François Lévy On the Power of BIM For Sustainability

AUSTIN, TEXAS, IS KNOWN FOR ITS FESTIVALS, especially South by Southwest (SXSW), which combines music, film, and interactive media. That event has long garnered the attention of luminaries across media and industry.

However, much is not known about Austin—outside of Austin. Most do not know that Austin is nicknamed “Silicon Hills” due to its concentration of technology companies. Apple, IBM, Dell, Google, and Facebook all have a major presence there, and those are just some of the big names. Another surprising fact is that Austin, Texas, isn’t exactly like the dry Wild West landscapes we see in Western films.

Austin, Texas, has a unique environment characterized by its humid subtropical climate. This climate presents specific challenges and opportunities for residential architecture in the city.

Enter François Lévy Architect

For local architect François Lévy, the specific design task for most of his clients is balancing a range of site constraints and opportunities that will naturally quarrel with the realities of the Austin environment—especially that Texas sun.

Lévy is an accomplished Austin-based architect, author, and former educator who specializes in developing architecture that is both sustainable and highly responsive to climate and energy use. His practice is 80 percent residential and 20 percent commercial architecture.

“We are cooling dominant here in Austin,” says Lévy, “and it can be tricky,” referring to whether the design of a building’s cooling and heating systems is more challenged on one or the other of those tasks. In Austin, as in most of Texas, the task of a building’s systems to keep its occupants comfortable amounts to cooling the building much more than heating it on an annual basis.

The reader may be thinking, doesn’t that just mean you run the AC units more than you run the heater? What’s so difficult about that?

That’s the tricky part Lévy was referring to. “We will be in the mid-80s today, and we are in late November,” he adds during our hour-long Zoom interview. “But the sun is on a low winter sun path, and it can be quite challenging.” That low sun path means the roofs are designed to shade the harsh Texas sun during the hotter months of the year while allowing the sun to penetrate and warm the house during the cooler months of the year. These are working as devised, yet due to climate change, the house and its occupants must contend with an increasingly less rare mid-80 degree day, like today, in late November.

This is what makes it challenging but also fun for an architect like Lévy. In an ideal scenario, the way to design a house in Austin that optimizes its response to the effects of the sun during all the changing months of the year is to develop a long, skinny house that runs east to west. The large north side can capture abundant non-glaring indirect light, while the south side, shaded with deep overhangs, protects against sun exposure. In contrast, the narrower east and west sides present a smaller surface area (target) for heat-inducing low sun angles.

However, long bar-shaped residences often don’t fit property boundaries or sloping grades as gracefully as one might desire. That was exactly the issue with one such Lévy project for a couple that desired an energy-efficient home they could gracefully age in place in. It needed to be on one level, capture views, and respond to the Texas sun so as to optimize energy use. The house also needed to fit the best it could on the site to balance cut and fill challenges with the sloping grades. (see image above and below)

Data-Driven Iteration

To accomplish this challenge—a careful balancing act between the cost of site grading adjustments, working with existing site grades, and setting the house’s orientation for optimal energy utilization—Lévy relied on a data-driven process using Vectorworks BIM software.

He first set the house in the optimal solar orientation, exactly east-west. This resulted in the highest site cost for cut and fill operations. It also negatively impacted valuable existing trees. Next, he set the house orientation for optimal relations to existing grades, yielding superior cut and fill operations. But this resulted in inferior solar orientation.

 

 

 

 

He then tested rotating the house orientation in small steps to arrive at an optimal balance between the best solar orientation and the best scenario with cut and fill against the existing site grades. Importantly, if one reviews the sun path data on a solar elevation graph, the angle of sunlight impinging on a surface (insolation) graphed against orientation or azimuth is a sinusoidal curve (see image lower down in article) with the peak always at due south (180 degrees). However, the curve is flatter at the top, so small percentage adjustments off of due-south orientations result in similar sun path angles.

