Energy Savings From 

System Efficiency 

Improvements in Iowa’s 

HVAC SAVE Program

S. Yee, J. Baker, L. Brand, and J. Wells

Partnership for Advanced Residential Retrofit

August 2013
NOTICE

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August 2013
iii

Energy Savings From System Efficiency Improvements in 

Iowa’s HVAC SAVE Program 

Prepared for: 

Building America

Building Technologies Program

Office of Energy Efficiency and Renewable Energy 

U.S. Department of Energy 

Prepared by: 

S. Yee, J. Baker, L. Brand, J. Wells

Partnership for Advanced Residential Retrofit 

Midwest Energy Efficiency Alliance (MEEA)

20 N. Wacker Dr. Suite 1301

Chicago, IL 60606

NREL Technical Monitor: Stacey Rothgeb

Prepared Under Subcontract No. KNDJ-40346-02

August 2013
iv

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v 

Contents

List of Figures ............................................................................................................................................ vi

List of Tables .............................................................................................................................................. vi

Definitions .................................................................................................................................................. vii

Acknowledgments ................................................................................................................................... viii

Executive Summary................................................................................................................................... ix

1 Introduction and Background ............................................................................................................. 1

2 Experimental Methods ......................................................................................................................... 3

2.1 Research Questions ..............................................................................................................3

2.2 In-Home Evaluation Procedures ..........................................................................................3

2.3 Data Collection ....................................................................................................................5

3 Results................................................................................................................................................... 7

3.1 Field Data Summary Statistics .............................................................................................7

3.2 Ten Test Homes .................................................................................................................10

3.2.1 Three In-Depth Case Study Homes .......................................................................10

3.2.2 Seven Supporting Test Homes ...............................................................................17

2.3.3 Test Home HVAC System Upgrades ....................................................................18

4 Discussion........................................................................................................................................... 20

4.1 Next Steps ..........................................................................................................................24

5 Conclusion .......................................................................................................................................... 25

References................................................................................................................................................. 26

Appendix A: Supplementary Data ........................................................................................................... 27

Appendix B: Topics Covered in the HVAC SAVE Training................................................................... 29

Appendix C: Data Collected During the Test-In and Test-Out Procedures......................................... 32
vi

List of Figures

Figure 1. Map of trained contractors (circles represent 50-mi radius).................................................. 2

Figure 2. Furnace input capacity............................................................................................................... 6

Figure 3. Recommended and measured airflows by individual home .................................................. 7

Figure 4. Measured ESP (i.w.c) of blower motors rated at 0.5 i.w.c. ..................................................... 7

Figure 5. Recorded static pressure drop, by component....................................................................... 8

Figure 6. Btu/h input to furnace................................................................................................................. 9

Figure 7. Results of flue gas testing (Condensing and Induced draft furnaces) ................................. 9

Figure 8. Label AFUE versus test-in steady state efficiency................................................................ 10

Figure 9. Test home #1 ............................................................................................................................. 11

Figure 10. Test home #1, natural gas usage pre- and post-retrofit ..................................................... 12

Figure 11. Test home #1, HDD (base 65) per month.............................................................................. 12

Figure 12. Test home #2 ........................................................................................................................... 13

Figure 13. Test home #2, natural gas usage per month (therms) ........................................................ 14

Figure 14. Test home #2, HDD (base 65), per month............................................................................. 14

Figure 15. Test home #3 ........................................................................................................................... 15

Figure 16. Test home #3, natural gas usage per month (therms) ........................................................ 16

Figure 17. Test home #3, HDD (base 65), per month............................................................................. 17

Figure 18. Distribution of calculated conversion efficiencies.............................................................. 20

Figure 19. Percentage of required airflow across heat exchanger as measured in the home ......... 21

Figure 20. Percentage of required airflow across heat exchanger as measured in the home ......... 21

Figure 21. ESP restriction, by location ................................................................................................... 22

Figure 22. Measured fire rate as a percentage of nameplate input ..................................................... 23

Unless otherwise noted, all figures were created by PARR. 

List of Tables

Table 1. Age of Furnaces in Test Homes.................................................................................................. 5

Table 2. Test Home #1 .............................................................................................................................. 11

Table 3. Test Home #2 .............................................................................................................................. 13

Table 4. Test Home #3 .............................................................................................................................. 16

Table 5. HVAC System Replacement and Tune-Up Diagnostic Data (Shaded Columns Underwent 

Equipment Replacement): Post-Tune-Up Minus Pre-Tune-Up Diagnostic Data.......................... 18

Table 6. HVAC System Replacement and Tune-Up Diagnostic Data: Average Differences ............. 18

Table 7. Test Home Repairs and Adjustments (Replacements Shaded)............................................. 19

Table 8. Supporting Data for 7 Additional Homes That Have Undergone System Tune-Ups and 

Equipment Replacement.................................................................................................................... 28

Unless otherwise noted, all tables were created by PARR. 
vii

Definitions

ACCA Air Conditioning Contractors of America

AFUE Annual fuel utilization efficiency

ASHRAE American Society of Heating, Refrigerating and Air-Conditioning 

Engineers 

Btu British thermal unit

CFM Cubic feet per minute

ESP External static pressure

HDD Heating degree day

HVAC Heating, ventilating, and air-conditioning

i.w.c. Inches of water column

MEEA Midwest Energy Efficiency Alliance

MBtu Million British thermal units

NCI National Comfort Institute

SAVE System Adjusted & Verified Efficiency
viii

Acknowledgments

PARR would like to thank Energy Stewards International and Cenergy for the collection of the 

data used in this project. 
ix

Executive Summary

The objective of the Iowa HVAC System Adjusted and Verified Efficiency (SAVE) program is 

to train contractors to measure installed system efficiency as a diagnostic tool that can then be 

used to reduce space heating and cooling energy consumption. For heating system performance, 

SAVE provides training in energy measurement tools, techniques used to tune furnaces, and 

procedures to reduce losses from duct distribution systems. Through a system efficiency 

approach, the program ensures that the homeowner achieves the energy reduction target for the 

home rather than simply performing a tune-up on the furnace or having a replacement furnace 

added to a leaky system. This report uses pre- and post-system upgrade data to analyze the 

energy savings associated with Iowa’s HVAC SAVE program for space heating. 

