EbeneAllgemein-EinsatzSimulationen/en
Aus IBPSA-Germany
Inhaltsverzeichnis |
Traditional way of design process
Especially in Germany the traditional way of building design process is divided into several special disciplines, which are priced by the German Fee Structure for Architects and Engineers; the existence of this official fee list (it has the rank of a law) also manifests a strong hierarchy in design team and - as a consequence - the completely divided design process. The dominance of architectural aesthetics often yields to neglecting building physics or, in other words, to neglecting energy efficiency, sustainability and building performance - a fact, which might be similar to design processes in other countries all over the world.
Typical energy consumption of air-conditioned office buildings
Sustainable climate concepts that lead to good building performance for non-residental buildings, such as office and administration buildings, require first to focus on passive measures for the intelligent utilization of environmental sources and rejection of undesired loads to limite the building's energy demand. The optimized delivery of the building's remaining energy demand must be the second step.
The results of a study, which had investigated a lot of office buildings in Switzerland during the 1990s years, are shown below. Newer studies performed in Germany have yield similar results and thus confirmed following fundamentals of energy consumption:
The predominant fraction of primary energy consumption by air conditioned office buildings is not caused by heating! In most buildings, air conditioning, cooling and lighting energy use dominate a building's energy consumption. Consequently, passive measures through enhanced building constructions and geometry instead of improved technical systems are auspicious and cost-effective for reducing energy consumption in the first step.
These passive measures, such as window ventilation, effective shading, thermal masses and daylighting cause interactions between architecture, in particular the facade, building statics and building physics. Therefore, for the design and optimization of energy efficient buildings, a much more communicative - and integrated - design process is essential, which requires trade-offs between all participating design disciplines.
Future planning process - an integrated design process
A growing number of building owners, developers, contractors, real estate managers, atchitects, engineers, etc. realize that the traditional way of planning - with it´s splitted disciplines - is not satisfying any more. For getting a real sustainable building a new way of planning is required definitely - often called an integrated building design process.
During such an integrated building design the planning team is facing new questions often, which are not covered by the traditional way of planing, e.g.
- What´s the necessary size of windows for providing the user with enough fresh air and for a sufficient heat discharge of the rooms ?
- To what level will the summer indoor temperatures raise during summer ?
- Is an active cooling/chilling really necessary ?
- ......
A lot of design teams negate these important design questions during design (by reasons of incompetence or costs ? Or might exist even other reasons ... ?) and therefore overtake a really high design risk. It is known by experience, that such design questions require to call in an appropriate expert (e.g. a building climatologist); these experts are using simulation techniques very often (but only as second most important tool; the most important tool still will remain brain resp. know-how for ever). Because only simulations are able to model the time-various and very complex interactions between all components of a climate concept (e.g. solar heat gain, window ventilation, thermal masses, etc.) with sufficient accuracy and thus enabling their optimization. However these simulations require a higher knowledge resp. competence of the accomplishing expert in comparison with the use of simple method listed in tables, e.g. German standard for overheating in summer: DIN 4108-2.
Any similar, simple ASHRAE-standard ?
Designing energy efficient building concepts requires simulation
Sustainable and energy efficient concepts aim for the reduction of plant systems (heating, air-conditioning, cooling, lighting, etc.) and their energy consumption, which is necessary for the operation of a building. At the best a cooling system and/or a mechanical ventilation can be prevented completely (in regions with a moderate climate) and nevertheless overheating during summer as well as to less fresh air supplement can be avoided. This ecological and economical sensefull aim can be obtained by increased utilization of the environmental sources (daylight, ambient air, sun, etc.).
As a consequence of this aim the design team is facing the "planning" of very dynamic parameters like daylight, window ventilation, thermal masses, night ventilation, solar heat gain, etc. Due to their extremly dynamic behaviour and also the extensive interactions among themselves these time-varying parameters can not be designed by simple table methods (like e.g. the constant air change rate of an air-condition).
Therefore more sophisticated design tools - the simulation technics - are necessary for an estimation or design of these "soft" components of a sustainable building climate concept. For this background the fact is very important, that not all design questions of a sustainable building concept can be answered by one, single simulation. Depending on the design topic different types of simulations are required.
