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LEED And Green Buildings

The U.S. Green Building Council, USGBC, developed the Leadership in Energy & Environmental Design, LEED™, Green Building Rating System™. LEED™ is a voluntary, consensus-based national standard for developing high-performance, sustainable buildings. The U.S. Green Building Council members represent all segments of the building industry and continue to update the program. LEED™ standards are currently available for:
  • New construction and major renovation projects (LEED 2.1)
  • Existing building operations (LEED-EB, Pilot version)
  • Commercial interiors projects (LEED-CI, Pilot version)
LEED™ was created to:
  • define "green building" by establishing a common standard of measurement
  • promote integrated, whole-building design practices
  • recognize environmental leadership in the building industry
  • stimulate green competition
  • raise consumer awareness of green building benefits
  • transform the building market
More information about the USGBC and LEED™ can be found on the USGBC website at www.usgbc.org.

LEED™ Rating System

Using the LEED™ rating system, a project can become LEED™ certified by obtaining points for “green” building processes, systems, and materials. There are several levels of certification. General Certification requires 26-32 point. Silver certification is 33-38 points. Gold certification is 39-51 points. Platinum certification is 52-69 points.

The Project Checklist has several sections with several topics, called Credits, in each section. The sections are:

  • Sustainable Sites (SS)
  • Water Efficiency (WE)
  • Energy & Atmosphere (EA)
  • Materials & Resources (MR)
  • Indoor Environmental Quality (EQ)
  • Innovation & Design Process (ID)
The Credits related to air distribution are:
  • Optimize Energy Performance - Credit 1 of Energy & Atmosphere
  • Building Reuse - Credit 1 of Materials & Resources (for renovation)
  • Regional Materials - Credit 5 of Materials & Resources (dependent on location of site)
  • Indoor Air Quality - Prerequisite 1 of Indoor Environmental Quality
  • Ventilation Effectiveness - Credit 2 of Indoor Environmental Quality
  • Controllability of Systems - Credit 6 of Indoor Environmental Quality
  • Thermal Comfort - Credit 7 of Indoor Environmental Quality

Energy & Atmosphere

The Energy & Atmosphere section has three prerequisites: Fundamental Building Systems Commissioning, Minimum Energy Performance, and CFC Reduction in HVAC&R Equipment.

Credit 1 is Optimize Energy Performance. The intent of this credit is to achieve increasing levels of energy performance above the prerequisite standard to reduce environmental impacts associated with excessive energy use. Credits are based on percentage of reduction and range from 15% reduction (1 Point) to 60% reduction (10 Points) for new buildings.

The requirement for credit is to reduce the design energy cost compared to the energy cost budget for systems regulated by ASHRAE/IESNA Standard 90.1-1999. Per LEED™, regulated energy systems include HVAC, service hot water and interior lighting.

An access floor system may have higher HVAC equipment efficiency because access floor air systems use warmer supply air (60o to 65oF) than conventional systems that use 55oF supply air. The energy consumption of many types of systems is reduced by raising discharge temperatures.

Access floor systems can move a larger volume of air with overall lower pressure drops. The underfloor plenum needs 0.1 in. of water pressure or less for proper diffuser performance. This results in less fan horsepower needed for access floor systems resulting in lower energy usage.

The energy savings of an access floor system should be considered as part of the system to receive an Optimize Energy Performance credit.

ECM motors are another option that should be considered for the Optimize Energy Performance credit. The ECM motor has efficiencies of up to 70% across its entire operating range (300-1200 rpm) and 80% over 400 rpm. The ECM motor is available in the Titus TQS, FLS, LHK, and PFC fan powered terminals. See the ECM Application Guide, AG-ECM, for more information of ECM motors.

Material & Resources

The Material & Resources section has one prerequisite Storage & Collection of Recyclables.

If the project is a renovation, Credit 1.1, 1.2, or 1.3, Building Reuse, may be applicable. Credit 1.1 is for maintaining 75% of existing walls, floors, and roof. Credit 1.2 is for maintaining 100% of existing walls, floors, and roof. Meeting Credit 1.1 qualifies for 1 point and meeting Credits 1.2 and 1.3 qualifies for an additional point each.

Utilizing access floors systems can update a building for meet current technology needs without demolishing the current building structure. In situation where the architect wants to leave an ornamental ceiling open, access floor air distribution may be the perfect solution.

Additional points are given for utilizing local building materials. Depending on the project site, the project may qualify for Regional Material points, Credit 5. Credit 5.1 qualifies the project for 1 point for using 20% regionally manufactured material. Credit 5.2 provides an additional point for 50% regionally manufactured material.

The intent of the Regional Materials credit is to increase demand for building materials and products that are extracted and manufactured within the region, thereby supporting the regional economy and reducing the environmental impacts resulting from transportation.

Titus manufacturers product all over the country so many of the terminals, diffusers, and grilles used in a project may help qualify for Regional Material points.

