kuò)建，旨在解決英國(guó)公共政策帶來(lái)的學(xué)生人數(shù)大幅增長(zhǎng)的問(wèn)題。

UEA將教學(xué)大樓視為一項(xiàng)長(zhǎng)期投資，因此，希望采用一種“全生命周期”的方法，對(duì)學(xué)校的發(fā)展路線進(jìn)行分析。當(dāng)學(xué)校從這一角度進(jìn)行考慮時(shí)，低能耗建筑顯示出了其明顯的優(yōu)勢(shì)。

起初，我們修建了兩個(gè)低能耗學(xué)生宿舍樓群；這兩個(gè)建筑群節(jié)能效果明顯，不但降低了運(yùn)行成本，還為學(xué)校進(jìn)行了免費(fèi)宣傳。這次成功說(shuō)明，盡管非常高的建設(shè)標(biāo)準(zhǔn)對(duì)低能耗建筑提出了新的技術(shù)挑戰(zhàn)，但是這些挑戰(zhàn)都是可以實(shí)現(xiàn)的。此外，還說(shuō)明了低能耗建筑的建造可以在不增加成本的情況下進(jìn)行，而且如果向常規(guī)建筑公司提供詳細(xì)的設(shè)計(jì)指導(dǎo)和現(xiàn)場(chǎng)監(jiān)理知識(shí)，那么無(wú)論先前在合同中是否有此要求，這些建筑公司也可以建造低能耗建筑。因此，學(xué)校針對(duì)今后所有的建筑采取了一種低能耗設(shè)計(jì)政策，這一政策一直沿用至今，并且其適用范圍不斷擴(kuò)大，包括了對(duì)早前建筑的翻新，使之更加節(jié)能高效。

在修建伊麗莎白教學(xué)樓時(shí)，我們努力使這項(xiàng)政策的實(shí)施達(dá)到新高度，使這一建筑能夠成為低能耗設(shè)計(jì)的代表作。這棟建筑的面積并不太大（僅3 500m2），盡管其設(shè)計(jì)具有創(chuàng)新理念，但建筑的原則實(shí)際上頗為簡(jiǎn)單，即修建一棟堅(jiān)固耐用的建筑。建筑設(shè)計(jì)工作由約翰·米勒及合伙人設(shè)計(jì)事務(wù)所（John Miller and Partners）擔(dān)當(dāng)，設(shè)計(jì)中特別注意了保證設(shè)計(jì)各個(gè)方面（技術(shù)和美學(xué)方面）的協(xié)調(diào)一致，從而達(dá)到了預(yù)期的效果（即修建一棟既美觀又實(shí)用的低能耗建筑）。

該建筑是一棟教學(xué)樓，有4間可容納100人的教室演講室，一層用作研討室/教室，兩層用作單人辦公室和員工配套服務(wù)設(shè)施，其中包括餐飲設(shè)施和商用廚房。由于整個(gè)大學(xué)都可以集中預(yù)定這些教學(xué)設(shè)施，所以所有這些教學(xué)設(shè)施的使用率會(huì)很高。傳統(tǒng)設(shè)計(jì)分析會(huì)建議此類(lèi)大樓大量采用冷風(fēng)系統(tǒng)，即使英國(guó)的氣候比較溫和；但學(xué)校堅(jiān)持認(rèn)為不應(yīng)向?qū)W生用樓配備任何空調(diào)設(shè)備。根據(jù)這一情況，我們充分利用我們的建筑物理學(xué)知識(shí)，從而在遵循無(wú)空調(diào)成本這一準(zhǔn)則的同時(shí)修建一棟舒適且能耗低的大樓。值得高興的是，我們成功了（圖2、3）。

2 住戶滿意度調(diào)查結(jié)果——住戶對(duì)大廈的健康、管理和控制策略均表示滿意/Results from the occupant satisfaction survey: Occupant satisfaction with the building’s health, management and control strategies

3 住戶滿意度調(diào)查結(jié)果——伊麗莎白教學(xué)樓建筑的舒適條件，總體滿意/Results from the occupant satisfaction survey: Overall satisfaction with comfort conditions at the Elizabeth Fry Building

對(duì)于溫度控制，我們采用了現(xiàn)在氣候控制方面被廣泛應(yīng)用的建筑結(jié)構(gòu)熱塊( Building Thermal Mass)方法，利用大樓外露吸熱材料白天和夜晚的溫度變化，均衡溫度起伏。通常情況下，該方法需要拆除吊頂，使樓板中的吸熱材料充分暴露在空氣以及房間使用者的周?chē)惯@些吸熱材料在白天溫度達(dá)到峰值的時(shí)候能吸收熱量，然后在晚上房間中無(wú)人的時(shí)候使房間中的空氣流通，從而將積蓄的熱量從建筑物中排出去。這種方法效果很好，但是對(duì)于伊麗莎白教學(xué)樓而言，在整個(gè)夏天，大樓內(nèi)部正常預(yù)期積蓄的熱量過(guò)多，因此不可避免地，大樓內(nèi)的溫度還是過(guò)高。

要解決這一問(wèn)題有兩種方法：

（1）降低獲熱量

通過(guò)建筑物的具體設(shè)計(jì)降低熱負(fù)荷，首先需要了解負(fù)荷增加的原因，然后詳細(xì)研究如何以一種經(jīng)濟(jì)有效的方法降低各個(gè)影響因素。

對(duì)于伊麗莎白教學(xué)樓這樣的非居住建筑，太陽(yáng)能熱增量是一項(xiàng)主要問(wèn)題。因此與建筑師進(jìn)行合作非常重要，從而在提供適當(dāng)?shù)恼陉?yáng)的同時(shí)使玻璃裝配面積達(dá)到最優(yōu)。這種情況下，采用帶有2+1三玻中空玻璃的斯堪的納維亞風(fēng)格窗戶，其通風(fēng)良好的外層中空腔體中裝有軟百葉簾。當(dāng)時(shí)采用了這種方法，因?yàn)榭捎玫娜Ｖ锌詹ＡУ母魺岷腿照湛刂菩阅苓h(yuǎn)遠(yuǎn)優(yōu)于市場(chǎng)上可購(gòu)得的雙玻中空玻璃，并且這也是一種有效、價(jià)廉且可控性高的遮陽(yáng)方法。

其他可控的熱增量來(lái)自于建筑物的傳導(dǎo)以及空氣向質(zhì)量較差的建筑物滲入而造成的室外向室內(nèi)的熱傳遞（盡管英國(guó)的氣候較溫和，但在冬天熱傳遞仍然是個(gè)頗受關(guān)注的問(wèn)題）。我們特別注意從更高水平進(jìn)行外表隔熱（墻體導(dǎo)熱系數(shù)為0.2 W/m2K）并完全消除冷橋，這些冷橋在U值升高時(shí)會(huì)成為重大問(wèn)題。設(shè)計(jì)階段也同樣強(qiáng)調(diào)了氣密性的重要，就此我們采用了專(zhuān)家EAA的大衛(wèi)·奧利弗的意見(jiàn)。氣密性的設(shè)計(jì)目標(biāo)定為氣壓為50Pa時(shí)每小時(shí)換氣次數(shù)為1次，并且英國(guó)建筑服務(wù)研究與信息協(xié)會(huì)（BSRIA）于1994年11月首次用Fan Rover（一種氣密試驗(yàn)工具）對(duì)伊麗莎白教學(xué)樓進(jìn)行氣壓試驗(yàn)時(shí)，每小換氣次數(shù)為0.97ac/h（等于氣壓為50Pa時(shí)每平方米每小時(shí)換氣量為4.2m3，圖4）。

4 記錄在BRE/ BSRIA數(shù)據(jù)庫(kù)的伊麗莎白教學(xué)樓空氣泄漏量/The air leakage rate of the Elizabeth Fry Building plotted on the BRE/BSRIA database.

