BIM for Sustainable Design...

In 2009 buildings accounted for about 43% of all the UK's carbon emmissions. Buildings and other developments also can damage the enviroment, through poor waste management or the inefficient use of resources. Complex analysis and processes used to be very expensive to perform and very laborious but BIM software supports key aspects of sustainable design and green certification. BIM allows us to apply similar tools to building design that used to be the preserve of the airplane and racing car industries where sophisticated tools deliver continuous and immediate feedback on a far greater range of characteristics than conventional design tools. Material quantities and properties, energy performance, lighting quality, site disturbance, and what-if comparisons between new construction and renovation are some of the types of information now available to us.

This approach to building design is so different from using conventional CAD software that the industry needed a new name and that name is BIM. As building growth intersects with enviromental concerns and the rising costs of energy, a growing field within building design has emerged- sustainable design, the practice of designing, constructing, and operating buildings in a manner that minimises their environmental impact. The goal of sustainable design is to produce green buildings that are environmentally responsible, profitable and healthy places to live and work. Sustainable design is not new exactly, there are examples of older designed buildings around the world that have roof top gardens and openable windows (aspects that we now consider green), but the energy crisis of the 1970's and the emerging enviromental movement launched the modern era of eco-friendly design.

The enviromental assessment of buildings is not new either with the first national scheme, BREEAM (the Building Research Establishment Enviromental Assessment Method) starting in 1990. BREEAM has spread all over the globe and expanded in its methods as it used to have 19 pages and 27 credits available and now exceeds 350 pages with 105 credits. The principles of BREEAM also spread with the US Green Building Council launching its LEED assessment in 1998.Both systems can work together and there are buildings with both systems used for their assessment. There are also systems in Australia, known as Greenstar and CASBEE in Japan.

Before BIM, many digital building models did not contain enough information to perform analysis and evaluation. As with traditional physical models and drawings, evaluating building performance based on graphic representations of conventional CAD or object based-CAD solutions requires a great deal of human intervention and also interpretation, this renders the analyses too costly and/or time consuming. The parametric building modeller which we use in our Revit software represents the building as an integrated database of coordinated information. Beyond graphically depicting the design, much of the data needed for supporting sustainable design is captured naturally as design on the project proceeds.

We are able to integrate the BIM model into available analysis tools which greatly simplifies the often cumbersome and difficult analysis required before. This process gives us immediate feedback on design alternatives early on in the design process. Our BIM models are therefore very well suited to address the problems that sustainable design bring up, it has also opened up the embodied energy and complete lifecycle costings for further evaluation and optimisation. For projects going for LEED and/or BREEAM the drawings we can supply can prove the qualification for the credit. Its true that drawings like this could be produced conventionally, but the BIM model produces these drawings more efficiently as part of the building information model and has the big advantage of parametric change technology, this coordinates changes and maintains consistency at all times. There is no intervention required to update either drawings or links.

A LEED or BREEAM requirement documented in the model is far less likely to fall out of synch or be overlooked (and maybe violated) during project design than a requirement documented in a conventional CAD or object-CAD-based application. The model also carries a wealth of information necessary for many other aspects of sustainable design and/or BREEAM / LEED certification. Examples are, schedules of building components can be obtained directly from the model to determine percentages of material reuse, recycling, or salvage. Alternate design options for sustainability can be studied and tracked in the model. Advanced visualisation techniques can be obtained and can help in showing that green design can notonly perform well but can also look good. The BIM model can be used with other software tools for energy analysis, lighting studies, etc., to quantify the green effects, and the 3D visualisations possible and the walk-throughs allow the design team and the client to see the greener design.

Daylighting...

Natural light when used to illuminate buildings, makes people more comfortable and more productive if in a work setting.This natural light also reduces the loads from electrical lighting, and the subsequent heat and energy loads. A sustainable, high performance design can derive much of its ultimate success from the effective relationship to, and integration of, the sun's energy into the design of teh building envelope and glazing. Although this fact is true, the complexity of performing effective daylighting analysis is rarely undertaken. There are computer software programs available that can accomplish these tasks, but their cost has prohibited their use along with the cumbersome and difficult methods of entering the building design information. The BIM model has also changed this by allowing the design team to perform these tasks within the standard design enviroment.

Energy Analysis...

Sophisticated energy analysis is critical to a building design strategy for reduced energy use. Like the daylighting above, there has been software available for years that can perform this analysis, but once again it was rarely used by design teams. On larger projects maybe the energy analysis would be out sourced (due to time and cost), as a result of this building energy performance information would only be available at fixed times in the project, usually later than needed for supporting the best decision making about the project. The BIM model allows us to complete these analyses earlier in the design cycle, and makes possible routine analysis carried out by us and obtain our own baseline energy analysis. The software that BIM Architectural Services use is directly linked to the Green Building Studio, an industry leader in the development and implementation of building energy analysis tools and web based solutions. We also use IES another industry leader based in Scotland.

These services creates a geometrically correct thermal model of the building, applies local building code assumptions, creates a DOE-2 input (a file type to import into building energy use and cost analysis software), runs the analysis, and returns summary results to our software. This process enables us to perform energy analysis throughout the design process. In very early design phases massing studies can be used with resulting energy analysis to make early decisions about how the building is placed on the site. As the design progresses, various design options can be evaluated for energy savings. If more detailed analysis is required we can import the DOE-2 files and combine with engineering analysis systems. This automated approach can save hundreds of hours of manual labour and therefore the costs.