The research conducted here first examined baseline energy usage from a sample of 48 existing 

homes, before any repairs or adjustments were made, to calculate an average energy savings 

potential and to determine which system deficiencies were prevalent. Test procedures used in the 

SAVE program consisted of measuring airflow, static pressure, and temperature across several 

components and the whole system to determine how well the furnace was performing compared 

to the manufacturer’s specifications and where the losses were occurring. After an initial 

assessment, duct distribution systems were sealed and insulated and in some cases additional 

drops were added from the return duct to the furnace to improve airflow. 

The results of the baseline study of 48 homes found that on average about 10% of the space 

heating energy available from the furnace was not reaching the conditioned space. Thirty-one of 

the 48 homes were identified as having a return duct that was too small to meet the required 

airflow across the heat exchanger, while 43 of the 48 showed that the static pressure across the 

filter significantly reduced the airflow due to face area, blockage, or improper selection. 

In the second part of the project, the team examined a sample of 10 homes that had completed 

the initial evaluation for more in-depth study. In these homes, the furnaces were tuned or 

replaced and duct systems were modified. Four homes had equipment replacement and duct 

upgrades, and six homes had system tune-ups for both furnaces and ducts. 

For these 10 homes, the diagnostic data show that it is possible to deliver up to 23% more energy 

from the furnace to the conditioned space by doing system tune-ups (furnaces and ducts) with or 

without upgrading the furnace. The increase in system efficiency from this study also varied 

significantly, but it appears from the results that it is possible to deliver 80%–90% of the heat 

generated by the furnace to the conditioned space. Replacing the furnace provides additional 

energy reduction. The findings of this study indicate that residential heating and cooling 

equipment should be tested and improved as a system rather than as a collection of individual 

components. 
1 

1 Introduction and Background

The installed performance of natural gas furnaces is dependent on the rated annual fuel 

utilization efficiency (AFUE) of the furnace, the skill of the installation contractor, the degree to 

which the furnace has aged or drifted off its initial settings, and the condition of the duct 

distribution system. Although federal, state, and utility programs have increased the market 

penetration of residential high efficiency furnaces, there is evidence that the potential energy 

savings resulting from higher efficiency equipment are not being realized in the field (Walker 

and Modera 1998). A possible explanation for these lost savings is that one or more of the key 

dependencies mentioned above are suboptimal. For the furnace itself, the airflow setting, fuel 

input rate, and burner performance can all have an impact on how well the furnace performs in 

the field. Low airflow across the heat exchanger can have a number of negative consequences for

the performance of a furnace, including cycling on high limit and poor heat transfer. Low airflow 

may be caused by improperly designed distribution systems, overly restrictive filters, dirty 

evaporator coils, and incorrectly set fan speeds. Some of these causes are simple to correct and 

some require extensive renovation of the ductwork. Contractor training in diagnostics and repair 

is a critical success factor in optimum system performance. 

To address these challenges, the Midwest Energy Efficiency Alliance (MEEA), in partnership 

with Energy Stewards International, developed a program that allows heating, ventilation, and air 

conditioning (HVAC) contractors to easily diagnose the performance of a furnace in-situ. This 

training program and contractor certification is named HVAC SAVE: System Adjustment and 

Verified Efficiency. The HVAC SAVE program was developed by MEEA to train HVAC 

contractors in the skills necessary to determine in-place efficiency of functioning HVAC 

systems. Energy Stewards International has been training HVAC professionals for many years 

on how contractors can use static pressures, system temperatures, and airflows to identify 

existing system deficiencies, allowing them to make targeted repairs or adjustments. These 

principles are taught over the course of a two-day class, described in Appendix A, which 

prepares contractors to implement these diagnosis and improvement practices on new and 

existing systems. The format of the class is a combination of classroom instruction using 

PowerPoint presentations, as well as white-board diagrams, explanations and examples, handson testing modules, and interactive workbook exercises to prepare contractors to integrate these 

concepts into their regular business activities. Classes are either held at a location with working 

systems available for testing or Energy Stewards International brings a functioning 

demonstration kit to allow the air diagnostic concepts and procedures to be demonstrated on a 

live model “system.”

The target audience for this course is HVAC technicians, installers, designers, and business 

owners. The curriculum provides for approximately 15 hours of total course material. At the 

conclusion of the second day, students are given a certification exam. Upon successful 

completion of the exam students are awarded the SAVE certification from MEEA and the 

National Comfort Institute (NCI). Using these methods MEEA and NCI have trained roughly 

600 HVAC contractors across the state of Iowa to date, as shown in Figure 1.
2 

Figure 1. Map of trained contractors (circles represent 50-mi radius)

HVAC SAVE aims to have contractors take the information they have learned in the classroom 

and translate it into to energy savings in the field. Currently the market for system evaluations 

and improvements is limited. To address this issue, the program offers a financial incentive from 

the State of Iowa to trained contractors when they evaluate the performance of any new furnace 

installation by recording static pressures, temperatures, system airflows, and fuel input—putting 

their training into practice. In order to be eligible for this rebate, the furnace must be installed 

and performing at or near the manufacturer’s specifications. In many cases adjustments to the 

equipment or system will need to be made by the contractor to meet this level of performance. 