在內(nèi)部，我們盡可能延長(zhǎng)可用可控的日光，并安裝高效的照明和控制設(shè)備。由于小型電源和ICT產(chǎn)生的熱增量與建筑的使用和管理方式直接相關(guān)，因此設(shè)計(jì)組在設(shè)計(jì)階段基本沒(méi)有將這些熱增量考慮在內(nèi)。電源被設(shè)計(jì)為低速且具有占用傳感功能的裝置，以將風(fēng)扇和泵所需要的能耗降到最低。

（2）吸熱材料的散熱

除了盡可能降低熱增量，使樓板中的熱量以更有效的方式散出，從而使樓板在更長(zhǎng)的時(shí)間內(nèi)保持涼爽，能進(jìn)一步幫助降低散熱需求。對(duì)于這種情況，我們作為工程師決定采用瑞典率先使用的方法，讓新風(fēng)首先在預(yù)制樓板中循環(huán)，然后進(jìn)入房間，實(shí)現(xiàn)通風(fēng)。利用預(yù)制板上的空心孔（這種預(yù)制板最早使用時(shí)是為了減輕重量和材料含量），這些孔可用作通風(fēng)管道。通過(guò)使涼爽的新風(fēng)穿過(guò)樓板，這些空氣吸收樓板中散發(fā)的熱量然后進(jìn)入房間，此時(shí)空氣的溫度接近于室溫，空氣穿過(guò)建筑，實(shí)現(xiàn)通風(fēng)，然后被排出。

在冬季則按照完全相同的方式利用高效（>90%）熱回收裝置進(jìn)行熱傳遞，從而從排風(fēng)中回收熱量。

最后，作為建設(shè)真正意義上低能耗建筑的策略性方法的一部分，對(duì)大樓啟動(dòng)了為期兩年的建筑使用后檢測(cè)和評(píng)估項(xiàng)目。首先，由設(shè)計(jì)組向進(jìn)駐大樓的使用者開(kāi)辦講座，并將簡(jiǎn)單情況通報(bào)給大學(xué)的設(shè)備管理部。與建筑檢測(cè)承包商、控制供應(yīng)商、建筑師、屋宇裝備工程師和設(shè)備管理員舉行定期季末性能評(píng)審會(huì)議。舉行定期會(huì)議的目的在于定位并解決不會(huì)嚴(yán)重影響舒適程度但會(huì)影響能耗的一系列問(wèn)題。調(diào)整控制設(shè)定點(diǎn)并采用一種簡(jiǎn)化的控制方法直接調(diào)節(jié)樓板溫度。通過(guò)這段時(shí)間的精細(xì)調(diào)節(jié)，供暖系統(tǒng)的能耗量減少了一半。

為期兩年的項(xiàng)目結(jié)束后，進(jìn)行了建筑外部使用后研究，作為政府進(jìn)行的能耗和建筑使用者滿意度研究項(xiàng)目的一部分[1]。報(bào)告中歸納了以下情況：

“不管是用什么樣的關(guān)鍵標(biāo)準(zhǔn)進(jìn)行評(píng)判，伊麗莎白教學(xué)樓在獲得得天獨(dú)厚的環(huán)境條件方面取得的成績(jī)是顯而易見(jiàn)的。在整體舒適度、冬季和夏季空氣質(zhì)量和照明等方面，該教學(xué)樓的使用分?jǐn)?shù)在建筑使用研究（BUS）數(shù)據(jù)庫(kù)中是最高的。伊麗莎白教學(xué)樓在其他所有評(píng)判標(biāo)準(zhǔn)排名中均位列前20%。在探析研究（圖5）中，這棟教學(xué)樓是第二座夏季舒適度優(yōu)于冬季的建筑。”

伊麗莎白教學(xué)樓的經(jīng)驗(yàn)表明了兩種關(guān)鍵的策略上的可能性，現(xiàn)在，福坤的建筑設(shè)計(jì)核心方法中也考慮了這兩種可能性：

5 探析研究中顯示的CO2排放量和用電量數(shù)據(jù)/CO2emissions and electricity consumption data in PROBE Studies

·“整體建筑通風(fēng)”：此理論將過(guò)道和空氣流通空間作為回風(fēng)路徑的一部分，將壓力損失降至最低并盡可能充分利用“新風(fēng)”。

·“平衡負(fù)荷”：通過(guò)將通風(fēng)系統(tǒng)和建筑設(shè)計(jì)為一個(gè)整體系統(tǒng)的兩個(gè)組成部分，兩者一前一后和諧運(yùn)作。以伊麗莎白教學(xué)樓為例，利用通風(fēng)良好的樓板作為散熱器和吸熱器，這樣我們可以充分平衡負(fù)荷，從而完全成功地?cái)[脫對(duì)分布式供暖系統(tǒng)的需求。此方法已被廣泛利用在德國(guó)的“被動(dòng)房屋”運(yùn)動(dòng)，盡管有伊麗莎白教學(xué)樓這一先例，建筑沒(méi)有分布式供暖系統(tǒng)的建筑這種想法在英國(guó)仍然普遍被認(rèn)為是不可能的（圖6）。

6 通風(fēng)結(jié)構(gòu)水泥板系統(tǒng)/TermoDeck slab

將表面積很大的房頂用作供暖和散熱表面，與有限的供暖需求正確結(jié)合，這意味著外部溫度為-4℃時(shí)，樓板的溫度只需要達(dá)到23℃（最高）。相反，在夏季，樓板溫度只要達(dá)到19-20℃就能營(yíng)造出有效舒適的涼爽環(huán)境。因?yàn)椋鼰岵牧蠈?duì)溫度變化所作的反應(yīng)緩慢，這有助于為房間使用者提供一個(gè)更加舒適的環(huán)境。例如在冬季，如果樓板溫度為21℃，而此時(shí)門(mén)大開(kāi)使冷空氣進(jìn)入房間，那么樓板像一個(gè)散熱器一樣，使室內(nèi)的溫度逐漸回升——必要時(shí)將通過(guò)排風(fēng)的熱傳遞作用使室內(nèi)溫度回到原來(lái)的溫度。同樣，如果突然有許多人涌入房間，樓板會(huì)幫助吸收熱量，使房間溫度達(dá)到?jīng)鏊某潭取＝ㄖ蔀橛行У木彌_器，也可叫做調(diào)節(jié)器，而其結(jié)構(gòu)便是通風(fēng)系統(tǒng)。但是，為了使建筑的這種作用得到適當(dāng)發(fā)揮，建筑設(shè)計(jì)中需要按樓板的這種運(yùn)作方式設(shè)計(jì)樓板。設(shè)計(jì)組中的所有成員需要從最初階段就開(kāi)始密切合作，建筑和工程設(shè)計(jì)顧問(wèn)尤其應(yīng)當(dāng)如此。建筑設(shè)計(jì)需要與工程設(shè)計(jì)攜手合作，了解建筑物理知識(shí)，這樣建筑的各個(gè)部分都能作為單個(gè)協(xié)調(diào)系統(tǒng)運(yùn)作。如果方法得當(dāng)，那我們就有可能建成一座不僅外型美觀而且功能實(shí)用的建筑。

1.2布萊頓圖書(shū)館

10年后我們攜手班尼特建筑事務(wù)所共同設(shè)計(jì)了布萊頓圖書(shū)館（圖7、8）。自始至終，該項(xiàng)目的設(shè)計(jì)宗旨就是向所有持懷疑態(tài)度的人們展示：即使PFI[2]（私人融資計(jì)劃）的合約條件無(wú)比苛刻，我們依然可以交付美觀、可持續(xù)、低能耗的建筑設(shè)計(jì)作品。

