Saturday, March 15, 2008

Dynamic Virtual Design

A well-designed and constructed building should last for a century or longer. Design decisions last for generations, but they are often made with little more than guesswork. Experienced architects eventually learn from their mistakes, but those mistakes tend to outlast the architect. A better approach is to model the building in detail during early design and tweak the design to optimize the building's performance. When you optimize a design, you make it work better for less money - for a very, very long time.

Sun Path Diagram for a net zero energy public library (analysis by Nick Worden and Daniel Overbey, BDMD Architects - Green Dream Team)

With the advent of sophisticated computer modelling software, it is possible to get an accurate idea of how a building design will perform long before the building is constructed. A good suite of modelling software can tell you:

  • How much ambient light will be provided by natural daylight on December 21 on a cloudy day?
  • What is the effect of adding wall or attic insulation on the size of the heating and cooling system?
  • How many photovoltaic panels will I need to balance the energy needs of this building on an annual basis? What if I changed from fluorescent to LED lighting?
  • What size of clerestory windows will allow the best natural ventilation and will all parts of the building be adequately ventilated?
  • Will the building next door shade the solar panels on my building?
  • If I put a white roof on this building instead of a black roof, how does that effect my heat gain and heat loss for the year? What if I put on a vegetated roof?
  • How much energy will this building use and what will it's carbon footprint be?
Many architects today still use pencil and paper and build physical models (if any), but a growing number are moving to 3D software that allows a design to be "built" in the computer before it is built in the real world. One 3D modelling software program that anyone can learn to use is SketchUp, which provides some rudimentary evaluation tools, such as simple shading analysis. There are also add-ons to export these simple models as green building extensible markup language (gbXML) files which can then provide the basis for detailed energy and building performance analysis with energy, ventilation and daylight modelling software.

Daylighting analysis for a net zero energy public library showing daylight levels on a cloudy day in the middle of winter in Cass County, Indiana. (analysis by Nick Worden and Dan Overbey, BDMD Architects - Green Dream Team)

To get more accurate modelling data, however, sophisticated building information modelling (BIM) programs like AutoDesk's Revit Architecture are typically used. This software helps architects visualize the design but it also can help determine how well its systems will function. When the whole design team utilizes these tools during early design, little effort is wasted on guesswork. The computer model removes the guesswork and informs a more dynamic and accurate design process, which leads toward a more successful end.
I've been impressed with a relatively inexpensive analysis tool called ECOTECT from Square One Research, which generated the images in this post. Another interesting analysis tool is Green Building Studio, which is about to be acquired by Autodesk, which means it will probably cease to be free. GBS can do a whole building energy analysis of your model when you export it and upload it in gbXML format. GBS can also export to popular engineering energy analysis tools like DOE-2, eQuest, EnergyPlus and Trane Trace700, which can provide energy performance data for any hour of the day any day of the year.
We are finally entering a time when architecture is no longer just a fashion show. We want our buildings to look great and we want the experience of the architecture to be elevating, but we also want them to PERFORM! Green buildings perform by delivering delightful, healthful, daylit, comfortable spaces that are energy and resource productive. The best way to get there is by means of a dynamic collaborative design process assisted by state-of-the-art design tools that can tell us how well the building will perform before the shovels hit the ground and before you open your first utility bill.

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