Green + BIM = A Beautiful Marriage
April 2009Enter the virtual world of Building Information Modeling:
It’s a summer’s day, a cool breeze saunters in from the ocean. Even this late in the afternoon, the sunlight finds most of the long east-west façade of the building, providing enough light for most to do their work by it (a few need the automatically adjusted, inside lighting set low); and although the outside temperature is in the high seventies, enough of the breeze enters through operable windows to cool the inside.
An engineer, let’s call him Mr. Daylight, is walking around with a light meter, measuring light intensity in various places of the building, just to make sure the daylighting is strong enough to allow work, comfortably, and without eyestrain. His colleague, Ms. Cool, thermometer in hand, is on a similar mission, making sure that the natural air is cool enough to provide a comfortable work environment for all.
A third engineer, a Mr. Efficient, is keeping his finger on various energy pulses, measuring how much electricity is used not only by the building, but in each zone of the building—now and then changing the composition of the building envelope to one with a different R-value, while also changing the size of the HVAC system … yes, he’s a magician, too—and then taking new measurements to see which combination would make most sense, both economically and for long-term energy usage.
The building, of course, has not been built yet, not in the real world. Still, that does not make it less real for purposes of analysis and evaluation. Our engineers—Daylight, Cool and Efficient—are software simulation and analysis tools, as exact and as efficient as actual people walking around, taking measurements and noting the results.
Made for Each Other
BIM and Green Building appear to be a marriage made in heaven. Perhaps a little strongly put, but not so far from the truth.
Especially if you keep this in mind: A Building Information Modeling (BIM) 3D Model is as close to an actual building without actually building it. BIM allows you to construct the building virtually in such a fashion that you can run simulations and analyses to evaluate various aspects of the building’s performance.
In other words, you can let Daylight, Cool and Efficient loose to help make the building as green as possible.
What Makes a Building Green? Simply put, a building is "green” if it is not harmful to the environment.
Green is a term that has come to mean environmentally friendly to the man in the street only over the last few years. As late as 2004, if you told someone you were designing a green building, you also had to clarify that you were not talking about exterior color.
Today, to be deemed green, a building has to have "less of an impact on the natural environment than the traditional buildings the industry has completed over the last three decades.”
It is, however, only with the introduction of rating systems like LEED® (Leadership in Energy and Environmental Design), and with the use of BIM technology, that designers are now able to test for, quantify and pre-determine the building’s environmental impact prior to breaking ground.
Sustainable versus Green
Lately, the designation green has given way to sustainable, especially in the construction industry, as a way to indicate that we mean the building’s environmental impact over its full lifecycle.
Whereas green initially focused on the use of recycled materials, sustainable takes the concept of environmental impact much further.
Perhaps the best definition of sustainable design is the one offered by the World Commission on the Environment and Development (also known as the Brundtland Commission) in its 1987 report to the United Nations: "Sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs.”
LEED and Living Buildings
The U.S. Green Building Council’s LEED rating system—now the most widely used green gauge in the United States—goes a long way to determining the sustainability of a building’s design in these areas:
• Sustainable Sites (maximum value: 14 points)
• Water Efficiency (5 points)
• Energy and Atmosphere (17 points)
• Materials and Resources (13 points)
• Indoor Environmental Quality (15 points)
• Innovation and Design (5 points)
• 26-32 points earns LEED Certified
• 33-38 points earns LEED Silver
• 39-51 points earns LEED Gold
• 52+ points earns LEED Platinum
Feeling perhaps that LEED was not going far enough, the Cascadia Region Green Building Council at the 2006 Greenbuild conference introduced the Living Building Challenge, which, unlike the LEED building-rating systems, is based on actual performance as opposed to what the building is designed to achieve.
Living status means the building has zero net annual impact on the environment from both a construction and an operational perspective.
The Living Building is judged on 16 different achievements, which it either meets or not, in the categories of site design, energy, materials, water, indoor environmental quality, and beauty and inspiration.
If you plan to go greener than that, the next step up from the Living Building is a Regenerative Building, one that has a net positive impact on the environment.
The Role of BIM
It is BIM’s potential wealth and depth of building information that allows Daylight, Cool and Efficient to don their white coats and clipboards to track and analyze the various relationship between structure, mechanical, building orientation and envelope, in order to determine, say, cooling requirements, or how building orientation and placement of windows will affect daylighting.
Each object that is used to construct the building—it can be a wall, a ceiling, a window, a fluorescent light, a floor-tile, a cladding—contains, in its BIM parameter database, all the data the software analysis needs to arrive at a correct evaluation and conclusion—data such as R-value, acoustic property, color (and that color’s reflective properties), energy consumption, etc. It is against this parametric information that the software runs its tests.