布萊頓圖書(shū)館最初的原理得益于伊麗莎白教學(xué)樓，并采用了上文中曾提到的如下概念：大樓的整體通風(fēng)；得與失的平衡。

此外還運(yùn)用了一項(xiàng)新概念。通過(guò)這一概念，基本上將流通空間的通風(fēng)范圍進(jìn)一步延伸，并納入了“可控邊界”這一特點(diǎn)，即：在這一區(qū)域僅主動(dòng)控制靠近外側(cè)的條形狹長(zhǎng)地帶。

在布萊頓圖書(shū)館頭3層的三面布置辦公區(qū)域，第4層為全玻璃幕墻，面向城市廣場(chǎng)。建筑物的平面呈矩形，主要兩層的中央?yún)^(qū)域用作圖書(shū)館，面積約為5 000m2。

在我們的方案中，三側(cè)均采用了溫控且通風(fēng)良好的預(yù)制板結(jié)構(gòu)，這類(lèi)似于伊麗莎白教學(xué)樓的理念，但在這一項(xiàng)目中，可通風(fēng)板變?yōu)榱酥醒雸D書(shū)館區(qū)域的巨型置換通風(fēng)系統(tǒng)。在整個(gè)中央空間，這是唯一的環(huán)控措施。

為確保這一措施的有效性，將夾層地面設(shè)計(jì)施工為搭建于混凝土熱質(zhì)巨柱之上的超大混凝土臺(tái)，邊緣處用玻璃鋪設(shè)，除穿過(guò)數(shù)段橋狀邊緣外，未延伸至周?chē)鷧^(qū)域。混凝土臺(tái)在其平面圖中呈現(xiàn)為可穿透型，可使空氣和光線在其四周流動(dòng)。

7 英國(guó)布萊頓圖書(shū)館/The Jubilee Library in Brighton, UK

8 圖書(shū)館由3個(gè)樓層的辦公室、閱讀區(qū)及計(jì)算機(jī)房組成，圍繞著2層圖書(shū)館大廳/The Library is composed of three floors of office accommodation, reading areas and computer rooms, all surrounding the two-storey library hall.

利用大樓本身作為空氣流通的一部分的想法，不僅滿足了舒適度，還盡可能降低了風(fēng)扇的能耗。因此，冬季的回風(fēng)通道來(lái)自南面上部，面向玻璃幕墻，以獲取多余的太陽(yáng)能，然后傳至上面的屋頂。整個(gè)屋頂像一間機(jī)房，回風(fēng)集氣室內(nèi)有高效熱回收氣體處置裝置，將空氣輸入可通風(fēng)板。

夏季時(shí)，空氣在高空直接通風(fēng)，經(jīng)“通風(fēng)管道”排出。采用“通風(fēng)管道”設(shè)計(jì)的另一目的是將日光充分引入大樓內(nèi)部。屋頂照明可以遠(yuǎn)程控制，讓涼風(fēng)進(jìn)入，作為綜合模式通風(fēng)手段的組成部分。天窗由送風(fēng)機(jī)驅(qū)動(dòng)，確保空氣流通與預(yù)計(jì)的一致。這一功能在夜間顯得尤為重要。當(dāng)外界溫度較低時(shí)，空氣下沉，通過(guò)打開(kāi)的采光天窗進(jìn)入大樓內(nèi)部，然后經(jīng)強(qiáng)制送風(fēng)通風(fēng)，經(jīng)過(guò)熱質(zhì)超大“混凝土臺(tái)”，降低該結(jié)構(gòu)的溫度，最后經(jīng)中央“管道”排出。

在設(shè)計(jì)中既考慮建筑又融入環(huán)境工程，這一綜合方式的運(yùn)用使得如今的設(shè)計(jì)與1998年時(shí)的設(shè)計(jì)迥然不同。為了解并預(yù)測(cè)超大“不可調(diào)”空間的性能，廣泛運(yùn)用了計(jì)算流體動(dòng)力學(xué)（CFD），而10年前根本不具備這一方法。將這一方法與采光模擬軟件的進(jìn)展相結(jié)合，可以創(chuàng)造令人驚嘆的空間，而同時(shí)需要的主動(dòng)樓宇設(shè)備很少，因而用于控制這些設(shè)備的能耗也相應(yīng)減少。原本被動(dòng)的建筑物和建筑形式開(kāi)始在環(huán)控中發(fā)揮重要的作用。這一引領(lǐng)工程和建筑設(shè)計(jì)公司的進(jìn)程將在未來(lái)取得更大的發(fā)展。

布萊頓圖書(shū)館深得用戶好評(píng)，并榮獲了“英國(guó)首相最佳公共建筑獎(jiǎng)”以及“PFI年度建筑獎(jiǎng)”等諸多獎(jiǎng)項(xiàng)。同伊麗莎白教學(xué)樓一樣，布萊頓圖書(shū)館贏得大量關(guān)注，口碑效應(yīng)明顯，在全球吸引了眾多專(zhuān)程前來(lái)參觀的人流。設(shè)計(jì)團(tuán)體的共同努力足以令客戶留下深刻的印象。

布萊頓圖書(shū)館和伊麗莎白教學(xué)樓均為低能耗建筑。兩座建筑開(kāi)發(fā)時(shí)正值對(duì)于怎樣交付低能耗建筑尚未有太多約束之時(shí)。一方面，這意味著我們?cè)趧?chuàng)新設(shè)計(jì)上擁有更大自由度；另一方面，我們的設(shè)計(jì)既需要顧及商業(yè)上的可行度又要保證設(shè)計(jì)的長(zhǎng)遠(yuǎn)價(jià)值。福坤已將這些創(chuàng)意納入主要設(shè)計(jì)流程，并在過(guò)去幾年中成功地將其整體或部分加以運(yùn)用。實(shí)際上，這兩座大樓自建成以來(lái)，其開(kāi)創(chuàng)性、創(chuàng)新但擁有獨(dú)立監(jiān)測(cè)機(jī)制已影響了英國(guó)國(guó)內(nèi)《建筑規(guī)范》的演變，其所倡導(dǎo)的建筑要求在很大程度上正通過(guò)立法成為《建筑規(guī)范》。

2. 新政策驅(qū)動(dòng)

到了今天，世界發(fā)生了很大的改變。世界各國(guó)意識(shí)到了氣候變化，各國(guó)政府一直在尋找最好的對(duì)策。建筑環(huán)境對(duì)地球具有最明顯的直接影響。在發(fā)達(dá)國(guó)家，建筑環(huán)境更是我們多數(shù)人生活的地方，對(duì)我們的精神和身體健康產(chǎn)生重大的影響。我們的能源產(chǎn)生多達(dá)50%的溫室氣體（GHG）。出于這些原因，建筑環(huán)境的干預(yù)措施紛紛出臺(tái)。

在英國(guó)，《建筑規(guī)范》第L部分(主要講及燃料和能源保存) 在2006年進(jìn)行了調(diào)整，建筑物的預(yù)計(jì)CO2排放量和CO2目標(biāo)排放率（TER）的計(jì)算被納入為關(guān)鍵指標(biāo)之一。重大政策的驅(qū)動(dòng)才剛剛開(kāi)始，目標(biāo)是設(shè)法通過(guò)建筑環(huán)境實(shí)現(xiàn)顯著減排。

繼《建筑規(guī)范》調(diào)整之后，住房規(guī)劃部長(zhǎng)宣布截止到2016年，英格蘭和威爾士所有建成的新房屋將要求實(shí)現(xiàn)“零碳”排放，并公布了時(shí)間表，列出了按《建筑規(guī)范》定期改進(jìn)的安排：

