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ConstructionPro Week, Volume: Construction Advisor Today - Issue: 47 - 03/18/2010

NREL Hopes New Facility with Daylighting Features Will Spur More Energy-Efficient Construction

The U.S. Department of Energy (DOE) soon will open a facility that is intended to serve as a model for daylighting and energy-efficient construction. Upon completion, it is expected to be the largest net-zero building in the United States, National Renewable Energy Laboratory (NREL) spokesperson George Douglas told GBI.

 

Scheduled to open this summer, the DOE Research Support Facility (RSF) on NREL's South Table Mountain Campus near Golden, Colo., will house more than 800 staff and an energy-efficient information technology data center.  The construction cost of the building will total approximately $54.7 million, Douglas said.

Because 19 percent of the country's energy is used by commercial buildings, DOE plans to make this facility a showcase for energy efficiency. DOE hopes the design of the RSF will be replicated by the building industry and help reduce the nation's energy consumption by changing the way commercial buildings are designed and built.

 

To draw as much light into the building as possible, designers considered various window sizes and glass combinations that would maximize the amount of light, reduce glare, and prevent heat from entering and escaping the building.

 

"There's this push and pull between the size and the construction of the window and getting all of the benefits of daylight into the building," RSF Project Manager Philip Macey said.

 

"The south side RSF windows are a little smaller than the north side windows," Macey said. "That was so we could get the light to come into the building in just the right way. On the north side, the glass goes up considerably higher, and that's because north light is really gentle. It's soft and diffuse, and there really isn't much direct sun. The south side requires a lot more attention because you can get direct sunlight, and it's typically not helpful when it comes to conserving energy.

 

"The windows are literally the balance point in how the building manages energy. Get the windows too big and you'll get too much heat gain and heat loss; too small and you won't get enough daylight to light the interior of the building to the middle of the floor plan. You want to have nice even, balanced light across the floor plan."

 

Some Windows Feature 'Light Louvers'
To help boost the light to the middle of the office space, some of the windows have "light louvers" inside of the window. The light louvers look like miniature venetian blinds hung upside down in the window. The curve of the blind catches the light and bounces it very deep into the building. By literally helping to toss the light across the room, designers were able to maximize the sunlight increasing its distance from 20 feet to 30 feet inside of the office.

 

The windows in the RSF will serve double duty as a working part of the buildings' ventilation system. To help cool the building in the summer, employees will get notification to open windows to let cool air in or to shut windows to keep warm air out. While the windows and the louvers are fairly low-tech solutions, the windows on the west and eastern exposures will look to new technologies to help the building conserve energy.

 

"One of the challenges is that although windows let in the daylight, on the other hand, windows are also how you lose most of the energy out of the building," Macey said. "You have to find this really careful balance if you care anything about energy."

 

Special challenges like this mean looking for new technology. At the extreme ends of the office wings, there will be two kinds of special "dynamic" windows -- electrochromic and thermochromic -- to ensure energy savings.  To keep out the heat, western windows will employ electrochromic technology. Electrochromic windows tint once a small electric current is applied.

 

"When these windows tint, you control the solar radiation that gets in the room by shutting out more of the solar spectrum," NREL Research Scientist Dane Gillaspie said. "These types of windows help to reduce the heating loads -- especially the peak heat -- which is the most expensive in terms of electricity."

 

The other advantage to electrochromic windows is the ability to control when the windows tint. "Because the electrochromic windows tint when you apply voltage across the window, they are user controlled, which means they can be integrated into a building control system, allowing you to decide when to darken the window," according to Erin Whitney, NREL's dynamic window testing coordinator.

 

Another type of dynamic window will be used on the eastern balconies. Thermochromic windows also provide resistance to the transfer of heat by reacting to temperature changes.

 

"During winter days the sun comes up late, isn't high, and doesn't warm up the eastern exposure," Macey said. "These windows have glass resistant to heat transfer that will help us dramatically reduce the heat we would normally lose."

 

"Thermochromic windows react to changes in the environment so you don't have to wire them to the building, you just put them in," Gillaspie said. "You don't get the fine control of the electrochromic windows but, the thermochromic windows are cheaper and it's a killer technology."

 

While DOE is looking to the RSF to be a showcase building for energy efficiency, researchers at NREL see the RSF as a living laboratory to study building energy use, which includes the windows.

