Turning Standard 189.1 into code

The District of Columbia has created new construction codes, mirroring ASHRAE Standard 189.1.

11/20/2013


This shows the progression of the D.C. Green Construction Code. Courtesy: GHT LimitedIn early 2012, the District of Columbia initiated an effort to develop new construction codes. The process has been led by the Department of Consumer and Regulatory Affairs (DCRA) Construction Codes Coordinating Board (CCCB) and its Technical Advisory Group (TAG) subcommittees, comprising a diverse group of District officials and design and construction industry professionals. 

As a member of D.C.’s Green TAG, I had the opportunity to participate in the process of creating the District of Columbia Green Construction Code (DCGCC). The Green TAG met weekly over a period of six months, and while our primarily task focused on reviewing and proposing amendments to the 2012 International Green Construction Code (IgCC), we addressed ASHRAE Standard 189.1: Standard for the Design of High-Performance Green Buildings Except Low-Rise Residential Buildings and U.S. Green Building Council (USGBC) LEED standards as well. The model code we delivered completed three rounds of public comments, and as of the writing of this article, its approval is pending a final vote by the D.C. Council. 

The purpose of the DCGCC is to implement many of the strategies that architects and engineers are already experienced with into enforceable code language. Overall, the proposed code is not intended to create drastic changes to typical methods or represent a far deviation from good practice. Most language encompasses the processes likely followed by many design and construction teams as a matter of course. 

On a personal note, acknowledging no code is perfect, I believe the DCGCC has been well-vetted and that the intent of the model code and ASHRAE Standard 189.1 was preserved, though some requirements were removed or lightened. 

Outlining the code

The fundamentals:

  • The DCGCC will apply to all projects larger than 10,000 sq ft that are classified as either New Construction or Substantial Improvement.
  • It will apply to small tenant fit-outs, although in order to reduce burden on smaller projects, certain provisions of the DCGCC will not apply. These types of projects make up a large volume of work in the District.
  • There are three additional compliance paths if you elect not to follow the DCGCC: the D.C. Green Building Act of 2006 and amendments, LEED Silver certification or better, or ASHRAE Standard 189.1.
  • In addition to the primary code language, Appendix A contains options for Elective Credits. Projects must achieve 15 for New Construction and 13 for Level 3 Alterations. There are more than 75 potential options in Appendix A, which only applies to the primary DCGCC compliance path and not the alternative D.C. Green Building, LEED, or Standard 189.1 paths.
  • Commissioning will not hold up a certificate of occupancy (COO)—it has been replaced with a final inspection. 

Vegetation, soils, and erosion control:

  • Containment and removal of invasive plant species will be required.
  • 75% of land-clearing debris and excavated soil must be diverted.
  • For requirements in this domain, thorough planning and documentation is critical for success. Develop a plan for planting, and make sure the area is clear of debris before you excavate so there is no rubble. Leave 6 in. of topsoil for planting. 

Materials and resources:

  • 50% of construction waste (volume or weight) must be diverted. This is typically required in contract specs and should be fairly easy to achieve. Many contractors are achieving 75% on a regular basis.
  • 40% of materials must be:
    • Used
    • Recycled
    • Recyclable
    • Bio-based OR
    • Regional.

Note that materials that have more than one of these features can be counted multiple times toward the 40%—i.e., if a material is used, recyclable, and regional, its value is tripled.

Energy:

First, there are a handful of energy requirements that will apply to all buildings covered by the DCGCC.

  • Elevators and escalators have efficiency and control requirements to reduce energy consumption.
  • At least 50% of Energy Star eligible food service equipment shall be Energy Star rated.
  • Energy metering and distribution requirements:
    • Energy must be metered by source type (e.g., electricity, natural gas, district steam, etc.).
    • Energy must be distributed by use type (HVAC, lighting, plug loads, process loads, and miscellaneous). If not distributed separately, the various uses must be submetered for monitoring purposes. Submetering is only required for larger projects. The intent is to require the separate distribution on all projects so that uses can be measured in the future. Submeters can be provided on smaller projects if the design team decides it is more feasible to do that instead of separate distribution paths.
    • Projects larger than 50,000 sq ft must have meters capable of metering each use type in the building.
    • Projects that use a building management system must have the capability to use auto-demand response in which HVAC power is reduced by 10% of the design load upon a signal from the utility company that peak power consumption is in effect. This does not mandate the use of auto-demand response, just that it is available for use. 

Next, there are two primary compliance paths under the energy section of the code: prescriptive and performance. The prescriptive path is a simplified approach that may be best suited for projects of smaller scale. The performance path is envisioned for larger, more complex projects that do not want to be constrained by the prescriptive requirements and will document, through building energy modeling, that the designed building exceeds certain benchmarks. This is not unlike the energy code which currently offers a prescriptive path or an alternative performance path based on ASHRAE Standard 90.1 compliance.

  • Prescriptive path: In addition to specific insulation and mechanical efficiency requirements, new electrical controls are mandated to facilitate power conservation. Occupancy sensors are required for interior lighting, time clocks are required for non-emergency exterior illumination, and daylight harvesting controls are required for interior lighting near perimeter windows and under skylights.
  • Performance path: In order to pursue the modeled performance pathway, a building energy model must be performed demonstrating a specific level of efficiency in terms of zEPI (Zero Energy Performance Index). Unlike the energy use index used in ASHRAE 90.1 modeling, the zEPI allows buildings of different use types and different code years to be compared. Currently, the DCGCC requires a building to be designed to use no more than 90% of the source energy of a building designed to the performance requirements of ASHRAE 90.1-2010. 

Water:

The DCGCC sets maximum flow rates for standard plumbing fixtures. The flow rates are in line with current commercially available products. In most cases, the maximum flow rates are in line with the current plumbing code. Additional water conservation measures include:

  • Meters are required to measure water consumption based on a variety of uses outlined in the code.
  • Efficiency and water saving requirements have been mandated for most common water treatment systems including water softeners and reverse osmosis systems.

Patrick A. Kunze is a senior principal and mechanical section head of the interiors studio with GHT Limited. Kunze has provided mechanical engineering design for more than 20 projects that have achieved U.S. Green Building Council LEED certification, including the USGBC’s headquarters; contributed to the development of questions for the current LEED AP exam; and currently sits on the Green Technical Advisory Group subcommittee of Washington, D.C.’s Construction Codes Coordinating Board.



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