原文：Energy efficient museum buildingsHelmut F.O. Muellera,b,*aDepartment of Environmental Architecture, Faculty of Building Sciences, Technische Universität (TU) Dortmund, Dortmund, GermanybGreen Building R&D, 4greenarchitecture, Duesseldorf, GermanyArticle history:Available online 13 March 2012Keywords:Museum buildings Energy efficiency Conservation of exhibits Comfort Thermal conditioning LightingMuseum buildings perform ambitious demands for sound conditions of exhibits and comfort of visitors.There is a narrow allowance for room temperature and relative humidity, which has to be maintained forvarying situations of weather and occupancy. Lighting has to assure an excellent visual performance butto avoid deterioration of exhibits. Energy consumption can be kept extremely low contrariwise. Severalhigh quality and low energy museum buildings could be realized recently by utilization of energy effi-cient measures and renewable energies. Outstanding pieces of architecture, e.g. Kolumba Art Museum,Cologne (architect P. Zumthor), Emil-Schumacher-Museum, Hagen (architect M. Lindemann), arepresented and integrated advanced technologies like thermal active room surfaces, low air changeventilation, geothermal heating and cooling, and controlled daylighting are explained.1. IntroductionThere is a basic conflict between conservation and exposure of exhibits for museums. On the one hand minimal fluctuations of room temperature (21℃±3℃), relative humidity (55%±5%), and air flow throughout the year as well as low irradiation of light and ultraviolet radiation are required in order to reduce ageing of samples to a minimum. On the other hand visitors and staff demand excellent thermal comfort, air quality, room illumination,and visual perception of objects.The erection and operation of museum buildings with such high performance standards nowadays has to be energy efficient with a minimum output of green house gases over the life cycle. This means a low embodied energy in the building materials and construction, a low energy demand for heating, cooling, ventilation and lighting as well as a utilization of renewable instead of fossil energies.Last not least economical conditions have to be fulfilled. While building investments often tend to be increased by measures of energy efficiency, the operation costs for energy and maintenance will be reduced. Overall life cycle costs must clearly account for sustainability.This ambitious and complex task of high quality as well as ecologically and economically sustainable museum buildings can only be realized by a comprehensive design approach of architects,engineers and experts utilizing the latest knowledge about passive andactive means of architectureand technology. This challenge hascreated new principles of design, which differ a lot from the traditional and fully air conditioned museum building, as advancedexamples show [1].2. Principles of energy efficient museum buildings2.1. Thermal controlThe narrow bands of room temperature and relative humidityare traditionally aimed at by complete air conditioning with heat-ing, cooling, dehumidification, humidification of air and varying air change rates for exhibition rooms. The “ideal climate” supposed tobe created by these means provokes some doubts: The ac plants,which have to adjust by measurement and control technology tothe ever-changing influences of number and local concentration of visitors as well external climate factors, cannot warrant stableclimate condition in spite of their technical and financial input. The large volumes of heated and cooled air, which have to be trans-ported under peak loads (2 to 3 and up to 6 air changes per hour),make it difficult to avoid negative effects of draft and raised dust.For the case of failure redundant back-up systems have to beinstalled or exhibits have to be removed.The energy efficiency of completely air conditioned museumscan be improved by passive means like geometry, thermal insu-lation,thermal capacity of room surfaces, orientation and solar control of windows as well as by advanced systems and compo-nents, but the new principles of climate control, which are shown in Table 1, allow for higher efficiency and performance:Thermal capacity of indoor room surfaces in combination with chilled/heated ceilings, floors and walls are the basic principals ofa stable climate control. The room surfaces maintain the required temperature for exhibits by embedded water pipes (Figs. 1 and 2).Thus all conventional heat or cold distributers like radiators or convectors can be omitted with regard to conservatory reasons. Thematerials used are concrete (ceilings, walls), screed (floors), plasterwith cement, lime, gypsum or clay binder (ceilings, walls) or masonry (walls). Clay plaster has a relatively high sorption rate,which allows for storing excess humidity (e.g. for times of high visitor frequency).Components of the building envelope are characterized by air tightness and thermal insulation in addition to the described surface temperature control.The ventilation system can be reduced in comparison to complete airconditioning, as air change rates are mainly based onloads of occupants and lighting. The design of advanced ventilationand surface control systems requires dynamical simulations of the thermal behaviour and the air flow (Figs. 3 and 4).Geothermal energy is predestined for heating (in combinationwith a heat pump) and cooling (free cooling) of room surfaces inMiddle Europe. Boreholes of a depth until 100 m with heat exchangers are used for the basic loads of water systems. Hori-zontal earth airheat exchangers are applied for preheating/-cooling of fresh air (Figs. 5e7).Three examples of out a larger number of museums using these principles (compare ) are shown here, KolumbaArt Museum in Cologne and Emil-Schumacher-Museum in Hagen(ESMH), and Kunsthaus Bregenz. A comparison of energy consumption with traditional buildings could be demonstrated in Hagen, where the existing Osthaus-Museum (OMH) is located directly beside the new Emil-Schumacher-Museum, which was opened 2009. Fig. 8 shows, that the annual energy costs of the ESMH could be reduced to 11.85 V/m2a by means of energy efficiency and to 2.71 V/m2a in addition by