Lévy ultimately elected 15 degrees off of due south to avoid the existing trees and found a reasonable level in relation to existing grades and cut and fill quantities. Solar orientation wasn’t as optimal as directly due south but reasonably close.

To achieve this data-driven design approach, Lévy capitalized on the capabilities built into his favorite BIM software, Vectorworks Architect. Unlike 2D CAD software only, 3D BIM software inherently creates a virtual building with volumetric 3D data to power the types of calculations that make data-driven design possible.

“We could do calculations manually in CAD, but if you want to do that more than once, it quickly kills iteration,” adds Lévy. “That is the beauty of BIM, and you can almost say that the ‘I’ in BIM is for iteration.” Lévy is a long champion of Building Information Modeling (BIM) and the author of two leading books on BIM for the architecture industry, including BIM for Design Firms.

His suggestion that the letter “I” in BIM is for “iteration” is a clever twist on the meaning and advantages of BIM. As he will state, without the “information” or “I” in BIM, you lack the data to do the types of automated iteration. “The fact that I can run as many what-if scenarios as I want just makes it really more exploratory, and I can ask all the questions I like,” says Lévy. (see animation images below).

Drought and Sun

The environment of Austin, Texas, is no doubt hot at times. Battling the sun is crucial, and one can see from Lévy’s established body of work that many of his projects have large, low-slung roofs with big overhangs.

These large roofs are ideal for capturing rainwater and directing it into rainwater storage, such as cisterns. For Lévy, the roofs are also ideal form-givers in architecture, but they are constantly performative in that they serve multiple roles related to sustainable design goals, from solar energy harvesting potential via photovoltaic solar cells to rainwater capture to delivering precise volumes of shade on specific openings (doors and windows) on south-facing walls.

Regarding the challenges of the sun and shading, I asked Lévy when he calculates and reviews shading in the BIM model in Vectorworks Architect.

“I really look at October 20th,” he added. “That is the time of the year here in Austin when we start shifting from cooling loads to heating loads. But even at that time of year, the sun has a pretty low sun path.” With October 20th being the time to move slowly to heating loads, it makes sense that the roof overhangs are no longer casting shadows on south-facing openings. “In general, I don’t want to be over-shaded,” he says.

Lévy’s sun studies methodology involves more than just October 20th; it also considers the summer and winter solstices. “I don’t bother with the equinox,” he says. To accomplish these sun and shade studies, the 3D BIM model is run through very precise animations that are easy to do in Vectorworks Architect. (see image above). He also utilizes the built-in Heliodon tool in the software.

“The slider tool with sun studies is very handy,” adds Lévy, “but I can do multiple animations of the same design or competing designs at different times of the year, and those are so easy to do and share with clients.”

Vectorworks—Superior Flexibility

Lévy is a passionate fan of his software of choice, Vectorworks. The industry has long lauded Vectorworks for its hybrid nature as a leading BIM authoring application for the AEC industry and a powerful 2D and 3D CAD program that rivals AutoCAD’s legacy of past dominance. While most architectural practitioners now use at least a partial BIM workflow, Lévy has long adapted a full-fledged BIM process from the very earliest stages of design.

“The fact that you have data in BIM from the beginning, you can immediately generate calculations,” he says. He immediately analyzes the surface areas of roofs for rainwater capture and the total glazing areas of the cardinal (N-S-E-W) sides of his buildings. A critical calculation is the ratio of glass to solid wall, as Lévy leverages rules of thumb long documented in professional handbooks for architectural engineering.

Vectorworks captures and organizes this data from BIM objects like roofs and windows and doors into its powerful Worksheet features. These worksheets are like powerful Excel spreadsheets, complete with mathematical functions for calculations. The Vectorworks community has developed many of them for interesting needs, including quality assurance (QA) roles like checks to make sure all walls that are meant to be orthogonal are truly so.

“While I do love the Heliodon tool, if I am going to really nerd out, I would say I love the Worksheets and their functions inside Vectorworks the most,” adds Lévy, who contends that the Worksheets embody the best aspects of the power of flexibility with Vectorworks.

