ASHRAE Headquarters exemplifies Net-Zero Energy building design

ASHRAE are one of the foremost industry pioneers in the decarbonization of the built environment and their new global Headquarters building in Atlanta, renovated to operate as a net-zero-energy (NZE) building, is testament to this. The project design team, which includes IESVE users, Integral Group, employed a range of innovative design strategies to achieve this net-zero energy ready building.

Along with some fellow ASHRAE Members of Technical Committee 4.1, I recently had the pleasure of doing some building performance analysis on this ASHRAE Headquarters building.  From a simulation-aided design perspective, the following innovative categories from the project are worth highlighting.

(1)   Net-Zero Energy Building 
ASHRAE’s new headquarters is designed to operate as an all-electric at Net-Zero Energy (NZE) building, thanks to the installation of a 332-kW photovoltaic (PV) system. The PV system is a combination of three sub-arrays, which are sub-metered in the Building Energy Model shown below: 

• 187 kW ballasted rooftop array on east & west wings
• 65 kW ground mount on a south-facing hill adjacent to the building 
• 81 kW ground mount situated in an unused section of a car parking area
   

(2)   Simulation throughout Design Phases
Thanks to the PV installation, a limiting Energy Use Intensity (EUI) of 21 kBtu/ft2 was targeted for this existing building refurbishment.  Iterative design options throughout the design phases resulted in a range of low-energy solutions. These include:  

• A reconfigured window-to-wall ratio (WWR) and 18 new skylights.
• Common Dedicated Outdoor Air Systems (DOAS) for outdoor air ventilation, coupled with enthalpy heat recovery.
• Radiant panels and Ceiling Fans.
• Demand Control Ventilation (DCV) in high occupancy spaces and Displacement Ventilation (DV).
• Six water source-heat pumps (WSHPs)

(3)   Optimized Load Calculations using the ASHRAE Heat Balance Method

For over 20 years, ASHRAE has recommended the Heat Balance (HB) Method as the preferred method for calculating heating & cooling loads. With such a low-energy target in mind, a considerate zoning strategy and accurate load calculations are very important. Included in the load’s analysis: 

• Horizontal and vertical solar shading on most windows. 
• Sensible Loads analysis at the zone and Latent Loads Analysis at the AHU.
• Heat gains from the reversible ceiling fans.
• Analysis of Adaptive Thermal Comfort for Occupants and Operative Temperature.

   

(4)   Exceptional Daylight Performance (Spatial Daylight Autonomy, sDA)
Of the many daylighting metrics available, Spatial Daylight Autonomy (sDA) likely best considers the annual sufficiency of indoor daylight levels. In the in regularly occupied spaces of the ASHRAE HQ, the working plane analysis areas are considered for sDA, for the percentage that meets a minimum illuminance level of 300 lux, for 50% of the operational hours per year. The 18 new skylights provide an exceptional daylight performance, which is especially impressive considering the simultaneous requirements from a thermal/energy perspective. 
  

About ASHRAE
Founded in 1894, ASHRAE is a global professional society committed to serve humanity by advancing the arts and sciences of heating ventilation, air conditioning, refrigeration and their allied fields.  ASHRAE recently launched a Task Force for Building Decarbonization (TFBD), so they continue to demonstrate leadership and promote the organization’s mission. 

To learn more about ASHRAE’s state-of-the-art, high-performing net-zero-energy efficient global headquarters building, go to ashrae.org/newhq and integralgroup.com/ashraehq.