As HVAC installers increase the regularity of this type of evaluation on new or existing furnaces, 

they will subsequently increase their focus on the equipment’s installed performance. 

The objective of this project is to explore the energy savings potential of maximizing furnace and 

distribution system performance by adjusting operating, installation, and distribution conditions. 

Furnaces in existing homes were evaluated by home energy professionals and specially trained 

HVAC SAVE contractors. This evaluation consisted of measuring airflows, static pressures, and 

temperatures across the system to determine how well the furnace was performing as compared 

to the manufacturer specifications. If it was determined that the furnace was underperforming, 

possible causes were identified from the data so that repairs or adjustments could be made to 

maximize the performance. Through incentive programs like this one, proper furnace installation 

techniques and duct system upgrades that produce optimal system performance are rewarded and 

equipment retrofits are able to achieve their full energy savings potential.
3 

2 Experimental Methods

This project determines the efficacy of the HVAC SAVE program through examining the 

performance of HVAC systems in-situ both before and after tuning and distribution system 

changes are made. The project consists of two parts: 

1. Baseline system evaluation results from a sample of existing homes before any repairs or 

adjustments are made. These data are used to estimate energy savings if the heating 

system was operating at its full potential. 

2. In-depth study on data from a smaller sample of homes that have completed an initial 

evaluation, system modifications (tuning or replacement), and a post-work evaluation. Of 

this dataset, three homes are selected for in-depth analysis to compare the estimated 

energy savings pre- and post-testing. 

All in-home evaluations were completed by home energy professionals or specially trained 

HVAC contractors following performance testing methods taught in the HVAC SAVE training. 

A detailed description follows.

2.1 Research Questions

This project will answer the following research questions:

• What is the achievable improvement in HVAC system operating efficiency from 

common modifications and quality installation of new equipment? 

• What is the current typical installed HVAC system operating efficiency, as defined by the 

capacity of conditioned air reaching building occupants? 

2.2 In-Home Evaluation Procedures

A key component of the performance testing procedures is the “test-in,” an evaluation of the 

actual installed performance of the furnace and HVAC system prior to any improvement work 

being conducted. Information collected as part of this initial evaluation, with instrumentation 

accuracies, includes:

• Furnace nameplate data and general housing characteristics, including conditioned floor 

area and location of supply and return ducts. 

• Airflow at the equipment by one of three methods (below). The first two methods are 

preferred, as pressure matching is prone to errors.

o Traversing using a hot wire anemometer with a stated instrument accuracy of ± 6 

fpm (± 5% of the reading) 

o Using a flow grid with a manufacturers stated accuracy of ± 7% of the reading 

o Matching static pressure drops across the equipment with OEM values. 

• Fuel input rate by clocking the gas meter (timing the gas flow rate). 
4 

• Measured external static pressure (ESP) using a static pressure probe with at stated 

instrumentation accuracy of ± 2% of the reading. 

• Temperature rise across the equipment and at the supply and returns grilles with an 

instrumentation accuracy of ± 0.5°F. 

A complete list of information collected during the test-in process can be seen in Appendix B. 

All of the measurements listed above were taken when the furnace was warmed up and running 

steadily. Ensuring the furnace is warmed up is important because it allows for the calculation of 

steady-state efficiency. This information is compared with the equipment rated values and 

manufacturer nameplate to determine if the equipment is operating at optimal levels. 

The metric used to determine energy savings potential is conversion efficiency: 

Energy out (Btu delivered by the furnace to the circulating air) 

Energy in (Btu content of the natural gas*AFUE) (1) 

Energy out = CFM *Temperature Rise *1.08 (specific heat value)

Energy in = Measured gas flow rate * gas heating value * AFUE

In order to quantify the amount of energy entering the distribution system for each tested 

furnace, temperature rise and airflow across the heat exchanger are recorded while the furnace is

in operation. The amount of energy that should be delivered by the furnace is determined by 

taking the measured gas flow rate (i.e., clocking the gas meter), multiplying by the local gas 

heating value, and multiplying by the AFUE. The amount of energy added to the airflow is 

calculated by measuring the temperature of the air entering and leaving the furnace and airflow 

rate of air leaving the furnace. By comparing these two values (the conversion efficiency) the 

research team can determine what percentage of the theoretical maximum available energy is 

actually entering the distribution system.

Following HVAC SAVE protocols, if a furnace is delivering less than 90% of the post-AFUE 

energy available based on the fuel input (accounting for AFUE), then repairs or adjustments to 

the system are deemed appropriate. Other measurements taken during the test-in are used to 

identify possible improvement opportunities. The first such measurement is the airflow across 

the heat exchanger. If the airflow is lower than the manufacturer’s recommendation, then an 

adjustment to the blower motor speed is deemed appropriate. This simple step is often 

overlooked during installation. Once the setting has been confirmed or adjusted, static pressure 

measurements are taken and compared with the rating of the equipment. If this value is higher 

than 125% of the maximum ESP rating recommended by the manufacturer on the nameplate, it is 

considered to be above the desired range. Furnaces that are operating above this range are 

evaluated further by examining pressure drops across individual components in the system. Each 

section or component is allotted a specific portion of the total ESP. Allocation of external static 

pressure is determined using a standardized pressure budget table that takes into account fan type 

and coil placement. Exact proportions of the ESP allocated to the coil, filter, supply, and return 
5 

are dependent on type of furnace. The exact values provide a guide for the contractor to 

determine which locations in the system are restricting airflow. 

Once the airflow across the heat exchanger has been properly adjusted, the fuel input rate and 

temperature rise across the heat exchanger are examined. Furnaces with a firing rate not within ± 

5% of the nameplate rating are considered over- or under-fired and adjustments are required. 

After the fuel input rate is correctly set combustion tuning can be conducted using a handheld 

combustion analyzer. When all of these procedures are complete, the furnace is retested to 

determine if it is operating at or close to its rated capacity. 

