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Fig. 1. Generic laboratory plan for energy model analysis. Image: Cannon Design.
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Our experience has shown that there is a misconception among the industry that Leadership in Energy and Environmental Design (LEED) certification and sustainability are one and the same. Of course, the commitment to sustainable design is paramount on all projects regardless of LEED certification. The LEED rating system, Labs21 and American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) guidelines and standards provide good benchmarks and criteria for rating the sustainability of a design, but they often don’t consider the maintenance and operational costs associated with attaining certification.
Today, we are looking at not just certification but sustainable practices that go beyond ratings to satisfy our social responsibilities. In the use of new methods and technologies we have to evaluate and balance the costs at the earliest planning stages of the project so that they enhance the project and are not a burden to the project or the client in the long term. This is where the life-cycle cost analysis and Building Information Modeling (BIM) interconnect to determine the best value of sustainable design techniques.
Sustainability vs. LEED
Sustainable design strives to reduce the building’s impact on natural resources, its energy consumption and its carbon footprint, and to create healthy and productive environments. We focus on integrated design or a “whole building approach” to design, where the choices made will have consequences throughout the building and the site. These consequences must be tracked and analyzed for appropriateness. For example, adding glazing for daylighting can affect the heat load, glare, light pollution or cooling loads as well as construction costs.
Several strategies can be used to achieve sustainable design and monitor the process, including life-cycle analysis, detail design charrette, solar shading, energy generation, building proportion, daylight control, building orientation, and equipment “right sizing.”
The LEED rating system has become the standard for measuring sustainable design, both professionally and in the public eye. The original six categories provide a broad range of opportunities for points and use of innovation. The addition of the Regional Priority category now focuses additional points toward credits that have a greater impact in each state and zip code. As the LEED rating system continues to evolve into more specific categories for laboratories, healthcare facilities, homes, schools and so on, there will need to be a greater emphasis on sustainable practices and inclusion of life-cycle cost review based on building type rather than just LEED points.
Baseline building model for energy analysis
To analyze the cost-effectiveness of various sustainable strategies, we developed a model laboratory building in BIM to run our energy modeling software. The model is representative of recently completed projects and uses a typical layout of offices, labs, support labs and support spaces (Fig. 1 and 2). It is based on the following characteristics:
- The building is a 100,000-ft2 facility based in St. Louis, in the middle of America.
- The building is assumed to have been built to ASHRAE 90.1 standards for Climate 4A.
- Internal loads calculated were benchmarked against recently completed projects’ performance.
- Construction elements baseline: slab on grade, steel frame, masonry walls with insulation, low-E double glazing.
- Heating ventilation and air conditioning (HVAC) system baseline: Single-duct variable air volume (VAV), DX cooling from rooftop unit, gas-fired hot water boiler.
Process and methodology
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Fig. 2. Recent laboratory plan as basis for model. Image: Cannon Design.
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In recent years, the biggest change in determining accurate lifecycle cost analysis and energy performance has been the advent of BIM. This system allows us to integrate architectural and engineering information in a virtual 3-D world in real time. The real-time integration of the information database associated with the elements in the model can yield real-time analysis of cost changes, energy usage, heat load and daylighting.
We begin by modeling the baseline laboratory plan into Revit, including load data, site orientation and building performance characteristics. The model is then exported to either TRACE 700 or Integrated Environmental Solutions-Virtual Environment (IES-VE). The TRACE 700 software is used predominately for building load calculations, since this program is widely used and trusted in the industry. The IES-VE software is a newer product with both challenges and positives, but it provides a much better system for considering whole-environment effects such as shading control, glazing options, wall/roof construction, daylighting, weather patterns, solar radiance and wind flows.
The export or conversion from Revit to either of these two programs is still lacking in some respects and requires diligent monitoring of data output. Once the model is in place and the data is flowing back and forth between the BIM and energy-modeling software, we can begin to analyze the thermal performance of the building in many different ways, including energy use, a CO2 summary, room loads, and room environmental conditions as illustrated in Fig. 3.
