什么是合理的热舒适性？——保温参数在法国和德国的变迁

阿里亚纳·威尔逊/Ariane Wilson

司马蕾 译/Translated by SIMA Lei

什么是合理的热舒适性？
——保温参数在法国和德国的变迁

阿里亚纳·威尔逊/Ariane Wilson

司马蕾 译/Translated by SIMA Lei

从1970年代起，在法国和欧洲的其它国家，根据最舒服的温度确定的热舒适性开始让位于对建筑能耗问题的思考。近10年来，对于建筑能耗的立法越来越严格，范围也开始不仅针对新建建筑，也涉及既有的历史建筑。但同时，这些法规因为促使含有污染物的保温材料被大量使用，以及可能破坏历史建筑、损害建筑表现形式多样性而遭致了人们的批判。那么，有没有可能在提高建筑的热性能的同时兼顾建筑外观的差异性和美观性呢？而人们对于建筑能耗问题的关心，是否会掩盖了对其他能源浪费现象的重视呢？

热舒适，低能耗建筑，外墙外保温，法国，德国，建筑多样性

1970年代的一天，在一个有集中供暖、室温为19℃的舒适公寓里，我来到了这个世界。当时我并不知道那几年刚好是“舒适度”的概念在法国的住宅政策中被提及，并被法国社会广为重视的转折点。与此同时，注重物质舒适性的“现代主义”梦想也正在向着“后现代主义的幸福”[1]转型，热舒适第一的信条开始逐渐让位于对能源效率的考虑。

1970年代中期也刚好标志着法国“光荣的30年”的终结，二战之后长达30余年的经济繁荣被1973年发生的石油危机打断了。“光荣的30年”见证了社会公共住宅的疯狂建设。在1950年代后期，由政府兴建的公共住宅占了新建住宅的80%以上——战后重建的需要，以及安置不断涌入的移民工人和棚户区改造的需求催生了每年30万套的新住宅建设量。这种新形式的公共住宅让人们能在家庭内部更好地享受物质上的舒适性，也为社会生活的标准化进程做出了贡献。

而在如何规范舒适度的问题上，最早的全国性标准却是诞生在20世纪的更早时期1）。这项法规规定了房间的最小面积（9m2），最小的室内净高（一层和二层2.8m，以上楼层2.6m，这项标准后来被逐渐降低），窗墙比（房间表面积的1/6），阳光射入的角度，卫生设施的最低标准（所有住户需要通水，在大型的公寓中需要设卫生间，并在其中配备洗脸盆和光滑防水的墙面与地板）。室内温度当时尚未在规定之列，但是在同时期教导如何成为一个好主妇的培训用书中，推荐的室内温度为客厅14℃，客人来访时15℃，卧室11℃。

从1920年代起，水、煤气和电力也开始成为了普通住宅中的硬性配备。而直到1950年代，公共住宅舒适度的最低标准中才开始纳入了供暖。1955年颁布的《功能技术硬性规范》2）中规定了公共住宅的卧室温度根据所选用的不同的集中供暖系统，必须保证在12℃或16℃以上，但集中供暖本身并不是强制要求的。1960年代起的新规定开始要求集合住宅中必须有集中供暖，而法定的最低室内温度为18℃。

同时，1955年出台的建筑舒适度规范也得到了法国政府的健康部门和建设部门的承认，并作为建设部门的一项建造标准得到推广，加速了其立法。1958年颁布的“最低标准”旨在保证大众的最低生活舒适度，但是当时对“舒适”的概念本身的定义却并不是那么统一。这一标准在文中将舒适定义为三档：最低、一般和优越，每一档有其具体要求。而在法国人口普查部门的标准中，“舒适”意味着住宅配备有淋浴设施或浴缸，“非常舒适”则代表在配有淋浴或浴缸的同时有集中供暖。

1946年的一项民意调查显示，88%的城镇居民都希望住房中能有热水，63%希望有集中供暖，59%希望有浴室。到了1968年，类似的调查显示仅有10%的人还没能用上自来水，但有50%的人没有热水，65%没有集中供暖。1970年代成了解决这些日常生活中的舒适性问题的关键年代。到了此时，80%的住宅单元都已经配备了自来水和集中供暖，而电饭锅、洗衣机、冰箱、收音机、电视和电话等1950年代发明的家电设备也逐步得到了普及。

但与此同时，人们对舒适度问题的看法却也开始发生了变化。在法国，1970年代中期是大规模公共住宅街区建设的最后阶段，之后的新潮流则是去郊区购买具有产权的私人住宅，而不再是租房了。政府对住宅市场的干预因此不再专注于建设新房，而是向着提高现有住宅品质、重视过去被忽视的室内舒适度问题转型，并希望通过财务优惠政策鼓励住户翻新住所。

这些变化与国际石油危机以及“增长极限”3）问题开始得到认识基本是同时发生的。人们慢慢开始意识到了保护地球资源的重要性，现代化的舒适性概念因而开始从理论上受到了质疑。虽然我们都知道能源的消费量实际还是在迅速增长的，而经济的发展也驱动着能源消费的加速而不是减速，但人们的观念正从追求理想的生理舒适环境向着追求综合的“幸福感”发生了转变。这意味着对生理和心理、物质与非物质、个人与环境因素之间的更微妙的平衡关系的考虑。在法国的语言规范中，“质量”一词逐渐取代了“舒适”“宜居性”等用词。不同于过去的最低标准概念，“质量认证”这一建筑质量评价体系开始同时应用于公有和私有住宅。这一体系能通过复杂的计算方法，量化包括材料的可持续使用性、电气设备完善性、建筑安全性、能耗、隔音性、维护成本、夏季热舒适性、垃圾处理问题等在内的各种标准。

