Archive for ‘BIM’

January 30, 2011

Overview of Energy Modeling

What is an Energy Model?

An energy model is a simulation created with computer software to determine a building’s energy use given specific variables. There are many energy modeling programs (the Department of Energy has indexed nearly 50) that range from free software to highly proprietary software designed for specific types of buildings and thermodynamic conditions. Most models utilize information on building design, envelope, orientation, weather, schedules, controls, and energy-using systems to project comparative energy consumption and costs. While the energy model is not used to predict energy bills, it is used to compare the overall performance of building design versus a baseline approach which meets a common building standard, like the ASHRAE 90.1-2004 Energy Standard. What is even more useful is to compare specific or combined energy conservation measures versus a baseline design. These measures could include changing the building orientation, adding better glazing, improving chiller efficiency, or implementing daylighting strategies. The accuracy of the energy model largely depends on the quality of the data input, which requires the involvement of the architect and the MEP engineer. Once the information is collected the system will produce project comparative energy usage, demand and cost results over an average year.

When to create the Energy Model?

Energy modeling is most useful in the early stages of design. A proactive energy model allows architects, designers and engineers to create solutions rather than solve problems. Once the design of the building has been created in the energy model, it is relatively simple to compare various architectural and engineering energy conservation strategies. Project team members can evaluate preferred design options individually or in combination to determine the impact on energy and consumption and cost.   After each change, the modeler can evaluate the estimated energy use and cost to determine the combination of strategies and technologies will be most effective in reducing energy consumption. A similar approach can be taken with an existing building, but typically it is only useful to evaluate discrete energy conservation measures and not model an entire existing building. the value of an energy model reduces in relation to the stage of the building’s design – so start early!

Who Should Perform the Energy Model?

Choosing the right modeler is a critical key to success! A talented energy modeler typically has experience in building engineering or architectural design and has analyzed many buildings.

The modeling software must also be flexible and powerful enough to model various design scenarios with accuracy and speed. Through our experience, we prefer software that is based upon a DOE-2.2 simulation environment, like eQuest (available free-of-charge at

The modeler should be selected for their ability to model appropriate building types and unique energy-saving systems, including daylighting, under floor air distribution, radiant cooling, thermal storage, renewable energy and demand control ventilation. The modeler must also be knowledgeable and comfortable working with members of the design team to help identify new energy-efficient solutions that will meet project goals.


Currently there are no federal requirements for energy models to verify compliance with building codes. While some states do mandate energy models for new buildings, Arizona is currently on a voluntary basis. This is probably something to look for in upcoming legislation in response to climate change.

In relation to LEED certification, a significant portion of potential points are devoted to energy efficiency (10 of the 69 possible points for New Construction). While an energy model is not required to meet the Minimum Energy Performance Prerequisite, Green Ideas has yet to find an owner that has pursued LEED certification for a new building without performing an energy model.

For buildings over 20,000 SF it is necessary to complete an energy model under LEED-NC v2.2 to earn any of the ten points available under EA Credit 1: Optimize Energy Performance. Each point is awarded for increased energy efficiency relative to the ASHRAE 90.1-2004 baseline model.

An energy model is a powerful tool to help earn LEED certification, but more importantly, it is an indispensable tool for green building design. Energy modeling helps to maximize energy conservation, decrease environmental impact, and generate Life Cycle Cost savings that cover the expense of greening the building in the first place.

Energy Modeling

In March of 2007 the United Nations Environmental Program released the reportBuildings and Climate Change, stating 30-40% of energy worldwide is consumed in what is known as the Life-Cycle (the design, construction, operation and demolition) of a building. This report confirms what many of us in the green building industry already understand; addressing the energy use of the built environment could have the single greatest impact in reducing our energy demands as a society and therefore the negative effects on our environment, economy and well-being.

Of all the stages in the Life-Cycle of a building, the energy used in the operation phase has the greatest environmental impact. Accordingly focusing on this consumption is extremely effective in reducing a building’s overall consumption, yet determining energy use in a building’s operation phase is not always an intuitive process for even the most experienced designers.