Additionally, daylight studies and heat gain analysis can be integrated and graphically represented as seen in Fig.4.
The information generated from IES-VE benefits and informs the design process by allowing fine tuning of the controls, developing the energy model for LEED, demonstrating compliance with codes and ASHRAE 90.1, reviewing chiller and boiler options, and comparing energy usage of different systems (e.g. VAV, under floor distribution or chilled beams). The IES-VE software model also gives us the ability to do computational fluid dynamics (CFD) simulations. The simulation results are easy to understand and communicate so that complex air flow criteria can be reviewed (Fig. 5). The use of specialty consultants for CFD is often still needed to analyze more complex building issues, but this helps to target their efforts.
As the process of design has changed, information can now be evaluated on quantitative and graphic terms.
The methodology for reviewing the cost of LEED points is based on the nine sustainable strategies listed below, with four of the strategies expanded to include alternate locations and methods. The strategies are summarized on their performance in the categories below. Strategies that we investigated focused on the following areas: energy production, construction materials, HVAC equipment and cutting-edge technologies.
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Fig. 3. Thermal analysis data. Image: Cannon Design.
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Strategy 1: Wind turbines in multiple locations in the U.S. A vertical-axis turbine is used in our model. Typically, vertical-axis turbines are considered for urban environments. They allow better wind capture from multiple directions, improving their ability to cope with the turbulent wind patterns in urban environments. Furthermore, vertical turbines often capture rising wind (such as the gusts running up the side of a building) better than traditional, horizontal-axis turbines. However, horizontal-axis turbines are still cheaper and provide greater overall efficiencies, since they do not have to push a blade into the wind. For analysis we selected a 2.6 kW model made by Skystream, entered its actual power curve into IES and tested it with the actual wind data from four cities. The IES allowed us to pick the best location on site for the location of the turbine and rate its energy performance.
Strategy 2: Solar photovoltaic (PV) panels in multiple locations in the U.S. We estimated a $11.50/W cost to install panels on our project. A leading solar panel manufacturer (First Solar, Arizona) is developing a thin-film solar panel that could drastically reduce installed costs all the way to $6/W, but these panels are not yet used in the U.S. However, this thin film is being debuted in Europe.
Strategy 3: Glazing. The TRACE 700 model is used for analyzing seven different glazing types to measure the building’s performance change based on glazing changes. The ASHRAE building is based on a 30-40% glazed building, with window U-value = 0.41 and shading coefficient = 0.35. The closest matching glazing type is “6mm double-glazed low-E (e2=0.04) tinted with 6mm air gap”: already a high-performance window. Other glazing types that were tested include better low-E coating (lower emissivity), larger air gaps (increased conduction resistance), and argon-filled gaps (also for increased conduction resistance). The data show that the highest-performing windows had low U values (increased resistance to conductive heat) and high shading coefficients (they allowed more light to enter the building). This is at first counterintuitive; typically, engineers want to keep light out of the building to reduce solar gain. However, we found that the heating loads reduction due to solar gain actually outweighed the increase in cooling load, saving energy in the long run. This will need to be factored against local climate and energy costs.
Strategy 4: Water-cooled chillers. Surprisingly, even though our model showed the water-cooled system has a 20% longer life span and decreases annual utilities by almost $4,500/yr, the increased maintenance and installation cost outweigh the utility bill savings. The model building cooling load is about 405 tons, and our thought is that perhaps we would see better economies of scale on a larger building. We might be at that threshold where it still makes economic sense to run air-cooled. However, it certainly makes environmental sense to use water-cooled chillers.
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Fig. 4. Shading analysis showing how vertical tube shading can achieve the same performance as a building with punched windows with significantly better daylighting. Image: Cannon Design.
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Strategy 5: High-efficiency boilers. It should be stressed that boiler performance depends entirely on water temperature deltas. Thus to achieve high performance with a highperformance boiler, equipment should be sized and operated correctly. This model considers a simple drop-in replacement. There are few other costs to consider when selecting a higher efficiency boiler. We look at a typical 83% efficient boiler, and it cost about $12.10 per MBH for equipment. An Aerco Benchmark boiler operates around 93% efficient and costs $15 per MBH. The payback here occurs in about 14 years.
