Impact Of ASHRAE 90.1 On Controls And BAS Design
As states adopt more stringent energy codes, here is what you need to know.
In an effort to improve energy efficiency for commercial buildings, ASHRAE, IES, ANSI, and the DOE have been working diligently to increase the stringency of state energy codes. Today, most states have accepted a version of ASHRAE/ANSI 90.1 as the basis for their energy codes for all but low-rise residential buildings.
Beginning over 10 years ago, a series of aggressive goals were set in place that included a 30% decrease in new building energy use between the 2004 and 2010 versions of the standard. This was successfully accomplished in stages starting with improvements in the 2007 release (around 7%) and achieving the 30% goal in the 2010 release. The 2013 version of the standard is now complete and shows roughly another 8% improvement. While states have some leeway to set their own energy codes, they are being strongly encouraged by the DOE to utilize the latest 90.1 2010 as the baseline. To date, about 20% of the states have moved to 90.1 2010, and it is projected that over half will adopt the new code by the end of 2015. For more details on the plans state by state, see www.energycodes.gov.
As you would expect, providing the same level of services (light levels, comfort, ventilation, plug load, etc.) in a commercial building while using 30% less energy is not a trivial task. To achieve this level of efficiency, there are many changes required in the newer versions of 90.1. These range from improvements in building envelope, more efficient HVAC equipment, and reduced lighting power densities. Woven throughout the code though are specific requirements for controls. Optimized controls are now required for HVAC systems and lighting controls (for interior, exterior, and parking structures) as well as control over certain plug loads.
Here is a summary of changes required in the 2010 and 2013 versions of 90.1 related to controls.
- DDC controls are required for new systems and expansions of existing systems that are already DDC.
- Requires the use of optimization strategies including fan and pump static pressure reset based on valve and damper positions and supply air temperature reset.
- Increases required use of variable speed drives including the use on pumping systems (above 10 hp total) and for single zone air handlers (using a drive or two-speed fan).
- Demand controlled ventilation and energy recovery are now required on more projects.
- New code requirements for auto shutoff and lighting power density apply for new projects and can be triggered for retrofits with more than 10% of existing lighting.
- Auto shutoff (occupancy sensor, time clock, or BAS) is now required in all spaces.
- More spaces now must have occupancy sensors to automatically turn off lights.
- Requirements for bi-level zone switching or dimming.
- Requirements for daylight harvesting.
- Parking garages must have occupancy sensing and daylight harvesting.
- 50% of plug loads in offices and computer classrooms must be automatically controlled.
- Empty escalators and moving sidewalks must slow down.
- Additional requirements for submetering.
While the standard does not explicitly require the use of systems integration or an “intelligent building,” it does have much more extensive controls requirements. The use of an integrated approach is likely to both be more cost effective and provide the required performance of this more stringent code.