Since office buildings have long operating schedules, energy expenses can be among the highest operating costs. Space heating and air conditioning are normally the largest loads, and energy efficiency measures that target those systems can achieve the highest savings. Office lighting systems also operate for many hours each month, creating an excellent opportunity for an LED retrofit.
The energy consumption profile in office buildings changes depending on the season. During summer, the load is mostly electrical because air conditioning systems must operate at full capacity. On the other hand, natural gas tends to increase during winter, since space heating systems are normally based on combustion. However, electric heat pumps are emerging as a viable heating alternative.
Deploying LED Lighting in Office Buildings
Each building has a unique energy consumption profile, and the optimal combination of energy efficiency measures varies by property. However, energy consultants often recommend LED lighting, which is cost-effective for many types of properties. Continuous lighting is required during office hours, and efficient lamps can achieve a quick payback period.
Existing lighting installations can be upgraded easily with LED tubes. These tubes are designed for the same fixtures as conventional fluorescent tubes, which simplifies the upgrade. Some LED tubes are designed for the same ballasts and lampholders as fluorescent tubes, while other are designed for direct connection to the power supply, bypassing the ballast.
There are also integral LED luminaires, which are designed to replace fluorescent fixtures completely. Since this type of upgrade is more expensive and disruptive, it is normally recommended as part of a major renovation. Integral LED luminaires are a great option for new constructions, where they can be installed from the start to avoid fluorescent fixtures completely.
LED lighting systems for offices can become even more efficient with a daylight harvesting system. Under this configuration, lighting fixtures are equipped with photosensors and dimmers, which adjust their output according to the available sunlight.
Reducing Air Conditioning and Space Heating Costs in Offices
Energy efficiency measures for air conditioning and space heating often focus in equipment upgrades. However, even the most efficient equipment wastes energy if the building lacks an effective thermal envelope. Unwanted heat movement between the building and it surroundings is detrimental for energy efficiency; heat gain increases cooling loads during summer, and heat loss increases heating costs during winter. The performance of a building envelope can be improved with adequate insulation, an airtight construction and energy efficient windows.
Space heating and air conditioning systems are available in many configurations, and some equipment types offer a superior efficiency:
- Water-cooled chillers with variable speed compressors are among the most efficient cooling options for office buildings.
- In space heating applications, a boiler with a high fuel efficiency can yield high savings.
- Variable refrigerant flow systems also offer a high efficiency, and they can be designed to deliver both heating and cooling. This results in a more compact installation.
When the HVAC installation has a smart ventilation system that responds to occupancy, an even higher efficiency is possible. The concept of demand controlled ventilation consists on reducing airflow when indoor areas are not full. Since less air is being delivered to indoor areas, the associated heating and cooling costs are also reduced.
LED lighting can slightly improve the efficiency of air conditioning systems. Consider that lamps release heat, and LEDs have lower heat emissions than older types of lighting. As a result, the workload on air conditioning equipment is reduced slightly. Upgrading one lighting fixture to LED does not have a significant effect, but consider that office buildings may have hundreds or thousands of them.
Space heating and air conditioning account for a large share of energy expenses in office buildings, and lighting can also be a significant load. Therefore, energy efficiency measures that target these installations tend to be the most cost-effective for office buildings.
A building envelope assessment is recommended before upgrading the HVAC installations. Even if the new equipment has a high nameplate efficiency, air leaks and poor insulation can limit energy savings. If the thermal envelope of the building is improved first, the new equipment can have both a higher efficiency and a smaller workload.
By Michael Tobias
Michael Tobias is the founder and principal of Chicago Engineers, an Inc 5000 Fastest Growing Company in America. He leads a team of 30+ mechanical, electrical, plumbing, and fire protection engineers from the company headquarters in New York City; and has led over 1,000 projects in Chicago, New York, New Jersey, Pennsylvania, Connecticut, Florida, Maryland and California, as well as Singapore and Malaysia.
He is a graduate of Georgia Tech class of 2004, with a Bachelors of Mechanical Engineering with honors. His innovative approach to MEP engineering comes from graduating GE’s Engineering Leadership Program, where he designed wind turbines and biofuel power plant engines. Michael’s passion within design is energy efficiency and green technology. His focus is on integrating MEP/FP engineering design with architecture to create as seamless a system as possible. He is an advocate for green design and technologies, and has designed to both Passive House and Net 0 energy standards. He has spoken numerous times at the AIA, been featured in Georgia Tech’s Alumni magazine, and is an engineering expert on Discovery Channel’s show “Impossible Engineering”.
A New York native, Michael grew up in Rockville Centre, LI. He currently lives in Brooklyn with his wife and children. Outside of work, he enjoys exploring the outdoors, whether it’s on a bike, a pair of skis, or a surfboard. He is passionate about growing personally and professionally every day, and about doing innovative work in the engineering world to help disrupt the traditional construction industry.