Handbook of air conditioning and refrigeration / Shan K

25.6 CHAPTER TWENTY-FIVE
Energy Audits
Energy audit refers to a month-by-month accounting, survey, and analysis of energy use in a building.
This energy use is checked against a budget or an energy estimate based on an hour-by-hour
detailed system simulation in order to identify energy efficiency opportunities. According to
ASHRAE Handbook 1999, HVAC Applications, following an energy use estimate, an energy analysis
can proceed on three levels:
● Walk-through assessment analyzes energy bills and a brief survey of the building for the sake of
identifying low-cost/or no-cost energy efficiency measures.
● Energy survey and analysis include a more detailed building survey and energy analysis with a
breakdown of energy use within the building. Actual energy use can be compared with EUI of
corresponding building types and locations. This level identifies and provides the savings and
cost analysis of all practical energy efficiency measures that meet the owner’s economic
criteria.
● Detailed analysis of capital intensive modifications focuses on potential capital-intensive modifications
and involves more detailed field data collection, system simulation, and engineering analysis.
In the detailed analysis level, an energy-efficient and cost-effective energy use estimate can be
calculated according to the ASHRAE/IESNA Standard 90.1-1999 Energy Cost Budget (ECB)
method. Refer to Sec. 25.11 for more information. The actual month-by-month energy bill can
be compared against the ECB and energy cost breakdowns on the building envelope, load calculations,
and HVAC&R system and components. Energy efficiency opportunities can then be
determined.
Procedure for Energy Retrofit
MBtu/ft 2 � yr Electric, kWh/ft 2 � yr Natural gas, ft 3 /ft 2 � yr
Building Type Electric Gas Total NE MW SO WE NE MW SO WE
Assembly 27 39 64 7.1 9.5 7.3 57.5 25.9 45.8
Education 27 47 87 7.3 7.4 8.7 7.9 28.2 61.0 33.6 66.4
Health care 75 113 219 20.1 22.6 23.4 20.1 74.0 156.4 82.0 69.1
Mercantile/Serv. 44 46 85 15.1 12.5 12.1 13.4 62.9 62.1 29.4 31.1
Office 66 32 104 16.3 16.7 20.9 22.4 20.8 55.8 23.6 26.8
NE indicates northeast, MW midwest, SO south, and WE west.
Source: DOE/EIA (1992). Based on 4528 buildings. Reprinted by permission.
Energy retrofit is a project whose purpose is energy efficiency, i.e., to convert an existing system to
an energy-efficient system. Energy retrofit can often proceed as follows:
1. Organize a team. One individual should be chosen to be responsible for the team.
2. Draft a plan.
3. Make a field survey by walking through the building; talking with the operating manager, engineers,
operators, and electric utility representative; take field measurements and tests, if
necessary.
4. Proceed with an energy audit.
5. Justify the energy efficiency opportunities after cost analysis.
6. Implement the plan, starting with no-cost and low-cost opportunities.