Indoor Environmental Quality

The Indoor Environmental Quality section has two prerequisites: Minimum IAQ Performance and Environmental Tobacco Smoke (ETS) Control. The Minimum IAQ Performance prerequisite requires the project to meet the minimum requirements of voluntary consensus standard ASHRAE 62-1999, Ventilation for Acceptable Indoor Air Quality, and approved Addenda using the Ventilation Rate Procedure.

Credit 2 provide 1 point for Ventilation Effectiveness. The intent of this credit is to provide for the effective delivery and mixing of fresh air to support the safety, comfort and well-being of building occupants. The credit requires design ventilation systems that result in an air change effectiveness greater than or equal to 0.9 as determined by ASHRAE 129.

LEED™ specifies “…displacement ventilation, low-velocity ventilation, plug-flow ventilation such as under floor or near floor delivery…”as a potential technology or strategy to qualify for this credit.

Because the air is supplied directly into the occupied zone with access floor air distribution, the air change effectiveness of an underfloor system is higher than a conventional overhead system. The result of a higher air change effectiveness is that lower outside air is required to meet the outside air requirements of any given space.

Credit 6, Controllability of Systems, has two parts: 6.1 Perimeter Systems and 6.2 Non-Perimeter Systems. Credit 6.2 specifies “...underfloor HVAC systems with individual diffusers.” as a potential technology or strategy to qualify for this credit. The intent of Credit 6.2 is to provide controls for each individual for airflow, temperature, and lighting for at least 50% of the occupants in non-perimeter, regularly occupied areas. VAV diffusers, such as the Zcom, would also qualify for this section.

Credit 7.0, Thermal Comfort requires that the building comply with ASHRAE Standard 55-1992, Addenda 1995 for thermal comfort standards including humidity control within established ranges per climate zone.

It has been shown that individual comfort is maintained when the following conditions are maintained in a space:
  • Air temperature maintained between 73-77o F
  • Relative humidity maintained between 25-60%
  • Maximum air motion in the occupied
  • 50 fpm in cooling
  • 30 fpm in heating
  • Floor to 6’ level, 5-6oF maximum temperature gradient
The ASHRAE comfort standard state that no minimum air movement is necessary to maintain thermal comfort, provided the temperature is acceptable. To maximize energy conservation, we should attempt to maintain proper temperatures at the lowest possible air speed. The following ASHRAE comfort charts show the relationship between local air velocity and temperature difference in the ankle and neck regions.






Although the velocity and temperature of the occupied zone is important in all HVAC systems, access floor systems require careful consideration because the air is introduced directly into the occupied zone. The key to successful access floor systems is the ability of the access floor diffuser to rapidly mix room air into the supply air at low velocities. Slowing the supply air down 50 fpm and warming it up to 75oF as close to the diffuser face as possible provides the most occupant comfort. A typical access floor diffuser should reach the 50 fpm and 75oF point within a 1 to 2ft radius from the center of the diffuser. As the radius required to reach the 50 fpm and 75oF point increases, the useable floor space decreases.

Green Building Codes and Programs

With energy considerations growing, there has been an increased interest in “green” buildings, sustainable design, and energy savings. Although the U.S. Green Building Council is not a government agency, many local governing bodies are requesting, and in some cases requiring, green design features into their new construction requirements. Some states and cities offer tax incentives for buildings that meet green building codes or become LEED™ certified and other will most likely offer incentives in the future.

New York was the first state to implement a green building tax program. The credit allows builders who meet energy goals and use environmentally preferable materials to claim up to $3.75 per square foot for interior work and $7.50 per square foot for exterior work against their state tax bill. Maryland has implemented green building a tax credit program and Massachusetts is currently reviewing a green building program. Oregon’s tax credit program uses LEED™ certification levels to determine the level of tax credit.

Some cities do not specify green buildings or LEED™, but have energy codes designed around energy efficiency. For example, the Seattle Energy Code, Chapter 14, Building Mechanical Systems states that Fan motors less than 1 hp in series terminal units shall be either electronically-commutated motors, or have a minimum motor efficiency of 65% when rated in accordance with NEMA Standard MG-1 at full load rating conditions.

For more information on state energy codes, visit the Building Codes Assistance Project (BCAP) website at http://www.bcap-energy.org/. The Building Codes Assistance Project assists states in the development and implementation of statewide building energy codes. BCAP publishes a bimonthly newsletter showing the status of state energy codes by state. The newsletter is located at http://www.bcap-energy.org/backissues.html.

Summary

The green building concept has become more popular over the past couple of years. Owners are interested in saving money on energy costs while providing a comfortable working environment. State and local governments are implementing tax credits for energy efficient and environmentally friendly buildings.

More information about green buildings can be found on individual state websites and green building organizations’ websites, such as the U.S. Green Building Council (www.usgbc.org), WorldBuild (www.worldbuild.com), the American Council for and Energy-Efficient Economy (www.aceee.org) , and many others. The EPA also has information on green buildings on its website (www.epa.gov/greenbuilding/).