In our efforts to reduce operation phase energy use for our clients Green Ideas has found energy modeling as an indispensable design tool and has therefore integrated energy modeling into our service offerings. Energy modeling can help project team members evaluate a variety of energy conservation measures with little resource allocation to determine optimum strategies that maximize both energy and cost efficiency.

Energy Modeler’s role on the Project Team

Green Ideas has significant experience with computer energy modeling to meet LEED and ASHRAE 90.1 Standard requirements. Energy modeling services can either be performed in-house or by our energy modeling partner, Quest Energy Group.

Modeler’ Role

The Energy Modeler’s role in a project requires a close working relationship with the architect, lighting and mechanical designers throughout the design process to ensure an integrated building design. This approach facilitates critical decision-making regarding the impacts of the building envelope, the daylighting and interior lighting systems and the size of the heating, ventilation and cooling equipment. Accordingly, the Energy Modeler’s initial project involvement will occur during the schematic and early design development phase of the project to produce maximum impact. Green Ideas recommends performing energy analysis early enough in the design process to help the design team make design decisions that will affect energy consumption and comfort.

Schematic Design Phase

During the Schematic Design phase, the Energy Modeler will attend a kick off meeting or design charrette with the owner and design team to develop a preliminary list of energy efficiency measures (EEMs) and HVAC system alternatives that will be evaluated for the project. These EEMs typically include alternatives for wall and roof construction, window type and location, natural daylighting opportunities, high-efficiency package unitary equipment, etc.

The Energy Modeler will then develop an hourly computer model of the schematic design using the eQuest software program. Using this model, Green Ideas will develop a minimally compliant (ASHRAE 90.1) model of the facility. This baseline model will serve as the basis for evaluating potential energy efficiency measures and system alternatives. It will also be the basis for determining the number of credits available under LEED EA Credit 1: Optimize Energy Performance. A second meeting will be scheduled with the design team to present the results of the preliminary analysis. The Energy Modeler will provide the design team with the expected overall performance of the facility as well the economic viability (simple payback and life-cycle cost) of each of the energy efficiency opportunities.

Construction Document Phase

At the end of Construction Document phase, the Energy Modeler will reconcile the computer model of the facility to reflect the final building design. At this time, the Energy Modeler will complete the LEED documentation for both EA Prerequisite 2 and EA Credit 1. A final wrap up meeting or conference call will then be scheduled with the design team to share the results.




November 24, 2010

Revit and CFdesign

Moving to Building Information Modelling does not just assist in the co-ordination and production of plans and elevations. With an accurate 3D model, simulation and analysis can lead to better designs. Blue Ridge Numerics has recently hooked up its Computational Fluid Analysis solution, CFdesign, to Revit, writes Martyn Day.

Computational Fluid Analysis (CFA) sits at the high-end of the design analysis technology tree. It plays a major role in aircraft and automotive design, providing feedback about airflow and reducing drag. It similarly assists the aerodynamic design of Formula 1 cars, with access to wind tunnels limited by the regulations of the competition. However, CFD is not limited to just those cutting-edge professions, but has regularly been used by high-end engineering construction firms and consultants for many years.

With the focus of building design now largely pointing towards greener buildings, maximising efficiency and lowering energy usage, architects have a need to understand the physics of their designs. Like solar, lighting and heating analysis tools such as Autodesk’s Ecotect, CFD can play an active role in shaping the conceptual form, which is decided early in the design process. Putting analysis at the back end of a design process, if at all, when all the key decisions have been made and documented is a fundamental design-process error.

CFD can emulate gases and liquids, heat and mass transfer, multiphase physics, fluid-structure interaction and acoustics throughout any meshed 3D computer model. The move to Building Information Modelling (BIM) in the industry is providing the essential raw material for analysis and 3D models. For architects, a CFD solver would help solve traditionally tough design challenges: thermal comfort, energy audits, solar loading, condensation, smoke egress, occupant safety, thermal bridging and external wind loading. It is due to the increasing need for accurate physical modelling and the consequences of design decisions that Blue Ridge Numerics has built an integration between CFdesign and Autodesk’s popular Revit design suite.