而在热舒适的标准上，人们的观念也发生了由内而外的转变。过去人们的注意力总是集中在如何通过主动对内部空间进行加热、提高室内温度来满足使用者，现在的立法则开始假设建筑作为温度调节的中介，也能与外部空间发生互动。因此建筑的围护结构，而不仅仅是供热系统，也开始得到了重视，从而使整体环境，而非仅仅是人类能够受益于这种“舒适性”。当然，这并不意味着热舒适性的标准发生了倒退，而只是开始更多地关注节能的问题。尤其是1988年出台的建筑产品的官方目录4）上，开始使用“建筑节能理念”这章来代替原来的“使用者需求”一章。

新兴的对于能源效率的关注也改变了建造和建筑文化：“光荣的30年”的建设中最受青睐的钢筋混凝土、煤渣砌块、铝窗等建材都很少考虑保温隔热问题，这使得法国的大量既有建筑都与新的能耗标准相去甚远。德国和瑞士的建筑节能标准“Passivhaus”和“Minergie”都具有很强的先锋性，相比之下，法国的建筑文化在适应新的标准和对其进行立法上都进展得非常缓慢。法国自1970年代后期开始就出台了国家规范，并开展了几项相关的使用太阳能和其他节能技术的实验性建筑项目。但这一规范真正得到严格执行却是在2000年之后了，而公众能真正理解建筑节能的概念则是近10年的事情，这还要感谢国家和商业机构的积极推广。现在，“热效率”已经成为了热门词汇，催生了各种改善措施的实施，也引发了各种周全或有欠周全的实践，以及人们对此的各种矛盾态度、争议和忧虑。

RT1974是一系列相关规定中第一部规范了新建筑的热能耗要求，并对供暖、通风、气候适应、热水供应和照明的能耗做了限制的法案。起初，规定只针对新建住宅。RT1974中出现了对墙体保温和通风系统的要求，而在第二次石油危机之后出台的RT1982则希望通过利用太阳能来减少供暖的能耗。到了RT1988，两部分的条款都开始延伸到非住宅建筑领域，同时也引入了基于能源消费非能量损失的计算法则，并基于此创造出了“建筑能耗”这一新概念。而相比RT1988，RT2000则将针对新建住宅建筑的最大能耗标准削减了20%，对其他第三产业建筑物的能耗标准削减了40%。仅仅又经过了5年，RT2005在RT2000的要求基础上又提出了再削减15%的进一步要求。

这一规范的最新版本为RT2012。这一版本再次提出了对供暖、照明、空调能耗的限制策略，旨在减少温室气体的排放，鼓励新技术发展，对象则涵盖了包括大学、商场、机场、医院在内的各种公共、私人和商业建筑。法规为新建建筑设置了根据不同地区确定的50kWh/m2的最大能耗标准（在1960年代这一标准为250kWh/m2，1970年代则为100-150kWh/m2）5）。RT2012同时也设置了在申请建造许可时必须提交能耗证明的要求。到2020年，新版本的RT则将会要求所有的新建建筑都实现正能量平衡（能量生产大于消费）。

为了鼓励使用更高效的供暖和空调系统、双层玻璃和隔热措施，最近出台的与能耗相关的规范都关注一个新关键词：保温。在1970年代，为了纠正建筑的立面构件热传导性过强的问题，建筑的保温措施都被设置在外墙的内侧。而今天，外墙外保温——即在整个外立面包裹连续的保温材料，被证实比使用同等厚度的内保温材料有效两倍，能够彻底解决热桥问题，也不会侵占室内的使用面积。但这种貌似理想的方式却受到了环保主义者、保守人士、建筑师们，甚至是公众的强烈批评。其中的一条批评是关于保温材料自身的环境和技术性能。另一条批评则指出其使用可能破坏历史建筑的外观，并损害建筑表现形式的多样性。

外墙外保温让建筑外墙的软硬两面发生了反转。德国许多民族的文化都在外墙上使用抹灰，因此外保温的实施不会造成像在法国那样大的文化冲击——在法国，古典主义和新古典主义的建筑多喜欢通过使用石材结构或贴面来表现高贵感，而现代主义的建筑则喜欢使用清水混凝土来彰显其先进性。

因此，德国成了欧洲实践外保温的冠军国家。数百万立方米的Wärmedämm-Verbundsysteme（一种整合了防水层、保温层、钢丝网、防水底层和完成面的外墙外保温复合材料系统）取代了过去德国住宅中使用的抹灰（Putz）。在整个德国，外保温不仅大量地使用在新建建筑上，也被应用于大量战后建造的质量欠佳的建筑改造工程中。通过加设一层又一层非装饰性的表层，战后建造的这些建筑在材质、立面阴影、窗户周围的线脚等细部上都发生了变化，品质因此得到了提高。这种改造其实从整整一代人之前就开始进行了，但是德国2010年出台的雄心勃勃的新能源政策加速了这一进程——新政策定下了在2050年让存量建筑（包括新建筑和旧建筑）全部达到气候平衡的目标，并计划让每年进行节能改造的建筑数量翻一倍。

《愚蠢的外保温》 （Wahnsinn Wärmedämmung）是于2011年和2012年上映的两部电视纪录片，由此引发了对外保温问题的一股批判风潮。该片对广泛使用聚苯乙烯等石油制品作为外保温材料提出了质疑，认为虽然持有作为建材的安全认证，这种材料仍然非常易燃，会加速火势蔓延，释放有害气体，并让整堵外墙迅速地全部燃烧起来。片中同时也指出了这种材料不可循环使用、使用寿命短、可能将动物困在其内部、并常常因为安装错误造成凝结的水汽无法正常排出、让材料从内部发霉的问题。此外，保温材料外层涂料中包含的有毒成分会随着雨水渗入周边环境，污染土壤和河流。影片同时也指出，保温过于严密的住宅需要另外设置窗缝和需要消耗能源的机械系统来进行通风，促使空气进入室内，这是非常荒谬的。

