Small Improvements to Make Big Difference
January 26, 2011
Old memo from the boss: Your goal for 2010 — build one of the most energy efficient office buildings in the world on the campus of the U.S. Department of Energy's National Renewable Energy Laboratory (NREL). New memo from the boss: Your goal for 2011 — repeat 2010 goal and increase energy efficiency by 17 percent.
Fortunately for NREL, these goals are being achieved thanks to $39 million in funding for the new RSF wing from the 2009 American Recovery and Reinvestment Act (ARRA). The ARRA funding allowed a planned 138,000 square foot expansion of the Research Support Facility to get underway shortly after the finishing touches on the first phase of RSF were complete. Accelerating the building of the second phase of RSF means that NREL will finish the building years earlier than expected as well as provide a unique opportunity for research and contractors.
"A general rule of thumb for projects is you do something, you learn from it and then your ability to apply what you learned is limited by the next project that you get to do," Philip Macey, Division Manager, High Performance Buildings for Haselden Construction said. "Buildings are individually unique. You almost never get to apply what you just learned as is the case with the RSF expansion project. This has been an amazing opportunity for everybody."
Once the expansion is complete, visitors to the RSF will not see two different projects. In the end, the RSF will look and feel like one building.
Same … but Different
"The overall goal is one building. However, one of the biggest differences between the initial project and the expansion is the ease of constructability," NREL Senior Research Engineer Shanti Pless said. "You don't often get to take everything you've learned in one building and immediately replicate it and improve it."
Even though the first phase of the RSF used many of the best construction practices and energy efficiency technologies available, both Macey and Pless have been impressed by the improvement in commercially available building systems for the RSF expansion.
"I've been surprised by how many things have gotten incrementally better — energy performance, thermal performance, and windows. That's usually tough when you are out there on the edge of what is commercially available," Macey said.
"As the design firm, we relished the opportunity to specify improved products for the RSF expansion," added Wendy L. Weiskopf, Interior Design Project Manager for RNL. "The product improvements that occurred during the short time since the completion of the project's first phase are truly impactful. Given the RSF's status as one of the nation's most energy efficient office buildings, increasing the efficiency for the project's expansion was a welcomed challenge."
Once of the more significant changes in the RSF expansion project is the windows. However, those changes won't affect the day-lit work spaces.
"The first RSF project had one of the most advanced window framing systems available," Pless said. "But, they can still get cool, especially on the north side of the building on the coldest days."
What design teams discovered while working on the RSF expansion design was two-fold. First, they could make the windows slightly smaller and not hurt the day lighting yet still help the thermal performance. Second, the thermal breaks could be improved to further slow cold air getting into the building from the windows.
"It's down to really fine details," Macey said. "In the first set of windows, there was a 'key' that hooked the windows together and it was a piece of structural plastic. For the RSF expansion, it's a much larger 'key', this time made with specially engineered fiberglass. It's that critical place where there's more material that acts as a big washer and stops the thermal transfer."
But according to Macey, small design changes such as this have a lasting impact when multiplied over the nearly 600 windows in the RSF expansion wing.
Solar Air Collector Shoulders More Work
While many of the improvements to the RSF expansion will not be visible to people visiting the NREL campus, one change will be very apparent. The transpired solar air collector will be 50 percent larger on the south side of the expansion wing.
"The transpired solar air collector on RSF has been amazing," Macey said. "We modeled it for a 35 degree change in air temperature. It has regularly produced a 50 degree change in temperature when it heats the outside air being drawn into the building. It has become so reliable that it is a big piece of the expansion project."
Although the transpired solar air collector has exceeded expectations, it hasn't been needed too often thanks to a mild Colorado fall and winter. In the first six months the RSF has been in operation, the data center has provided enough waste heat so that the transpired solar collector has kicked on mostly for the sunny and really cold, sub-zero days. But there is no data center in the expansion, so the transpired solar air collector will be doing all of the work to warm the need fresh outside air.
A significant, but not visible, change is the one made to the thermal storage battery in the RSF basement — also known as the labyrinth. There are no interlaced structural concrete grade beams for thermal transfer in the crawl space of the RSF expansion.
"We were really conservative with the labyrinth design for the first phase of RSF because there was no commercially available software to tell us how to design one," Macey said. "We knew intellectually that warm air will transfer energy into something massive. What we found after we had it operating is that the energy transfer is direct and happens much faster than we imagined. So, there is no labyrinth in the RSF expansion. Instead, it has a large open concrete crawl space."
Users Make All the Difference
"Due to the flexibility designed into the first phase, office workspaces stayed very much the same in the RSF expansion," Weiskopf said.
Talking to engineers and designers alike, one theme stands out. Any building can be incredibly energy efficient, but if the staff does not "walk the talk," the energy savings will be diminished.
"We are studying how well the various occupants in RSF are using energy," Pless said. "We've got energy monitors in 12 work stations throughout the building to understand how people are using the energy efficient work stations.
"Occupant education has been key in all of this. People should understand that it is important for them to put their computer in standby mode when they leave. It is the easiest thing they can do to help save energy."
The great news is that the NREL staffers in the RSF so far are sticking to their "energy budget," which works out to only 55 watts per workstation. The staff has been doing a phased move in over the last few months. Soon the first RSF wings will be completely filled giving researchers an accurate picture of how the computer energy model matches real life.
"Our models have proven to be amazingly accurate so far, especially on the lighting," Pless said. "One interesting note from the computer energy modeling is that people are at their desk less than anticipated. They appear to be in meetings, in conference rooms, or on travel. The model assumed we had people sitting at their desk pretty much all day."
But then again, collaboration is an integral part of life in the RSF.
"The design team was able to cost-effectively add additional conferencing space in the RSF expansion, including the including conference rooms that enhance digital collaboration , which are proving to be a much needed and very successful space for employees," Weiskopf said.
The Research Support Facility (RSF) was designed by RNL and built by Haselden Construction, under a design-build, integrated project delivery method. Stantec served as sustainable design consultant and mechanical/electrical engineer.
|$57.4 million (construction)
$64 million total
|$34M (construction) /
|$91.4 (construction) /
(Construction cost only)
(Construction cost only)
(Construction cost only)
|35.1 kBtu/sf/yr||33.2 kBtu/sf/yr||34.4 kBtu/sf/yr|
The RSF will serve as a "living laboratory." The expansion includes the following technology and design improvements and enhancements:
- More efficient solar panels were purchased at a lower cost
- Less window area, while still fully day lighting office spaces
- Larger transpired collector, creating more "free" warmed air
- Better thermal breaks in the window frames, leveraging the latest in commercial windows and aluminum frames, driving down energy consumption and increasing comfort
- Hand crank operable windows, increasing user friendliness
- Automatically controlled outlets, simplifying energy savings for staff
- Displacement ventilation in conference rooms, improving thermal comfort
- Natural passive cooling in stair wells, vs. mechanical ventilation in the RSF
- Triple pane east/west curtain walls, as compared to double glazing in the RSF
- More flexible lighting controls with more lighting zones, allowing easier reconfiguration and enhanced user experience
- Additional use of LEDs, further reducing the installed lighting power density.
- Simplified labyrinth design and reduced costs through enhanced thermal modeling
- True vacancy sensors rather than switched occupancy sensors, simplifying lighting controls and occupant understanding of controls
- Day lighting controls in day-lit stairwells, allowing enhanced energy savings during the day.