Airflow at the equipment was measured using one of three methods: traversing using a hot wire 

anemometer, flow grid, or matching static pressure drops across the equipment with original 

equipment manufacturer values. Procedures for measuring airflow using the flow grid are 

described in ANSI/ASHRAE 152-2004, while the traverse procedures are described in 

ANSI/ASHRAE 111-2008. While ideally a single method of measurement would have been 

used, the variability of installations in the field did not allow for this. The preferred method of 

measurement was either the hot wire anemometer or the flow plate. In instances where neither of 

the two preferred measurement methods was appropriate, the static pressure drop matching was 

used. This method is less accurate and is prone to potential errors. 

2.3 Data Collection

The sample set for this project came from a database of homes that have been evaluated through 

the test-in process as a part of the HVAC SAVE program in Iowa. This program began in 

November 2010 with limited program participation and thus the sample set was modestly sized. 

Initially this set contained 102 homes but the research team eliminated all but 48 homes as only 

these met the selection criteria of having received a complete test-in of a forced-air natural gas 

furnace. The team removed 22 homes that had data on central air conditioners only and 10 that 

were geothermal heat pumps, air source heat pumps, or strip heat. Four were removed for being 

commercial buildings and the remaining 18 were removed due to having not completed the entire 

test-in procedure. 

The 48 Iowa homes that were evaluated as part of this project had average conditioned floor 

space of 2,645 ft2

, ranging from 780 ft2 to 4,760 ft2. Supply and return ducts in these homes were 

located completely (100%) in conditioned space in all but four of the homes. Of the furnaces 

tested, 33 were condensing (AFUE 90%–95%). The minimum recorded AFUE was 78%. The 

furnaces ranged in age from brand new to greater than 15 years old and had an average rated 

input of 81,781 Btu/h. Table 1 illustrates furnace age. Figure 2 shows the furnace input capacity 

sorted from smallest to largest.

Table 1. Age of Furnaces in Test Homes

Furnace Age Number of Furnaces

New 4

0–5 Years Old 3

5–10 Years Old 17

10–15 Years Old 6

> 15 Years Old 18
6 

Figure 2. Furnace input capacity

In the second part of the project, the team studied 10 homes that had completed test-in, system 

modifications, and test-out procedures. The objective of this work is to determine the energy 

savings that could actually be achieved from the HVAC SAVE procedures. Three of the 10 

homes were chosen for in-depth case studies, including utility bill analysis. “Test-out” follows 

the same procedures as the “test-in” (see Section 3). Comparing test-in and test-out allows for 

performance improvements resulting from the repair or modification to be clearly measured. 

Similar to the case study homes, the remaining seven homes analyzed in this part of the study 

have undergone HVAC equipment replacement and system tune-ups. All seven of these homes 

received a test-in before the work was completed and a test-out after the work was completed. 

These seven additional homes will assist in investigating the hypothesis that many furnaces are 

installed outside their recommended operating settings and can benefit from system tune-ups. 

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

Capacity, Btu/hr

Furnace capacity sorted from smallest to largest
7 

3 Results 

3.1 Field Data Summary Statistics

In the first part of this study, field data were evaluated from 48 existing homes with natural gas 

furnaces located in central Iowa. The data were collected during test-in evaluations completed by 

home energy professionals who have several years of experience conducting this type of testing. 

Equipment static pressures were measured with a static pressure probe using the methods 

described in ASHRAE Standard 111-2008. Figure 3 shows the recommended airflow values 

sorted from smallest to largest with each home’s corresponding recorded airflow. Figure 4 shows 

the distribution of measured ESP for the 47 homes that had blower motors rated at 0.5 i.w.c. (one 

home was removed from this set as its blower motor was rated at 0.2 i.w.c.; this furnace had a 

measured ESP of 0.55 i.w.c.). Recorded airflows ranged from 540 CFM to 1,877 CFM, with the 

recommended levels ranging from 520 CFM to 1,650 CFM (ASHRAE 2008). 

Figure 3. Recommended and measured airflows by individual home

Figure 4. Measured ESP (i.w.c) of blower motors rated at 0.5 i.w.c. 

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Airflow, CFM

Individual homes, sorted from lowest to highest recommended airflow

Measured

Recommended

Linear (Recommended)

0

1

2

3

4

5

0.01 0.11 0.21 0.31 0.41 0.51 0.61 0.71 0.81 0.91 1.01

Measured External Static Pressure (i.w.c), of blower motors rated at 0.5 i.w.c

Distribution of Measured External Static Pressures (n=47) 
8 

Pressure drops across individual components were also measured to identify where restrictions in 

the system exist. As shown in Figure 5, the four locations where pressure drops were measured 

are the coil, filter, supply duct, and return duct. Individual component static pressure 

measurements are important because they shed light on how measured static pressure compares 

with the pressure budget. The average ESP values for external coil, filter, supply ducts, and 

return ducts are 40%, 20%–30%, and 20%–15%, respectively.

Figure 5. Recorded static pressure drop, by component

By clocking the gas meter on these sample homes, the team was able determine the fuel input to 

the furnace. Figure 6 shows the actual measured input to the furnace compared with the rated 

input. Measured inputs on the 48 sample homes ranged from 37,037 Btu/h up to 163,636 Btu/h. 

Combustion analysis testing was also conducted on 36 of the 48 homes. Flue temperatures 

ranged from 314°F to 519°F on induced draft furnaces and 91°F to 138°F on condensing 

furnaces. Equipment temperature (the temperature of the air leaving the furnace) and percentage 

of oxygen were also recorded on these homes. Results of the flue gas testing are shown in Figure 

7. The two furnaces that have oxygen percentage readings in the 4% range also had high carbon 

monoxide readings. 