A Computational Fluid Dynamic model can be generated to calculate airflow both around and in the building; or a Geographic Information System analysis can show how far the project is from certain product and material sources (which LEED wants to know), and how much sunlight the building will receive at any given time, and, by the way, what the local temperature fluctuations will be—the better to determine building orientation and material.
The only caveat about BIM analyses—and it’s a big one—is the old adage (or not so old): Garbage In/Garbage Out. In other words, the analysis will only be as accurate, and the result only as reliable, as the data entered into the BIM 3D model parameters.
Given, however, that engineers need accurate data at the start, care is normally taken to make sure the parameters are correct. And based on such a model, engineers and designers can now easily determine how green, or sustainable, the building will be from angles such as building orientation, building massing, daylighting, water harvesting, energy modeling, renewable energy and sustainable materials .
Each of these areas has direct bearing on LEED certification, and on whether or not the building will meet the Living Building criteria.
Building Orientation. Talking sustainable design, building orientation means the way a building is placed on the Earth relative to the path of the sun, which in turn can have a great impact on the energy efficiency of the building, and the comfort of its occupants.
As a rule, the longer façade of the building would face the sun, while openings of the building—such as operable windows—should be set to catch prevailing winds or breezes.
Proper building orientation permits utilization of natural daylight to reduce the need for electric inside lighting, while it also affords maximum deployment of solar panels for renewable energy—taking advantage of the prevailing winds can greatly reduce cooling costs in the summer months.
To analyze this properly, you need to determine the geospatial location of the project, solar south and the direction of prevailing winds. Once you have this data, several analyses can be run against the model, such as daylighting, energy need and renewable energy generation.
Building Massing. In sustainable design, the building’s shape and structure—as defined by its component parts, and including footprint, number of stories, roof, etc.—is informed by the climate, and to which extent passive design strategies are deployed. A passive design is one that reduces the energy consumption of a building by taking advantage of natural heating, cooling and lighting.
A building that will rely on daylighting will most likely have a long and narrow footprint to allow natural light in from both north and south façades, and will probably also sport an atrium to bring daylight down into the center of the building.
An important part of the building’s mass is the choice of envelope material, which is determined by the R-value required to meet the green goals for the building.
Again, given a sufficiently detailed BIM 3D model, an array of analyses can be run—many of a comparative "what-if” variety, meaning an initial test is run as a benchmark, then, after a change has been made—such as substituting ICF for EIFS as cladding—a second test is run and the results compared.
This way various alternatives can be tested to determine what form and envelope will best meet the sustainable design criteria for the project, as well as which of the tested alternatives is economically feasible.
Daylighting. Daylighting is the use of natural light as the main source of internal illumination. A well-designed building can reduce greatly the need for interior artificial light, which in turn will reduce interior heat generation, as well as energy usage.
An effective daylighting design rests squarely on building orientation, massing and envelope design. A well-integrated daylighting system can greatly enhance visual acuity and comfort as well as the beauty of internal spaces.
Water Harvesting. Both LEED and the Living Building criteria for green design feature water prominently. As water is a finite resource, this should come as no surprise, especially in areas of little rainfall. Although 70 percent of the Earth’s surface is covered with the stuff, unfortunately, only one of those percents can be used for consumption, hence the attention.
Energy Modeling. For many, energy modeling and analyses lie at the heart of green design. And not surprisingly, since, according to the U.S. Energy Information Administration, buildings in the United States account for 30 percent of the world’s energy and 60 percent of the world’s electricity usage; while many of our buildings are almost cookie-cut with oversized HVAC systems regardless of where in the country they are constructed.
There is room for improvement.
In analyzing energy usage, the analyzing software looks at climatic data along with various building loads such as the heating, ventilation, and air-conditioning system (HVAC); solar heat gain; the number of building occupants and their activity levels; sunshading devices; daylight dimming and lighting levels .
The energy model takes into account and combines not only all these factors, but also the building orientation, the massing, the exterior cladding and other factors, to arrive at the energy requirement of the building.
Here, again, various "what-ifs” can be run—and should be run—to try to lessen the energy consumption of the building. Shifting the building orientation slightly may have an impact, as may a higher R-valued envelope, more energy efficient lighting, heating, and cooling systems.
Renewable Energy. Renewable energy is that which comes from free, replenishable sources, and as a rule include these seven: solar, wind, biomass, hydrogen, geothermal, ocean and hydropower.
Climate and place have the greatest impact on how much of which source a sustainably designed project may attempt to harness.
