Overview of USGBC LEED-NC Credits for HVAC System

This page is for users seeking a quick introduction to the US Green Building Council (USGBC) LEED (Leadership in Energy and Environmental Design) Green Building Rating System©, focused on where the rating system applies to HVAC control systems. In the LEED-NC system the -NC indicates coverage of New Construction, including major renovation projects.

To obtain a LEED-NC Green Building certification the project must first meet minimum requirements, including preservation of green fields, prevention of topsoil loss, improved indoor environmental quality, minimum energy performance and reduced use of HCFCs in HVAC&R equipment, and reduced burden on landfills and water treatment plants. These mandatory thresholds are combined with a scoring system for "LEED credits", or points, to generate a building score.

LEED-NC credits are available in five major areas. The five areas are Sustainable Site Development, Water Savings, Energy & Atmosphere, Materials Selection and Indoor Environmental Quality. The LEED credit scores granted across the various categories are summed up to determine the building's overall score.

There are 69 points in LEED-NC version 2.1, but it is virtually impossible for a building to attain maximum points. The minimum Green Building certification is the Certified level (40-50% score). Levels continue through Silver (50-60%), Gold (60-70%), and finally Platinum (75+%).

The design, processes and products used in the HVAC&R system can determine a significant fraction of the total building score. The Energy & Atmosphere metric offers up to 17 available credits. Opportunities for the HVAC&R system to gain credits are in the areas of:

• Overall building energy efficiency - 1 to 10 points

• Additional Commissioning - 1 point

• Measurement & Verification - 1 point

• Ozone Depletion - 1 point

The Indoor Environmental Quality metric offers a total of 15 credits. The opportunities for the HVAC&R system to gain up to 6 credits are in the areas of:

• CO2 monitoring - 1 point

• Controllability of Systems (Perimeter) - 1 point

• Controllability of Systems (non-Perimeter) - 1 point

• Thermal Comfort (ASHRAE 55-1992 compliance) - 1 point

• Thermal Comfort (Permanent Monitoring Systems) - 1 point

• Ventilation Effectiveness - 1 point

The LEED guidelines are comprehensive but don't provide exact templates. They are "performance-based requirements" that allow leeway in attaining performance thresholds through a combination of products, processes and/or operating strategies.

The design team applies the LEED scoring guidelines to the specifications for the HVAC system, and a LEED certification consultant reviews the design to interpret whether the project meets the LEED requirements and can attain credits.

The LEED verification process specifies that data must be provided to verify that LEED performance thresholds have been met. An extensive series of tests is conducted during commissioning to assess system behavior and measure performance across a variety of scenarios.

The LEED rating system also includes "Innovation Credits" for performance beyond the requirements for LEED credits, and for innovative performance in green building not otherwise measured in the credit system.

While the number of certified green buildings remains small relative to the total market, the cost and performance differences of an HVAC system designed for a Green Building as compared to a regular building are much smaller today than they were when DDC first entered the HVAC market. Use of new technologies, processes and practices in LEED Green Buildings can provide the HVAC industry with measures of performance, applicability and suitability for other building environments. Experience and practice will help bring new technologies, processes and practices into the mainstream.

The USGBC has made great progress over the last few years in achieving the consensus necessary to advance green building technologies and practices. We hope USGBC's ongoing efforts to improve the LEED scoring system and process enable LEED to gain further acceptance from both construction professionals and environmental advocates. For full details, updated scoring guidelines, descriptions of past certified projects, and further information please visit the USGBC website.

Please let us know any comments or feedback you have for us regarding sustainable building practices and technologies.