0

0.2

0.4

0.6

0.8

1

1.2

Static Pressure, i.w.c

Test homes, sorted from smallest to largest measured ESP

Return Duct Pressure Drop

Supply Duct Pressure Drop

Filter Pressure Drop

Coil Pressure Drop
9 

Figure 6. Btu/h input to furnace

Figure 7. Results of flue gas testing (Condensing and Induced draft furnaces)

Figure 8, below, shows the comparison between label AFUE and test-in steady-state efficiency. 

Note that steady-state efficiency varies both above and below the AFUE; this is likely due to 

natural variations in the observed operating condition. 

20000

40000

60000

80000

100000

120000

140000

160000

180000

Btu/hr

Sample homes, sorted from smallest to largest input capacity

Rated Input

Measured Input

0

2

4

6

8

10

12

14

0

100

200

300

400

500

600

O2, % 

Temp, °F 

Flue Temp,

Induced Draft

Flue Temp,

Condensing

Equip Temp

%O2
10

Figure 8. Label AFUE versus test-in steady state efficiency 

3.2 Ten Test Homes

For the second part of this experiment, test-in and test-out data for 10 homes have been analyzed. 

Four of the 10 homes have undergone equipment replacement and system tune-ups and the 

remaining six have undergone system tune-ups only. Two of the three in-depth case studies have 

undergone equipment replacement and one test home had the tune-up only. The results presented 

here shed light on how directed system-level improvements can improve the efficiency of 

residential heating and cooling systems. 

3.2.1 Three In-Depth Case Study Homes

Test home #1, shown in Figure 9, is located in Johnston, Iowa. Built in 1993 it has 2,414 ft2 of 

conditioned floor space and 100% of the supply and return ducts are in conditioned space. This 

home contained a 100,000 Btu induced draft furnace rated at 80% AFUE. At test-in the recorded 

airflow was 1,016 CFM versus the recommended level of 1,300 CFM. Measured ESP was 0.88 

i.w.c with the blower motor having a rating of 0.5 i.w.c. The following repairs or adjustments 

were made to test home #1: 

• Furnace replaced, reducing capacity from 100,000 Btu 80% AFUE to 66,000 Btu 95% 

AFUE

• Combustion tuning conducted on new furnace once airflow was set correctly

• Ductwork leaks repaired and entire duct system sealed using the Aeroseal process. 
11

Figure 9. Test home #1

Table 2. Test Home #1

Pre-Retrofit Post-Retrofit

AFUE, % 80 95

Rated Input, Btu 100,000 66,000

Total ESP, i.w.c. 0.88 0.4

Target ESP (Nameplate), i.w.c. 0.5 0.8

Temperature Rise Across the Equipment, °F 45.1 49.4

Supply Register Average Temperature, °F 107.3 103.7

Required Fan Airflow, CFM 1300 990

Recorded Fan Airflow, CFM 1016 1089

These repairs were completed in February 2011 and a test-out of the system was done shortly 

after completion of the work. The new equipment is a 66,000 Btu 95 AFUE condensing furnace, 

airflow across the equipment was measured at 1,089 CFM, slightly above the recommended 

level of 990 CFM. After the ducts were repaired and sealed, the new furnace had an ESP of 0.4 

i.w.c., well below its rated 0.8 i.w.c. Figure 10 below shows the natural gas consumption of the 

home pre- and post-retrofit. While the most recent winter was warmer than the previous two, 

based on heating degree days (HDDs), the natural gas consumption post-retrofit over the four 

billing periods ending in October, November, December, and January (2011–2012) was 32% less 

than the same four-month period (2010–2011) when the summer base load is factored out. The 

HDDs over the same four-month period are 16% fewer post-retrofit than pre-retrofit. When 

adjusted for HDD differences, the savings was approximately 16%. Data were normalized for 

weather using ENERGY STAR® Portfolio Manager’s Methodology for Accounting for Weather 

procedure. Further data collection, especially over a typical winter with temperatures close to 

design conditions, is required to assess the energy savings from this upgrade. 
12

Figure 10. Test home #1, natural gas usage pre- and post-retrofit 

Figure 11. Test home #1, HDD (base 65) per month

Test home #2 is located in West Des Moines, Iowa. It was constructed in 1986 and has 2,698 ft2

of conditioned space and 100% of the supply and return ducts are in conditioned space. The 

home contains a 100,000 Btu condensing furnace with airflow at the equipment during initial 

testing of 988 CFM, below the required 1,500 CFM. The measured ESP was 0.29 i.w.c. versus 

the blower motor rating of 0.5 i.w.c. Based on the conditions found in the home the following 

repairs or adjustments were made:

• Ductwork repaired; returns that were found to be communicating with the outdoors 

sealed

• Additional returns added 

• Fan speed increased 

• Entire duct system sealed using the Aeroseal process.

0

50

100

150

200

250

7/1/2009

7/31/20098/19/20099/21/2009

10/19/200911/17/200912/18/2009

1/23/20102/25/20103/25/20104/23/20105/21/20106/22/20107/23/20108/20/20109/21/2010

10/20/201011/18/201012/21/2010

1/24/20112/22/20113/23/20114/21/20115/20/20116/21/20117/21/20118/19/20119/20/2011

10/19/201111/17/201112/20/2011

1/23/20122/21/2012

Therms

0

200

400

600

800

1000

1200

1400

1600

1800

HDD (base 65)
13

Figure 12. Test home #2

Table 3. Test Home #2

Pre-Retrofit Post-Retrofit

AFUE 93 93

Rated Input, Btu 100,000 100,000

Total ESP, i.w.c. 0.29 0.38

Target ESP (Nameplate) i.w.c. 0.5 0.5

Temperature Rise Across the 

Equipment, °F 57 59

Supply Register Average

Temperature, °F 138 144

Required Fan Airflow, CFM 1500 1500

Recorded Fan Airflow, CFM 988 1238

The modifications on test home #2 were completed in December 2011. The test-out showed an 

increased airflow to 1,238 CFM, which raised the ESP to 0.38 i.w.c. The original equipment was 

not replaced as part of this job.