片中也提到了生产这些保温材料的公司的经济利益问题（在德国，这是一个有着18亿欧元产值的市场）。这些公司会不会通过鼓励出台严格的保温规范，来促使住宅的业主们将房屋用保温材料包裹起来，或是购买通风设备呢？2005年，德国的建筑上用了2450万m3的保温材料（包括外墙的内外两侧、墙体和屋顶等所有的建筑表面上的使用量）。这些材料中，约41%是经过膨化或挤压的聚苯乙烯和聚氨酯，54%是矿棉6）。但即使是污染性较小的材料，也还是含有添加剂和溶剂。而较为天然和有机的材料，例如软木、亚麻和羊毛则因为价格更贵而很少被使用。虽然据称这20～30年来，由于外保温的推广而节约的能源要比取得这些原材料、进行生产、加工成合成材料所消耗的能源要多，但生产所需的这部分灰色能耗，以及因为在生产中排放有害物质而造成的环境问题都不应该被忽视。此外，拆除原有的窗户、使用新的塑料框双层玻璃窗的过程也会对环境造成影响。而其中，究竟哪种材料最有利于建筑节能仍是最关键的问题，但相关的规范以及对于低能耗住宅的定义中都没有提及这一点。

另一条对于彻底转向使用外墙外保温的批判则是源自建筑学的角度。对于新建项目，人们确实希望新的建筑规范能更多地支持使用新科技、新材料、新形式和新的建造方法，以便形成新的建筑语言——例如使用柔软的外围护结构，将建筑用多层表皮、具有一定厚度的金属板包裹、覆盖或穿戴起来，也许也能藉此形成一种全新的装饰设计效果。但这些元素被应用在既有建筑时则会产生种种问题。

在法国，由于规范不仅涉及新建筑，也涉及根据新的能耗要求对旧建筑进行改造，批判者因此描述这将会让巴洛克宫殿、罗马教堂、19世纪装饰风格的住宅街区，以及整个历史保护区都像被包裹在茶壶套里的茶壶一样凄惨。2007年起实施的一些规范已经将节能要求加诸到了既有建筑之上——建筑的改造工程必须满足相应规范，进行能耗评测，在房屋进行买卖和租赁的时候都需要出示其结果。其中决定性的一步是在2015年5月出台的法国“能源过渡法案”，这一法案经过了重重争议，目前仍在修订中。该法案希望在2050年前实现减少4倍的温室气体排放量，并让能源消耗量相比2012年的标准减少一半，并减少核能的使用比例（这是法国政治中的一个敏感点）。这些目标也有赖于对既有建筑进行改造，以使其符合新的建筑节能标准。这些措施都涉及了法国大量的既有建筑，外保温问题也因此在这个时间点上成为了重中之重。

但同时，“能源过渡法案”豁免了在1948年前7）使用传统技术建造的建筑，以及被认定为20世纪建筑遗产的建筑。法案也允许旧建筑按照“逐个元素”进行改造。尽管如此，处于对建筑遗产保护和建筑多样性问题的关心，建筑师们仍然对这种缺乏细致考虑的节能法案，以及为了获得节能建筑补助而进行的轻率的改造工程心怀警惕。他们尤其对其中的一条条款非常不满，即让当局（即市长）有权对城镇的规划条例进行修改，以利于节能措施的实施。这使得即使在历史和自然文化保护区内，使用依据能源过渡法案确定的材料和设备将会“不能被阻止”。这些保守者的组织“法国农民之家”（Maisons paysannes de France）在其杂志中发表了几篇文章，其中展示了各种建筑立面被套上了外保温材料后的可怕情景：卢瓦尔河畔19世纪装饰风格的教堂，在厚厚的保温层形成的光滑、洁白的表皮的包裹下完全认不出原来的样子了，上索恩省的石砌的农民住宅表面被贴上工业化的木材质，阿尔萨斯地区的半木结构住宅外被裹上了聚苯乙烯材料，木制窗框也被换成了厚塑料框[2]。

这些不幸的结果都源自对热性能标准的简单化、肤浅的应用，而忽视了根据实际情况进行评估、以及根据历史建筑的建造技术确定解决方案（显然会更贵）的重要性。要解决这些问题，就需要对建筑物的不同部分采取“区分各个元素”的态度进行分别讨论，并综合使用高技术和低技术的不同保温材料，例如含有麻成分的涂料，含有高科技粒子的传统涂层，以及由混合石膏和石灰的空气构成的喷涂泡沫等。

巴黎作为一个有趣的案例，明显地体现了这种建筑美学品质和热性能规范要求之间的矛盾。作为首都，巴黎在2007年颁布了自己的“气候计划”：温室气体排放量和建筑能耗能各自降低25%，而可再生能源的使用量增加25%。根据这些目标，2009年，《城市规划条例》（PLU）中部分与建筑历史遗产保护相关的条文进行了修改，以便在建筑外立面上嵌入太阳能电池板，并允许外保温层能向公共空间外凸20cm。由于巴黎有80%的建筑都建于1940年之前，人们开始讨论这种为了热性能标准而进行的改造会不会让巴黎鲜明的建筑特色发生变化。

较为乐观的一派认为建于奥斯曼时期8）之前的巴黎街区，建筑立面多使用抹灰而较少进行装饰。因此，加设外保温材料不会从根本上改变建筑外观（但是在增加的立面层的影响下窗户会看上去凹陷的更深，出檐则会变浅）。此外，这部分人认为面向城市街道的立面通常装饰得最繁复，但这部分墙体只占热量损耗的20%，因此可以考虑排除沿街面，而将山墙、屋顶、面向内院的简单抹灰墙面以及窗户作为改造的重点，在不影响沿街立面的石材装饰效果的情况下对这些建筑进行保温改造。

