Implementing commissioning strategies to achieve energy savings in buildings
Facility managers are tasked with keeping building systems running effectively and efficiently – a challenging job as buildings experience natural wear and tear of their systems over time. According to research conducted by Texas A&M, as much as 20 percent of energy consumed in a commercial building can be attributed to poorly operated systems.1 While it is possible to limit overall system performance decline through maintenance, it remains difficult to eliminate it all together.
Building management is further challenged by the strains of budget limitations, energy expenses and changes to operating conditions. Properly installed and tested systems that adhere to original intentions for design and performance are essential to achieving peak building efficiency.
Commissioning, a process of recalibrating building systems to optimal performance requirements, is a low-cost, high-return solution estimated to deliver energy savings in buildings between five and 25 percent. Global research continues to name commissioning among the top energy conservation approaches available today.2
Benefits of commissioning
Commissioning is a strategy that can help building owners manage and reduce energy consumption and related costs. Research from the Lawrence Berkeley National Laboratory indicates that energy savings achieved through commissioning tends to persist well over a three to five year time frame.3
The same study found that commissioning resulted in 16 percent median energy savings in existing structures and 13 percent in new construction with payback timelines estimated to be 1.1 years in existing buildings and 4.2 years for new buildings. Additionally, a properly executed commissioning process enhances occupant comfort and reduces safety concerns.
Beyond energy savings, commissioning delivers several other benefits to both building occupants and owners. These include:
- Improved occupant comfort and satisfaction resulting in higher productivity
- Increased building system life
- Improved documentation of the operational processes
- Efficient and optimal performance from the systems leading to lower complaints
- Compliance to global energy certifications and ratings
- Increased asset and rental value associated with a building.
The benefits of commissioning projects are governed by several factors including building sise and type, system complexity, comprehensiveness of a commissioning study and measures implemented. While commissioning services are deployable at any stage in the life cycle of a building, it is important to match the type of commissioning with the needs of a building.
Types of commissioning
There are several types of commissioning strategies to bring and restore systems and equipment to maximum performance levels. New building commissioning (NBCx) is the strategy implemented in new construction. In an ideal scenario, planning for NBCx would begin during the design stage itself. In this process, newly installed systems are fine-tuned and calibrated based on design and customer requirements. This is an essential step to ensure systems run at top performance right from installation.
In case of existing and already operational buildings, system components, for example controllers, etc., can fall out of alignment with their original performance states. Two strategies apply in such existing buildings, recommissioning (ReCx) and retrocommissioning (RCx). ReCx is the process of revisiting previously commissioned building systems to recalibrate to original design criteria and owner requirements.
Changing operating conditions like usage, occupancy or environment also require adjustments to the systems and equipment. The process of testing, validating and fine-tuning systems according to current facility requirements is referred to as RCx. Both ReCx an RCx are known as existing building commissioning (EBCx). In these scenarios, systems can be restored to their original design intent or adjusted to meet the current facility requirements to enhance overall performance.
“By selecting the commissioning methodology most aligned with building needs for optimised performance, building owners and facility managers can achieve measureable results throughout a building’s life cycle.
Buildings that collect and analyse system performance trend data through a building management system (BMS) have a third option for commissioning. Ongoing commissioning also known as monitoring-based commissioning (MBCx) uses a combination of the insights obtained from continuous stream of building performance data from a BMS and standard RCx strategies to return systems to optimal performance. MBCx can be implemented in existing and new structures to determine deviations over time, monitor changing building conditions and address system performance in a timely manner.
In the MBCx process, data collected from a BMS is run through an analytics engine to establish which equipment requires fine-tuning and which measures will lead to energy efficiencies and optimised performance. Ultimately, engineering expertise and firsthand experience cannot be entirely replaced by automated analytics, and it is crucial to have experts review findings by superimposing actual site conditions on the analysed results. For buildings with BMS, MBCx solutions are scalable, efficient and unite automation with human expertise.
Overview of the commissioning process
Implementing commissioning strategies is part of a process, inclusive of construction and operations. Ideally, these strategies are incorporated into building design, long before the first brick of a building is ever laid, to pave the way for on-site commissioning. Any system, even a best-in-class one, cannot perform at its peak level in the absence of commissioning.
The process of commissioning involves five main steps:
- Design – If the commissioning agent/party is not involved in the designing process, then it is imperative for the agent to understand the design criterion by collecting and referring to the designs, system documentations, performance guidelines, etc.
- Action Plan – After this step, the commissioning agent/party develops a plan of action with clearly identified objectives and timelines. If the commissioning agent/party is not directly conducting systems testing, control sequences for testing purposes also need to be identified. A few test sequences can be developed to help validate that the systems have been commissioned and confirm that objectives have been met.
- Performance Testing – The testing of equipment is carried out in two stages: pre-functional performance testing (Pre-FTP) and functional performance testing (FTP). In Pre-FTP, equipment is tested in a stand-alone environment. In FTP, equipment is tested for performance in the integrated setup. In the case of initial commissioning for a new building, point-to-point validation of each piece of equipment or system is essential. In existing building commissioning, the focus shifts to ensuring that all the systems and equipment are fine-tuned and calibrated.
- Reporting – After equipment testing, a report on the findings is prepared and submitted for final sign-off. The report includes checks run, results obtained, issues identified, possible solutions and an implementation overview. This report is also used to determine which measures will need to be implemented as a follow-up to the commissioning exercise.
- Seasonal Testing – An integral part of commissioning is to carry out post-occupancy seasonal testing. This is done by monitoring the building operation, analysing short-term trend data captured in the BMS and developing an understanding of all issues faced by the occupants and/or operator over different seasonal conditions.
Commissioning has been established as one of the most useful approaches for solving energy and controls performance deterioration while ensuring a high ROI. By selecting the commissioning methodology most aligned with building needs for optimised performance, building owners and facility managers can achieve measureable results throughout a building’s life cycle. Building owners and facility managers seeking a scalable approach that reduces energy consumption at a low cost should employ commissioning in their facilities.
The author, Cara Ryan, is offer manager, building performance centre at Schneider Electric.
1. Texas A&M Energy Systems Laboratory. Retrieved from http://esl.tamu.edu/continuous-commissioning.
2. ENERGY STAR. (2007). Retrocomissioning. Environmental Protection Agency. Retrieved from https://www.energystar.gov/sites/default/files/buildings/tools/EPA_BUM_CH5_RetroComm.pdf.
3. Mills, E. (2009). Building commissioning: a golden opportunity for reducing energy costs and greenhouse gas emissions. Lawrence Berkeley National Laboratory. Retrieved from http://cx.lbl.gov/documents/2009-assessment/lbnl-cx-cost-benefit.pdf.