Many of the energy efficiency (EE) features that are included as part of new building construction are more difficult to incorporate in existing buildings. Researchers at Oak Ridge National Laboratory (ORNL) experimented with installing various energy conservation measures in an occupied office building and found that a number of measures can be implemented with minimal disruption to the building’s employees.
- Plug loads – Assessments showed plug loads consumed nearly 30% of the building’s energy use, and the majority of consumption occurred at computer workstations. Additionally, much of the energy the plug loads consumed occurred during nights and weekends. As a result, to substantially reduce loads:
- Energy management software was installed on all personal computers (PCs). The software puts the PCs into a very low energy state when not in use, but provides a means for remotely "waking" the PCs to perform system maintenance and run software updates.
- Older PCs, peripherals, and appliances were replaced with the latest ENERGY STAR rated models.
- Two types of energy saving power strips were installed at workstations. One uses a motion detector to sense workstation occupancy. The other monitors the load from the PC. When a PC goes into sleep mode, the device will switch off monitors, peripherals, and other attached loads, including illuminated desk lamps that are not needed when the workstation is unoccupied.
- Lighting – EE lighting options for offices have improved dramatically. Current T8 lamps and electronic ballasts are more efficient today than those manufactured even a few years ago. If nothing else, it is a good idea to replace older fixtures with new high efficiency units. The modern systems have features such as auto-dimming and daylight harvesting. There are ways that building managers can make these changes without unduly disrupting employees. For example, in the case of the building featured in this study, as a simple low-cost approach, half of the lamps were removed from the existing T8 fixtures and motion sensor switches were installed. Light levels were measured to ensure adequate lighting for offices that voluntary chose to remove lamps. This resulted in more than a 30% savings in lighting use and costs.
- HVAC – Originally, the building in the study had individual packaged terminal air conditioning (PTAC) units in each office, similar to the type used in many hotels. High efficiency heat pump units replaced any air-conditioning units that were nearing the end of their useful lives, resulting in significant energy savings. Heat pumps have a much higher EE in heating mode than the electrical resistance heaters in PTAC units.
- Insulation and Roofing – It is often impractical to add wall insulation to an occupied building. However, if the roofing is nearing the end of its useful life, there is an opportunity for substantial EE gains if insulation and a cool-roof membrane are added when the roof replacement is done. Before applying the roofing membrane to the ORNL building, workers added an additional 3-inches of foil-faced polyisocyanurate (polyiso) insulation to the existing 1½ to 2 inches of perlite insulation, increasing the R-value from approximately R-5 to R‑23. It is important to use faced polyiso insulation boards in this sort of upgrade, because unfaced polyiso boards may lose up to 20% of their insulating quality over time. The researchers observed substantial energy savings during the heating season that followed this installation, and also expect to see savings during the summer months as well.
Please share any observations or experience gained after implementing energy improvements in your existing building stock. For questions on other non-disruptive ways to maximize a building’s energy efficiency, provide a comment to this post or contact a technical expert for assistance.
Content and photo for this Blog post courtesy of John Rast, Oak Ridge National Laboratory