而针对这些老建筑提出改造对策无疑还是相对容易的，更难对付的是饱受诟病的“光荣的30年”期间建设的那些过于舒适、保温性能却不佳的建筑。这些建筑的平均年能耗量为400kWh/m2，因此成为了巴黎既有建筑中的黑天鹅。对这些建筑的改造中涉及了一种不同的审美立场。和德国人不甚欣赏那些在战后时期建造的建筑情况类似，法国人对于维持国家和当局在1970年代建造的那些大型公寓街区的立面形象无甚兴趣。这些建筑被认为是平庸和丑陋的，因此改造涉及的建筑美学品质主要是关于能带来何种新的建筑形象，而不是如何保持其原有特色的。最近的一期德国建筑杂志《建筑细部》（Detail）上刊登了几个较为成功的办公楼或住宅街区的外保温改造案例[3]。在这些案例中，加设的保温性能优异的玻璃外墙将建筑从完全被不透明墙体包裹的状态中解放了出来。同时，加设的外保温层让墙体设计可以在厚度上大做文章：倒角窗、经过装饰的外表皮、不同纹理的完成面取代了原本貌似无趣的现代化、光洁的墙面。一般而言，在当时不受人喜爱的建筑，其建筑美学特质通常会在隔了几代人之后被重新欣赏，但这些建筑没有这种机会了：在他们的价值被发现之前，外观就已经为了增加保温性能而变了样。

如果说这些战后建造的建筑的能耗浪费问题确实无可争议的话，在1948年之前建造的那些建筑则并没有那么糟糕。不少研究都发现，在工业时代之前建造的本土建筑其实并不存在能源浪费问题9）[4]。事实上，在法国，直到RT2000要求新建建筑提高节能性能之前，新建建筑的能耗表现一直都不如老建筑。按照传统经验和知识建造的这些老建筑既然能引入空气和水分，自然也能让它们顺利排放出去。这些建筑的朝向一般都最为符合当地的气候特征，墙体则具有热惰性，利于热量的保存。基于毛细管作用的透气性能让水蒸汽自动进行调节。厚厚的石灰和麻布内层、灰泥或泥土外层、方格窗、传统挂毯等的使用都减少了墙体的热能损耗。芦苇席或是薄薄的空气层则充当了保温层。在钢筋混凝土出现之前的石砌墙体和木构造的民居建筑中，其实都没有出现过热桥的问题。

具有讽刺意味的是，这些发现都说明许多历史建筑需要的其实不是改造，而是去除过去的改造！后期被加到这些建筑上的现代元素，例如水泥砂浆抹面层、墙体防水层等都阻止了建筑原本精妙的温度和湿度调节系统发挥作用，因此应该被去除。在许多案例中，这都应该是改善老建筑热性能的第一步。

而对老建筑热性能的检验同时也启发了另一种应对节能规范的方法。这涉及对于舒适的一种完全不同的定义。在过去，对于舒适度的最低要求，以及对于低能耗的追求都基于希望能形成稳定、均质的室内热环境。但是在20世纪以前，或是在工业社会到来之前，建筑、气候和社会行为在对热舒适性的追求上却是互相作用的。建筑应对不同气候的方法具有社会和文化上的双重重大意义：这既表现在建筑的环境适应性上，也融入到了建筑的外观设计中。各个房间在夏季和冬季、白天和夜晚会有不同的使用方式，人们则根据热环境的变化在一栋建筑的朝南侧到朝北侧、底层到顶层中不停移动着。壁炉、阳台、百叶和窗帘、窗洞口和四柱床等与热性能相关的元素同时也成为了建筑中的装饰要素。芬兰的桑拿浴室、罗马和日本的浴池、伊斯兰的园林这些建筑形态都是源自于对气候、温度、健康上的功能性的追求，但同时也具有重要的社会和象征意义。在这些文化中，热舒适性都超越了原有的意义，并且因为关系到人们的记忆和感情而具有了心理上的价值。同时，在冷的环境中时感到温暖，在热的环境中感到凉爽，在不舒适的环境中感到舒适——这种不停的变化也构成了环境的舒适性能被人察觉和感知的要素。

莉萨·海斯庄在1979年所写的《建筑中的热环境舒适性》一文刚好发表于舒适性观念发生变革的时期。她在当时就提出了不应该使用机械的热环境控制系统（通常能耗很高）来中和热环境[5]，认为现代社会依赖集中供暖、空调和密闭的建筑环境来维持室内的恒定环境的做法损害了我们自身调节和感知热环境变化的能力。通风设备藏在了天花吊顶中，热水管道则埋在混凝土楼板里，这些建筑设备都被隐藏了起来，使得现在的供暖设备大多数时候都看不见，而能耗似乎成了一种“抽象”的物质。我们很少有机会与这些为了维持我们的热舒适而存在的机械设备产生互动。海斯庄强调相关规范已经成为了高度自治的对象，与社会和文化系统毫无关联，仅仅根据自身的逻辑来维持运作。

那么在今天，应该如何在迫切的节能需求下，以更符合人类学的方式来追求热舒适度呢？如何才能改变我们的行为，巧妙地将一个建筑中的不同环境区域用作不同功能，并且用建筑学的方式来表现这些不同，进而以不那么一刀切的方法来达到节能的目的呢？建筑学领域的太阳能和生物气候运动都在引领这一新方向，并已经出现了一些独立但具有象征意义的案例，例如威尔士议会大楼（英国）和尼翁城堡历史博物馆（瑞士）的改造10）等。但这些例子目前尚属特例，大部分欧洲的新建筑和改造工程都还没有站在文化层面考虑热舒适性和能耗的问题。

最后，让建筑的能耗变得“隐形”也可能会掩盖一些其它的能源浪费问题。例如，计算机、手机、互联网、照明、近来在公共场所越来越多见的视频广告、每个商店和机构橱窗里的液晶屏都在日夜不停地运行着。因为司空见惯，这些设备的能耗很少被人注意到，成为了日常生活中被忽视的问题。而技术的“非物质化”神话也掩盖了数字时代的这些人工制品给环境带来的沉重负担。即使如此，那些支持执行严苛的节能规范条文的人还是强调建筑占了所有能源消耗的30%。即使如此，建筑是不是就有必要牺牲其外表的美观和个性，从而背负起节能的重责？而作为一个关心环境、但是也热爱建筑的人，我不禁要问：在其它的能源浪费行为如此大行其道的情况下，建筑凭什么就没有权利保有一定的特色和基本的美感呢？□