Pre- and post-retrofit utilities bills were gathered to examine the energy saving from the repairs 

made. Figure 13 shows the natural gas consumption of the home from September 2010 through 

February 2012. The last two columns of the graph show post-retrofit consumption. Since this 

installation was so recent, energy savings from these repairs is difficult to quantify. The natural 

gas usage from January and February 2012 is 33% less than the same period in 2011, while the 

HDDs over the same periods are 27% less. Since the most recent winter was milder (based on 

HDD) than the same period during 2010–2011, short-term year-over-year energy savings are 

difficult to predict. Original equipment remained in use post-retrofit; therefore, this home is a 

good candidate for longer term monitoring. The research team will continue to collect utility 

billing data on this home over the course of the next year to quantify the energy savings from 

these system repairs.
14

Figure 13. Test home #2, natural gas usage per month (therms)

Figure 14. Test home #2, HDD (base 65), per month

Figure 15 shows test home #3, located in Des Moines, Iowa. It was built in 1963 and has 1,520 

ft2

 of conditioned floor space. The home contained a 100,000 Btu/h furnace, with a measured 

airflow at the equipment of 1,425 CFM. The temperature rise across the equipment was 56 °F 

with an average supply register temperature of 127.9°F. ESP was 0.83 i.w.c., with the blower 

motor rated at 0.5 i.w.c. The following repairs or adjustments were made to test home #3: 

• 100,000 Btu furnace replaced by a 66,000 Btu, 97% AFUE condensing furnace 

• Duct system repaired and sealed. 

0

50

100

150

200

250

Therms

0

200

400

600

800

1000

1200

1400

1600

HDD(base 65)
15

.

Figure 15. Test home #3
16

Table 4. Test Home #3

Pre-Retrofit Post-Retrofit

AFUE 92 97

Rated Input, Btu 100,000 66,000

Total ESP, i.w.c. 0.83 0.6

Target ESP (Nameplate), i.w.c. 0.5 0.8

Temperature Rise Across the 

Equipment, °F

56 56

Supply Register Average 

Temperature, °F

127.9 126.3

Required Fan Airflow, CFM 1,500 990

Recorded Fan Airflow, CFM 1,425 875

Repairs were completed on test home #3 in December 2011. “Test-out” data on the new 

condensing furnace showed measured equipment airflow of 875 CFM and an ESP of 0.6 i.w.c. 

The temperature rise and supply register temperatures were similar to the pre-retrofit conditions. 

Since this repair was completed recently, natural gas utility bills pre- and post-modification do 

not provide significant insight into whether any energy savings were achieved. Figure 16 and 

Figure 17 show the billing and HDD data. The billing cycles ending in January and February 

2012 show 21% less natural gas use than the same two-month period in 2011 when summer 

natural gas usage is factored out. During this same two-month period, the number of HDDs was 

20% fewer this year versus the previous year. Since the most recent winter was milder (based on 

HDD) than the same period during 2010–2011, short-term year-over-year energy savings are 

difficult to predict. 

Figure 16. Test home #3, natural gas usage per month (therms) 
17

Figure 17. Test home #3, HDD (base 65), per month

3.2.2 Seven Supporting Test Homes

An additional seven test homes were studied to determine if furnaces installed outside their

optimal operating settings and can benefit from system tune-ups. The seven homes being 

reported here have undergone HVAC SAVE system repairs, system adjustments, and equipment 

replacements. Similar to the three case study homes, test homes #4 through #10 (TH-4 to TH-10) 

were located throughout Iowa and the work was performed by HVAC SAVE certified 

contractors. The HVAC diagnostic data depicted in this section is identical to the three casestudy homes except utility bill analysis is not included (Appendix A). Analysis of these seven 

homes shows significant improvements in HVAC equipment and system efficiency. Table 5 lists 

the difference (after tune-up minus before tune-up) before and after either equipment 

replacement or system tune-up. 

Four test homes have undergone equipment replacement and six homes have undergone system 

tune-ups without replacement (Table 5). All six homes that underwent tune-ups have shown 

noticeable improvements in conversion efficiency and overall system efficiency. Measured 

conversion efficiency improvement, for system tune-ups only, ranged from 7% to 23% and 

system efficiency improvement ranged between 1 percent and 23 percent (Table 5). Eight of the 

10 total test homes showed an increase in equipment temperature rise and in seven out of 10 test 

homes there was an increase in system temperature rise (Table 5). Changes in equipment and 

system temperature rise were 0°–13°F and 2.1°–19.5°F, respectively (Table 5). Specifically, the 

six homes that underwent system tune-ups only showed increases in conversion efficiency, 

system efficiency, equipment temperature rise (except TH-10), and system temperature rise

(Table 5). Table 6 lists the average changes between the pre- and post-test in data. 

0

200

400

600

800

1000

1200

1400

1600

1800

09/22/200910/21/200911/19/200912/21/200901/26/201002/25/201003/26/201004/26/201005/25/201006/23/201007/26/201008/23/201009/23/201010/22/201011/19/201012/22/201001/25/201102/23/201103/25/201104/22/201105/23/201106/22/201107/22/201108/22/201109/21/201110/20/201111/18/201112/21/201101/24/201202/22/2012

HDD (base 65)
18

Table 5. HVAC System Replacement and Tune-Up Diagnostic Data (Shaded Columns Underwent 

Equipment Replacement): Post-Tune-Up Minus Pre-Tune-Up Diagnostic Data

Table 6. HVAC System Replacement and Tune-Up Diagnostic Data: Average Differences 

2.3.3 Test Home HVAC System Upgrades 

Six out of the 10 homes analyzed in this study underwent system tune-ups only and the 

remaining four underwent equipment replacements. The four homes that underwent equipment 

replacement installed new furnaces with reduced rated output capacity and improved AFUE 

(Table 7). Along with a proper installation, these four homes were also able to appropriately size 

their furnaces to meet their heating demands. The system tune-ups largely involved the improved 

delivery of conditioned air. System tune-up information for each test home is listed in Table 7. 

