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    New technical solutionsfor energy efficient

    buildingsState of the Art Report

    Energy efficient building design

    Authors:

    Heimo Staller, Angelika Tisch, IFZ

    Oct. 2010

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    Background

    In the building sector the highest energy saving potentials can be realized by energy efficient building

    design. The energy efficiency of buildings is significantly influenced by architectural design aspects, such

    as orientation, shape of the building structure, where the openings of windows are located, etc. Therefore

    in the Working Group New technical solutions for energy efficient buildings besides the presentation of

    single technical solutions (e.g. innovative HVAC-systems and renewable building materials) a focus is also

    on energy related design aspects. Especially in tendering procedures for architectural competitions public

    clients have to take strong notice on these energy related design aspects. On the following pages a short

    overview of the most important innovative design strategies for energy efficient building design is given.

    Climate Design Adaptation to climate conditions

    Looking back in history we can see that building design, besides other factors (social aspects, availability

    of building materials, etc.) always was a result of the climatic conditions on the building site. Today the

    mainstream of modern architecture is neglecting these climatic conditions, compensating inefficient

    building design with enormous efforts concerning the energy supply for heating, cooling and lighting. To

    design energy efficient buildings (Low-Tec Buildings) architectural concepts have to integrate this old

    knowledge and develop new innovative design solutions based on climatic aspects.

    Most important aspects with strong influence on the building design are outdoor temperature, solar

    radiation, humidity and wind.

    In figure two an office building in Vienna with an innovative design solution based on climatic aspects is

    shown. The design of the south faade of the building is based on the climatic conditions of Vienna,

    enabling highest solar gains (reduction of space heating demand) in winter and avoiding solar inputs insummer (reduction of cooling demand). The south faade has a fanfold structure with 400 m2 of PV-

    Elements for shading in summer, producing electrical energy all over the year.

    Fig. 1 Similar geographical and climatic conditions => similar architectural solutions

    Megaron Houses in Hennan, China (right) and in Gharian, Libya (left) [1]

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    Fig. 2: Section showing winter and summer situation, ENERGYbase, pos architekten schneider ZT KG, Vienna [2]

    General strategies for energy efficient buildingsIn general there are following strategies for the design of energy efficient buildings:

    Minimization of losses

    Maximization of solar gains Heating case

    Minimization of solar gains Cooling case

    Minimization of electricity demand for artificial lighting

    Depending on the degree of latitude strategies with stronger focus on gains or stronger focus on losses

    might more efficient, in general it can be stated that on most European sites a combination of all measuresmake sense.

    Minimisation of losses - Compactness

    In Europe transmission heat losses play an important role for the energy performance of buildings. Depen-

    ding on the building type (housing, office, schools, etc.) transmission losses can have the highest ratio of

    all losses. Therefore the first design relevant measure should be the reduction of heating losses by minimi-

    zation of the shape/volume ratio. Especially for an economical realization of passive houses or zero- and

    plus energy- houses compactness is of highest importance, as worse compactness means higher

    construction costs (improvement of u-values => more insulation materials => higher costs).

    winter

    - emen s

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    Fig. 3 Compactness: Monte Rosa mountain refuge, Wallis, Switzerland, architects: Bearth & Deplazes [3]

    Maximisation of solar gains Heating case

    In the heating period a maximization of passive solar gains should be the main target to reduce the hea-

    ting energy demand. Optimized interaction of orientation, size of windows and disposable thermal mass

    are the key elements. In figure four a school building in Vella, canton Grisons, Switzerland without tech-

    nical heating system is shown, only using passive solar energy and mechanical ventilation with heat reco-

    very for heating. Special design of windows and a special sunblind with reflector (reflecting sunlight to theceilings) enables a maximization of solar energy gains for the classrooms. Massive floors, walls and special

    designed ceilings (ribbed concrete slabs with large surface area) are used for the storage of solar energy.