注释：

1）第一部标准为1902年颁布的《省级卫生规范》。2）也被称为C.P.T.F.M. 功能技术硬性规范。

3）此为1972年出版的著作的书名。该书由罗马俱乐部主编、Donella H. Meadows, Dennis L/ Meadows, Jørgen Randers 和Wiliiam W. Behrens III撰写。

4）也称为R.E.E.F. 建造元件与零件目录。

5） 指传统的主要建筑能耗内容，包括了供暖、空调、通风、附属设备、热水和照明能耗。这些建筑将被授予BBC（低能耗）标志。

6）这些材料的市场占有率出自德国保温材料行业的相关机构：德国保温行业协会的调查。

7）1948年是法律认定的分界线，之前建设的建筑属于“老”建筑，之后的则被认定为现当代建筑。

8）奥斯曼男爵在1853年至1870年间对巴黎进行了大规模的城市改造，提升了巴黎市中心的建筑与公共空间的个性。

9）相关案例见于“法国农民之家”的调查。

10）威尔士议会大楼 : 理查德·罗杰斯建筑事务所, 2001-2006。尼翁城堡历史博物馆 : 克里斯托弗·阿姆斯负责, 1993-2006。

Little did I know, when I came into the world in the mid-1970s, in a comfortable, centrally heated apartment with an ambient room temperature of 19°C, that these very years were a turning point in the notion of comfort promoted by French housing policies and aspired to by French society. At the same time as the "modernist"’s dream of material comfort reshaped itself into one of "post-modern well-being"[1], the creed of thermal comfort gave way to that of energy efficiency.

The mid-1970s marked the end of the Trente Glorieuses in France, three decades of economic boom that began just after the Second World War and were interrupted by the petrol crisis of 1973. In particular, the Trente Glorieuses witnessed frenetic building of public apartment blocks. At the end of the 1950s, housing supported by the State constituted more than 80% of new homes, with 300,000 units built yearly, to respond to the postwar need for reconstruction, to accommodate the inflow of migrant workers and to eradicate shanty towns. Efforts to bring material comfort to families – contributing also to a process of social normalisation – were realised principally through this new social housing.

The first nation-wide regulations that sought to establish a norm for comfort were enacted in the early twentieth century.1)Criteria covered minimum size of rooms (9m2), minimum ceiling height (2.80m for the two lower floors, 2.60m for subsequent floors – a height significantly reduced since then), the proportion of openings (1/6 of room surface), a suitable orientation for sunlight to enter, and minimum sanitary equipment (water in the building accessible to all inhabitants and, for larger flats, a toilet with a sink and smooth, water-proof walls and floors). Room temperature did not yet feature in these regulations. We know however, through manuals of the same period for the education of good housewives, that recommended temperatures were 14°C for the living room, 15°C when guests visited, 11°C in bedrooms.

While water, gas and electricity became compulsory for mid-standard housing in the late 1920s, only in the 1950s did heating become part of the minimal requirements for comfort in social housing. The "minimum technical functional prescriptions"2)of 1955 stipulated a bedroom temperature in social housing of 12°C or 16°C according to two different types of central heating, but central heating was not obligatory. In 1960, new prescriptions established 18°C as the minimum legal temperature and made central heating mandatory in collective housing.

In the meantime, in 1955, the regulation of comfort in buildings had passed from the Ministry of Health to the Ministry of Construction and expanded in parallel with the latter's building activity. Legislation proliferated. The "minimal prescriptions" issued in 1958 were intended to guarantee minimal comfort to all, but the notion of comfort was not quite universal: another body of texts defined three categories, modest, middle and superior, each with its criteria. For the French population census office "comfort" meant homes equipped with a shower or bath, and "full comfort" with a shower or bath and central heating.

In 1946, a poll had shown that 88% of town dwellers dreamt of having hot water, 63% of central heating, and 59% of a bathroom. In 1968, 10% did not yet benefit from running water, 50% did not have hot water and 65% were not equipped with central heating. But the 1970s were the decisive decade for the inscription of such comfort in daily life, shown by the fact that 80% of housing units were now equipped with running water and central heating, as well as by generalised use of electric household equipment yearned for since the 1950s -electric cookers, washing machines, fridges, radios, televisions and telephones.

Simultaneously, however, the first signs of a change in perspective appeared. In France, the mid-1970s saw the end of massive construction of large-scale public apartment blocks, and new trends towards suburban individual private housing and ownership rather than rental of homes. State intervention was now directed less towards new construction and more towards the improvement of existing buildings that had often been neglected by programmes for domestic comfort, through financial incentives allocated to encourage owners to refurbish their homes.

These changes coincided with the international oil crises and realisation of the "limits to growth".3)The notion of modern comfort, theoretically at least, was challenged. It came head to head with the need to preserve the planet's resources. Though we all know that, in reality, consumption continued to accelerate, and that economic forces have a greater interest in fostering than in slowing it, there was a shift in discourse from an ideal of physical comfort for all to one of "well-being", implying a more subtle balance between physical and psychological, material and immaterial, individual and environmental factors. In the language of regulations in France, the word "quality" gradually replaced "comfort" or "liveability". Rather than the previous notion of minimal requirements, a ranking system of quality labels was instituted for both state-aided and independent housing: the Qualitel label. Its complex method of calculation included criteria such as sustainability of materials, electric installations, safety, energy consumption, acoustic protection, maintenance costs, summer thermal comfort and disposal of garbage.

In matters of thermal standards, there was a kind of turning inside-out of concerns. While attention had been bent on improving room temperature for human beings through active heating of inner space, legislation now contemplated the building in interaction with outside space, as an active agent in regulating temperature. The building envelope, more than the heating system, became the performer. The environment, more than or as much as the human being, became the beneficiary of "comfort". Though of course, there was no turning back on standards of thermal comfort, a shift had occurred towards a concern for energy performance. Significantly, the 1988 official inventory of building products4)replaced its chapter on "human requirements" by a section entitled "concept of performance in the building" .

