Last year was an eventful one for the U.S. Green Buildings Council (USGBC), culminating with two successes at the end of the year: the Greenbuild Conference in Portland, Ore., and the release of LEED-NC v2.2 for initial public comment. Now, the USGBC is making plans to expand the reach of the sustainable buildings movement with several new and innovative programs, including:

  • A pilot testing of a new LEED Green Building Rating System for Core and Shell development.

  • The development of market specific application guides for LEED-NC.

  • The evolution of the LEED brand to include a rating systems covering homes and neighborhood development.

  • Initial plans for LEED v 3.0.

Perhaps the biggest event on the horizon for USGBC is the development of LEED v 3.0 Many industry leaders are interested in what LEED v 3 .0 will entail. The vision for this launch has expanded and contracted. We've learned quite a bit about how to develop and implement LEED since the release of LEED-NC v 2.0 in 2000. One of the USGBC's major goals is to review the lessons learned from the past five years and develop a program that accelerates LEED's market penetration and maximizes the positive impact green buildings have on the environment.

One issue that the USGBC is struggling with is life-cycle assessment, for which there is currently no consistent industry definition.

LEED'S REFRIGERANT SELECTION CREDIT

One of the factors being considered for future LEED certifications is quantifying the true atmospheric impact of the various HVAC refrigerants on the market. On July 19, 2004, the LEED Technical & Scientific Advisory Committee (TSAC) published a final public review draft titled, “Report on the Treatment by LEED of the Environmental Impact of HVAC refrigerants.” This report addresses the tradeoff between ozone depletion and global warming caused by the release of refrigerant commonly used in HVAC systems. For the full report go to www.usgbc.org/Docs/LEED_tsac/HCFCTG_draft_final_report_7-19-04.pdf.

While a comparison between ozone depletion and global warming is beyond the report's scope, the TSAC offers guidance regarding which refrigerants are environmentally preferable in variable situations.

Hydrochlorofluorocarbons (HCFC-123, HCFC-22) have a small, but not insignificant, ozone depletion potential (ODP). These compounds are stable within their usage in HVAC components, but have a relatively short atmospheric life compared with chlorofluorocarbons (CFCs). Nonetheless, HCFCs are scheduled to be banned in the future.

In contrast, hydrofluorocarbons (HFC-134a, HFC-410a) have an ODP of zero, but their global warming potential (GWP) is substantial. In and of themselves, HFCs are greenhouse gases, leading to a direct GWP through leaks into the atmosphere. Moreover, HFCs are less efficient refrigerants than HCFCs, causing an indirect release of greenhouse emissions from the extra electricity required to operate the equipment.

Version 2.1 of LEED awards one credit for avoiding the use of chlorine containing refrigerant such as HCFCs. It also awards credits for energy savings, rewarding the use of HCFCs. The current version does not take into account the direct GWP of leaking HFCs into the atmosphere. According to the report, there is no win-win solution and an engineer must choose between competing environmental damages.

The LEED v 3.0 committee's analysis has led it to recommend a new credit structure that deals with both ozone depletion and all global warming impacts of refrigerants. According to the statement, an Energy & Atmosphere Credit 4 should be awarded to compounds that score “very well” in one category and “well” in the other. There are no compounds that score “very well” in both.

This approach does not single out any refrigerants, but focuses on the impacts on the atmosphere of a refrigerant as applied in specific HVAC configurations. For example, according to the report, not all configurations using HCFC-123 will qualify; those with a relatively high specific charge or leakage rate would not. The report states that HCFC-22 almost qualifies, but not quite. Therefore, if a manufacturer produces a new piece of equipment that reduces the refrigerant charge per ton or reduces the annual leakage rate, then it is possible for that equipment to earn the credit even if other equipment using the same refrigerant does not.

The committee's current policy is to award the top 25 percent of the combined ODP/GWP metrics with eligibility for this credit. This is subject to change based on more precise information from manufacturers and the improvement of equipment over time.