    Fig. 4 Maximisation of solar gains, school building in Vella, canton Grisons, Switzerland, architects: Bearth & Deplazes [4]

    Minimisation of solar gains Cooling case

    Transparent building elements (windows)

    Orientation and size of transparent building elements (windows) have important influence on the cooling

    demand. In central European climate pure south orientation is the best orientation for the reduction of

    the heating and the cooling energy demand. Intelligent shading elements with different orientation (e.g.

    south windows with horizontal elements, west and east windows with vertical elements) are further

    measures for the reduction of solar gains.

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    Natural cooling with passive night ventilation

    In office buildings up to 2/3 of the total cooling load (around 200 250 Wh/m2/day) can be managed by

    passive cooling without mechanical energy. Night temperature in summer around 15, adequate

    thermal building mass and the possibility of natural stack ventilation (e.g. in atriums, see figure below)

    are requirements for this kind of cooling.

    Fig. 5 Passive cooling (without mechanical energy) through stack ventilation in the night, office building W.E.I.Z. II, Weiz,

    Austria, architects: A plus ZT GmbH Weiz [5]

    Natural ventilation by wind-

    For high rise buildings natural ventilation concepts by wind are innovative alternatives to conventional

    mechanical ventilation systems. The new office building of the European Central Bank in Frankfurt

    (architects: Coop Himmelb(l)au, energy concept: Univ. Prof. Brian Cody) will be the first office building

    using only natural ventilation. The design of the building is based on wind and ascending forces around

    and in the building.

    Fig. 6 Natural ventilation concept by wind, Head European Central Bank, Frankfurt, Univ. Prof. Brian Cody and CoopHimmelb(l)au [6]

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    Minimisation of electricity demand for artificial lighting

    Besides heating and cooling the energy demand for artificial lighting is of importance for the energetic

    performance of buildings. Buildings with huge overall width, like office buildings, tend to have substantial

    energy demand for artificial lighting. The development of innovative daylight concepts is the most

    important strategy to decrease the energy demand for lighting. Daylight concepts always have to be

    considered in combination with aspects for heating and cooling.

    Fig. 7 Sunblind with daylight reflector, 1= alu panel, 2= daylight reflector, 3= glare shield, office building SOKA-BAU,

    Wiesbaden, Germany, architect: Thomas Herzog, Munich [7]

    Active use of solar energy

    Compared to other HVAC-systems active use of solar energy (thermal and photovoltaic solar collectors)

    on one hand has strong input on the design of the building and on the other hand the use of solar

    energy also has strong influence on the environmental performance of the building. The intensive use of

    solar energy requires a comprehensive integration of solar panels in the architectural design concept

    and influences the design of buildings strongly. Solar panels can be mounted on walls and roofs,

    whereas in urban context roofs offer better conditions (less shading by other buildings, free choice ofdeclination enabling higher degrees of efficiency).

    Clouded sky

    Sun

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    Fig. 8 Holistic approach: Solar panels (PV), passive night cooling and integrated day light concept, architectural competition

    Technology Centre Aspern, Vienna, architects: Treberspurg & partner and Frank & partner, Vienna [8]

    References[1] Left picture:Rudofsky, Bernhard: Architecture without architects: A Short Introduction to Non-Pedigreed Architecture. Museum of ModernArt, New York, 1964, page 16[1] Right picture:Daniels, Klaus: Technologie des kologischen Bauens. Birkhuser Verlag, Basel, Boston, Berlin, 1995, page 12

    [2] ENERGYbase, pos architekten schneider ZT KG, Vienna

    [3] http://www.bearth-deplazes.ch

    [4] Wirz, Heinz (editor): Bearth & Deplazes, Konstrukte/Constructs. Quart Verlag GmbH, Luzern, 2005, page 64

    [5] A plus ZT GmbH, Weiz, architect Heimo Staller

    [6] http://www.kleinezeitung.at/allgemein/bauenwohnen/2512922/stadt-zukunft.story

    [7] LichtLabor Bartenbach: Das Licht der Welt. Aristos Druckzentrum, Hall in Tirol, 2007

    [8] Treberspurg & partner ZT GmbH and Frank & partner ZT GmbH, Vienna