Tune-up measures are home specific because they are largely dependent on the pre-existing 

distribution system conditions. For instance, high static pressure in the return system would lead 

to an improvement or addition to the return system ducts. Although the actual tune-up 

components vary widely, the end result of the tune-up is an increase in both the equipment and 

system efficiency. 
19

Table 7. Test Home Repairs and Adjustments (Replacements Shaded)

 

Test home # 4 Test home # 5

Test home # 6 Test home # 7 Test home # 8 Test home # 9 Test home # 10

Mount Vernon, IA Mount Vernon, IA

Test home # 1 Test home # 2 Test home # 3

Johnston, IA

 , 

West Des Moines, IA Vernon, IA 52314

Furnace replaced, 

reducing capacity from 

100,000 Btu to 66,000 

Btu 97% AFUE, Duct 

system repaired and 

sealed

Duct work repaired, 

Additional return ducts 

added, Fan speed 

increased, Ducts sealed

Furnace replaced, reducing 

capacity from 100,000 Btu 80% 

AFUE to 66,000 Btu 95% AFUE, 

Combustion testing conducted, 

Ductwork repaired and sealed

Council Bluffs, IA 3 Council Bluffs, IA 4

Increased airflow, Insulated 

supply ducts and adding more

Furnace replaced, 

reducing capacity from 

100,000 Btu 80% AFUE 

to 54,000 Btu 89% AFUE

Furnace replaced, 

reducing capacity from 

60,000 Btu 71% AFUE to 

45,000 Btu 93% AFUE 

Supply duct system 

repaired filter 

replacement, Coil 

cleaned, Supply ducts 

added

Increased delivered 

Btu(s) to match 

equipment capacity 

Increased delivered 

Btu(s) to match 

equipment capacity 

Increased delivered 

Btu(s) to match 

equipment capacity, 

Return ducts added

Lisbon, IA Council Bluffs, IA 1 Council Bluffs, IA 2
20

4 Discussion 

For the set of 48 homes evaluated in the first part of this project, the average calculated 

conversion efficiency, as defined in Equation 1 in Section 3, was 81%. Based on the authors’ 

previous experience, a conversion efficiency of 90% or better is easily achievable and can be 

reached by taking simple, low-cost actions such as properly setting fan speed or tuning the 

combustion. Of the 48 sample homes, only eight (17%) were considered to be operating with a

conversion efficiency of 90% or better at test-in. Figure 18 shows the distribution of calculated 

conversion efficiencies.

Figure 18. Distribution of calculated conversion efficiencies

Achieving close to 100% conversion efficiency is not out of reach, but may require making 

costly repairs or adjustments to the equipment and distribution system. Adjusting a system to 

operate at 90% conversion efficiency is a more realistic objective. If the average efficiency of the 

equipment in the homes were raised to this meet this objective, there would be an average of 9% 

reduction in energy input. When factoring in the average space heating energy consumption per 

household for the Midwest, the historical average heating load (36.85 kBtu/ft2

/yr), the average 

AFUE (88%) and the average conditioned floor space (2,644 ft2

) of the 48 sample homes, this 

would result in a savings of 13.7 MBtu (site) or 9% of the total annual household heating energy 

consumption. The estimated source annual energy savings based on these assumptions and a 

conversion factor of 1.092 (Uneo and Straube 2010) is 14.96 MBtu. The average conditioned 

floor space in our sample 48 homes was significantly larger than the average conditioned floor 

space for the region based on the Energy Information Administration’s Residential Energy 

Consumption Survey (EIA 2009). The average floor space for the West North Central Region, 

which contains Iowa, was 1,930 ft2. When the estimated energy savings is calculated using this 

value instead of the floor space from the sample homes, the estimated energy saving are 10 

MBtu (site) and 10.9 MBtu (source). 

In order to achieve these energy savings in the field, many of the homes tested through this 

project would need repairs or adjustments made to the system. The first step in most cases should 

0

1

2

3

4

5

6

7

62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100

Count

Conversion Efficiency, as measured in the field
21

be to evaluate airflow at the heat exchanger and verify that the equipment is achieving the 

desired level. The airflow at the heat exchanger measured in these homes was outside of the 

recommended range (100% ± 15%) in 20 (42%) of the 48 homes, as shown in Figure 19. This 

range was chosen based on recommendations published in ANSI/ACCA 5 QI-2010. For airflows 

outside of this range, fan speeds should be verified and static pressures across system 

components should be evaluated to locate restrictive locations. 

Figure 19. Percentage of required airflow across heat exchanger as measured in the home

Of the 48 homes in the sample set, 32 (73%) had an ESP higher than 125% of that recommended 

by the manufacturer, as seen in Figure 20. This maximum value was chosen based on 

ANSI/ACCA 5 QI-2010. It should be noted that the outlier on the far right side of Figure 20 is 

the single home in our sample set that had a blower motor that was rated at 0.2 i.w.c. When 

tested the ESP on this system came it at 0.55 i.w.c, or 275% of its rated static pressure. 