Strategy 6: Heat recovery. In laboratories, we condition so much air only to expel it in a short amount of time. It makes sense to try to recover some of that conditioning energy. If we re-route our exhaust air to help condition incoming air, we see considerable energy savings. There are myriad types of heat-recovery systems that fall into two basic categories: sensible recovery (temperature only) and enthalpy recovery (temperature and moisture). It is surprising how much of an effect this equipment can have—not only on our building’s energy consumption, but also on our peak loads. Peak loads dictate HVAC equipment sizes, and decreased peak load translates to lower HVAC equipment cost.
The sensible recovery system we looked at is a glycol-runaround loop with a coil at the exhaust feeding a coil at the air handling unit. With pumps, piping, accessories and coils, this option can get pretty expensive. We see typical effectiveness in the 40 to 50% range.
The enthalpy recovery system studied is a cutting-edge product from Renewaire. It allows the transfer of heat and moisture from exhausted air without contamination of other particulates. Typical effectiveness is in the 60 to 80% range, depending on season. The glycol loop makes sense for energy savings, but might have a longterm payback. The interesting finding shows that an enthalpy recovery system, however, downsizes our peak heat loads by about 22%, and our peak cooling loads by almost 55%. This saves us tens of thousands of dollars in equipment sizing, which more than pays for itself. The moral of the story: If you can use them, enthalpy exchange systems can often decrease initial building cost, not to mention utility bills.
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Fig. 5: Surgery room air flow patterns. Blue arrows indicate stagnant air; red indicates high velocity. Although the room was designed to supply clean air above and exhaust below to minimize particles, we found stagnant zones of air. Image: Cannon Design.
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Additional sustainable strategies
In addition to the strategies discussed, our team has investigated chilled beam cooling, ground source heat pumps and vegetated roofs. Here is our analysis of these three techniques as informed by lifecycle costing.
Strategy 7: Chilled beam cooling. The system cost is similar to installing a fan-coil setup. To estimate cost, we look at how much we could decrease our air distribution system, our cooling generation, and our heating generation. Unfortunately cost premiums arise when we consider the extra piping and the actual chilled beam units themselves. We expect this technology will, in time, see major price reductions since it is still seen as a premium, exotic system. If we look at chilled-beam for all rooms and some labs, we see marked improvement. This is attributed to the fact that our labs require most of our outdoor air (74%), and the chilled beam units are extremely expensive. If we use cheaper methods of flooding labs with air we can capitalize on the efficiency in low-flow environments like offices: the perfect application for chilled beam.
Strategy 8: Ground source heat pumps. This system involves running tubing into the ground, either in a horizontal field of loops about 10-ft deep, or in vertical wells around 150 to 200 ft deep. We can estimate about a 600,000-ft2 horizontal field for our building, or a more practical 80,000-ft2 vertical field. The 80,000 ft2 is more feasible given our building’s footprint (33,000 ft2). Again we will see cost cutting primarily from decreased peak loads. Imagine using “free” ground heat to pre-heat incoming outdoor winter air with 65° water, before we ever have to apply natural gas heating. Also consider cooling outdoor summer air with “free” 65° water before we ever need to condition it.
The significant cost of this technology is the excavation. We looked at actual excavation costs for vertical field installation on our past projects to extrapolate how much it would cost per unit of cooling/heating. This excavation cost is drastically offset by the decreased load peaks. Heating peak is reduced by over 60%, and cooling peak is reduced by almost 50%. At over $1,000 per ton and $25 per MBH, that is a great cost saver.
Strategy 9: Vegetated roofs. Although vegetated roofs come in many different varieties, we picked extensive green roofing specifically to look at feasibility, as it is the least expensive per ft2. Options range from lightweight extensive systems that can be installed in trays, to massive intensive systems that require a foot or more of soil and can support trees and shrubbery. We decided to look at an extensive lightweight system from Xeroflor. This system is installed in the world’s biggest green roof on top of the Ford Rouge plant in Dearborn, Mich.
