On the Record: NZE Expert Roundtable - Featured Special Sections

Aldo Leopold Legacy Center (see ED+C July 2008). Photo courtesy of Image Studios.

Editor’s Note

To candidly discuss sustainable and net-zero energy building concepts, processes and software needed to achieve innovative new facilities, sustainable consulting architect Bruce Haxton partnered with ED+C and 16 others (as noted throughout this article) to host a groundbreaking net-zero energy building (NZEB) roundtable.

Spearheaded by Haxton and ED+C senior editor Michelle Hucal, the following article is based on an original roundtable event on NZEB conducted in May 2010. Haxton led and participated in this NZE overview teleconference, which was sponsored by participant Russ Drinker, managing director of the San Francisco office of Perkins+Will. In this unique, in-depth, on-the-record discussion, industry experts analyze NZEB.

Roundtable experts explore the process used in designing a typical NZEB, integrating the owner, users, architects, engineers, contractor and consultants. Roundtable experts also share their NZEB expertise from their respective projects.

The buildings most specifically discussed in this roundtable include: 1. Research Support Facility at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) in Golden, Colo., and 2. the Aldo Leopold Legacy Center in Wisconsin.

Introduction to NZE

Bruce Haxton reminds the panel, as well as readers, that NREL has been the leader in renewable energy and high-performance buildings. The NREL buildings are at the forefront of sustainability and cutting-edge renewable energy buildings.

RNL, Stantec Inc., Haselden Construction LLC, and the NREL have just completed the construction phase of the DOE Research Support Facility (RSF), an approximately $64 million, 220,000-gross-square-foot project. The design-build team has developed a very unique NZEB using a new design and construction delivery methodology discussed below.

Haxton requests that Ron Judkoff describe the DOE RSF design.

Ron Judkoff: The Research Support Facility is the culmination of a number of years of building cutting-edge, energy-efficient buildings at the National Renewable Energy Laboratory (NREL) in Golden, Colo. The RSF was our first design-build project; a lot of our effort was upfront in the initial programming and writing the energy specifications for the building. We also did a lot of energy analysis, simulation and optimization to help set what the energy specifications would be. So, from my perspective, the RSF is the culmination of an evolution process of highly energy-efficient buildings on our campus.

Haxton asks Jeff Baker, director of laboratory operations at the Office of Energy Efficiency and Renewable Energy, NREL, to describe the project implementation phase for the new RSF.

Jeff Baker: Let me speak to our project acquisition strategy. It was fairly unique for the Department of Energy as we don’t do much design-build. We chose the performance-based, progressive design-build method to create more project value for the dollar than traditional design-bid-build methods deliver and to deliver the project quicker. We believe that this method, built on well-defined goals such as energy performance, number of people to be housed, flexibility for future reconfiguration, etc., unleashed the creativity of the design-build firms and reduced performance and financial risk to all parties.

To ensure we attracted the best talent, we issued a national Request for Qualifications (RFQ) describing our project and received 10 qualified responses. We narrowed the group down to the three best teams and provided these teams with the draft RFP. As Ron already mentioned, the Request for Proposal (RFP) included performance goals and metrics developed through an extensive planning process, including a design charrette. However, we needed to make sure our RFP was thoroughly understood by all parties and as good as it could be.

Both the Department of Energy and DOE’s National Renewal Energy Laboratory were very serious about trying to draw the best teams into this unique process and enable them to be as creative as possible, and we realized we were asking the teams to take a risk. To that end, we committed to pay stipends to the two teams that did not win. We believe that the stipends went a long way to demonstrate to the design-build firms that we recognized the uniqueness of the challenging performance-based approach and that we were willing to share the cost to encourage creativity.

Paul Torcellini: We set some very specific goals. We prioritized those goals and stuck with those goals throughout the whole project. One of those goals was the energy goal. We had created an energy goal of 25,000 Btu per square foot per year. We also produced a method for proving this through each stage of the project. At every stage of the project, the design-builder had to show us that they were on target to meet the energy goals.

Phil Macey: This contract stipulates the energy performance of the building. That is a very different contract. So, there were a lot of checks and balances developed in the contract from the beginning.

You know, so much about achieving zero energy isn’t the question. The question becomes, What does it cost, and can you deliver it reliably, responsibly, on budget, on schedule? The more definition you have upfront, the more likely you will be able to achieve the final goals.

