原文：
Energy efficient museum buildings
Helmut F.O. Muellera,b,*
aDepartment of Environmental Architecture, Faculty of Building Sciences, Technische Universit?t (TU) Dortmund, Dortmund, Germany bGreen Building R&D, 4greenarchitecture, Duesseldorf, Germany
Article history:
Available online 13 March 2012 Keywords:
Museum buildings Energy efficiency Conservation of exhibits Comfort Thermal conditioning Lighting
Museum 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), are
presented and integrated advanced technologies like thermal active room surfaces, low air changeventilation, geothermal heating and cooling, and controlled daylighting are explained.
1. Introduction
There 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 and
active means of architectureand technology. This challenge has
created new principles of design, which differ a lot from the traditional and fully air conditioned museum building, as advanced examples show [1].
2. Principles of energy efficient museum buildings 2.1. Thermal control
The narrow bands of room temperature and relative humidity are 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 to be created by these means provokes some doubts: The ac plants, which have to adjust by measurement and control technology to the ever-changing influences of number and local concentration of visitors as well external climate factors, cannot warrant stable climate 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 be installed or exhibits have to be removed.
The energy efficiency of completely air conditioned museums can 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 of a 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. The
materials used are concrete (ceilings, walls), screed (floors), plaster with 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 air
conditioning, as air change rates are mainly based on
loads of occupants and lighting. The design of advanced ventilation and 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 combination with a heat pump) and cooling (free cooling) of room surfaces in Middle 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 www.euleb.info) are shown here, Kolumba
Art Museum in Cologne and Emil-Schumacher-Museum in Hagen