This new emphasis on energy efficiency required a change in building and architectural culture: the Trente Glorieuses had favoured reinforced concrete, breeze blocks and aluminum windows with little regard for thermal insulation, leaving France with a large legacy of buildings in outright contradiction with new thermal requirements. In France, compared for example to Germany or Switzerland, known for their pioneering Passivhaus and Minergie standards, building culture has been slow to adapt and legislation slow to evolve. The French State had, since the late 1970s, introduced regulations and several programmes in experimental solar and other low-energy buildings, but standards became truly demanding only from 2000, and only in the last decade has the general public become conscious of the notion of energy-efficient buildings thanks to active State – but also commercial – campaigns. Today, thermal efficiency is a buzz-word, leading all at once to improvements, thoughtless or thoughtful implementation, contradictory attitudes, controversies and worries.

The RT (réglementation thermique) 1974 was the first of a series of regulations framing thermal requirements for new buildings and fixing a limit to the consumption of energy by heating, ventilation, climatization, the production of hot water and lighting. At first, only new residential buildings were concerned. The RT 1974 imposed insulation of walls and regulation of ventilation systems, while the RT 1982, after the second petrol crisis, aspired to reduce needs for heating by using solar energy. Their provisions were extended to new non-residential buildings in the RT 1988, which also introduced calculations based not on energy loss but on consumption, thus coining a notion of performance of the buildings. Compared to the 1988 standards, the RT 2000 reduced maximum consumption of new residential buildings by 20% and by 40% for buildings of the tertiary sector. Only five years later, RT 2005 stipulated a further improvement by 15% of the RT 2000 requirements.

The regulation currently applied is RT 2012. It returns to the strategy of limiting consumption of heating, lighting and cooling, aims to reduce the emission of greenhouse gases, encourages the development of new technologies and covers a large range of public, private and commercial buildings including universities, shops, airports and hospitals.For new housing, it sets the standard of a maximum consumption of 50 kWh/m2.year, with variations according to regions (for comparison, the standard in 1960 was a consumption of 250 kWh/m2·year and in 1970, 100-150).5)RT 2012 also instituted the submission of an energy performance certificate when asking for a building permit. In 2020, a new RT should require all new buildings to have a positive energy balance (production exceeding consumption) and will take into account the grey energy of insulation products.

As well as encouraging more efficient heating and cooling systems, double-glazing and suitable exposition to the sun, recent thermal legislation has led to a watchword: insulate! In the 1970s, to correct building faults and the excessive conductivity of façades, insulation was stuck on the inner side of walls. Today, exterior insulation – a continuous insulation covering the entire facade – is promoted as being twice more efficient for an equivalent thickness of insulating material, a palliative to thermal bridges and a solution that does not reduce the surfaces of living spaces. This apparently angelic measure, however, is meeting strong criticism from environmentalists, conservationists and architects, but also the broader public. One criticism addresses the environmental and technical viability of insulation materials. Another alerts to the risk of disfiguring historical buildings and reducing the variety of architectural expressions.

External insulation inverses the relation between soft and hard in a building's envelope. In Germany, whose vernacular tradition is largely one of plastered buildings, exterior insulation did not come as a cultural shock as much as it did in France, where architecture of the Classical and Neoclassical traditions tends to express its nobility in visible stone construction or finishings and modern architecture its progressiveness in raw concrete.

Germany is the European champion of thermal insulation. The Putz (plastering) of German housing is being replaced by millions of cubic meters of Wärmedämm-Verbundsysteme (an integrated composite system for external insulation including a water-resistive barrier, insulation board, reinforcing mesh, water-resistant base coat and finish coat). Across the country, exterior insulation is massively implemented on new buildings but also on the large legacy of little-loved post-war housing. A coated non-ornamented surface for a coated nonornamented surface: none but the enlightened lover of post-war buildings sees the difference in texture, façade depth or detail like a thin imprinted line around a window. The phenomenon started a full generation ago, but accelerated with Germany's ambitious 2010 energy policy, aiming to reach a climate-neutral building stock (old and new) in 2050 and to double the proportion of buildings submitted yearly to energetic refurbishment.

Wahnsinn Wärmedämmung ("The folly of thermal insulation"), two TV documentary films shown in 2011 and 2012, gave the trend a bashing.The programmes inquired into the extensive use of polysterene and other oil-based products as external insulation. They showed the insulation systems to be dangerously inflammable, despite their certification as safe building products, conducive to fires that release toxic gases and swiftly inflame the entire facade. They showed them to be unrecyclable and short-lived, to shelter animals and to cause rot under their surface when water vapour from condensation is not properly released, often because of faulty mounting. They also revealed the extent of soil and river pollution provoked by pesticides contained in the paint that coats the insulation, washed out by rain. They pointed at the absurdity of over-insulated homes requiring ventilation to let air back in, through slits in windows or via mechanical systems that consume energy.

The programmes also raised the question of the financial interests of companies producing these insulating materials (a market of 1.8 billion euros in Germany). Do they not encourage stringent thermal norms in order to incite owners of houses to wrap up their buildings or buy ventilation devices? In 2005, 24.5 million cubic meters of insulating materials had been used in German buildings (all surfaces, inner and outer, walls and roofs). Then, as today, about 41% were polystyrene – expanded or extruded –and polyurethane, 54% were mineral wools6), but even these less polluting materials contain additives and solvents. More natural organic materials like cork or hemp or sheep's wool are more expensive, and thus seldom used. Despite the claim that the thermal energy saved over a period of 20 or 30 years thanks to external insulation is superior to the energy required for the acquisition of raw materials, production and processing of its synthetic materials, this grey energy cannot be ignored. Neither can the toxic substances released in their production. Added to the equation is the environmental impact of removing old windows and introducing new plastic-framed double glazing. The question of what materials will make sense of efforts to reduce energy consumption of buildings is thus vital, but is not included in regulations or in the attribution of aid to low-energy housing.