表1：對(duì)《建筑規(guī)范》的更改提議

除了提議如何加強(qiáng)國(guó)家責(zé)任感以降低國(guó)內(nèi)碳排放之外，政策方面也將有助于應(yīng)對(duì)燃料缺乏、物價(jià)飛漲的問(wèn)題，從而提高住房的整體質(zhì)量。非官方組織的《可持續(xù)住宅標(biāo)準(zhǔn)》（CSH）[4]的出臺(tái)，鼓勵(lì)設(shè)計(jì)團(tuán)隊(duì)考慮可持續(xù)開(kāi)發(fā)的更多元素。這一標(biāo)準(zhǔn)旨在激勵(lì)早期接管方之間的競(jìng)爭(zhēng)，力求通過(guò)提供規(guī)范化的尺度，進(jìn)行自我衡量而得以展現(xiàn)設(shè)計(jì)表現(xiàn)的提升。

3. 實(shí)現(xiàn)零碳目標(biāo)

“零碳排放”政策和《可持續(xù)住宅標(biāo)準(zhǔn)》無(wú)疑已經(jīng)引起了英國(guó)建筑業(yè)的廣泛關(guān)注（圖9）。如今，各企業(yè)如電力公司、大型住房建筑商、建筑師以及產(chǎn)品制造商等，都急于炫耀他們的“綠色”資格證書(shū)。然而，由于該定義逐漸被細(xì)化，從而出現(xiàn)了如下一些問(wèn)題：最初的定義中要求：低排碳熱源設(shè)備的采用能同時(shí)滿足一處住宅或住宅庭院范圍內(nèi)的年度總能量需求。盡管有一些早期的示范設(shè)計(jì)以及財(cái)政部的稅收優(yōu)惠政策[5]，但是，由英國(guó)綠色建筑委員會(huì)[6]進(jìn)行的研究表明，對(duì)于高達(dá)80%的潛在重建工地，即使不考慮額外的費(fèi)用，這種嚴(yán)格的要求從技術(shù)上來(lái)看可能也是不可行的。高密度城市用地中，比如缺乏屋頂空間安裝太陽(yáng)能光伏，風(fēng)力條件、湍流風(fēng)及燃燒物件對(duì)空氣的不利影響，造成許多工地將難以產(chǎn)生足夠的零碳能源滿足他們的需要。此外，英國(guó)綠色建筑委員會(huì)說(shuō)明了可以實(shí)現(xiàn)的其他利益。這些利益的實(shí)現(xiàn)途徑包括鼓勵(lì)開(kāi)發(fā)商在更廣泛的建筑環(huán)境綠化領(lǐng)域發(fā)揮更大的作用；幫助輸送更多電量，促進(jìn)與現(xiàn)有的基礎(chǔ)設(shè)施相匹配的其他基礎(chǔ)設(shè)施建設(shè)等，以此實(shí)現(xiàn)更大幅度的總體廢氣減排目標(biāo)。英國(guó)綠色建筑委員會(huì)提出了一個(gè)干預(yù)措施層次圖，該圖的結(jié)構(gòu)對(duì)設(shè)計(jì)團(tuán)隊(duì)的激勵(lì)作用促使設(shè)計(jì)團(tuán)隊(duì)在進(jìn)入下一個(gè)階段之前為前一個(gè)階段設(shè)定限制。

預(yù)留解決方案：

·碳減排超出最低標(biāo)準(zhǔn)及最高可達(dá)100%的總能耗；

·具能源效益的設(shè)備或先進(jìn)控制系統(tǒng)；

·對(duì)現(xiàn)有建筑輸出低碳零碳熱源或冷源；

·規(guī)劃規(guī)范第106條的義務(wù)；

·電子工程措施，改造現(xiàn)有的市場(chǎng)；

·在LZC能源基礎(chǔ)設(shè)施投資情況（在英國(guó)境內(nèi)和將“所有權(quán)擁有者的好處”傳遞給能源購(gòu)買(mǎi)者）；

·發(fā)展區(qū)外通過(guò)可再生能源發(fā)電的 “直接物理連接”；

·任何政府可能在未來(lái)公布符合資格的其他措施。

英國(guó)綠色建筑委員會(huì)提出的建議，得到了業(yè)界的廣泛支持。但是，政府卻沒(méi)有完全執(zhí)行這些建議。財(cái)政部發(fā)現(xiàn)，盡管基金的理念在業(yè)界甚為流行，但由于它很可能被歸類(lèi)為“稅”，而缺乏吸引力。作為一種折衷，政府提倡一部分“可能的解決方案”由私營(yíng)部門(mén)提出。然而，這項(xiàng)工作如何執(zhí)行，并且對(duì)于設(shè)計(jì)團(tuán)隊(duì)來(lái)說(shuō)意味著什么，尚不明確。

4. 2010年《建筑規(guī)范》的修改

當(dāng)我們著手進(jìn)行2010年《建筑規(guī)范》的修改時(shí)，不確定的情況加劇。這是政府的零碳計(jì)劃時(shí)間表中的第一步。

在結(jié)束了對(duì)“零碳排放”定義的討論后不久，政府立即展開(kāi)了對(duì)于計(jì)算方法更新的討論[7]，隨后，又進(jìn)一步展開(kāi)了對(duì)《建筑規(guī)范》修訂的討論[8]。業(yè)界此前預(yù)計(jì)相比2006年的標(biāo)準(zhǔn)將會(huì)有25%的提高。然而，當(dāng)針對(duì)第L部分的《2010年建議書(shū)》[9]的細(xì)節(jié)內(nèi)容在2009年6月公布時(shí)，似乎再次說(shuō)明早期采用者的努力都是徒勞的。咨詢文件中的建議書(shū)中說(shuō)明了若干重大變化，這意味著下一步新計(jì)劃取得的結(jié)果，并不能與2006年版相比，即整個(gè)2016年的時(shí)間表現(xiàn)在需要審查，以期是2010年的基準(zhǔn)。此外，由于已經(jīng)開(kāi)始了關(guān)于“零碳排放”定義的討論，這意味著，對(duì)此定義討論做出回應(yīng)的業(yè)內(nèi)人士未能給出相關(guān)的觀點(diǎn)。

關(guān)于擬定的2010年標(biāo)準(zhǔn)的討論于2009年9月結(jié)束。但是，到2009年底仍然沒(méi)有就新的規(guī)范生效時(shí)的要求給出進(jìn)一步的說(shuō)法[10]。

5. 對(duì)政策的回應(yīng)

作為可持續(xù)發(fā)展領(lǐng)域的先行者，人們可能預(yù)期福坤咨詢公司在響應(yīng)政府針對(duì)“零碳排放”建筑采取的促進(jìn)措施時(shí)能有較大的優(yōu)勢(shì)。然而，在某種程度上，政府推動(dòng)“零碳排放”的積極性在許多方面都是一把雙刃劍。一方面，可持續(xù)發(fā)展不再被視為一個(gè)小眾領(lǐng)域。主流開(kāi)發(fā)商和客戶都在尋求專(zhuān)業(yè)意見(jiàn)，而以前只有極有遠(yuǎn)見(jiàn)的客戶，或那些對(duì)于特定的法律做出回應(yīng)的相關(guān)方才會(huì)就專(zhuān)業(yè)建筑物理或可持續(xù)發(fā)展征詢意見(jiàn)。但是反過(guò)來(lái)，我們現(xiàn)在卻受到政策細(xì)節(jié)的約束，而客戶的注意力也往往（可以理解地）幾乎完全集中在對(duì)于規(guī)范的要求上，而不是良好的工程解決方案的構(gòu)成上，這可能導(dǎo)致一些有害的結(jié)果。此外，政府執(zhí)行的政策的規(guī)范性以及不斷修改定義造成的混亂使我們更難向客戶提出決定性的答案。更有甚者，這么多的混亂使設(shè)計(jì)隊(duì)伍更難在公平的環(huán)境下競(jìng)爭(zhēng)，獲得真正被認(rèn)同的創(chuàng)新。具有諷刺意味的是，一個(gè)旨在促進(jìn)和鼓勵(lì)企業(yè)創(chuàng)新并推動(dòng)可持續(xù)設(shè)計(jì)界限的政策，實(shí)際上已經(jīng)成為創(chuàng)新的障礙。這個(gè)被我們稱(chēng)之為“政策悖論”。