Luc Lefebvre, product marketing manager at Vectorworks, Inc., says that the company has added many worksheet functions in recent years so that users can report on all kinds of data embedded within each object. Unlike any other BIM software, data can be linked to external databases such as Excel and communicate (or sync) bi-directionally with Vectorworks worksheets. While Lévy doesn’t utilize this capability in his workflows, he acknowledges its power to connect data to those used by others, such as consultants and contractors. 

 

 

 

 

“I would say the aspect of Vectorworks that makes it most compelling to me is its flexibility and the fact that I can have an entire project from its Parti diagram up to a complete CA file that reflects the last-minute design decisions all within the same application,” says Lévy. “That is very powerful to me and something I would never want to give up.”

“For me, design really happens throughout all phases of the project,” he adds. “If I had to use different tools for each phase of a project, then I would find a lot of opportunities for things to fall through the cracks, in addition to the general inefficiency of moving between different design tools.”

Data, AI, and the Future

I asked Lévy if there were any recent projects other than custom residential work that were particularly interesting from the point of view of sustainability. He noted an Austin city historical building project that has long been in the works. 

“The most sustainable building is the one you don’t have to throw away,” remarks Lévy. “Local buildings that pre-date mechanical cooling, while not up to modern energy standards by any means, do benefit from having been designed and built with climate in mind: high ceilings for stratification of warm air, appropriate roof overhangs for shade, and they tend to have ample natural ventilation.”

Perhaps somewhat ironically, for someone who’s built a practice on technology, Lévy himself lives in a 120-year-old former train depot, where he and his wife relocated to Austin. A current project of his involves the restoration of a circa-1899 grocery store turned private residence. Lévy worked on the project well over a decade ago, but an earlier owner abandoned it, and the building’s been boarded up ever since. When a new client appeared to save this historic landmark, Lévy had the good fortune to be called in once again. It’s a testament to Vectorworks’ robustness that his BIM files from the early 2010s opened right up and are the basis for the current design work.

 

 

 

 

While the firm’s sustainable-oriented residential projects are Lévy’s specialty, he has sometimes served as a sustainability consultant for other architectural firms. The city of Austin has long been focused on climate change and sustainable design. “Austin has a robust program that actually predates LEED,” adds Lévy. “So, in some cases—as in the historical project just noted—that may be the benchmark we are striving for in projects, or it may be LEED or something else.”

As energy—and climate-focused design becomes more critical to the practice of architecture, architects need more data to help them make better decisions. Lévy is thrilled to see that Vectorworks Architect’s future includes developing a Sustainability Dashboard, a web-based palette that will show in graphic form how design decisions are impacting your project compared to a set goal.

Other items under the “active research” category of the Vectorworks Public Roadmap include a daylight analysis feature set, which could be critical in Lévy’s work in Austin, which has large southern overhangs that clearly impact daylighting. 

“Another big trend we see related to sustainability is the growing proportion of adaptive reuse projects for all project types,” says Luc Lefebvre. “This is a huge opportunity to develop a solution to address building renovation workflow. This will significantly improve what you can currently do to document renovation or adaptive reuse projects. Currently in development, this new feature utilizes object data to generate the documentation needed for these types of projects quickly.”

Data and AI are big evolving stories within the Nemetschek Group and its daughter companies like Vectorworks, Inc. “There is huge potential there,” adds Lefebvre. “We are looking at a lot of things both internally and within the Nemetschek Group. 

MORE: Nemetschek Group announces vision for Artificial Intelligence

While the Nemetschek Group and Vectorworks continue to push forward on BIM, data advancements, and AI technologies, Lévy has long learned to extract value from his expert knowledge of a BIM solution, one that he values more and more as he continues to stay solely focused within one application for his entire workflow, as he adds: “Vectorworks’ big tent approach is super appealing to me.”