Energy

Achieving net-zero energy requires optimization and integration of all the energy flows and systems of the building with a reliance on many passive energy strategies. Lighting is an integrated system of daylighting, daylight control systems, occupancy controls, and high-efficiency lighting.

Thermal comfort is addressed using an integrated system of thermal mass, radiant slabs, night purging, and natural ventilation. Heating in particular takes a whole-systems approach to energy conservation. The building includes a large thermal labyrinth under the two main office wings. The labyrinth can store heat from the transpired solar collectors located on the south building facades. This heat is used to passively temper the ventilation air during the heating season. The labyrinth also serves as a thermal sink for reject heat from the data center, dramatically lowering the cooling load of the data center year round.Bioclimatic section with a variety of heating, cooling, and ventilation strategies explained.
Courtesy of Stantec

The building’s extremely detailed energy model predicts an energy use intensity of 33 kBtu/ft2/year. The onsite photovoltaic system is sized to meet net-zero site energy at an EUI of 35 kBtu/ft2/year. The onsite PV coupled with the passive strategies, such as thermal mass, natural ventilation, and daylighting, are also strategies for passive survivability in the event of a power outage.

Bioclimatic Design

The building is shaped around the climate to optimize passive energy strategies. The 60' wide section for the main office wings was driven by the objective to daylight and naturally ventilate the main office wings. The narrow footprint results in two long office wings oriented along the east/west axis and linked by a central connector space consisting of the lobby and conference facilities.
floor plans courtesy of RNL

The solar geometry of the site dictated the shading and daylighting strategies. The seasonal and diurnal temperature changes of the climate influence the integration of thermal mass and night-flush capability in the building interior and in the thermal labyrinth in the crawlspace. The geometry of the building was studied in a wind tunnel to fine-tune the effectiveness of the operable windows and cross ventilation, as well as pedestrian comfort in the exterior courtyards.

This building begins to hum as soon as the sun hits it, which is ideal given the number of sunny days in Colorado. The building creates its own electricity, heats its own ventilation air with a transpired solar collector, and shades all windows during the summer while providing an exemplary daylit space all year round.

Materials & Resources

The multi-story wall pictured in the photo is made from beetle-kill pine. Credit: Photo by Frank Ooms The incorporation of passive design features led to the narrow building footprint and to a correspondingly high quantity of exterior envelope. One of the largest challenges of the project was to design and construct the exterior envelope within the overall budget of the project.

One key strategy employed was the use of modular construction. The exterior wall is composed of insulated precast wall panels with finished interior and exterior surfaces. The other key strategy was to optimize the amount of glass and therefore not over-glaze the main office wings. The optimization of the glazing allowed cost control and solar gain control while maintaining fully daylit office spaces.

The material choices for the building were driven by the desire to have flexible and durable materials with low health impacts and reduced resource consumption. Construction waste diversion (75%), low-emitting materials, recycled-content materials (34%), regional materials (13%) and certified wood materials (59%) were all incorporated based on LEED compliance. Several highly visible, innovative materials were also incorporated into the project, including the use of reclaimed natural gas pipe as structural columns and beetle kill pine used as decorative wall elements throughout and as a multi-story feature wall in the lobby.

Staff members working in the open office area in the main office wing.
Photo by Frank Ooms Reclaimed natural-gas pipes were used as structural columns.
Photo by Frank Ooms

Design for Adaptability to Future Uses

Flexibility and adaptability are key sustainable design features but also very important workplace design strategies. The 60' deep office wings have column-free interiors, and the cores are small and decentralized to allow the basic core and shell of the building to have tremendous flexibility.

The workplace is designed with modular components, such as a raised floor, demountable walls, and modular furniture solutions. These systems make the workplace highly adaptable over time. These systems also created a very efficient space plan that allows the owner to add more occupants to the building with less overall building area.

The building is designed for a long service life of 50 years or longer. The main exterior wall finishes are highly durable, long-life materials, including architecturally finished precast concrete wall panels and natural zinc panels. The building is also designed to be expandable. In fact, a 138,000 ft2 extension to the building is already under way and is taking full advantage of the lessons learned from the original building. The building expansion is predicted to be 17% more energy efficient at a cost that is $13 lower per square foot than the cost for the original building.

Lobby features a wall made of salvaged beetle-kill pine.
Photo by Frank Ooms

Indoor Environment

The project utilizes strategies that leverage light and air to increase energy performance and improve workplace performance. Daylighting is the keystone strategy for the project because it significantly impacts lighting energy, cooling energy, and productivity.

The building massing and window design optimize control and harvesting of daylight. Virtually every workspace in the main office wings is daylit. Overall, 92% of all regularly occupied spaces are daylit. Air quality is enhanced by increasing the amount of outside air delivered to spaces.

All office spaces have 100% outside ventilation air delivered through an underfloor air distribution system. The ventilation system is decoupled from the space conditioning system, saving significant energy.

The building also has operable windows and is designed for effective cross-ventilation by using a narrow 60' deep floor plate for the main office wings. Effectively all spaces in the open office area, as well as the conference rooms and lobby spaces in the central connector space between the two main office wings, have excellent access to natural ventilation. A small icon appears on everyone’s computer informing them when it is an appropriate time to open a window.