9 零碳層次的允許解決方案/Zero carbon hierarchy-allowable solutions

6. 公共和私營(yíng)部門(mén)的推動(dòng)作用

英國(guó)的經(jīng)驗(yàn)不可避免地提出了這樣的疑問(wèn)：多少推動(dòng)力應(yīng)來(lái)自政府，而多少推動(dòng)力應(yīng)來(lái)自私營(yíng)部門(mén)。政府的干預(yù)是至關(guān)重要的，這種干預(yù)可以確保行業(yè)的參與，并且能創(chuàng)造規(guī)模經(jīng)濟(jì)并為投資者帶來(lái)確定性，有助于將可持續(xù)性從小眾市場(chǎng)推向大規(guī)模的市場(chǎng)。對(duì)于建筑行業(yè)這樣如此龐大而復(fù)雜且產(chǎn)品生命周期在數(shù)十年才能計(jì)量的行業(yè)，如果政府沒(méi)有適當(dāng)?shù)牧⒎ǎㄖ袠I(yè)不太可能以需要的速度去應(yīng)對(duì)并且適應(yīng)，以避免最壞的氣候變化。然而，英國(guó)的建筑環(huán)境已成為一個(gè)政治上的棋子，最終影響發(fā)展活力的技術(shù)決策的制定并沒(méi)有充分的證據(jù)或?qū)?wèn)題充分的理解。這一行業(yè)已經(jīng)被一系列的討論淹沒(méi)了，往往在無(wú)益的秩序下發(fā)布。在某些情況下，即使一個(gè)想法（如基金）得到了業(yè)內(nèi)廣泛的支持，出于政治考慮，政府也選擇了拒絕。在最壞的情況，我們正在破壞我們自己的努力應(yīng)對(duì)氣候變化帶來(lái)的挑戰(zhàn)。事實(shí)上，當(dāng)我們?cè)谥謱?shí)現(xiàn)“零碳排放”軌道的第一步時(shí)[11]，反而比以往任何時(shí)候都更加不確定；隨著英國(guó)國(guó)家經(jīng)濟(jì)的衰退，以及我們的政治家們都在為換屆選舉以及政府的更迭做準(zhǔn)備，目前仍不清楚該行業(yè)何時(shí)能夠做出所需的投資以便成功地實(shí)現(xiàn)“零碳排放”。

總之，值得稱(chēng)贊的是，英國(guó)政府制定了大膽且雄心勃勃的目標(biāo)，并且顯示出應(yīng)對(duì)緊迫問(wèn)題的眼界。然而，政策中的技術(shù)細(xì)節(jié)問(wèn)題，應(yīng)該由技術(shù)專(zhuān)家基于嚴(yán)謹(jǐn)?shù)难芯拷Y(jié)果做出決定。

7. 學(xué)習(xí)英國(guó)的經(jīng)驗(yàn)

世界上的其他國(guó)家可以參考英國(guó)的模式，因?yàn)樗堑谝慌歼@樣一種根本性政策動(dòng)向的國(guó)家之一。但是所有盼望進(jìn)一步發(fā)展的國(guó)家，必須仔細(xì)考慮如何才能做到可持續(xù)的發(fā)展。相對(duì)于政府而言，行業(yè)尤其需要意識(shí)到，建立一個(gè)行業(yè)帶頭的驅(qū)動(dòng)機(jī)制所能帶來(lái)的機(jī)會(huì)和利益，而不要被動(dòng)地等待政府立法。大多數(shù)國(guó)家的政府都希望能夠做出決定性的政策，如果他們還在等待研究或測(cè)試結(jié)果，通常可以假定，那就是政府承認(rèn)不知道該怎么做。在其他行業(yè)，這樣的結(jié)果已導(dǎo)致私營(yíng)部門(mén)占據(jù)了領(lǐng)導(dǎo)地位，他們把在最佳實(shí)踐的基礎(chǔ)上建立起來(lái)的現(xiàn)成政策提供給政府，用于向政府表明行業(yè)會(huì)承擔(dān)相應(yīng)的那部分責(zé)任。然而，在對(duì)最終產(chǎn)品性能的理解上，建筑行業(yè)往往落后于其他行業(yè)，加上復(fù)雜而分散的價(jià)值鏈，協(xié)調(diào)建筑行業(yè)的領(lǐng)導(dǎo)地位可能是很困難的。但是，允許好的意圖被不同的既得利益者牽制，仍然是可取的。

8. 展望未來(lái)

建筑環(huán)境是人類(lèi)對(duì)這個(gè)星球所施加的最直接、最明顯的影響。但是建筑環(huán)境不僅僅涉及建筑行業(yè)，還包括戰(zhàn)略上基礎(chǔ)設(shè)施的部署，尤其是能源的產(chǎn)生、分配以及供應(yīng)。從英國(guó)的經(jīng)驗(yàn)中我們得知，打破傳統(tǒng)行業(yè)間或政府部門(mén)間的界限，需要一個(gè)真正統(tǒng)籌綜合的方法。這樣的需求不僅僅是因?yàn)樗兄诮鉀Q我們所面臨的挑戰(zhàn)，還因?yàn)樗兄谝缘统杀尽⒏咝б娴亟鉀Q問(wèn)題。

通常，要影響一個(gè)觀念，在它形成的時(shí)候比較容易，而不是在它形成之后。雖然要行業(yè)方面具有長(zhǎng)遠(yuǎn)的觀點(diǎn)往往很困難，但英國(guó)的經(jīng)驗(yàn)說(shuō)明：現(xiàn)時(shí)無(wú)視這些問(wèn)題，等到計(jì)劃不周的政策已經(jīng)獲得了政界以及公眾的支持后再試圖去糾正它，必然導(dǎo)致未來(lái)增加大量的補(bǔ)救工作。相反的，開(kāi)展先發(fā)制人的研究和創(chuàng)新會(huì)使設(shè)計(jì)公司在相關(guān)法律付諸實(shí)施的時(shí)候從容應(yīng)對(duì)，不管是直接應(yīng)對(duì)政府的政策，還是應(yīng)對(duì)需要了解本政策的客戶，或者是為本公司做出業(yè)務(wù)決策。

我們先前（本政策在英國(guó)實(shí)行之前）的經(jīng)驗(yàn)說(shuō)明，低能耗的建筑是一個(gè)很有吸引力的商機(jī)，值得關(guān)注和開(kāi)創(chuàng)。此外，從長(zhǎng)遠(yuǎn)來(lái)看，它在能源安全和應(yīng)對(duì)社會(huì)事務(wù)方面還會(huì)帶來(lái)很多額外的好處，那些有遠(yuǎn)見(jiàn)、現(xiàn)在就思索行動(dòng)的人，一定能借此創(chuàng)造一個(gè)美好的未來(lái)。□

10英國(guó)首次使用 ATES (季節(jié)性能源儲(chǔ)存) 的Westway Beacons，為廉價(jià)住房開(kāi)發(fā)上提供質(zhì)量和可持續(xù)性新的基準(zhǔn)/Westway Beacons- First UK application of ATES (Aquifer Thermal Energy Storage),setting new benchmarks in quality and sustainability for affordable housing developments

