Recent years have seen an increase in the use of Building Information Modelling (BIM) software, a trend that has changed the working methods of the Architecture, Engineering and Construction (AEC) industry. BIM has played an essential role in increasing collaboration among multi-discipline professions, making cost savings and reducing timeframes, facilitating smarter construction and fabrication, and facilities management. In this article, we explore the importance of sustainable building design as a key concern, and identify how BIM-compatible computational fluid dynamics (CFD) can optimize performance further, particularly during complex and challenging scenarios.
Sustainability in the Built Environment
Sustainability has been a major issue in the Architecture, Engineering and Construction (AEC) industry for some time, especially in light of rising concerns around climate change. Azhar and Brown (2009) concluded that the best opportunities for improving building environmental performances occur in the early design or pre-construction stages. Despite this, architects have tended to analyze building performance in the latter stages, often outsourcing these services to an external engineering consultant. A number of factors can be attributed to this decision including a lack of suitable methods for architects and a perception of complex modelling and input knowledge required to run an accurate simulation.
Computational fluid dynamics (CFD) brings major value to the AEC industry, particularly when it comes to complex HVAC requirements including:
- Creating optimal thermal comfort for occupants
- Reducing capital equipment needed to manage airflow
- Factoring in outside heat for passive heating scenarios
- Evaluating building wind loading
- Understanding acoustic pathways and noise sources
- Increasing health & safety compliance
- Managing contamination risk in sensitive areas such as clean-rooms
- Improving output of crops in indoor agricultural settings
Fig.1 CFD simulation being used in a challenging operating room environment.
Better Integration in the Design Process
Despite the importance of sustainability in the built environment, efficiency gaps often remain in the overall design process. This is perhaps unsurprising, with an architectural design process divided into multiple stages and a variety of interested parties often working independently in their area of expertise. In many cases, architectural design data is not centrally managed among all project departments and the ability to execute any major changes can therefore be time consuming and impractical due to communication or knowledge gaps.
Over recent years, the Integrated Project Delivery (IPD) has been promoted as a new design process concept to address these areas of inefficiency. Essentially, IPD optimizes the architectural design process in which stakeholders including owners or designers actually cooperate and communicate throughout all stages of the design project.
Fig 2. BIM - Lifecycle of a Building
To fully realize IPD, designers have adopted the use of Building Information Modelling (BIM) - a standard information model that hosts lifecycle data of the facility, to be utilized for the various simulations relating to architectures. There are a number of BIM tools available with simulation capability varying among each application. The information consisted in a BIM model can be directly extracted for building performance analysis simulation in high performance CFD tools like EXN/Aero, where optimization of the modelling and simulation process as well as output performances can take place. Using a reliable and high performance simulation tool is particularly important when simulating complex environments such as cleanrooms, indoor agricultural facilities, grow rooms and LEED certified buildings, where acquiring a thorough understanding of the flow inside or around a structure can prove particularly challenging. For companies who aren't currently doing simulations, there are ways of understanding if it plays a role in your organization. The Envenio Discovery Program is a hands-off way of seeing CFD in action and to find out what simulations can do for you.
Thanks to BIM and CFD technology, complicated building modeling can be digitally constructed with precise geometry and accurate information to support the project construction, fabrication, analysis and procurement activities. Both BIM and CFD have the potential to provide the architecture, engineering and construction (AEC) industry with extensive building data resulting in a more effective design process, increased accuracy in project cost estimation, a reduction in project time, and more energy efficient structures.
Barriers to BIM/CFD Integration
Despite the advantages provided by CFD software applications, they are not always fully integrated within the BIM process. Surprisingly, BIM models of architectural spaces are often not utilized as the object domain in a CFD simulation, despite the advantages and insight that could be provided.
A number of contributing reasons are at play here including:
- A perception remains around the complexity of CFD and its results, with many thinking CFD tools are purely for engineers.
- CFD is still not fully understood by many, so architects and designers may be reluctant to use simulation tools.
- The cost of traditional CFD resources have made running simulations expensive.
- More complex simulations have traditionally taken too long to produce results.
- Complex software tools have made the learning curve too steep or time-consuming.
- Engineers and architects are working separately rather than collaborating.
Fig 3. Potential BIM Lifecycle Participants & Beneficiaries
Overcoming Barriers to BIM/CFD Integration
One of the critical challenges in implementing BIM-based sustainability analyses is the lack of well-defined transactional process models and practical strategies for integration of information. Despite researchers investigating BIM-based analysis workflow according to various design development stages, there is no standard guideline for BIM-based modelling - especially for indoor environmental performance evaluation. This (combined with the challenges facing the CFD industry specifically) in fact hinders the adoption of BIM-based sustainability analyses in the AEC industry. More efforts are required from the industry as a whole to further develop framework and guidelines for BIM-based design and analysis process in order to achieve comfortable indoor environments and energy-efficient buildings.
The cloud has helped BIM and CFD tools to make great strides in their accessibility and usability by all in the built environment. This has already helped to overcome some of the barriers that prevent full BIM/CFD integration. The on-demand nature of such tools provides freedom away from expensive and restrictive license agreements. For example, EXN/Aero is available on an affordable pay-as-you-go subscription.
Modern CFD tools are user-friendly for designers and architects too, not requiring advanced mathematical calculations or advanced engineering knowledge. Of course, an overall understanding of the process is useful and important so vendors provide ongoing support and training services like Envenio's Onboarding Program, whereby users are guided through the platform during a live project.
Collaboration, Integration and an Open Mind
To reach the goal of more sustainable building development, engineers, architects and designers should work closely throughout the entire design process, remaining open minded to the use of BIM and CFD tools as a way of quickly understanding environmental challenges. This close relationship and an integrated BIM/CFD process will allow all parties to acquire a full understanding of available input data and required simulation output.
Azhar, S. and J. Brown, 2009. BIM for sustainability analyses.
McGHC, 2012. The Business Value of BIM. in North America-Multi-Year Trend Analysis and User Ratings (2007-2012).
Schlueter, A. and F. Thesseling, 2009. Building information model based energy performance assessment in early design stages.