330 Energy Project Financing: Resources and Strategies for Success
- addition of radiant barriers in an attic, and
- HVAC system changes not enabled by the fixed options within
some whole-building hourly simulation programs.
The creation and calibration of a simulation can be time concerning.
The use of monthly data for calibration is usually less costly than hourly
calibration. Calibrations based on monthly utility data can achieve an ap-
proximate mean bias error (MBE) of ±20% compared to monthly energy
use. Hourly calibrations can achieve ± 10% to ±20% CV (RMSE) of hourly
energy use, or ± 1 % to ±5 % of the monthly utility bill.
3.4.4.3 Option D: Best Applications
Option D is best applied where:
- either baseyear or post-retrofit energy data unavailable or unreli-
able. - there are too many ECMs to assess using Options A or B.
- the ECMs involve diffuse activities which cannot easily be isolated
for the rest of the facility, such as operator training or wall and
window upgrades. - the impact of each ECM on its own is to be estimated within a mul-
tiple ECM project and the costs of Options A or B are excessive. - interactive effects between ECMs or with other facility equipment
is complex making isolation techniques of Options A and B exces-
sively complex. - major future changes to the facility are expected during the period
of savings determination and no realistic means can be found to
track or account for their energy impact. - an experienced energy simulation professional is available and
adequately funded for gathering suitable input data and calibrat-
ing the simulation model. - the facility and the ECMs can be modeled by well documented
simulation software, and reasonable calibration can be achieved