注釋?zhuān)?/p>

[1] www.useablebuildings.com

[2] PFI是一種采購(gòu)模式。在這種模式下，公用建筑物的設(shè)計(jì)和施工是以招標(biāo)的形式委托給私營(yíng)承包商，并同時(shí)簽署一份為期25年的運(yùn)營(yíng)合約。這一籌資機(jī)制要求進(jìn)行“盡職調(diào)查”。同時(shí)，設(shè)計(jì)的穩(wěn)健性也必須能令同行的設(shè)計(jì)團(tuán)隊(duì)所折服。

[3] 1年內(nèi)房屋所有能耗產(chǎn)生的碳凈排放量將為零。

[4] http://www.communities.gov.uk/planningandbuilding/buildingregulations/legislation/codesustainable/

[5] 印花稅、土地稅減免

[6] 英國(guó)綠色建筑委員會(huì)（GBC）“零碳工程”定義。

[7] http://www.bre.co.uk/sap2009/page.jsp?id=1642

[8] http://www.communities.gov.uk/publications/planningandbuilding/partlf2010consultation

[9] 《建筑物規(guī)范》的第L部分討論了節(jié)約燃料和電力。

[10] 原定于2010年4月生效，但是現(xiàn)已延遲。預(yù)計(jì)將于2010年10月生效。

[11] 時(shí)間表

Whilst every country is unique in terms of its climate, culture and economy, the global drive to reduce carbon emissions has, in the UK, led to some particular policy decisions which should provide interesting lessons for other countries around the world. Being aware of the UK experience should help policy-makers, architects, engineers and clients in other countries respond more effectively to the challenges of transitioning to sustainable development.

Fulcrum Consulting has been helping design teams deliver low-energy buildings through integrated environmental engineering design for more than 25 years. In that period we have helped deliver many examples, several of which stand out as seminal steps.This paper looks back at these key examples, examines more recent work, and discusses the impact of recent Government policy interventions pushing the industry to deliver “zero carbon” buildings as standard within the next 10 years.

1. Low energy design and the impact of the push for“zero carbon”new buildings in the UK

Two significant innovative buildings:-

1.1 Elizabeth Fry Building (Fig.1)

The Elizabeth Fry Building at the University of East Anglia (UEA) was the last of a series of low energy buildings that were constructed to our engineering designs at the UEA during the last recession in the 1990’s. The client was a modern campus university with a plan to expand in order to cope with a significant increase in student numbers driven by public policy.

The UEA were able to view the buildings as a longterm investment and, as a result, were interested in taking a“whole life cycle”approach to analysing options for development. When viewed in this way,low energy buildings show a clear benefit.

Initially two low energy blocks of student accommodation were completed with Rick Mather Architects; these worked well, delivering reduced running costs and significant free publicity for the university. This successfully demonstrated that the technological challenges of building to very high standards were novel, but achievable. Furthermore,that it could be done without increased cost, and by mainstream builders who had not previously been required to deliver this in their contracts provided that they were given detailed design guidance and knowledgeable on site supervision. As a result the university adopted a low energy design policy for all future buildings which endures to this day and has even been expanded to include retrofitting earlier buildings in order to make them more energy efficient.

The Elizabeth Fry Building sought to take the implementation of this policy to a new level, delivering an icon of low energy design. The building is not particularly large (3 500m2), and although the design highly innovative, it actually relies on relatively simple principles, making it very robust. The architectural design was undertaken by John Miller and Partners,but care was taken to ensure all aspects of the design(technical and aesthetic) worked in harmony to deliver the intended outcomes (namely an attractive, useful,low energy building).

The building is a teaching building containing four 100 seat capacity lecture theatres, a floor of seminar / teaching rooms and two floors of individual office and staff support services including a dining facility and commercial kitchen. All the teaching accommodation was anticipated to be heavily used as it was centrally bookable by the whole university.Traditional design analysis would suggest large amounts of cooling was required for such a building,even in the temperate UK climate; but the university was adamant that it should not provide air conditioning for student buildings. Responding to this brief required us to push the limits of our building physics knowledge in order to deliver a comfortable building within non-AC cost guidelines that was also low energy. Happily it worked (Fig.2,3).

For temperature control we followed the now widely understood approach in climates which exhibit day to night temperature variability of exposing the thermal mass of the building to even out fluctuations.Typically this involves omitting false ceilings to allow the thermal mass of the slab to be fully exposed to the air and occupants within the space so it can absorb heat during daytime peaks then ventilating the space during the night in unoccupied hours to remove the stored heat from the building. This approach works well but, in the case of Elizabeth Fry, the normal predicted internal gains were too high to prevent overheating entirely in summer.

There were two approaches to solving this:

⑴Reduce thermal gains

Reducing the thermal loads through detailed design of the building fabric involves understanding what contributes to them, then looking in detail to see how to reduce each contributing factor in a robust and cost-effective way.

For non-domestic buildings such as Elizabeth Fry,solar gain is a major issue. It was therefore important to work with the architect in order to optimise the glazing area while providing suitable shading, in this case by specifying 2+1 triple-glazed Scandinavian windows which include a venetian blind in the ventilated outer cavity. This approach was taken at the time, because the insulating and solar control properties of triple-glazed were far superior to the commercially available double-glazed units that were available and it’s a robust, cheap and highly controllable way of providing shading.

The other controllable gains are caused by heat transferred from outside due to conduction through the fabric and air infiltration through poorly constructed fabric (although in the UK climate this is usually more of a concern in winter). Extreme care was taken to insulate externally to a high level (0.2 W/m2K for walls)and completely eliminate cold bridges which become a significant issue as U values improve. Air tightness was addressed with equal thoroughness at design stage and a specialist air tightness consultant (David Olivier of EAA) was employed. A design target of 1 air change per hour at 50Pa was imposed and when the Elizabeth Fry Building was initially pressure tested by the BSRIA Fan Rover in December 1994 it achieved 0.97ac/h(equivalent to 4.2m3/h/m2@ 50Pa, Fig.4).

Internally we maximised useful and controllable daylight and installed high efficiency lighting and controls. The heat gains from the small power and ICT were mostly outside of the design team’s control at design stage as they relate directly to the way the building is used and managed. Plant was designed with low velocities and occupancy sensing to minimise energy need for fans and pumps.

⑵Removing heat from the thermal mass:

In addition to reducing the heat gains where possible, removing heat more effectively from the slab so that it was able to be cooler for longer would further help reduce the cooling demand. In this case as engineers we proposed to use an approach first explored in Sweden, circulating fresh air through the precast floor slab to directly control the slab temperature before discharging it into the room to provide ventilation. Taking advantage of hollow cores in a precast unit, originally introduced in order to minimise weight and material content, the cores are used as ventilation ducts. By passing the air through the slab the cool supply-air absorbs heat from the slab and enters the room at close to ambient temperature,passing through the building to ventilate it before being exhausted to outside.

In winter heating is delivered in exactly the same way using a highly efficient (>90%) heat recovery unit to recover heat from the exhaust air.

Finally, as part of the strategic approach to delivering a genuinely low energy building, a 2 year post-occupancy monitoring and evaluation program was instigated. This began with a lecture by the design team to the incoming users and briefing of the university’s Facilities Management department.Regular end-of-season performance review meetings were held with the building monitoring contractor,control suppliers, Architects, Building Services Engineers and Facilities Managers. The meetings were used to track and solve a number of issues which did not significantly affect comfort levels but did impact on the energy use. Control set points were adjusted and a simplified control approach introduced to moderate the slab temperature directly; over this period of fine-tuning the heating energy-use was halved.