Solar is probably a given in California and New Mexico. Wind is rarely even considered jokingly in New York City. A location close to a strong water-flow, such as a river, may consider hydropower. If the shale is easily drillable—especially in the western United States—geothermal (utilizing steam or hot water from more than a mile below the surface) might be considered.
However, most of the technologies used to harness this "free” energy come with a hefty price tag. In many cases, this becomes a matter of ROI (or how much money you can afford versus how green you want to be). But as our non-renewable sources of energy deplete daily, and will one day vanish, the technology to harness the renewable sources will not only improve, but will hopefully also become price- and cost-efficient.
Here we would use the BIM model mainly to calculate current energy needs (which we will have optimized by envelope, orientation, etc.) and then work out how much of that we can supply with renewable sources. This way, we can determine how much of an impact the project will have on the grid over the lifetime of the building.
Sustainable Materials. Buildings are gluttons for material.
When viewed from a sustainable angle, the materials used to construct a building are not only viewed as a cost, but also as something that took a certain amount of energy, and water, to manufacture, and which required additional energy to store, transport, and then install.
While there are no off-the-shelf software analyzers of sustainable materials at this time, BIM still proves very useful in determining, and tracking, what materials could be made greener.
The concrete work—foundation, slabs, ICF even—can be built with a certain amount of fly ash (up to 45 percent). Using BIM, you can determine precisely how much concrete the building calls for, and so compute how much fly ash to add to the mix.
Additionally, the parametric data for any one object in the BIM 3D model can contain green information as well, such as percentage of recycled material and whether it is locally produced (a LEED criterion).
As a side-note: There is also the fruitful avenue of reclaiming materials from demolished buildings, which can factor heavily in the sustainability of the materials used to construct the project.
BIM Supported Analyses Tools. There are many BIM data analysis tools on the market, and more in the pipeline. Also, most major BIM vendors are looking to incorporate analyses tools within their main software suites.
Not so far-fetched, actually.
On paper, at least, building LEED criteria into the parametric BIM database is not that much of a reach. The technology is certainly there to accommodate all necessary information, and the tools exist to test various scenarios to evaluate LEED compliance.
The question is, will software, anytime soon, combine these functions into one seamless system?
Actually, at the Chicago Greenbuild 2007 Conference and Expo in November 2007, Phil Bernstein with Autodesk explored whether a design team could receive real-time feedback on the carbon, energy and water usage impact of their design choices; all the while tracking their LEED credits as well, also in real-time.
He did this in the form of a futuristic demonstration of Building Information Modeling that allowed designers to change their plan on a touch-screen and immediately see the environmental ramifications of those choices.
The software would hold historic data to allow the designer to view immediately the comparative result of design choices, and so further enable him to adjust these choices to maximize LEED credits.
To be sure, this software does not exist yet, but it is far more than a glint in someone’s eye at this point.
As Rick Fedrizzi, USGBC’s president, CEO and founding chairman, put it at the conference, "This kind of tool will have a tremendous impact on our ability to integrate sustainability effortlessly as a priority in everything that we do.”
USGBC and Autodesk Agreement. This development effort is the result of a 2006 agreement between Autodesk and U.S. Green Building Council, which aims to transform the practice of sustainable design and to reduce the man-made causes of climate change through expanded use of Building Information Modeling.
Specifically, the November 2006 press release stated that the Autodesk and USGBC agreement aimed to "expand the use of technology and to facilitate further adoption of sustainable design and green building.”
According to the same release, Autodesk and the USGBC plan to work on several initiatives to make sustainable design easier and more efficient through the use of technology such as the Autodesk Revit platform for Building Information Modeling, ultimately reducing the causes of climate change by increasing the number of green buildings that emit less carbon dioxide.
As part of this agreement, USGBC and Autodesk are to explore opportunities to integrate Autodesk’s technology with the USGBC’s Leadership in Energy and Environmental Design (LEED) green building rating system to help the building industry more easily and rapidly meet goals for reduced carbon dioxide emissions. Potential areas for collaboration are to include consulting, joint development of new technology initiatives, as well as industry education.
To facilitate rapid adoption of sustainable design practices, Autodesk and the USGBC also plan to share the knowledge and results of their partnership with the building industry.
Till Death Do Them Part
BIM and green design is a marriage that not only looks good on paper, but plays out in the real world as well. The wealth and depth of parametric data in the BIM 3D model allow the owner, the architect and the engineer to specify, and test, and so know, how green the project is going to be when constructed. It is the ultimate "know before you go.”
And so, may they live happily every after.
Coeur d’Alene, Idaho–based Ulf Wolf writes for the construction industry as Words & Images.