A second critique of systematic resort to external insulation is an architectural one. For new buildings, there is scope to invent a new architectural language based on the technologies, materials, and construction logic created by the new regulations – a language composed of soft envelopes, cladded, coated or dressed, with multiple layers, with thickness and the relative depths of material planes, perhaps leading to a novel design of ornament. However, adapting existing buildings poses problems.

In France, as regulations begin to encompass not only new buildings but the refurbishment of older ones according to current energy requirements, critics depict apocalyptic visions of Baroque palaces, Romanesque churches, nineteenth century ornamented housing blocks, entire historic town centres clad in tea cosies! Since 2007, a number of decrees have extended thermal legislation to existing buildings. Buildings undergoing refurbishment must meet the norms, and a diagnosis of energetic performance must be presented whenever a house is sold or rented. The decisive step however will be the enactment of the French "law on energy transition", that was adopted in May 2015 and is currently under revision, after much controversy. Besides aiming at a fourfold reduction of the emission of greenhouse gases by 2050, halving energy consumption compared to 2012 standards, and reducing the proportion of nuclear energy (a sore point in French politics), itimposes the refurbishment of existing buildings to the standards of low energy buildings. These measures concern an enormous proportion of the French building stock. Exterior insulation is therefore a burning issue at this very moment.

The law on energy transition provides for exemptions such as listed buildings, buildings built before 19487), buildings constructed with traditional techniques and buildings labelled as 20th century heritage. It also allows for a treatment of older buildings "element by element". Nevertheless, architects concerned with architectural heritage and diversity are wary of insensitive interpretations of thermal regulations or thoughtless refurbishment stimulated by the wish to tap public aid towards low-energy buildings. In particular, they are worried by an article of the law that allows authorities delivering building permits (namely mayors) to waive town planning rules in favour of energysaving measures. Even in preserved historic or natural areas, it will be "forbidden to forbid" materials or devices that allegedly forward the energetic transition. The conservationist group Maisons paysannes de France has circulated several articles in its magazine showing nightmare cases of exterior insulation covered with diverse materials : an ornamented nineteenth century church in the Loire unrecognisable under a thick layer of insulation with smooth white rendering, a stone farmhouse of the Haute Saône clad with industrial wood, half-timbered houses in the Alsace region covered in polystyrene, their wood-frame windows replaced by thick plastic frames.[2]

These mishaps are obvious results of simplistic, blanket application of thermal standards, ignorant of the importance of case by case diagnosis or of (admittedly more expensive) solutions adapted to the construction techniques of historic buildings.These alternatives include the "element by element" attitude of multiple interventions on different parts of the building or current developments in low-tech and high-tech insulating materials such as coatings containing hemp, traditional coatings with hightech particles, or the projection of foams composed essentially of air, covered by plaster and lime.

Paris is an interesting case of the apparent conflict between architectural quality and thermal regulation. The capital city enacted its own "climate plan" in 2007, aiming to reduce both greenhouse gases and energy consumption by 25% and to use 25% more renewable energies. In accordance with these objectives, certain rules of the 2009 planning regulations (PLU) that contributed to preserving historical heritage were changed, in order to allow solar panels to be fixed to façades or for external insulation to stick out by 20 cm into public spaces. 80% of Parisian buildings date from before 1940. Will refurbishment to meet requirements in thermal performance transform the strong architectural identity of Paris ?

The more optimistic parties argue that most Parisian housing blocks built before Haussmann8)were coated with plaster and had few ornaments. Applying external insulation will therefore not radically modify their aspect (but won't windows be sunken deep and cornices drown in the additional layering?). Besides, argue these parties, façades on the street side, those that are usually most elaborate, represent only 20% of thermal losses, and so need not be treated. Gable ends, roofs, simple plastered façades on the courtyards and windows carry most of the responsibility and can be insulated without affecting the ornamented stone façades along the street.

No doubt will it be easier to defend the specific care needed for older buildings than the decried buildings of the Trente Glorieuses, that bear the stigma of good comfort and bad performance. With an average consumption of 400kWh/m2·year, they are the black swans of the French building stock. The aesthetic question of their refurbishment is posed in different terms. Little interest is seen in preserving the original aspect of large apartment blocks built by the State or 1970s offices, as is the case in Germany for under-appreciated post-war architecture. They are generally considered to be banal and ugly. The architectural quality of their refurbishment is judged not according to whether it respects their original characteristics but in terms of the new architectural status it confers. A recent issue of the German architectural magazine Detail shows examples that it deems successful of thermal refurbishment of office buildings or housing blocks.[3]In these examples, thermally efficient glass liberates buildings of their opaque walls ; external insulation offers the possibility to play with its thickness: chamfered window openings, ornament in the coating, finishings with different textures replace the supposed drabness of smooth modernist walls. These buildings, however, will never benefit from the distance of a generation needed to appreciate the architectural qualities of unloved buildings: they will have been thermally redeemed before they are architecturally recognized!

If nothing can save these post-war buildings from the accusation of thermal wastefulness, pre-1948 buildings can more easily be discharged. A number of studies have raised awareness that preindustrial vernacular buildings are not wasteful of energy.9)[4]Indeed, in France, until the performance of new constructions improved following the RT 2000, new buildings performed less well than older ones. If houses built according to traditional empirical knowledge let in air and humidity, they are also able to let them out. Their orientation is most often climatically sensible. The thermal inertia of their walls stocks and restitutes warmth. Their permeability, through micro-capilarity, allows self-regulation of the movement of water vapour. Thick lime and hemp, plaster or earth renderings, panelling, or tapestries traditionally reduce the effect of cold walls. Reed sheeting or thin blades of air play the role of insulators. Dreaded thermal bridges do not occur in the masonry walls or wooden structures of residential buildings predating reinforced concrete.

Ironically, rather than their refurbishment, these conclusions call for the de-refurbishment of many historic buildings! Modern additions to these buildings, such as cement renderings or waterproofing of walls that prevent them from functioning according to their subtle thermal and hygrometric logic, should be removed. In many cases, this would be the first step towards improvement of the thermal performance of older buildings.

