The Signature Centre’s long and narrow profile, along with the nearly floor to ceiling windows on each side, allow 90% of the occupied space to have an outside view, reducing the energy used for lighting. However, this design also adds a large perimeter skin-load. Passive chilled beams near the ceiling and hydronic radiant baseboard heaters help to condition this load.

The Signature Centre is an 186,000-sq-ft office building developed by Aardex LLC and designed by the world-renowned architect Binh Vihn. As of September 2007, the building is 100% pre-leased including the now relocated headquarters of Aardex. Located at Denver West in Jefferson County, the Signature Centre is now officially the Denver metro area’s greenest building, having become the first commercial LEED® Platinum structure in the state.

Aardex is known for its book,User Effective® Buildings, which outlines the methodology to create an overall harmonious work environment. Aardex invests in its own designs to create sustainable, energy efficient, more productive work environments that, within a few years of use, pay for themselves.

LEED® Core and Shell

The Signature Centre recently received a Platinum LEED for Core and Shell certification. It was part of the Version 1.0 Core and Shell Pilot Program and received 46 LEED credits toward the certification. To acquire this many credits, the Signature Centre had to fully encompass the green design in both its architecture and mechanical systems, and therefore include many green innovations.

One of the office building’s green innovations is its use of natural lighting. The long and narrow profile of the Signature Centre, along with the nearly floor to ceiling windows on each side, allows 90% of the occupied space to have an outside view. This lighting design reduces the energy used to light the building during daylight hours and gives the building a more open feel, which improves occupant comfort and thus productivity.

However, this design also adds a large perimeter skin-load. To condition this load, passive chilled beams near the ceiling and hydronic radiant baseboard heaters are used. Chilled beams provide radiant cooling and create a natural convection process with rising hot air and falling cooled air. An AAON LL Series roof-mounted packaged evaporative cooled condenser chiller with a factory-installed distribution-pumping package provides the 61°F chilled water for the chilled beams.

Another green innovation of the Signature Centre is its HVAC system. The interior loads of the building are conditioned with an underfloor air distribution cooling (UFAD) system.

Randy Rinker, an AAON sales representative with Engineered Mechanical Systems, LLC, described the overall system as “ideal for maximizing energy efficiency, indoor air quality, and allowing individual occupant comfort control.” In the building’s UFAD system, 65° conditioned air is supplied from the air handler at a low velocity to an underfloor plenum.

From there, the conditioned air leaves passive floor diffusers and slowly mixes before reaching return air vents near the ceiling. With user adjustable floor diffusers, occupants have moderate control over thermal comfort conditions in their environment. Four AAON RL Series evaporative-cooled condenser packaged rooftop units provide supply air to the UFAD system. “This system allows at least 130% more use of the economizer mode of free cooling because of its higher discharge air temperature,” stated Ben Weeks, Aardex executive principal.

Contributing to Credits

The AAON units contribute to the building’s LEED credits in a couple of ways. By using the AAON patented evaporative cooled condenser with air cooled desuperheater coil, the chiller and packaged units use at least 22% less water than conventional evaporative-cooled condenser units and are more energy efficient than air cooled chillers and packaged units.

Because the pumps, chiller, and condenser are packaged together and installed on the roof, usable building space is also maximized by eliminating the need to house the chiller or pumps in an internal mechanical equipment room. Second, the chiller and packaged units all use R-410A HFC refrigerant. Third, the packaged units include modulating hot gas reheat, which provides the exact amount of dehumidification needed while still providing the consistent supply air temperature needed by the UFAD system.

Finally, the packaged units use pre and final MERV 13 filters to improve the building’s IAQ.

Signature Innovations

The Signature Centre’s many green innovations, including the lighting and HVAC systems, helped contribute to the building’s LEED certification and to create a “User Effective” work environment. This environmental development approach meant more upfront costs; however, with the enormous “built-in” efficiencies Aardex estimates, the average tenant will recoup any additional leasing costs in about three years. As Weeks commented, “The green designs included in the Signature Centre lead not only to LEED®Platinum certification, but also a more comfortable and productive work environment.”ES