Presented by David Herman, PE, LEED AP Principal, EnerG Associates, LLC
Energy Efficiency in
Multi-Tenant Office
Buildings
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Learning Objectives
1. List the principal sources and uses of energy in existing multi-tenant office buildings.
2. Identify energy-savings opportunities in existing multi-tenant buildings.
3. Understand the potential for savings through cost-effective building upgrades.
4. Recognize the value of the ENERGY STAR score as a tool to understand a building’s energy performance.
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• Building Energy Use Profile
• ENERGY STAR Score
• Building Energy Use Savings
• Building Energy Efficiency Measures
• Typical Office Building Example
• Building Stakeholders
Outline
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Average Office Building
Building Energy Use Profile
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Consumption per
Square Fool
Energy Use Intenstiy
(kBtu/sf)Cost per Square Foot
Electricity 15.5 kWh/sf 53.0 $1.60
Natural Gas 0.27 therms/sf 26.8 $0.31
Total 79.8 $1.91
• According to the Department of Energy, energy use is the largest operating expense in office buildings.
• The cost of maintenance and repairs is a close second.
Building Energy Use Profile
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What is the ENERGY STAR score?
• The ENERGY STAR score is a 1-to-100 assessment of a building’s energy efficiency, as compared with similar buildings nationwide.
• The score adjusts for climate and business activity.
• To qualify as an ENERGY STAR certified building, a building must be verified to earn a score of 75 or higher, indicating that the building performs better than at least 75% of similar buildings nationwide.
ENERGY STAR Score
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Improve energy use
• 30% -- amount of energy the average commercial building wastes
• 10% -- reduction of energy use with little or no cost
• 2.4% -- annual reduction of energy use for buildings that benchmark their energy use on a regular basis, on average
Building Energy Use Savings
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• A savings of 2.4% for three consecutive years is equivalent to the following for a 500,000 square foot office building:
–Cumulative energy cost savings -- $120,000
– Increase in asset value -- over $1 million
Building Energy Use Savings
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• Energy efficiency: one step at a time
– Upgrades should be made throughout the entire property NOT just in common areas.
– A phased approach can help with financing and reduce any tenant inconvenience.
Building Energy Efficiency
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• Building recommissioning
• Lighting
• Building envelope
• Fans and motors
• Heating and cooling systems
• Controls
Building Energy Efficiency
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• Recommissioning is a systemic, documented process.
– Ensures building systems are operating according to the design intent, as well as the current needs of property owners and occupants.
– Identifies energy-saving opportunities.
• Recommissioning is an on-going process.
Building Recommissioning
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• Lighting upgrades offer a quick payback and an enhanced visual environment.
• Upgrading from T12 fluorescent lamps with magnetic ballasts to higher-efficiency T8 lamps with electronic ballasts can yield savings up to 25%.
Lighting
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• Upgrade and seal walls, roofs and windows.
– Improves occupant comfort.
– Reduces heating and cooling costs.
• Ensure insulation levels match recommendations in ASHRAE 90.1 Energy Standard for Buildings Except Low-Rise Residential Buildings.
Building Envelope
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• Converting constant volume systems to variable air volume units can reduce air flow by 40%.
• Installing variable speed drives can lower fan speed and reduce energy use by up to 50%.
Fans and Motors
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• Upgrading to more energy-efficient furnaces, boilers and air conditioning systems can reduce energy costs by up to 15%.
• Ensuring new energy-efficient systems are “right-sized” further saves energy.
– An oversized energy-efficient system will continue to waste energy.
Heating and Cooling Systems
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• Building energy-management system
• Programmable thermostats
• Occupancy sensors
Controls
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• Get everyone involved.
– Optimizing efficiency requires cooperation between building management and tenants.
• Education is key.
– Conserving energy benefits everyone.
• Form an energy team.
– Establish energy-saving goals.
– Implement a strategy.
Tenant Involvement
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• Baseline Building
– High-rise office building
– Chicago, IL
– 250,000 SF/800 occupants/900 computers
– 7 AM-6 PM Mon-Fri (55 hours per week)
– Centrifugal chiller/gas-fired hot water boiler
Typical Office Building Example
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• O&M/Recommissioning Measures – Optimize temperature set points – Optimize HVAC scheduling – Optimize ventilation to minimum required for code – Chilled water reset controls – Implement janitorial best practices – Power management enabling for PCs, printers and
copiers – Turn off plug loads at night – Specify ENERGY STAR equipment-office equipment,
vending machines
Typical Office Building Example
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• Lighting Measures
– Efficient lighting (high-performance T8/T5s, CFLS, LED exit signs)
– Occupancy sensors
– Perimeter daylighting controls
Typical Office Building Example
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• All Measures
– All O&M/recommissioning measures
– All lighting measures
– High-efficiency chillers
– Variable speed pumps and fans
– Premium efficiency motors
Typical Office Building Example
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Typical Office Building Example
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ScenarioElec Use
(kWh)
Elec
Savings
(kWh)
Elec
Savings (%)
Nat Gas
Use
(therms)
Nat Gas
Savings
(therms
Nat Gas
Savings (%)
Baseline 3,760,000 - - 109,500 - -
O&M 3,306,000 454,000 12% 90,500 19,000 17%
Lighting 3,471,000 289,000 8% 112,900 -3,400 -3%
All Measures 2,483,000 1,277,000 34% 98,100 11,400 10%
Scenario
Peak
Demand
(kW)
Demand
Reduction
(kW)
Demand
Reduction
(%)
Baseline 1,224 - -
O&M 1,169 55 4%
Lighting 1,164 60 5%
All Measures 877 347 28%
ScenarioAnnual EUI
(kBtu/SF)
EUI
Reduction
(%)
Eenrgy
Cost ($)
Energy
Savings ($)
EPA Energy
Rating
Baseline 95 - $482,078 - 62
O&M 81 15% $418,946 63,132 74
Lighting 93 3% $455,092 26,986 66
All Measures 73 23% $340,323 141,755 85
• Tenant – Reduce total cost of occupancy
• Owner – Increase net operating income
Increase return on investment
Building Stakeholders
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• Investing in energy efficiency increases asset value and makes available space more attractive.
• A phased approach to efficiency upgrades can help with financing and reduce tenant inconvenience.
• Optimizing energy savings requires a collaborative effort between property managers and tenants.
Key Points
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