2721 MV Methods Existing Buildings

In general, a common theme between the NEMVP, IPMVP and ASHRAE's Guideline 14-2002, is that M&V methods for measuring energy and demand savings in existing building are best represented by the following three approaches: retrofit isolation approach, a whole-

building approach, and a whole-building calibrated simulation approach. Similarly, the measurement of the performance of new construction, renewables, and water use utilize one or more of these same methods.

27.2.1.1 Retrofit Isolation Approach

The retrofit isolation approach is best used when end use capacity, demand or power can be measured during the baseline period, and after the retrofit for short-term period(s) or continuously over the life of the project. This approach can use continuous measurement of energy use both before and after the retrofit. Likewise, periodic, short-term measurements can be used during the baseline and after the retrofit to determine the retrofit savings. Often such short-term measurements are accompanied by periodic inspections of the equipment to assure that the equipment is operating as specified. In most cases energy use is calculated by developing representative models of the isolated component load (i.e., the kW or Btu/hr) and energy end-use (i.e., the kWh or Btu).

27.2.1.1.1 Classifications of Retrofits

According to ASHRAE's Guideline 14-2002 retrofit isolation approach, components or end-uses can be classified according to the following definitions:68

• Constant Load, Constant use. Constant load, constant use systems consist of systems where the energy used by the system is constant (i.e., varies by less than 5%) and the use of the system is constant (i.e., varies by less than 5%) through both the baseline and post-retrofit period.

• Constant Load, Variable use. Constant load, variable use systems consist of systems where the energy used by the system is constant (i.e., varies by less than 5%) but the use of the system is variable (i.e., varies by more than 5%) through either the baseline or post-retrofit period.

• Variable Load, Constant use. Variable Load, constant use systems consist of systems where the energy used by the system is variable (i.e., varies by more than 5%) but the use of the system is constant (i.e., varies by less than 5%) through either the baseline or post-retrofit period.

• Variable Load, Variable use. Variable Load, variable use systems consist of systems where the energy used by the system is variable (i.e., varies by more than 5%) and the use of the system is variable (i.e., varies by more than 5%) through either the baseline or post-retrofit period.

Use of these classifications then allows for a simplified decision table (Table 27.5) to be used in determining which type of retrofit-isolation procedure to use. For example, in the first row (i.e., a CL/TS-pre-retrofit to CL/TS-post-retrofit), if a constant load with a known or timed schedule is replaced with a new device that has a reduced constant load, and a known or constant schedule, then the pre-retrofit and post-retrofit metering can be performed with one-time load measurement(s). Contrast this with the last row (i.e., a VL/VS-pre-retrofit to VL/VS-post-retrofit), if a variable load, with a timed or variable schedule is replaced with

Table 27.4: Evolution of M&V Protocols in the United States.
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