Raised Access Floors Contribute to Energy Efficiency and LEED^® CI Gold Certification

The tallest skyscraper in downtown Kansas City, Mo., is now among the city’s greenest commercial offices, thanks to its newest tenant, Kansas City Power & Light (KCPL). One year ago the subsidiary of Great Plains Energy relocated its corporate headquarters to twelve floors at One Kansas City Place, renewing the company’s commitment to Kansas City’s economic growth and development while minimizing KCPL’s environmental impact.

KCPL is a full-service energy provider and resource that services more than 820,000 customers in 47 northwestern Missouri and eastern Kansas counties. Prior to September 2009, the company operated for 17 years out of another Kansas City office building – 1201 Walnut – just blocks from its current location. The need for additional office space, punctuated by the acquisition of Aquila, a midwest utility, in July 2008, forced the company to explore other options within the city that offered room for growth and the opportunity to deploy more sustainable design solutions.

According to Jim Flucke, KCPL manager of corporate facilities, the decision to move to the 42-story One Kansas City Place capped a search that targeted new construction within the city as well as renovated office space. “We evaluated new construction, but it was not going to be cost effective, either from a purchase of land and new construction approach or the lease of land and new construction on that property. Ultimately, the decision to renovate One Kansas City Place afforded us the best opportunity to meet our defined goal of creating an energy efficient, collaborative, LEED^® certified workspace in downtown Kansas City, which is the heart of our service territory, and do so in a cost-effective way.”

Renovating the 20-year-old icon on the Kansas City skyline meant gutting 270,000 square feet of leased space down to concrete and hiring BNIM Architects to oversee the remodel. “KCPL signed a lease for 23 years, so we wanted to develop design strategies that would not only meet their needs on day one, but would offer the flexibility to accommodate change over the course of the 23-year lease,” said Adam Cohen, BNIM associate and project manager for the KCPL project.

Although LEED certification was a goal shared in the initial discussions between KCPL and BNIM, Flucke emphasized that it was not the driver of design decisions. “We worked with BNIM to design the space we wanted to occupy,” he explained. “To everybody’s credit, in the process of achieving our energy efficiency and sustainability goals, we were also able to achieve LEED for Commercial Interiors Gold certification.”

To Flucke’s point, the decision to install a Tate^® access floor system throughout all but 25,000 square feet of the leased space was made early in the design process, not to garner LEED points, but to offer the flexibility Cohen referenced and contribute significantly to energy efficiency goals outlined by KCPL. The fact that the floor system also contributed to LEED certification was secondary. “We made that decision to use a raised access floor systems early on,” said Flucke, “and we basically designed the rest of the space around that system.”

An access or raised floor system is comprised of an understructure and 24-inch square floor panels welded steel floor panels filled with lightweight cement. The panels are supported on understructure that provides positive positioning, lateral retention and leveling adjustments to ensure that the floor is soundly supported on all contact points.

The resulting underfloor pathway created by the raised floor panels provides housing for any type of service distribution system, including modular wiring, passive or active zone cabling and heating, ventilation and air-conditioning (HVAC) service. Power-voice-data (PVD) terminations can be fed through the modular floor panels to provide convenient, flexible access to all of these services, while air diffusers supply fresh cool air from the underfloor plenum directly into the occupied space.

“All of our electrical and data cabling is underfloor,” noted Flucke. “As a result, we are able to make modifications to either system easily and cost effectively, by simply opening the floor, making whatever changes we need to make and closing the floor back up. We’re not expending time and resources trying to get into closed ceilings or behind walls to access our wiring and cabling, which is a big advantage.

“In addition, any changes we need to make in the future with regard to department moves will be much easier for us to make, thanks to the raised access floors and demountable walls. We now have the ability to redesign office space by moving walls and the diffusers in the floors, providing us with much more flexibility going forward than we’ve had in the past.”

According to Flucke these same demountable wall systems and raised access floors significantly increased the speed of build, which proved to be important in this fast-build project. “KCPL signed its lease for One Kansas City Place in October 2008, and our existing lease at 1201 Walnut expired September 2009, leaving us just under a year to design our new space, complete renovations and move in. We pursued an aggressive schedule, began construction March 1, 2009, and by Sept. 18 we had moved our 640 employees into their new offices. It was a very short construction schedule, and the demountable walls and raised access floors made it much easier for us to meet the construction goals than if we had had to install ductwork in the ceiling and drywall in offices.”