THE LEED MODEL AS A DESIGN TOOL

According to Daniel Nall, senior vice president of Flack+Kertz in New York City, the acceptance level has reached the point where his firm might start using LEED even for projects that are not applying for LEED certification.

LEED has proven to be a very useful design tool that helps identify sustainability issues, and Nall uses the standard quite regularly. But the value of the protocol remains in the certification, without which there would be no quantification of green buildings.

Nall's firm has participated on projects as geographically disparate as the William J. Clinton Presidential Center in Little Rock (certified LEED Silver), to the Hearst Headquarters in New York City (pending LEED Gold). According to Nall, understanding regional environmental conditions is the essence of successful LEED HVAC design.

The difference between the places that heat significantly, versus places that do not is, obviously, quite dramatic. But the most challenging variation, according to Nall, is that some locations have higher than desirable humidity most of the year.

“It's not necessarily recognized, but when you're trying to do innovative, energy efficient HVAC systems there is no such thing as passive dehumidification,” said Nall. “There is passive cooling, such as night flushing, storage of cool overnight, and evaporative cooling. Or if you're in a high altitude you can do radiant night cooling whereby you can encourage the building to radiate heat into the night sky. But if you live in a humid place, those options for passive cooling are less available. Secondly, you're going to have to do some kind of active cooling anyway to dehumidify.”

According to Nall, LEED's emphasis on energy efficiency makes engineers think twice about their choices, even on non-LEED projects.

Another engineer who has come to depend on LEED is Kim Shinn, principal and director of sustainable design for TLC Engineering for Architecture in Orlando. Shinn's firm does lot of work in the Gulf Coast and Southeast Atlantic regions.

In these areas, the heating systems are designed for humidity control and reheat, not space heating. Shinn routinely works with clients who need help deciding if and where to locate vapor retarders in the wall and roof sections. The conventional wisdom is to locate vapor barriers so that moisture is kept inside the building, but this is an extremely bad idea in the hot and humid south, said Shinn.

“We don't even bother with economizers,” said Shinn. “There are just not enough hours where the outdoor wet-bulb temperatures are low enough, and the leakage through the economizer intake and exhaust dampers can often do more harm than good. And humidification, forget it. We don't even put humidifiers in surgery suites.”

The LEED model contributes to better planning and collaboration on non-LEED projects. According to Shinn, the main difference between working with a LEED system versus a traditional system is LEED's emphasis on “integrated” design. This fosters early cooperation and consultation between owner, architect, contractor, and other engineering disciplines, and leads directly to an approach that pays more attention to “rightsizing” of systems and greater emphasis on individual user/occupant control, Shinn said.

Many modern buildings are supposed to operate 24/7/365, like hospitals. Running systems continuously can overcome a lot of design shortfalls. One does not have to be particularly elegant in the system configuration and control philosophies when there isn't an OFF button. While the “turn it off if nobody's using it” strategy offers a lot of bang for the buck, designers need to be careful that they design ways to allow systems to be shut down properly.

“For instance, it can be really bad news if an air handling system shuts down the supply fans, but leaves the exhaust fans running, pulling the building negative and inducing a lot of infiltration through the building envelope,” says Shinn. “Understanding the thermal inertia of building construction is pretty important in taking advantage of occupancy cycles, especially in optimizing pre-cooling or pre-warming startup.”

To mitigate the risk of dealing with so many variables, many LEED project engineers use models and simulation programs to explore their systems. Shinn's firm simulates many different HVAC systems, particularly when they need to evaluate utility rate effects (time of day rates and demand management). Shinn also investigates the economic return of high efficiency systems and equipment. Many of these tools were introduced to the engineering community at large thanks to LEED.

Another practice used in LEED and now finding greater applicability is a system to replace peer evaluation when the project at hand is so unique that there are no peers with which to consult.

“When you're doing a fairly commonplace system, you can review it with your peers,” says Nall. “But if you're doing stuff that people haven't done before, you have to use a lot of design assistance, simulation, and full-scale mock ups.”

LEED has provided the tools needed to do this, and now many of these tools are being used on non-LEED projects.

For previous Engineering Green Buildings columns, visit www.hpac.com.