renewable energies in comparison to 29.67 V/m2a of the OHM. In terms of energy the classification of consumers and renewable sources is given in Table 2.2.2. Light controlThere are three tasks for the lighting in museums, visibility of objects, conservation of objects, and illumination of rooms, which can be realized by daylight and/or artificial light.A good visibility of objects needs a minimum brightness, good contrasts without cast shadows, good colour reproduction, and avoidance of glare. Depending on the kind of objects, e.g. two-dimensional pictures with micro structures on the surface,three dimensional sculptures or large exhibits like building monuments, the object lighting will differ a lot, especially as thereplacement of exhibitions requires a certain variety. For a true colour reproduction of artwork it is highly important whether daylight or artificial light sources are used and which colour rendering is applied on the room surfaces.The conservation of objects often is in contradiction to good visibility, which increases with the brightness. The energy of absorbed light damages the object. The shorter the wavelength the higher the destructive energy of radiation is, thus UV or blue light has a higher damage factor than green or red. This means that a dark (absorbing) surface will be damaged more than a light one, and a red surface more than a blue one. In addition the sensitivity highly depends on the kind of material, e.g. paper is more sensitive than metal. Finallythe ageingof a material is influenced by the time of illumination. Because of these reasons maximum values for the energetic exposuretolight are defined. As 50 lux is the lowest valuefor good visibility, this illumination often is defined as maximumvalue for sensitive objects of paper or fabric, while 150 lux aredefined for paintings on canvas. This regulation is vulnerable fromthe scientific point of view, as it does not consider the spectral component and the time of illumination. Therefore many museumstry to define the conservation of objects by [4]:- Definition of varying maximum illumination depending on light source - Limitation of maximum duration of exhibition- Absolute protection against UV and blacking-out before/after visiting hours- Individual classification of artwork in light sensitivity categories.These regulations stress the necessity of light control in museums, concerning daylight as well as artificial light.For the orientation of visitors a general room illumination is needed, which can be object lighting simultaneously. Daylight openings should allow the visitors a view to the outside.Daylighting is applied in many museums, as it is characterizedby good colour reproduction, natural lighting conditions, contin-uous spectral distribution, and energy efficiency. Although integralpart of the architectural design lighting experts should be consulted. For illumination purposes skylights are more efficient than vertical windows. Transmission of direct sunlight must be avoided because of glare. For cooling situations solar heat gains must be minimized. This can be doneby fixed or movable shading devices. Solar control glass without additional shading or light diffusion cannot be used, as glare is bound to occur. Movable shading devices, e.g. lamellas, havea high adaptabilityand allowfor an accurate daylight control and, may be, for thermal control as well as total light black-out. Fig. 9 shows the annual illumination of an exhibition room with a skylight and fixed shading devices,which is designed to guarantee a maximum illumination of 400 luxunder maximum external illumination. For poor daylight condi-tions inwinter and under covered sky the room illumination is very poor and (power consuming) artificial light has to be switched on.A movable shading device with variable light transmission, as shown in Fig. 10, can offer controlled daylighting for a significantlonger time of the year. Fig. 10 shows an example of a skylight constructionwith light control (positions from top down): External glazing (ventilated), movable solar and glare control (lamellas),highly insulated glazing, conditioned air gap, artificial lighting, light diffusing ceiling.Fig. 11. Light diffusing ceiling for daylighting from glazed faced facade and artificial lighting from clear storey. Kunshaus Bregenz, A., Architect: Peter Zumthor.As shown in Fig.10 daylight and artificial light systems are often integrated the same building elements, e.g. skylights. A good example is the Kunsthaus (art house) in Bregenz with a suspended light diffusing ceiling and a clear storey above, distributing daylight from the glazed facades and artificial light sources (Fig. 11).Artificial light will vary a lot depending on the kind of museum room and exhibit, and accordingly the energy consumption will.The installed capacity can range from 10 W/m2(general room illumination) to 100 W/m2. The annual electricity consumption willbe influenced strongly by the daylight facilities and the automatic control of artificial light (dimming and switching).3. ConclusionsMuseum buildings can be highly energy efficient although the performance requirements for comfort and object conservation are ambitious. Advanced passive and active means of temperature andlight control were developed, which are predestined for utilizationof geothermal energy and daylight. Energy consumption can be reduced to less than one tenth compared to traditional museum buildings with standard air conditioning. Comfort and conservationof exhibits are improved and lifecycle economy is given. To achievethis result forenergyefficient museum buildings, an integral design process of architects, engineers and experts and the application ofsimulation tools are necessary.References[1] V on Naredi-Rainer P, editor. Entwurfsatlas Museumsbau. Basel, Berlin, Boston:Birkhäuser e Verlag für Architektur; 2004.[2] www.Kolumba.de.[3] www.esmh.de.[4] Müller HFO, Schmitz H-J. Lighting design for museums. In: V on Naredi-Rainer P,editor. Entwurfsatlas Museumsbau. Basel, Berlin, Boston: Birkhäuser e Verlag für Architektur; 2004.博物馆建筑的节能赫尔穆特•四时米勒环境体系结构部门、建筑学院科学技术大学(TU)多特蒙德,多特蒙德,德国绿色建筑研发、绿色建筑4,杜塞尔多夫,德国文章历史：网上2012年3月13日关键词:博物馆建筑节能保护展品舒适性热调节照明博物馆建筑执行雄心勃勃的展览要求声音条件和舒适的游客。