Revit offers the potential to build a single digital model of a design, from the initial concepts to a full building, containing all the Mechanical, Electrical, Plumbing (MEP) and structural components. At each design phase, CFD tools have an active role to play.

On installing CFdesign 2010, a CFdesign icon is added to the Revit toolbar. When an analysis is required simply click on the icon and the design study manager window is brought up. Here one selects which geometry is allocated to the various simulation options. Once selected, CFdesign launches with the corresponding geometry, where various simulations can be run to analyse the airflow, heat, smoke and a number of other possibilities. With each change to the design, the geometry can be resubmitted to CFdesign for analysis. As the design progresses, the CFD analysis will provide valuable feedback on the performance, indicating problem areas that need to be addressed or are introduced by design teams or client changes.

CFdesign displays two wind analyses of the faces of a building side by side, showing the velocity magnitude profile for the design. Results like this will quickly alert the designer to any issues that can be rectified early in the conceptual design phase.

For instance, at the initial concept stage, the wind pressure may be a concern. A 3D model, with or without terrain, can be exported directly into CFdesign, together with weather information for the location. The more geometry that is imported the longer the analysis will take, so elements like trees or small building details should not be selected for export for quick ‘what if?’ scenarios.

As this is the first version of the link, CFdesign only deals with the geometry, ignoring any additional building information that Revit holds, this is expected to be leveraged in future releases.


CFdesign is a very rich visual package and pretty easy to use. The thermal and airflow results are provided in colour-banded 3D models, which feature all the forces or temperatures on building surfaces together with arrow and ribbon animations, indication of wind speeds, directions and any currents or vortexes that the form generates.

The software provides results in a graphical feedback with many options for how to display the results, arrows, ribbons, animation and a variety of graphs, which can immediately provide clear feedback for design refinement. The results are projected onto the 3D model in CFdesign and they can be interacted with and the view can be manipulated. It is even possible to bring up the 3D solutions of two different analyses side by side, which is really useful when trying to understand the results or the effectiveness of proposed solutions.

From my experience I have seen firms use CFD analysis for conceptual design of complex tall buildings that have louvre systems for shading. Obviously in a city and at considerable altitude, the louvre systems need to stay attached to the building and not buckle under extreme wind loads. Here, a CFD analysis can give critical and accurate feedback to determine the loads that any design will have to survive.

CFD is complex as there are many levels of interaction, together with the complexity of fluid physics. In this example it is not just the interaction between the airflow and the louvre, or the air and the building skin, but also how the surrounding buildings impact the airflow prior to reaching the building’s envelope. When considering large-scale analysis such as these, CFD is also used in pollution analysis, as well as the wind deflection impact of new building designs to existing buildings.

CFD tools can model the movement of hot and cold air for thermal emissions and MEP analysis. This can be used in the simulation of residential, commercial and industrial building scenarios, including natural solar heating as well as heat from equipment like servers and PCs. Obviously, CFD is highly useful for simulating the cooling and heating provided by MEP systems. Here complete high-efficiency heating, ventilation and air-conditioning (HVAC) building systems can be simulated and the complex interactions between airflows understood, which will hopefully minimise building running costs.

HVAC and MEP analysis is where CFdesign really excels. Here a floor at Yale University has been analysed as built. The colour mapping shows the lack of consistency in the coverage. The analysis depicted next to it is after this information has been used to optimise the ducting design, providing consistent coverage.

CFdesign offers excellent tools to simulate the effect of smoke from a building fire throughout a model, as demonstrated on page 20. This will help establish the visibility in the event of a fire and any design changes that could be made to give occupants the maximum possibility of escaping.


Historically, CFD solutions not only cost tens of thousands of pounds, but also have typically been licensed per year and at additional licenses per individual processor. Blue Ridge Numerics has a reputation for bucking that trend and have brought the price of CFD down, but it is still a significant investment of many thousands of pounds.