Haxton asks Paul Torcellini to describe the early design phase of programming and program verification on the NREL RSF.

Paul Torcellini: As the owner, we put together a very detailed RFP that included energy goals, programming elements, adjacencies and other requirements. Some consultants helped with that process in putting the RFP together. When we put the RFP out for bid, everybody was playing by the same set of rules.

Ron Judkoff: A number of the buildings research people at NREL who really cared about the energy goal passionately were involved in the design charrette process. All three competing design teams were at the design charrette. Our in-house analysis showed that we needed to move to a 60-foot standard section for the building width and not an 80- or 120-foot standard section, which are much more common widths for office buildings in this size range. The 60-foot section, while resulting in more wall area, has many energy advantages. It enables natural ventilation and daylighting to 90 to 95 percent of the floor plate.

Haxton asks Tom Kubala to give a brief overview description of the Aldo Leopold Legacy Center.

Tom Kubala: The Leopold Legacy Center is a four-building structure completed in the fall of 2007 by The Kubala Washatko Architects Inc for The Aldo Leopold Foundation located in Baraboo, Wis. The foundation, which is internationally known for its environmental initiatives, was driven to achieve carbon-neutral status for this 12,000-square-foot LEED Platinum office, exhibit and conference center in response to the question Aldo Leopold himself posed: “How can we build on a piece of land without spoiling it?” The foundation took the quote — and the larger idea it represented — seriously and attempted to be carbon-neutral in operation. In the process of achieving carbon-neutral status for the site, we exceeded net-zero energy operation for the facility.

Haxton asks Tom Kubala to describe the early stages of the Aldo Leopold Legacy Center. Haxton comments that both buildings achieved a very high level of sustainability and net-zero energy results but from very a different design process.

Tom Kubala: We took the approach of developing an overall energy budget first and then working backward to arrive at a design that worked within available energy. We asked ourselves, “What is the total sum of potential energy — sun, wind, biomass, geothermal, etc. — available on the site?” For instance, because we knew the approximate roof area suitable for photovoltaics, we could calculate with reasonable accuracy the amount of energy it would produce on an annual basis. That calculation, along with contributions from solar hot water and wood-fired heating, became our energy budget.

Every design decision we made for the building and mechanical systems was to meet the amount of energy available to us over a year, a figure we calculated to be approximately 20,000 to 25,000 Btu per square foot per year. This is a figure very similar to the NREL energy target.

We minimized the full floor plate depths and, in most cases, stayed within 40 feet in width. We have 100 percent of our usable area of the building taking advantage of natural daylighting. The daylighting aspect of the building was the most remarkable part of the energy savings. We used a number of models to test the amount of energy we’d use for electric lighting. We came in well under even a carbon-neutral amount of energy for lighting.

This is mainly due to occupant training and to the narrowness of the building.

Haxton noted that the NREL team had a different design process than the Aldo Leopold Legacy Center. He asks the team, “Would you characterize your design process as one with numerous interactive design sessions?”

Tom Kubala: Our design process — and the success of the project — relied heavily on the development of a written set of patterns. Our pattern development process is similar to the methodology of Christopher Alexander and addressed how the building would be used, how it would feel, and how the energy would flow throughout the building. Essentially, we wrote a description of how the building would operate before it was designed. Patterns are very useful for helping all stakeholders understand and achieve consensus on key aspects of the building.

Phil Macey: You know, the short answer to Bruce’s question is that energy made the architecture. It was eminently clear to everybody in the room that we had to get a building that was going to respond to the energy requirements.

As John Andary pointed out, his staff, at our request, had started early on that so that we’d have some guidance. If you’re going to hit this really low-energy target, it’s a bad thing to just make up a form or to plug in on the site abstractly.

It was the energy that made the building. The energy model really told us that we were going to have a fairly thin building. Once you ran the numbers and did some rough plans, you began to see what kind of buildings you were going to have.

Haxton asks Scott Shell, principal at EHDD Architecture, to add experience regarding the same topics.

Scott Shell: Getting to actual measured zero energy is where the rubber meets the road; the energy model doesn’t count anymore; it’s all about, Do the systems really work? In my view, this is a profound shift, with designers no longer able to make excuses that “it wasn’t built right” or “the occupants aren’t operating it properly.” It moves away from the abstract idea of design to a real building lived in by real people.

