Sustainable building design through CFD and BIM integration

[edit] Introduction

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 between different professions, making cost savings, reducing timeframes, and facilitating smarter construction, fabrication, and facilities management. This article explores the importance of sustainable building design, and identifies how BIM-compatible computational fluid dynamics (CFD) can optimise performance further, particularly during in complex and challenging buildings.

[edit] 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 performance occurs in the early design or pre-construction stages.

Despite this, architects have tended to analyse 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 and safety compliance.
• Managing contamination risk in sensitive areas such as clean-rooms.
• Improving output of crops in indoor agricultural settings.

Read more about how CFD is playing a key role in the built environment and bridging the gap between architecture and engineering.

[Fig.1 CFD simulation being used in a challenging operating room environment.]

[edit] Better integration in the design process

Despite the importance of sustainability in the built environment, efficiency gaps 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 many cases, architectural design data is not centrally managed among all project departments and the ability to execute any major changes can be time consuming or even impractical due to communication or knowledge gaps.

Over recent years, Integrated Project Delivery (IPD) has been promoted as a new design process concept tto address these areas of inefficiency. IPD optimises processes in which stakeholders, including owners or designers, actually cooperate and communicate throughout all stages.

To fully realise IPD, designers have adopted the use of Building Information Modelling (BIM) - a common information model that hosts lifecycle data about the facility, to be utilised (amongst other things) for the various simulations relating to architectures. There are a number of BIM tools available with simulation capabilities.

The information in a BIM model can be directly extracted for building performance analysis simulation in high performance CFD tools like EXN/Aero, where optimisation 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 clean-rooms, indoor agricultural facilities, grow rooms, LEED or BREEAM certified buildings, where acquiring a thorough understanding of the flow inside or around a structure can prove particularly challenging.

Thanks to BIM and CFD technology, complicated building modelling 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 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.

[edit] Barriers to BIM/CFD integration

Despite the advantages offered by CFD software applications, they are not always fully-integrated within the BIM process. Surprisingly, BIM models of architectural spaces are often not utilised 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:

• The perception of 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.

[edit] 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 the 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, hinders the adoption of BIM-based sustainability analyses in the AEC industry. More effort is required from the industry as a whole to further develop frameworks and guidelines for BIM-based design and analysis processes to achieve comfortable indoor environments and energy-efficient buildings.

The cloud has helped BIM and CFD make great strides in their accessibility and usability. 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 from expensive and restrictive license agreements.

Modern CFD tools are more user-friendly for designers, not requiring advanced mathematical calculations or advanced engineering knowledge. However, an overall understanding of the process is vital, and vendors provide ongoing support and training services.

[edit] Collaboration, integration and an open mind

To reach the goal of more sustainable building development, engineers, architects and other 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.

[edit] References

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.

[edit] Related articles on Designing Buildings Wiki

• A Practical Guide to Building Thermal Modelling.
• Beyond BIM: Knowledge management for a smarter built environment.
• BIM articles.
• BIM resources.
• BIM.
• CFD HVAC Analysis For Sustainable Building Design.
• Computational fluid dynamics in building design: An introduction FB 69.
• Computational fluid dynamics.
• The thermal behaviour of spaces enclosed by fabric membranes (Thesis).
• Thermal behaviour of architectural fabric structures.

Comments

Software such as Ingrid-Cloud www.ingridcloud.com addresses at least 5 of the barriers mentioned. CFD Democratization is finally here, there are no excuses for not using CFD on any stage of the design process :)