I would envisage an architectural firm having one licence of CFdesign, which would be used by multiple teams as a central resource, providing quick design results, as well as more detailed analysis as the design progresses. Should the practice be mixed with MEP, then that is more users and more benefit from the investment.

The move to 3D in design construction is still in its early days but is now starting to benefit from years of research in other design fields. While the AEC 3D modelling tools are now reaching a mature and usable level, in only a matter of years, high-end, bullet-proof analysis tools are now available for enhanced iterative design.

CFdesign is a very, very impressive tool, its results are as visually appealing as Autodesk’s Ecotect and intuitive to use. The comparison function and design-test-edit methodology will undoubtedly lead to rapid improvements in the creation of performance-driven, energy efficient buildings.

Written by Martyn Day

Published 25 January 2010

November 24, 2010

Rhino Grasshopper

Popular among students and professionals, McNeel Associate’s Rhino modelling tool is endemic in the architectural design world. The new Grasshopper environment provides an intuitive way to explore designs without having to learn to script, writes Martyn Day.

Generative modelling is undoubtedly becoming one of the most exciting CAD developments adopted by the industry. While architectural practices lagged mechanical designer’s appetite for 3D by about 20 years, there has been a sharp increase in the use of 3D and advanced form-creation tools and Rhino is one of the more popular solutions.

Zaha Hadid’s Guggenheim Hermitage Museum, Vilnius. This will be the new centre for international art house pieces from collections of both the New York-based Solomon R. Guggenheim Foundation and the St Petersburg-based State Hermitage Museum.

Rhino has played a predominant role within that move to 3D because of its low cost, ease of use and powerful feature set. Bob McNeel, the man behind McNeel and Associates, developer of Rhino, estimates that it possibly has around 50,000 architectural users worldwide. However, Rhino is developed to be a non-industry specific surface modelling tool, at home designing a yacht, a ring, a shoe or a skyscraper it produces surfaces that are useful for all designers.

McNeel has developed a number of Rhino add-ons and plug-ins, mainly offering additional broad-functionality for rendering and animation in the guise of other animals ‘Penguin’ and ‘Flamingo’, as well as ‘Bongo’ and ‘Brazil’. The latest enhancement is called Grasshopper and comes free of charge while it is in development. Aimed at the emerging generative shape designers, Grasshopper is tightly integrated into Rhino and allows the user to interactively drive geometry via a plug and play interface, removing the need for learning the RhinoScript language.

Bob McNeel said that Grasshopper was developed as an attempt to make scripting more accessible to users that wanted generative modelling tools. “During the design process, designers set-up sophisticated relationships between the parts of the design problem. Before Grasshopper, Scripting, .NET, or C++ code was the only way to do that in Rhino. Writing code is not something designers really want to get their head into. It seemed like most bigger firms have a few ‘scripting geeks’ that could not keep up with the designers’ demands. So more and more designers were asking for scripting training… but then they hated it once they figured out how tedious coding was.

“Grasshopper is a way for designers to look at design problems as a set of sophisticated relationships and to map those relationships graphically and programmatically into a system that allows them to interactively play with alternatives. At first Grasshopper was very simple but, based on user feedback, it now allows for very complete systems, including the ability for expert users to extend the system with C# and Visual Basic components.”

Grasshopper works within Rhino and uses standard Rhino geometry but has its own slick interface window. Algorithms and manipulators are dragged, dropped and connected, as if they were being wired together like effects pedals. It is about as easy as it gets to use but still requires a methodology and understanding of geometry to get a desired result.

Rhino in London

Rhino is particularly popular with expressive London-based architects, such as Zaha Hadid, Buro Happold, HOK Sport and Foster + Partners. Fostering Grasshopper’s usage in London is SimplyRhino, the largest Rhino reseller.

The company runs the annual Shape to Fabrication event which focuses on the use of Rhino and Grasshopper in modelling forms and shapes, through to complex engineering analysis and final manufacturing. McNeel programmers and even Bob McNeel usually make an appearance and are very accessible. The Simply Rhino Shape to Fabrication events are always complete sell outs and well worth attending.