The biggest challenge is not designing a thin building with lighting controls but designing daylighting that actually works – where glare is controlled so the occupants don’t lower the shades (and leave them down for the next week!) and then getting the lighting controls dialed in so the lights are really turned off.

This kind of architecture is completely dependent on the initial phase of a project, where you are letting the sustainability goals, the site and the program shape the design — from the very first sketches trying to figure out how to daylight every single space, yet control heatgain and glare, whilealso creating a beautiful building. Fundamentally, you are letting the site, daylighting, solar control, and the program all come together to shape and sculpt the architecture. For me, this is where the real magic happens.

Integration & Analysis

Peter Rumsey: It all makes so much sense that we would work together in the initial design of the building as engineers and architects. But so many people out there still don’t realize that the critical part of the process is the entire team working together early in the design phase.

So we have to, as engineers, be assertive and work hard to get our comments integrated into the design. When we’re working with architectural professionals who are also highly motivated and experienced, the engineers still need to be assertive to hit these very low energy goals.

Noah Eckhouse: What I sense is a changed workflow incorporating the vision that detailed energy modeling must be used throughout the design process to ensure the highest performing building.

What we see as the new best-practices approach is to have all of the design team members — from architects, engineers and energy analysts to cost estimators and owners — in sync and at the table from the earliest stages of the design charrettes. This creates an informed process for orientation and building form and also creates a trusted set of data that exists from the earliest point on in one software tool. You get away from the silo thinking where nobody trusts each other’s data. Critical energy factors, form and other decisions then trickle down to more-detailed decisions (such as building envelope and HVAC) without loss of fidelity.

The key is to have everyone collaborating from the beginning using building performance tools that can take you all the way from conceptual design to detailed engineering analysis.

John Kennedy: Enjoyment and energy analysis tend not to occur in the same sentence in the design community. We are focusing on making net-zero building design very easy, yet very powerful, by providing users with tools at the earliest phase of conceptual design, to understand the building’s total energy use, water use, and carbon emissions while understanding the renewable energy potential on site as well as the natural ventilation potential for the building.

Ron Judkoff: From an NREL building energy scientist point of view, the design-build process in the beginning was in some ways a bit frustrating for us.

Except for at the very beginning where we set targets and had the charrettes, contractually, we were limited in our participation in the design process. Paul and Shanti did participate in design reviews throughout, but we had to be careful not to violate the spirit of the design-build contract, which says more or less — once the specifications are set — to let the design-build team do their work in their own way.

I have to say, though, the process really did work. One of the things I really love about the building is that it develops its own aesthetic based on responding to the energy performance goal. The windows are a great example where we got away from the glass curtain wall. Many times, when we talk to architects about daylighting, they think of it as a “license to glaze.”

Greg Collette: A couple of things that I think we noticed during the design process and also through construction was that it was imperative upfront that the integration of all of the energy features represented in this facility were thought about before determining the buildings architecture. Importantly, the energy and other performance goals drove the architecture rather than the reverse. For example, our extensive use of daylighting dictated a narrower footprint for the wings and higher ceilings as well as careful use of glass and shading to create the optimal situation for building heating and cooling.

Innovation

Haxton asks Tom Kubala to describe the Aldo Leopold Legacy Center innovative ground source heat pump along with some of the underground concrete passive storage for temperature control.

Tom Kubala: During the early design phase, we relied heavily on energy modeling and were lucky to be able to work with Thermal Energy System Specialists (TESS), Madison, Wis. TESS uses a modeling system called TRNSYS, which is capable of simultaneously dealing with natural ventilation, radiant cooling and heating, and other design criteria we wanted to use in the building. That modeling guided us all the way through many of our decisions.

One of the biggest decisions made was to separate ventilation from heating and cooling, which has become a more-standard approach to low-energy-use construction. We have a slab that is both heated and cooled through a ground link to the geothermal and heat pump system. The ventilation air is 100 percent outdoor air, which comes preheated and cooled through an earth tube system. No air is recirculated. The reason we selected an earth tube system is because of the insights gained through energy modeling.