For materials, installation, shipping and so on, we calculated a cost of about $15/ft2. Some intensive roofing companies we spoke with estimated prices as high as $25 to $42/ft2. While for the sake of LEED points we are looking at stormwater runoff savings, the soft benefits of growing vegetation in or near the working environment should also be considered. Increased wildlife activity and less tar, cinders and concrete can have a remarkable effect on residents and employees.
| Fig. 6. Sustainable techniques scorecard. |
| Sustaie Technology |
Rate of
Return (ROI) |
Annual Cost
Savings |
Cost per
LEED credit |
| Heat Recovery - Enthalpy |
Initial Savings |
$5,059.10 |
$ (207,389.14) |
| Ground Source Heat Pump |
5.2% |
$13,666.60 |
$254,377.57 |
| Glazing |
9.4% |
$2,535.01 |
$135,148.50 |
| Wind Turbines - Amarillo |
2.4% |
$4,838.69 |
$181,265.65 |
| High Efficiency Boiler |
7.2% |
$792.40 |
$185,550.12 |
| Heat Recovery - Glycol |
3.1% |
$3,455.30 |
$421,607.21 |
| Solar PV - Phoenix |
0.5% |
$6,196.35 |
$1,365,293.45 |
| Chilled Beam - Non-Lab |
0.8% |
$6,196.35 |
$1,365,293.45 |
| Chilled Beam |
0.3% |
$4,245.36 |
$1,550,559.30 |
| Vegetated Roof |
0.0% |
$12.58 |
$208,921.12 |
| Solar PV - St. Louis |
0.2% |
$3,137.39 |
$1,794,131.86 |
| Wind Turbines - St. Louis |
-0.3% |
$(1,677.46) |
$481,485.62 |
| Wate Cooled Chillers |
-2.8% |
$(1,971.37) |
$1,205,159.62 |
Summary of costs and LEED points
Highlighted in Fig. 6, are the sustainable strategies and their return on investment (ROI), annual energy savings, and the cost to achieve a LEED credit. In a laboratory building the use of heat recovery enthalpy systems provides not only energy savings in operation but is also reduces the size of the needed HVAC system, providing first-cost savings. Other methods such as solar PV and wind turbines vary widely by geography as well as potential local tax/utility incentives and need to be investigated for appropriateness in each region.
Life-cycle analysis has numerous advantages, especially when performed early in the design process. It allows for the early targeting of strategies that will yield a high return on investment. The earlier strategies are identified, the better cost data and performance can be achieved.
In determining the cost per LEED credit and the economic and social impacts, we are able to apply resources where they will make the greatest impact. The ability to target the best value for LEED credits is useful, especially when first cost outweighs the total life cycle and maintenance costs to achieve a LEED certified building. The analysis and evaluation of first costs vs. operational costs through BIM provides key information on annual building savings.
There are also some significant challenges to the process that must be addressed individually and regionally:
- The analytical process and the associated software are still in a developmental stage. The integration of models and software can be challenging, so the targeting of strategies is important to keep costs down.
- Accurate cost of sustainable strategies can be difficult to determine, as the cost of new technology can vary widely. Green roof insulating data is still being developed and cannot effectively be calculated against the costs of installation.
- The data often must be adjusted to the local climate, making some strategies more expensive in different regions.
- Working with the authority having jurisdiction and local codes may also change strategies employed. The interpretations of the code by the authority having jurisdiction can often eliminate proven strategies used elsewhere.
By using the evolving technology of BIM, life-cycle costing can bring additional clarity to sustainability decisions.
Daniel Niewoehner, AIA, is associate VP and senior laboratory planner at Cannon Design, Chicago (www.cannondesign.com). This article is based on a presentation given at the Fall 2009 Laboratory Design conference. For information about the upcoming Spring 2010 meeting, see www.rdmag.com/tags/conference