But examining the thermal performance of older buildings suggests yet another response to thermal regulation. This amounts to a very different notion of comfort. Both the effort to establish minimal comfort standards and the objective of low energy consumption are approaches that suppose stable, homogeneous thermal environments. Yet before the twentieth century, or in pre-industrial societies, architecture, climate and social behaviour interacted in a quest for thermal comfort. Adapting to different climatic situations within a house took on a ritualised social and cultural meaning, that made environmental sense and was translated expressively in building design. Rooms were used differently in summer and winter, daytime and evening, with migrations from the southern to the northern side, from the bottom to the top of the same house, according to thermal conditions. The hearth fire, the loggia, shutters and blinds, window openings and four-poster beds, are all elements of thermal regulation that became elaborate architectural elements. The Finnish sauna, Roman and Japanese baths, the Islamic garden are amongst architectural typologies that arose from functional needs linked to climate, temperature and health and had a central social role and symbolic status. Thermal comfort, in these contexts, is as much psychologicial, and linked to memory or affection, than absolute. Its variability is part of what makes it perceptible and therefore appreciable: warmth when it is cold, coolness when it is hot, comfort after discomfort.

In her essay "Thermal delight in Architecture", Lisa Heschong had, in 1979, just at the time of the change of paradigm, already sounded the alarm against thermal systems using (often high-energyconsuming) mechanical methods to neutralise the thermal environment[5]. She argued that the modern emphasis on central heating systems, air conditioning and hermetically sealed buildings to reach constant indoor conditions has actually impaired our strategies for adapting to and sensing thermal variations. Ventilators in false ceilings and hot water pipes in concrete slabs conceal thermal mechanisms: today, heat production is largely invisible and energy is an "abstraction". The machines destined to maintain our thermal comfort are mechanical servants with which we rarely interact. The norm, stresses Heschong, has become a largely autonomous object, isolated from social and cultural systems and operating according to its own logic.

Today, how could an anthropological approach to thermal comfort contribute to the urgent necessity of reducing energy consumption? How could adapting our behaviour, using different climatic zones within a same building for different functions and expressing these architecturally, condition a less standardised approach to reaching global energy performance ? The solar or bioclimatic movement in architecture has worked in this direction, as have isolated emblematic examples of public architecture like the Welsh Assembly (Great Britain) or the refurbished Nyon Castle Historical Museum (Switzerland).10)But these are exceptions, and most new buildings or refurbishment projects in Europe are not designed with a cultural understanding of thermal comfort and performance.

Finally, the problem with the "invisibility" of energy consumption is that it eclipses other forms of wasteful consumption. Computers, cell-phones, the internet, lighting, the recent proliferation of video advertising in public space, plasma screens in every shop window or institution are left permanently running. Little is done to raise awareness of the energy guzzling of these devices that very quickly become normal and therefore unnoticed elements of our daily environment. The myth of the "dematerialisation" of technology conceals the heavy environmental impact of artefacts of the digital age. Even though supporters of stringent regulations emphasize that buildings are accountable for 30% of energy consumption, should buildings bear the brunt of this responsibility to the extent of sacrificing their architectural expression or identity? As someone both concerned with the environment and a lover of architecture, I ask : Why violate buildings of exceptional or even modest architectural quality when other wasteful practices remain unbridled ? □

Reference:

[1] Sèze, Claudette. Confort moderne. Une nouvelle culture du bien-être, Paris, éditionsAutrement, 1994.

[2] Maisons paysannes de France, nr. 195, March 2015: 38-39.

[3] Schoof, Jakob. "Klimarettung oder Kulturstörung. Energische Sanierung am Scheideweg", Detail Green 01/2015: 22-30.

[4] Fredet, Jacques "Les enseignements hygrothermiques des bâtiments d'habitation préindustriels", in d'A nr 207, April 2012: 48-51.

[5] Heschong, Lisa. Thermal delight in architecture, MIT Press, 1979.

Note:

1) The first being the 1902 réglement sanitaire départemental.

2) The C.P.T.F.M. (Cahier des prescriptions techniques fonctionnelles minimales).

3) This was the title of a 1972 book commissioned by the Club of Rome and written by Donella H. Meadows, Dennis L/ Meadows, Jørgen Randers and Wiliiam W. Behrens III.

4) The R.E.E.F. (répertoire des éléments et ensembles fabriqués).

5) Taken into account is the consumption of socalled conventional primary energy : heating, cooling, ventilation, auxiliaries, production of domestic hot water and lighting facilities. Such buildings are assigned the BBC (low-energy) label.

6) Figures for market shares of the materials : Gesamtverband Dämmstoffindustrie–German umbrella organisation for the insulating materials industry.

7) 1948 is the date before which legislation considers architecture to be "old" and after which it considers buldings to be modern or recent.

8) The baron Haussmann undertook a vast urban renovation of the city of Paris between 1853 and 1870 and gave rise to the distinct aspect of the architecture and public spaces of the centre of Paris.

9) See for example the studies produced by Maisons paysannes de France.

10) Welsh National Assembly : Richard Rogers Architects, 2001-2006. Nyon Castle Historical Museum: refurbished by Christophe Amsler, 1993-2006.

Thermally Correct? – Sliding Parameters in the French and German Contexts

In the 1970s, in France as in other European countries, the concern for thermal comfort in terms of optimal temperature gave way to a notion of energetic performance of buildings. Legislation on energy consumption of buildings has become more stringent in the last decade and now encompasses not only new but historical buildings. Criticism is arising of the massive use of polluting insulating materials and of the risk of disfiguring old buildings and reducing the variety of architectural expressions. Can an improvement of the thermal performance be made compatible with the preservation of architectural diversity and quality? Does the focus on the energy consumption of buildings conceal other wasteful practices?

thermal comfort, low-energy buildings, external thermal insulation, France, Germany, architectural variety

巴黎－马拉盖国立高等建筑设计学院

2015-06-19