Mike Utzinger: The other part of the system innovation, and this is from Dave Bradley at TESS, is the placement of a thermal storage tank between the ground source heat pump and the building loads. The heat pumps charged the tank with hot water in the winter and chilled water in the summer, operating at maximum efficiency. Pumps circulated water from the tanks to the floor slabs and the AHU coils. As the slabs required cooling water temperatures during heating and warmer temperatures during cooling than the air-handling unit, we used a mixing valve on the slab return to control the slab supply water temperature.

Tom Kubala: Since this is a somewhat smaller project, the team developed early. There were fewer distinctions between schematic design and design development. It was a continuous unfolding of the design. We design with an energy model; we get feedback from the owner; we design; we get energy model and get feedback from the owner.

So, there was pretty much a continuous process. I might add to this that the contractor had been selected just a month after the architects. They were a part of that whole design and development team as it moved forward.

Bruce Haxton: That must make it a little easier to have readily available cost information so that you can make energy design and cost decisions simultaneously.

Tom Kubala: That’s exactly why that happened.

Cara Carmichael: This is a very important piece of implementing successful life cycle cost assessments (LCCA) on a project, which is a very difficult process to get right but extremely valuable if the team is able to do that. In my experience, the best thing that can happen for successful LCCA is to have a good working relationship between the cost estimator, the energy analyst and the person pulling together the decisions that need to be made. Information needs to be exchanged quickly and seamlessly between these parties in order to be able to model and remodel different efficiency measures and repackage them to come up with an optimized net present value (NPV) to take to the owner for approval. Of course, the owner must also be on board to think of the pricing exercise in terms of NPV rather than just initial cost or simple payback.

Phil Macey: You know the challenge really is one of identifying the right energy contingency, and it’s absolutely 100 percent similar to cost contingencies. There’s no difference in the sense that as you would continue to layer a project with more cost contingencies, you can take it right out of a constructible price range. And there’s a real important dialogue that you have to have on an ongoing basis as the design-build team or as a design team to understand where to set those markers, where to establish those points for the energy contingencies or cost contingencies.

Paul Torcellini: One of the most important things for us is the three quarters or more of the year that the building is unoccupied; there are a lot of nighttime hours — the building needs to know how to turn itself off.

Scott Shell: We’ve done quite a bit of work on plug loads on zero-energy buildings working with Rumsey Engineers and Integrated Design Associates. I used to think reducing plug loads was mostly about occupant behavior and power management settings, and these are important. But what we’ve found is that, if you really pay attention, you can usually find an absolutely equivalent piece of hardware that uses about half as much energy as your standard. Rather than just specify ENERGY STAR, sort the ENERGY STAR spreadsheet and choose from the absolutely most-efficient equipment, including operational and sleep mode.

Verifying and Educating

Haxton asks for final thoughts related to the construction phase, operations and post-occupancy evaluation.

Tom Kubala: What you need is a commissioning agent with a large stick and no mercy because even though we had primed everyone on this team — both design and on the construction end — as to what was required, it still took someone with an amazing fortitude to drive home all the details.

When you’re considering an energy-efficient building like the Leopold Center, every detail is important. We looked at fan efficiency, pump efficiency, every aspect of where power could be conserved. And it takes a meticulous observation and a big stick to keep everybody in line.

Scott Shell: Tom’s comment about fortitude is exactly right. As we’ve measured the performance of our zero-energy buildings, we keep finding all sorts of surprises. New loads show up that we hadn’t anticipated: an irrigation booster pump or an old energy-sucking 48-inch commercial refrigerator someone donated to the school. We find operational disconnects, such as an owner’s security consultant telling them to leave the entire site lighting on at night, which comprised 20 percent of the annual electrical load. We find schedules are off, controls sequences that aren’t dialed in, occupants that need understanding, and lighting that is not dimming. The failure mode isn’t noticed by occupants; the systems appear to work fine, but they just aren’t turning off when they should to save energy.

Tom Hootman: One of the great things about the NZEB concept is that it’s really a measurement of operation. It is not a measurement at the end of the design energy model. And it gets proven out over a year of operation. It is important to get the operational side of the building integrated with the design and construction side. Transparency and communication is critical through the entire process.

