First Edition – January 2015

The NEBB Handbook for Energy & Water Calculations establishes a methodology that can be used when performing Retro Commissioning of Existing Buildings.  This NEBB Guideline is intended to be utilized by NEBB Certified Commissioning Professionals for the deployment of Retro Commissioning services of Existed Buildings. 

The purpose of this guideline is to assist the commissioning professional in performing energy calculations.  Retro Commissioning (RCx) is the process of optimizing existing building systems to provide optimal comfort and optimal energy and water performance.  It is intended to provide improved systems to reduce utility costs and to improve the comfort and productivity of its occupants. 

SCOPE

To provide a basis for reliable and accurate energy reduction calculations of existing building energy and water usage, when system changes are recommended, while performing Retro Commissioning.

UTILIZATION

This guideline is intended to present basic, practical calculation formulas and procedures for estimating the energy and water usage of isolated systems and to provide practical procedures and input parameters for utilization of spreadsheet type simulation models.

There is a balance that must be made, regarding the degree of effort required to calculate energy savings, without spending unnecessary effort over analyzing a measure.  The general approach taken in this handbook is to look at common measures that are typically seen during RCx, and provide a simplified approach that ben be used to obtain a reasonable degree of accuracy in estimating the potential energy savings.

There will be times, when performing RCx, that specific measures may require a more complex calculation, for example, analyzing a waterside economizer or energy recovery system.  Calculations for these types of measures can be made by obtaining 8760 Typical Meteorological Weather (TMY) data and building a spreadsheet for the specific climate zone where your project is located.  Using specialized building energy simulation software is another method that is available.

Separate approaches will be shown where appropriate so the commissioning professional can utilize the approach that best fits the system issue or project.  This guideline is not intended to instruct on the use, setup or results of simulation software such as eQuest or other simulation software programs which are beyond the scope of this document.

This handbook is intended to be used by trained technical commissioning and engineering professionals who can utilize calculation procedures outlined in this guideline.  These calculation processes can be utilized for all types and sizes of buildings, from small simple buildings or systems to large very complex buildings and systems.  The basic process of accurately calculating energy and water usage is dependent upon accurately accessing operating conditions and properly calibrating the calculated usage.