 

"Part of the test is to see how normal office workers react to the technology," Gillaspie said. "As researchers, we'll love seeing it, and other tests have shown people really like the technology -- but we'd like to see that for ourselves."

 

Through the years, NREL has worked with many companies to test window technologies, but seeing products in a real-world environment is something that Whitney is looking forward to. "We have no way of simulating how those lab results will transfer to use in the real world, so this is a great real-life test of these windows that have not been tested in a building situation. It will be an interesting comparison of the two technologies and how well they each respond to different situations."

 

Haselden Construction and RNL are building the 219,000-square-foot RSF building, which RNL designed. Stantec Consulting served as the project's engineering, energy modeling, and sustainability consultant.
Sage Electrochromics Inc. is making the electrochromic windows, Douglas said, adding that Ravenbrick LLC is providing the thermochromic windows, Douglas said.

 

"I might add [a note about] the general location/use of the electrochromics in a few locations on east- or west-facing windows in the connector conference rooms," NREL engineer Shanti Pless told GBI. "In general, the window area for the building has been optimized for daylighting, resulting in less window area over typical commercial office buildings. This cost savings is used to pay for triple-pane and operable windows. The north window to wall ratio is 26 percent, and the south is 25 percent; a typical commercial office often exceeds 40 percent."

 

Christopher Powers, chief of external affairs for DOE's operations in Golden, told GBI, "DOE's goal with the RSF project from the beginning has been to reduce the nation's energy consumption by changing the way commercial office buildings are designed and built. When 19 percent of the nation's primary energy is consumed by commercial buildings, we have a real opportunity here to reduce our energy costs and protect our environment. With that goal in mind, we are reaching out to builders, developers, investors, architects, educational institutions, and state and local governments to show them what can be done when you design a building with energy efficiency in the mix. We are just getting started with this effort but plan to spread the word via the news media, social media, hosting tours, speaking engagements, attending conferences, and whatever else makes practical sense to do."

 

NREL Provides GBI with Additional Details About the Facility's Green Features
Here are green highlights of the building, according to Douglas:
Building orientation -- The relatively narrow floor plate (60-feet wide) enables day­lighting and natural ventilation for all occu­pants. Building orientation and geometry minimizes east and west glazing. North and south glazing is optimally sized and shaded to provide daylighting while mini­mizing unwanted heat losses and gains.

 

Labyrinth thermal storage -- A labyrinth of massive concrete structures is in the RSF's crawl space. The labyrinth stores thermal energy and provides additional capacity for passive heating of the building.
Transpired solar collectors -- Outside ventilation air is passively preheated via transpired solar collectors (a technology developed by NREL) on the building's south face before delivery to the labyrinth and occupied space.

 

Daylighting -- All of the workstations are daylit. Daylight enters the upper por­tions of the south-facing windows and is reflected up to the ceiling and deep into the space with a light-reflecting louver.
Triple-glazed, operable windows with individual sunshades -- Aggressive window shading is designed to address different orientations and positions of glazed openings. Occupants can open some windows to bring in fresh air and cool the building naturally.

 

Precast concrete insulated panels -- A thermally massive exterior wall assembly using an insulated precast concrete panel system provides sig­nificant thermal mass to moderate the building's internal temperature.

 

Radiant heating and cooling -- Approximately 42 miles of radiant piping runs through all floors of the building, using water as the cooling and heating medium in most workspaces instead of forced air.

 

Underfloor ventilation -- A demand-controlled dedicated outside air system provides fresh air from a raised floor when building win­dows are closed on the hottest and coolest days. Ventilation is distributed through an underfloor air-distribution system. Evapora­tive cooling and energy-recovery systems further reduce outdoor air heating and cooling loads.

 

Energy-efficient data center and work­stations -- A fully contained hot and cold aisle datacenter configuration allows for effective air-side economizer cooling with evaporative boost when needed while cap­turing waste heat for use in the building. Plug loads are minimized with extensive use of laptops and high-efficiency office equipment.

 

Onsite solar system -- Approximately 1.6 megawatts of on-site photovoltaics (PV) will be installed and dedicated to the RSF. Rooftop PV power will be added through a power-purchase agreement, and PV power from adjacent parking areas will be purchased with 2009 American Recovery and Reinvestment Act funding.

 

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