At the end of the 2 year period an external postoccupancy study was carried out as part of a Government program which looked both at energy use and occupant satisfaction[1]. The report summarised conditions thus:

“Elizabeth Fry stands out in achieving exceptional conditions across a wide variety of key criteria. On overall comfort, winter and summer air quality and lighting, the occupancy scores are the highest in the Building Use Studies (BUS) dataset. In all other criteria Elizabeth Fry comes in the top 20%. It is only the second building in the PROBE studies (Fig.5) to achieve better overall comfort in summer than winter”.

This experience of Elizabeth Fry identified two key strategic possibilities which become a core approach to building design:

“Whole building ventilation”－this philosophy uses the corridors and circulation spaces as part of the return air path to minimise pressure losses and maximise use of“fresh”air.

“Balance gains and losses”－by designing both the systems and building as two parts of a single system, working in tandem. Using a ventilated slab as the heat emitter and absorber in the case of Elizabeth Fry allowed sufficient load balance to remove the need for a distributed heating system completely and successfully. This approach has since been widely demonstrated in the PassivHaus approach developed in Germany. Despite this, and the example of Elizabeth Fry, the idea of such buildings operating without a distributed heating system is widely considered impossible in the UK (Fig.6).

Using the very large surface area of the ceiling as a heating and cooling surface, correctly combined with a restricted heating demand, means that the temperature of the slab need only be 23℃ (maximum)when the external temperature is -4℃. Conversely, in summer, slab temperatures of just 19-20℃ can provide effective comfort cooling. Because the thermal mass responds slowly to temperature change it helps to provide a more comfortable environment for occupants.For example, in winter if the slab is at 21℃ and a opened door allows a rush of cold air, the slab will act as a heat emitter and help to bring the temperature back up－topped-up if necessary by heat transferred from the exhaust air. Equally, if there was a sudden influx of people in the room, the slab would help to absorb the heat, providing cooling. The building fabric effectively becomes a buffer, or moderator, and the structure is the ventilation system. However, in order for this to work properly the building design needs to allow for the slab to work in this way. All actors in the design team need to work in close collaboration from the earliest possible stage, particularly the architectural and engineering consultants. Architecture needs to work hand-in-hand with engineering design,informed by building physics, so that every part of the buildings works as part of a single coherent system. If done properly it is possible to create a building that is beautiful both in form and function.

1.2 Brighton Library:

A decade later we designed Brighton Library (Fig.7,8) with Bennetts Associates Architects. From day one the intention of the design was to show to a sceptical world that beauty and sustainable, low energy building design could be delivered in the harshest of contractual environments － The Private Finance Initiative (PFI)[2].

Brighton Library was based on the philosophy derived from the Elizabeth Fry building and utilised the previously described concepts of :

·Whole building ventilation

·Balanced gains and Losses

As well as introducing a“Controlled Edge”. A new concept which essentially stretches the original idea of circulation space ventilation, in that only a narrow strip near the outside of the building is actively controlled.

In Brighton Library, three sides are occupied office areas over three stories, and the fourth is a fully glazed facade fronting an urban square. The building is rectangular in plan and the main two storey central area of around 5000m2creates the Library space.

The engineering approach was to utilise ventilated precast slab construction on three sides, similar to the Elizabeth Fry concept, but in this case the ventilated slab becomes a massive displacement ventilation system for the central library zone. This is the only environmental control in the entire central space.

To ensure this works the Mezzanine floor is designed and constructed as a huge concrete table on thermally massive concrete columns and the space is designed so that air flows around the structure. The thermal control is again the exposed thermal mass of the concrete isolated from the external environment by the“Controlled Edge”.

To take the idea of utilising the building as part of the air circulation both for comfort and to minimise fan energy the return air path in winter is from above the south facing glazed facade, picking up surplus solar gain. The whole roof above is a plant room and return air plenum containing high efficiency heat recovery air handling plant which delivers air to the ventilated slabs.

In Summer the air is ventilated directly out at high level through“ventilation chimneys”which are also designed to bring light into the depth of the building. The roof lights are remotely controlled and allow cool air to enter as part of a mixed mode ventilation approach, driven by supply fans to ensure air circulation is predictable. This is particularly important at night when the external air is cooler and falls as a result as it enters through the open rooflights before being circulated by the forced supply, past the thermally massive“concrete table”, cooling the structure before exhausting out of the central“chimneys”.

The ability to design both the architecture and the environmental engineering in this integrated manner is the major difference between now and 1998. In order to understand and predict the performance of the huge“unregulated”space,extensive use was made of Computational Fluid Dynamics (CFD) which was simply not available in the previous decade. This, combined with advances in daylighting simulation software, allowed the creation of spaces that look and feel amazing whilst requiring little active building services, and as such, little energy,to control them. The passive building fabric and form have begun to take on a significant part of the environmental control. This is a process that leading engineering and architectural design companies will take much further in the future.

The building has been a great success with its users and has won many awards including “Prime Minister’s Best Building”and the“PFI Building of the Year”As with the Elizabeth Fry building, there has been a great deal of interest in the building,generating large amounts of free publicity and a continuous stream of visitors from around the world coming specifically to see the buildings. This external interest is a by product of the design teams efforts in integration is a beneficial by product for clients that take innovation to heart.

Brighton Library and Elizabeth Fry are both low energy buildings developed at a time when there was no great prescription about what exactly should be done to deliver low energy-use. While this meant that we had greater freedom to innovate, our design still had to be commercially viable, and we had to be able to prove the long-term value.. The result was innovation and as engineers we have taken these innovations into our mainstream design process and have used them successfully over the years together or in part. Indeed the groundbreaking nature of the innovative approach integrated with independent monitoring has since influenced the evolution of the Building Regulations in this country and much of the fabric requirements championed in them are now legislated for in Building Regulations. Furthermore,the buildings’ in-use performance is similar to or better than many buildings constructed to current Building Regulations, in the case of the Elizabeth Fry,nearly 20 years later.

2. A New Policy Drive

Jumping forward to today, the world is very different. As the world has woken up to the threat posed by climate change, Governments around the world have been trying to decide on the best approach.The Built Environment is the most immediately obvious impact we have on our planet. For people in developed countries, it is also where we spend the vast majority of our lives and therefore it has a significant impact on our mental and physical health. It is also where we use a large amount of the energy we generate resulting in up to 50% of our Greenhouse Gas (GHG). For these reason, the built environment has been an attractive place to make interventions.

In the UK the Part L of the Building Regulations(which deals with the conservation of fuel and power)was restructured in 2006 to include a calculation of a Target CO2Emissions Rate (TER) as one of the critical criteria. This was the beginning of a significant policy drive seeking to achieve significant emissions reductions via the built environment.

Following the restructuring of the Building Regulations, the Minister for Housing and Planning announced that by 2016, all new homes built in England and Wales would need to be ‘zero carbon’. A timeline was announced outlining periodic updates to the Building Regulations:

Table 1: Proposed changes to Building Regulations,taken from“Building a greener future: policy statement”

Date Carbon Improvement as compared to 2006 2010 25%2013 44%2016 True zero carbon[3]

As well as addressing our nation’s responsibility to reduce its national carbon emissions, it was said that the policy would help to address concerns about fuel poverty and rising prices and result in an overall better quality of housing. A voluntary“Code for Sustainable Homes”[4](CSH) was introduced to encourage design teams to consider wider elements of sustainable development. The Code was intended to incentivise competition among early adopters, eager to be able to demonstrate the increased performance of their designs by providing a standardised scale against which they can measure themselves.

