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Step 3

The owner mandates that all future tenant systems be VAV (Figure 3). This saves increasing amounts of money for the owner by reducing base-building fan energy. Savings for the tenant are not as easy to define, particularly if HVAC charges are bundled into the tenant's lease at a fixed rate. If a space is VAV, an astute tenant will negotiate a lower HVAC charge. To protect its interests during the lease-negotiation process, a tenant may want to enlist the help of the engineering firm involved in designing the fit-out.

Step 4

After base-building savings are optimized, the tenant installs demand-controlled ventilation (DCV). With DCV, a floor's outside-air requirement is reset based on actual occupancy, as determined from carbon-dioxide measurements. (See "Multiparameter Demand-Controlled Ventilation") Figure 4 shows occupancy sensors controlling VAV boxes, shutting off ventilation air to unoccupied spaces. This arrangement is feasible only when each floor was built or retrofitted with an ACU/AHU. If that is the case, tenants have control of outside air for their floors and can (in theory) save by limiting that outside air and reducing supply-fan volume through conventional VAV operation.

FIGURE 3. Tenant-installed variable-air-volume systems save for the tenants and increase savings for the owner.

Tenants will not see savings if their HVAC charges are bundled into their lease agreement at a fixed cost. They must negotiate a lease whereby the energy consumption of their ACU is sub-metered. Although this kind of lease negotiation is rare, it is imperative if tenants are to be rewarded for employing sophisticated energy management.

LEED BENEFITS

FIGURE 4. Variable-air-volume operation with carbon-dioxide (CO₂) measurement increases savings for both the tenant and the owner.

An important benefit of energy conservation is certification of a building under LEED for Existing Buildings: O&M and certification of individual tenant spaces under LEED-CI. Decreasing energy use increases the Energy Star rating of a facility and earns up to 18 points under LEED for Existing Buildings: O&M Energy & Atmosphere (EA) Credit 1, Optimize Energy Efficiency Performance. As tenants install CO₂ sensors, a building starts moving toward earning a point under LEED for Existing Buildings: O&M Indoor Environmental Quality Credit 1.2, IAQ Best Management Practices: Outdoor Air Delivery Monitoring. When tenants install submetering for their individual AHUs (Step 4), the owner is on the way toward receiving points under LEED for Existing Buildings: O&M EA Credit 3.2 and 3.3, Performance Measurement: System-Level Metering. When 75 percent of a building's floor area is occupied by tenants who have achieved LEED-CI certification, the building automatically gains four points under LEED for Existing Buildings: O&M Sustainable Sites Credit 1, LEED Certified Design and Construction. Thus, it is advantageous to an owner to negotiate a fair lease agreement with any tenant who wishes to sub-meter and be charged for energy accordingly.

For a tenant wanting to obtain LEED-CI certification, LEED 2009 has increased the number of points attributable to energy efficiency, zoning, and modulating to 10 points. Installing sub-metering equipment, tenant payment of energy and energy use, and measurement and payment accountability earn a total of 10 additional points. Those 20 points put a tenant halfway to the 40-point minimum required for LEED-CI certification. When a building meets LEED for Existing Buildings: O&M certification, tenants automatically gain five points toward LEED-CI certification.

DO NOT FORGET

Commissioning facilities reduces energy consumption while improving comfort, health, and safety. LEED for Existing Buildings: O&M EA Credit 2.1, Existing Building Commissioning: Investigation and Analysis; EA Credit 2.2, Existing Building Commissioning: Implementation; and EA Credit 2.3, Existing Building Commissioning: Ongoing Commissioning, offer a total of six points for commissioning, with a bonus point available in most regions. EA Credit 2.1 is used for energy audits or commissioning plans to help guide energy options for long-term capital plans. EA Credit 2.2 is earned automatically as low-cost/no-cost energy-saving ideas are implemented. EA Credit 2.3 requires only the creation of a long-term recommissioning plan and the completion of half of the work in that plan. Continuous recommissioning can be made part and parcel of a capital plan through updated cost estimates and energy savings.

For tenants seeking LEED-CI certification, fundamental commissioning of building energy systems is a prerequisite in the EA category, while five points are available through EA Credit 2, Enhanced Commissioning.

For past HPAC Engineering feature articles, visit www.hpac.com.

A commissioning project manager for AKF Group LLC and a longtime member of HPAC Engineering's Editorial Advisory Board, Ron Wilkinson, PE, LEED AP, is the author of the first commissioning training program for the Leadership in Energy and Environmental Design for New Construction and Major Renovations Green Building Rating System, the chair of the recently formed commissioning advisory committee of The American Institute of Architects (AIA) Committee on the Environment, and the recording secretary for American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Guideline Project Committee 0.2/1.2, The Commissioning Process for Existing Building Systems and Assemblies/The Commissioning Process for Existing HVAC&R Systems. An ASHRAE Distinguished Lecturer and an AIA Continuing Education Lecturer, he has spoken on commissioning practices internationally.