Guaranteeing Energy Performance: Mission Impossible?
By AdamCooling Engineering Green Technology Heating HVAC Systems Plumbing Refrigeration
Most energy models produce best-case scenario goals for the design team, assuming perfect construction and operation. However, owners/operators quickly realize that energy models are typically not exact predictors of energy use. But that is changing: design teams and constructors/operators are being required to hit energy model predictions – or else.
With the rise of P3s (Public Private Partnerships) has come energy guarantee modeling. also known as painshare/gainshare or aggregate energy targeting. This type of modeling provides an energy performance prediction during the proposal phase that the constructor/operator guarantee will be met. And there are penalties (or rewards) for the operator depending on if the energy savings predicted are achieved. In 2006, Enermodal helped Infrastructure Ontario craft one of the first painshare/gainshare contracts in the country. Since then, the number of similar projects have increased quickly, with many P3 projects using this model today. A typical contract will see the developer/operator pay 50 to 100 per cent of excess energy use (more than predicted by the model) and receive 50 to 100 per cent of any energy savings (see Figure 1).
While energy guarantees, and P3s in general, provide challenges and risks, the result is often a better building from an energy efficiency perspective. This is because of some fundamental differences in the creation of an energy guarantee model versus a typical energy model, including more coordination between the design and construction team, which adds ‘weight’ to the input of the energy modeler.
Traditional/LEED energy models contain a variety of assumptions to prevent energy modelers from inputting unrealistic numbers or ‘cheating’ the software to create unachievable energy savings predictions. These assumptions include the number of occupants, operating schedules, process loads (i.e., elevators, kitchen equipment), and plug loads (i.e., computers and electronic equipment). An Energy Guarantee Model must be more accurate, so more precise detail on the building as well as plug and process load calculations are required.
Since the energy model’s predicted savings must be carried from the proposal stage through design and then construction, much more effort is put on coordinating between phases. Also, the design team is highly motivated not to ‘value engineer’ out energy efficiency items, which often happens in green building projects.
The energy modeler’s voice is heard much louder and given more weight when a certain level of energy efficiency is a guaranteed requirement. This ensures sustainability is prioritized at the same level as budget, timelines, and the personal preferences of members of the design team.
The most significant affect energy guarantee modeling has on the design/construction process is providing a fundamental shift in the incentive each player has in creating the best, most energy-efficient building possible. In a typical design process, the design team (and the developer if they are not operating the building) has little incentive to ensure the building performs as efficiently as possible. In this process, the developer, operator, and design team all have a stake in ensuring near-perfect design, construction, and operation.
Keys to Success
1. Understand process and plug loads
Since the energy modeler must carefully calculate and (if possible) reduce process and plug loads, this professional must have extensive experience in understanding these loads. They also must know how to use the ‘back end’ of energy modeling software, not just the interface used on many projects.
2. Have experience in actual energy performance
Many members of the design team, including some energy modelers, go through their entire career never truly understanding how their buildings are operated and how they perform in actual practice. Their focus is on creating a great design – in theory. The construction and operation are someone else’s job. Not anymore. Energy guarantee modeling requires design teams to understand how building systems work and perform in real life, not just on paper.
3. Do not forget to measure and improve
Many owners and design teams still do not realize the absolutely vital role extended commissioning and ongoing energy metering and monitoring play in an energy-efficient building. It usually takes several months to one year to fully commission a building, particularly a complex, large building, but the result is typically a 10 to 25 per cent reduction in energy use by improving operations, adjusting control settings, and correcting construction errors. A measurement and verification program ensures sufficient metering to uncover unexpected energy use and provide the information necessary to correct these problems. Both these services are key to operating a building that meets the energy model predictions. <>
Source: Enermodal Engineering www.enermodal.com