Matt Stansberry is a commissioned staff writer for the USGBC. He has written extensively on the built environment and sustainability. Stansberry is the former managing editor of Today's Facility Manager magazine, and current News Editor of the Data Center Media Group . He can be reached at mstansberry@techtarget.com.

The difference between the places that heat significantly, versus places that do not is, obviously, quite dramatic. But the most challenging variation, according to Nall, is that some locations have higher than desirable humidity most of the year.

“It's not necessarily recognized, but when you're trying to do innovative, energy efficient HVAC systems there is no such thing as passive dehumidification,” said Nall. “There is passive cooling, such as night flushing, storage of cool overnight, and evaporative cooling. Or if you're in a high altitude you can do radiant night cooling whereby you can encourage the building to radiate heat into the night sky. But if you live in a humid place, those options for passive cooling are less available. Secondly, you're going to have to do some kind of active cooling anyway to dehumidify.”

According to Nall, LEED's emphasis on energy efficiency makes engineers think twice about their choices, even on non-LEED projects.

Another engineer who has come to depend on LEED is Kim Shinn, principal and director of sustainable design for TLC Engineering for Architecture in Orlando. Shinn's firm does lot of work in the Gulf Coast and Southeast Atlantic regions.

In these areas, the heating systems are designed for humidity control and reheat, not space heating. Shinn routinely works with clients who need help deciding if and where to locate vapor retarders in the wall and roof sections. The conventional wisdom is to locate vapor barriers so that moisture is kept inside the building, but this is an extremely bad idea in the hot and humid south, said Shinn.

“We don't even bother with economizers,” said Shinn. “There are just not enough hours where the outdoor wet-bulb temperatures are low enough, and the leakage through the economizer intake and exhaust dampers can often do more harm than good. And humidification, forget it. We don't even put humidifiers in surgery suites.”

The LEED model contributes to better planning and collaboration on non-LEED projects. According to Shinn, the main difference between working with a LEED system versus a traditional system is LEED's emphasis on “integrated” design. This fosters early cooperation and consultation between owner, architect, contractor, and other engineering disciplines, and leads directly to an approach that pays more attention to “rightsizing” of systems and greater emphasis on individual user/occupant control, Shinn said.

Many modern buildings are supposed to operate 24/7/365, like hospitals. Running systems continuously can overcome a lot of design shortfalls. One does not have to be particularly elegant in the system configuration and control philosophies when there isn't an OFF button. While the “turn it off if nobody's using it” strategy offers a lot of bang for the buck, designers need to be careful that they design ways to allow systems to be shut down properly.

“For instance, it can be really bad news if an air handling system shuts down the supply fans, but leaves the exhaust fans running, pulling the building negative and inducing a lot of infiltration through the building envelope,” says Shinn. “Understanding the thermal inertia of building construction is pretty important in taking advantage of occupancy cycles, especially in optimizing pre-cooling or pre-warming startup.”

To mitigate the risk of dealing with so many variables, many LEED project engineers use models and simulation programs to explore their systems. Shinn's firm simulates many different HVAC systems, particularly when they need to evaluate utility rate effects (time of day rates and demand management). Shinn also investigates the economic return of high efficiency systems and equipment. Many of these tools were introduced to the engineering community at large thanks to LEED.

Another practice used in LEED and now finding greater applicability is a system to replace peer evaluation when the project at hand is so unique that there are no peers with which to consult.

“When you're doing a fairly commonplace system, you can review it with your peers,” says Nall. “But if you're doing stuff that people haven't done before, you have to use a lot of design assistance, simulation, and full-scale mock ups.”

LEED has provided the tools needed to do this, and now many of these tools are being used on non-LEED projects.

For previous Engineering Green Buildings columns, visit www.hpac.com.


Matt Stansberry is a commissioned staff writer for the USGBC. He has written extensively on the built environment and sustainability. Stansberry is the former managing editor of Today's Facility Manager magazine, and current News Editor of the Data Center Media Group . He can be reached at mstansberry@techtarget.com.