Test performance in-house with bim
Automatic, co-ordinated drawing creation is only one of many benefits that bim tools can bring technology-savvy practices
The initial sales pitch employed by cad developers when selling the first iterations of building information modelling (bim) software mainly concerned the benefits of co-ordinated and automatic drawing creation. While plans, sections and elevations are still the end goal of the documentation process, these 2D abstractions are probably the least important benefit that a bim modelling tool can provide.
The creation of a 3D “virtual” model offers designers the opportunity to run many different types of analysis and simulation calculations to optimise the design and performance of a structure. If the original design does not make the most of the location, orientation and materials, this will be expensive to correct with mechanical systems later on in the project.
Then, of course, there is the growing number of energy and sustainability certificates – among them Leed, Breeam, Energy Performance Certificates or Part L energy standards – for which designs must qualify. By using bim to build a 3D model, architects have the opportunity to see the environmental feedback of design decisions from the outset and work towards an optimum configuration.
Whereas, in the past, many firms would contract analysis out to the experts when a design was well underway, the latest range of bim tools are starting to include some basic, yet useful performance analysis and energy modelling features. By using these tools frequently, even at the concept stage, designs will benefit from iterative refinement, prior to building engineers running their heavy-duty analysis programmes. The net result will be better performing buildings and, for the architect, a quantitative understanding of the non-visual aspects of a design throughout.
There are many types of analysis that can be run on a bim model: daylight studies, thermal performance, solar radiation, water usage, acoustics, shadows and reflections, rights to light, computational fluid dynamics (CFD for wind and air movement), carbon emissions, structural analysis and whole-building energy analysis. The more information that can be added to the bim model, such as the U-value of materials, types of glazing and type of expected ventilation system, the more accurate the results. Through experimentation with geometry and materials, the best case configuration can be estimated.
While many of these analysis tools require some degree of expert knowledge, the cad and analysis vendors are striving to build a set of tools that provide meaningful results but remain easy to use and understand.
Revit is undoubtedly the most talked about bim modeller and Autodesk has been acquiring numerous analysis technologies to include in its suite of building design products. With Ecotect and Green Building Studio, the company already has a broad base of tools for 3D designers. However its Labs project, called Vasari (labs.autodesk.com/utilities/vasari) allows the company to experiment with a stand-alone environment for examining building performance at the massing stage. Models can easily be imported into Revit to flesh out the details. Vasari offers extensive planar solar radiation analysis, wind-rose analysis and sun studies.
The modelling capability with Vasari is quite remarkable for a free download. There have been rumours that Autodesk is considering a Revit LT product. Vasari might well turn out to be the Sketchup of the bim world.
While Archicad models can still be imported into other analysis systems, such as Autodesk’s Ecotect analysis tool, using the industry standard format gbXML, Graphisoft has its own energy and carbon analysis tool, called Ecodesigner. Using the bim model and materials data, energy use and carbon footprint are quickly calculated and presented in an easy-to-understand, certification-style PDF, providing a handy guide as to the current design’s performance.
Bentley Architecture and Structure are popular choices with London practices, and the company has set out to dominate the structural analysis market. After acquiring both Staad and Ram structural analysis tools, Bentley probably offers the most comprehensive tools for reinforced concrete, post-tensioned concrete, steel, wood, cold-formed steel, aluminium and masonry.
Integrated Environmental Systems is one of the leading independent analysis firms in this space. It is British, too. With its VE-Ware range of analysis tools, IES offers professional analysis tools for energy/carbon, UK regulatory compliance, daylight and lighting, solar, airflow and costs.
The company’s VE-Ware range of free tools will work in Autodesk Revit and even Google Sketchup. The idea here is these easy-to-use modules will give architects some basic energy and carbon feedback at the concept phase. When the design progresses, engineers will be able to apply the company’s higher-end VE-Gaia and VE-Pro for more accurate results.
In many respects, the building industry is starting to follow the manufacturing industry, which has adopted the methodology of modelling and testing virtual designs within the computer. Bim should not be considered as a replacement for 2D cad, it is simply about being better informed and designing better buildings.