Russ Drinker: I would like to step back and consider the bigger picture for a moment. We’ve primarily been talking about net-zero energy at the individual building level. To achieve really significant energy-reduction goals and work toward a climate-positive built environment, we need to jump scale and apply these ideas more broadly. We need to look for opportunities at the campus, district and community level. Then we can reduce energy loads through district heating and cooling and can benefit from efficient, clean-energy generation using technologies such as biomass and waste-to-energy systems. Net-zero energy and climate-positive developments are possible only if you generate clean energy, and the most cost-effective approach is to integrate buildings into a larger system to share resources.

John Andary: What we really want to do, as evidenced on these two projects, is we want to educate building owners because it’s really the building owners, the top-down mechanism, that allow the design professionals and construction professionals to do their really good work. Designing a zero-energy building is not nearly as difficult as getting the owners to believe that it can be done within their budget and allow the teams to do that and actually push that agenda from the top down. When we have that kind of scenario on a project — whether it’s design-build and really well thought out like NREL or when we have an owner that is passionate about zero-carbon or zero-energy solutions similar to the Leopold Center — that is when it happens.

Stephen Selkowitz: I think this is a good overview of the process used to get two very different buildings to very low energy use. There were two high-level comments that I would share with the conferees and the ED+C readership:

There was a lot of discussion about owners and their role but somewhat less discussion about occupants. Both of these buildings have occupants who are likely interested in the performance objectives of the buildings. If we want these design strategies and approaches to be adopted at scale, we need to ensure that these approaches will work for virtually all classes of occupants (and owners). What role does behavior play as an opportunity and constraint in a low-energy design? In particular, the focus on minimizing Btu and kilowatt-hours can impact environmental quality, thermal and visual comfort, etc. The technical trade-offs are challenging enough — design for the needs, desires and preferences of people can be a further challenge. Both projects have discussed the need to learn from occupants and provide that feedback both to current operations but also to future designs.

A second critical and recurring issue in many new high-performance designs is the degree of automation and centralized control. For example, should changes in key lighting and HVAC systems’ operations modes be controlled automatically via sensors, etc., or triggered by occupant action? If the former, how does one ensure robust, reliable operation initially and persistently (sensible design, careful installation, good commissioning, occupant understanding, appropriate overrides). If the latter, how do you inform and train people to take the right actions at the right time and address consistency and persistence. How failure-tolerant is the building performance to either automation failures or inadequate occupant operation? What role does information or motivation play on the different scenarios? In single occupancy offices, these issues may be easier to sort out; in shared spaces, to what degree should each occupant have control or influence over their private space and public space? There are no simple, absolute answers, but the good news is there are diverse solutions, many of which seem workable. Understanding them and improving upon them is still a work in progress.

Summary and Tips

Bruce Haxton, ED+C and the NZEB roundtable conferees hope that their experiences, hard work and struggles defined in this interactive session will allow other professionals and students to produce better buildings that will perform at very high levels. This will ultimately save our natural resources and conserve a significant amount of energy.

Haxton reminds us that there are numerous paths that a design team may choose to pursue a sustainable NZEB:

n          The entire team and users need to “buy into” the concept to create an effective client/design professional team.

n          Team building in the early stages will help set the tone of the entire project team.

n          Early in the project stages, identify the definition of NZEB that you are using.

n          Also define other concepts that are to be used in the design of the building, i.e., carbon-neutral, LEED, or some other project parameters.

n          Be sure to match goals with the budget to meet those goals.

n          Remember that just as there are cost-contingency factors for project planning, there should also be energy-contingency planning, sometimes as much as 10 to 15 percent at the beginning of the project.

n          Focus on reducing the energy requirements to the minimum, and then try to make up for the remainder of the energy with renewable energy.

n          Use the articles featured in ED+C magazine, for example, as tools, knowing that every site and building program is very unique and that it will require a significant amount of work to design an NZEB.

n          In that same spirit, the owner, client and users need to realize that they are part of the design and user team that needs to learn how to use the building and continue to strive to save energy. That process of learning how to use the building and save energy may last for years.

n          NZE building clients need to support their design professionals with extra fees to develop these buildings that take more time to design.

n          The architects and engineers need to anticipate extending their professional services into the occupancy period to be able to train the client users and operations staff on how to use the building to achieve a high-performing NZEB.

See the related sidebar “Conclusions and Lessons Learned” on page 54 for final thoughts compiled by Bruce Haxton on NZEB.

© Copyrighted May 2010 Bruce Haxton. This work may not be reproduced in whole or in part without written permission of Bruce Haxton. All rights reserved.