3. Achieving Zero Carbon

The“Zero Carbon”policy and Code for Sustainable Homes have definitely captured the collective imagination of the UK construction industry and now businesses regularly rush to flaunt their “green” credentials; from power companies and volume housebuilders to signature architects and product manufacturers. However, as details of the definition have emerged, some problems have arisen. The original definition required that the total annual energy demand of a dwelling be met by microgeneration equipment on or within the curtilage of the dwelling. Despite some early demonstration designs,and tax incentives from the Treasury[5], research by the UK Green Building Council[6](UK-GBC) suggested that such a strict requirement could be technically unfeasible,regardless of additional cost, for anything up to 80% of potential new-build sites. High-density urban sites in particular proved problematic, as a lack of roof-space for PV or Solar Thermal, turbulent wind conditions and concerns about adverse impacts on air quality from burning biomass meant that many sites would struggle to generate enough zero carbon energy to meet their needs.Furthermore, the UK-GBC identified additional benefits that could be realised by encouraging developers to play a greater role in the greening of the wider built environment; helping to deliver much of the generating capacity and facilitating infrastructure needed to engage with the existing stock in order to achieve greater overall emissions reductions. The UK-GBC proposed a hierarchy of interventions, structured so that design teams were incentivised to push the limits of each stage before progressing onto the next level:

Allowable Solutions

·Carbon compliance beyond the minimum standard upto 100% of total energy

·Energy efficient appliances or advanced controls systems

·Exporting LZC heat/cooling to existing properties

·Section 106 Planning Obligations

·Retrofitting EE measures to existing stock

·Investment in LZC energy infrastructure (within UK and with ‘benefits of ownership’ passed to purchaser)

·Off-site renewable electricity via ‘direct physical connection’

·Any other measures that Government might in future announce as being eligible

4. 2010 Changes

The uncertainty deepened as we approached the 2010 update to the Building Regulations, the first step on the Government’s zero carbon timeline.

Shortly after the consultation on the definition of“zero carbon” closed, Government began a consultation on an updated calculation methodology[7], followed by a further consultation on changes to the Building Regulations[8]. Industry had been expecting a 25%improvement over 2006 standards; however, when details of the 2010 Proposals for Part L[9]were released in June of 2009 it began to look as if, once again, the earlier adopters’efforts had been in vain. The proposals laid out in the consultation document contained a number of significant changes which meant that results obtained under the new scheme, were not comparable with the 2006 edition, meaning that the whole 2016 timeline now needed to be reviewed in order to refer to a 2010 baseline,. Furthermore, given that the consultation on the definition of“zero carbon” had already taken place, it meant that industry stakeholders responding to the consultations were not able to respond with a coherent view.

The consultation on the proposed 2010 standards closed in September 2009, but by the end of 2009, no further details had been released about what would be required when the new regulations come into force[10].

5. A company response to policy change

As a first mover in the field of sustainable development, one might expect that Fulcrum would have a considerable advantage in responding to the Government’s drive for“zero carbon”buildings.However the Government’s “zero carbon” initiative has been a bit of a double-edged sword in many ways.On the one hand, sustainability is no longer seen as a niche area and mainstream developers and clients are seeking out our advice, whereas previously only very forward-thinking clients, or those responding to a particular brief, sought out specialist building physics or sustainability advice. Conversely however, we are now constrained by the details of the policy and clients are often (understandably) focused almost entirely on the regulatory requirements, rather than what constitutes a good engineering solution, which can lead to some perverse results. Furthermore, the prescriptive nature of the policies implemented by Government and the confusion caused by the constantly changing definition make it much harder for us to give our clients definitive answers. What is more, so much confusion it makes it harder for design teams to compete fairly and receive recognition for genuine innovations. Ironically, a policy designed stimulate innovation and encourage business to push the boundaries of sustainable design, has actually become a barrier to innovation. Fulcrum have termed this“the policy paradox”.

6. Public VS. Private Push

The experience of the UK inevitably brings up the question of how much impetus should come from Government and how much should be left to the Private sector. Government intervention is crucial in order to ensure that the industry can compete on a level playing field, creating economies of scale as well as investor certainty, and helps to move sustainability from niche to mass-market. Realistically an industry as large and complex as the construction industry, with a product life-cycle measured in decades, is unlikely to be able to respond and adapt spontaneously at the pace that is necessary in order to avoid the worst of climate change without Government legislating as a driving force.However, in the UK the built environment has become a political pawn and technical decisions that will ultimate affect the viability of development are being made without sufficient evidence or understanding of the issues. Industry has been inundated with a slew of consultations, often released in a illogical or unhelpful order, and in some cases, even where there has been strong industry support for an idea (such as the Fund),Government has opted to reject it on Political grounds.At best we face confusion, at worst we are undermining our own efforts to respond to the challenges posed by climate change. Indeed, as we approach the first step in the trajectory toward“zero carbon”[11], there is greater uncertainty than ever, and it is unclear when the industry is likely to be able to make the investment decisions required in order to successfully achieve “zero carbon”.

In short, the UK Government should be applauded for setting bold and ambitious targets and demonstrating the vision to respond to the most pressing issues.However, arguably the detailed technical requirements of the policy should be driven by independent technical experts and based on rigorous research, much the same way as happens for medical issues.

7. Learning from the UK experience

Other countries around the world would do well to study the UK example as it was one of the first countries to announce such a radical policy move; but all countries with aspirations for further development will have to carefully consider how they can achieve this sustainably. Industry in particular, as opposed to Governments, should recognize the opportunities and benefits of establishing an industry-led drive, rather than waiting for Government to legislate. Most Governments like to be able to make decisive announcements, and often assume that waiting for the results of research or testing will be perceived as an admission that the Government doesn’t know what to do. In other industries this has led to privatesector leadership in order to demonstrate to Government that industry is shouldering its share of the burden while feeding Government ready-formed policy, based on established best practice. However,the construction industry is often way behind other industries in terms of understanding the performance of its end product. With a complex and fragmented value chain, co-ordinating industry leadership can be difficult, but it should still be preferable to allowing good intentions to be tripped up by vested interests and unnecessary complication.

8. Future gazing

The Built Environment encompasses more than just the construction industry, overlapping into strategic infrastructure provision, most notably the generation, distribution and supply of energy. The experience in the UK has taught us that a truly integrated approach is required, regardless of traditional sectoral or departmental delineation (within industry or Government). This is required not just because it will help us tackle the challenges we face,but because it will help us do so in a cost-effective manner.

It is always much easier to influence an idea during its formation, than after its proclamation. While it is often difficult for industry to take the long-view,the UK experience suggests that ignoring these issues will result in significant additional effort in the future,trying to rectify ill-conceived policy which may already have gained political and public support. Conversely,pre-emptive research and innovation will position your organization to respond more effectively when legislation is implemented. Whether this means responding directly to Government regarding the policies, responding to clients who need to be informed about the policies, or making business decisions on how your company should react.

Mott MacDonald Fulcrum’s early experiences,before the policy drive began in the UK, suggested that with a little care and creativity, low-energy buildings could be an attractive commercial option.Furthermore, the additional benefits that can be realised in the longer-term, in terms of energy security and responding to social issues, should make for an exciting future for those with the foresight to think and act now. □

Notes:

[1] Full details of this PROBE study are available from www.useablebuildings.com

[2] The Private Finance Initiative (PFI) is a procurement method where the design and construction of public buildings are tendered to a private contractor, along with a contract to operate the building for 25 years.Due to the funding mechanism ‘due diligence’is required and a separate duplicate design team must be convinced of the robustness of designs

[3] Over a year, the net carbon emissions from all energy use in the home would be zero.

[4]http://www.communities.gov.uk/planningandbuilding/buildingregulations/legislation/codesustainable/

[5] Stamp Duty Land Tax Relief

[6] UK-GBC Definition of Zero Carbon work

[7] http://www.bre.co.uk/sap2009/page.jsp?id=1642[8] http://www.communities.gov.uk/publications/planningandbuilding/partlf2010consultation

[9] Part L of the Building Regulations deals with the“Conservation of Fuel and Power”

[10] Originally scheduled for April 2010, but then delayed and now expected to come into force October 2010

[11] Table showing timeline