However, installing a raised access floor in an existing building did present several unique challenges for the design and construction teams. “Probably the single biggest challenge was the uneven slab. It varied as much as three to four inches in height, and we were trying to maintain a pretty hefty, level plenum for the delivery of air,” recalled Katrina Gerber, president of BGR Engineers, the firm responsible for the mechanical, electrical and plumbing engineering design for the project.

To meet the challenge, the contractor, JE Dunn Construction Co., performed a laser scan of the floor, which recorded floor elevations throughout the KCPL space. “Using that scan, we were able to determine the highest point and set the access floor from that point, adjusting the elevation of the floor to meet all our clearances at our pinch points,” Gerber continued. “As a result, there are areas where the access floor may be 16 or 17 inches above the slab and other areas where it is only 13 inches high.”

Elevators and existing stairs needed to be modified to create an integrated space. “We had to build new thresholds for the two banks of elevators, install new doors, raise the buttons and modify the elevator system so that the elevators stopped at a point 14 inches higher than they did prior to the installation of the floor system,” explained Gerber. “And where stairs were already in place, we added steps and railings to provide safe access to the original stairs.”

Similar steps were taken to access several rooms where water heaters and other large pieces of equipment made the installation of raised access floors impractical. “The important thing is, with careful planning we were able to overcome each challenge, and today, few people are aware of the things we did to make the design work,” noted Cohen. “And fewer still realize when they step off the elevator that they’re walking onto a raised access floor. We tried to make everything as seamless as possible, and by all accounts we succeeded, while still delivering the benefits that a raised access floor delivers.

“For example, by delivering air for heating and cooling under the raised access floor, KCPL is able to more effectively and efficiently heat and cool the renovated space. That’s because

a raised access floor that uses underfloor air distribution (UFAD), pushes fresh air from the floor to the occupied space, typically six feet above the floor, and replaces rather than mixes with, existing air. This ‘stale’ air is carried to the ceiling by natural convection and removed through return outlets, keeping it out of the occupied zone.”

“The result is improved air quality for our employees,” said Flucke, “and a system that consumes less energy.”

“Indoor air quality and energy efficiency were both important issues for KCPL,” said Gerber. “The existing building system limited their ability to improve ventilation, so the UFAD system was a definite improvement, enhancing the delivery of fresh air to occupants of the building and doing it in a way that required less energy.”

That’s because floor diffusers in an UFAD system supply air at warmer temperatures and low pressure, since only the six-foot-high occupied space needs cooling. The static pressure required for an UFAD system is typically .05-inch wg, which is significantly less than the amount of the pressure required to force air through rigid ductwork in an overhead system. As a result, the HVAC system uses less fan energy, while the increased supply temperature can expand the use of an economizer.

The KCPL building design offers additional opportunities for energy savings, the result of a high-efficiency lighting system that includes motion sensors in every office and conference room and is expected to reduce lighting energy consumption by 25 percent. In addition, photo cells around the perimeter of the space dim or brighten overhead light fixtures depending on the amount of incoming daylight. On bright summer days, less lighting produces less heat, which translates to a reduced cooling load.

“Daylighting is an important part of our design,” said Flucke. “We removed all the outside offices that existed prior to the renovation and created offices in the core of the building to make more daylight accessible to all of our employees. The raised access floors also impact daylighting by opening up ceiling space once covered by ductwork.”

The space occupied by KCPL incorporates a number of other features than enhance its sustainable design and reduce the environmental impact of KCPL: A recycling center diverts paper, cardboard, plastic and aluminum from landfills; 120-degree work stations increase efficiency and foster a collaborative work environment; Water-efficient restrooms are expected to reduce water consumption by 44 percent; and furnishings and building materials, including carpet, paint, countertops and millwork, meet or exceed LEED VOC requirements.

“But it’s our energy reduction strategies that are probably most significant, not only for what we expect to save annually in energy costs – more than 25 percent – but also for the reduced carbon dioxide emissions – as much as 1,612 metric tons – that are a direct result of these strategies,” said Flucke.

“We are, after all, a supplier of energy, and as such, we recognize the value of energy efficiency,” Flucke continued. “This space allowed us to be a role model, not only for tenants of office facilities, but also for landlords and developers, demonstrating the ability to introduce into existing office buildings and leased spaces, high-performance, progressive designs and cost-effective solutions that can impact energy efficiency in a positive way and contribute to LEED certification.”