Grasshopper works within Rhino and uses standard Rhino geometry but has its own slick interface window. Algorithms and manipulators are dragged, dropped and connected, as if they were being wired together like effects pedals.

Globally, Bob McNeel knows of 12,000 active Grasshopper customers, 90% of which are architects but admits there may well be more as users do not have to register to download. This liberal attitude permeates through McNeel’s business model and means the company is very customer focussed, leading to a very active user community.

One of the stand-out messages from Grasshopper was McNeel linking the modelling to fabrication. While other CAD vendors seem to only concentrate on the modelling aspect in creating the 3D forms, McNeel has always talked about what happens once the design is complete. “Our assumption is that Rhino is all about ‘design for digital fabrication’. Rhino has always been about free-form shapes that are accurate enough to manufacture. Architecture is the only market we are in that still requires complete 2-D documentation. In all of the other markets, the Rhino 3-D model is used in all phases of design through to fabrication. In many cases without any 2-D documentation.

“AEC is only beginning to catch up. Many of the limitations are not related to the CAD technology, instead the problem is with the AEC business model where everyone is trying to protect themselves from being sued by the other members in the process. Lucky for us, free-form architecture has become very fashionable and it is not possible to fabricate those buildings from 2-D drawings alone. In general, I would guess that more than half of all Rhino users are on the fabrication side rather than the design side.”

Grasshopper is being used and talked about by the same people that had advanced geometry needs and bought into Bentley Systems’ Generative Components (GC). However, GC is script-based and requires training. It is also based on MicroStation, which has a parametric modeller, while Grasshopper uses a very visual plug and play interface to automate the scripting and is based on Rhino, which is a non-parametric surface modeller.

Bob McNeel admitted that the company does not know much about GC, “except that people tell us that it is harder to learn and use than Grasshopper. Since Grasshopper is very flexible, users can set up most any kind of relationship they like, so I guess you could say some of those relationships are parametric. But if the user wants to organise their generative model more like a script, it is more script-like. We are trying not to limit anyone’s shape generation process by forcing them to think about it in a certain way. In most cases, Grasshopper is instantly interactive when you change an input (geometry or parameter) or when you change the definition.”


One of the biggest limitations of all parametric modelling tools is performance, it is very easy to create a script that forces the computer to make thousands of calculations and slow down. The shipping 32 bit version of Rhino suffers from the 2GB RAM limit. To access 64 bit it is suggested moving to the ‘work in progress’ Rhino 5 builds that are available. Bob McNeel explained the strategies to limit performance degradation: “Our goal is for the generative process to be completely interactive. If you make any change to the Grasshopper definition or an input, you see the change instantly. Of course, as the definition gets more complex and the model larger, it slows down. There are options to not regenerate every time you make a change. Also, it is easy to ‘disconnect’ part of a definition while you are working on others.”

The Mac

McNeel has said that Rhino is available as a ‘work in progress’ for the Apple Macintosh and it may be some time before Mac customers will be able to use it. “Grasshopper is a .NET application. It is not clear how we will be able to get Grasshopper over to OSX. The Rhino for OSX is still in development and we haven’t addressed any of the issues related to plug-ins yet,” said Bob McNeel.


Rhino has always been an impressive modelling tool but with Grasshopper, it becomes a very powerful design exploration conceptualiser. The interface for developing the generative designs is worthy of an ‘ease of use’ prize and shames established products like Bentley’s Generative Components. However, users still need to know what they are doing and how to get what they want from the geometry mathematically. The amazing work of Grasshopper users speaks volumes.

While Grasshopper is currently free, it may incur a cost in future. “Grasshopper is still in development. It will be free to all Rhino users as long as it is in development… at least another year. We are not sure yet if at some point it will be an option, or included with Rhino, or a special version of Rhino, or there is a basic version with Rhino and a full version option! In any case, it will not be a financial burden to anyone that wants to use it,” said Bob McNeel.

McNeel has recently launched a new website for the Grasshopper community, which offers tutorials, a gallery and an active forum.

Written by Martyn Day

Published 02 June 2009