Figure 20. Percentage of required airflow across heat exchanger as measured in the home

40

55

70

85

100

115

130

145

Percentage of Required Airflow

Individual homes, sorted from lowest to highest flow

Target: 100% ± 15%

0

50

100

150

200

250

300

Percentage of Recommended 

ESP

Individual homes, sorted from lowest to highest percentage of ESP 

Maximum 

recommended

level (125% of 

rated)
22

One method to identify where airflow restrictions in the system exist is to examine the pressure 

drops across individual components in the system. As described in Section 3, each section or 

component was allotted a portion of the total ESP: 40% for the coil, 20% each for the filter, 

supply, and return. Using these values as a guide, the project team examined the set of sample 

homes to conclude which locations in the system were restricting airflow. 

Based on these guidelines, and as shown in Figure 21, 43 of the homes were identified as having 

a restrictive filter and 31 were identified as having a restrictive return. Since both of these 

locations are on the return side of the furnace, performing system repairs targeted at one or both 

locations could prove to be cost effective. It should be noted that each home can have more than 

one restrictive location. 

Figure 21. ESP restriction, by location

Once the airflow has been corrected, the firing rate can be checked to see how it compares to the 

rated input. ANSI/ACCA 5 QI-2010 recommends that the firing rate should be within ± 5% of 

equipment nameplate input. Using this as a guide, 17 (25%) of the 48 homes were under-fired 

while 9 (19%) were over-fired (Figure 22). 

31

43

14 17

0

5

10

15

20

25

30

35

40

45

50

Number of Homes

Return Filter Coil Supply
23

Figure 22. Measured fire rate as a percentage of nameplate input

Based on the 48 sample homes, it can be seen that the furnaces looked at in this study are not 

operating under conditions recommended by the manufacturer or best practice installation 

standards. Further investigation is needed to quantify the impact of these adverse conditions on 

performance. PARR plans to build on the data presented in this report and conduct laboratory 

testing of vintage furnaces under conditions as found in the field to see how they affect common 

performance metrics, such as AFUE.

While the additional long-term energy use data need to be collected on the three sample homes in 

order to provide a more accurate prediction of energy savings, the initial results on two of the 

three homes suggest that the repairs or replacements did indeed save energy, while the third 

home had an effective energy savings of 1% over the first two months after the repairs were 

completed. Home #2 provides the most promise for future results, as the existing equipment 

remained in place after the repairs and system adjustments took place. On this home adding an 

additional return, increasing the fan speed, and sealing the distribution system show an effective 

energy savings of 6% over the first two months after the repairs were completed. Home #1 

showed an effective energy savings of 16% over the first four months after the repairs were 

completed. Savings on this home as a result of system repairs will be difficult to quantify, as the 

equipment was also replaced as part of this modification. The original 80% AFUE furnace on 

this home was replaced with a 95% AFUE model, so a portion of this energy savings can be 

attributed to the increase in conversion efficiency. 

The 10 homes analyzed in third part of this study are important, because they provide further 

evidence of how repairs to the HVAC system can achieve energy savings. Utility bill analysis is 

not available for the seven homes analyzed in this part of the study, but improvements in system 

and equipment efficiency correspond with improved delivery of conditioned air. The data 

presented in this study help support the idea that individual components comprising a residential 

heating system act as a system and must not be looked at independently. 

The data collected address the research questions as follows:

60

70

80

90

100

110

120

130

140

Percentage of nameplate input

Individual homes, sorted from lowest to highest percentage

Recommended

range (100% ± 

5%)
24

• Q: What is the current installed HVAC system operating efficiency, as defined by the 

capacity of conditioned air reaching building occupants? 

A: The installed system operating efficiency varies significantly in the 10 test houses in 

the second part of the study: from 40 to 80% at test-out. Clearly much work remains to be 

done to seal and insulate ductwork in these homes. 

• Q: What is the achievable improvement in HVAC system operating efficiency from 

common modifications and quality installation of replacement of equipment?

A: The increase in system efficiency from this study also varied significantly, but it 

appears from the results that it is possible to deliver 80%–90% of the heat generated by 

the furnace to the conditioned space (Table 5). 

4.1 Next Steps

The findings of this study establish important baseline data about the potential gains in energy 

efficiency associated with HVAC equipment replacement and system tune-ups. In future 

research, these findings could be expanded upon by increasing the sample size, including more 

extensive utility bill analysis, and more qualitative information regarding system tune-ups. In the 

future this project will attempt to locate additional homes to include in this study to provide a 

more complete picture of the energy savings from system repairs and adjustments.
25

5 Conclusion

This project investigated energy savings potential in existing homes from natural gas furnace 

system repairs and adjustments that were recommended based on an initial evaluation of a 

furnace performance in-situ, or test-in. This evaluation of home heating and cooling systems 

involved measuring airflows, static pressures, and temperatures across the system to determine 

how well the furnace was performing compared to the manufacturers specifications. From the 

data collected it was determined that, on average, the homes that underwent the initial evaluation 

were not realizing 9% of the space heating energy potential available from their furnace, based 

on how it was operating at the time of test. Further examination of the initial evaluation showed 

that the majority of these losses can be attributed to either an undersized return or a restrictive 

filter. In 31 of the 48 homes, testing showed that a return that was too restrictive did not provide 

the required airflow across the heat exchanger, while 43 of the 48 showed that the in-place filter 

was overly restrictive. 

In the second part of the project, the team examined a sample of 10 homes that had completed 

the initial evaluation for more in-depth study. In these homes, the furnaces were tuned or 

replaced and duct systems were modified. Four homes had equipment replacement and duct 

upgrades, and six homes had system tune-ups for both furnaces and ducts. For these 10 homes, 

the diagnostic data show that it is possible to deliver up to 23% more energy from the furnace to 

the conditioned space by doing system tune ups (furnaces and ducts) with or without upgrading 

the furnace. Replacing the furnace provides additional energy reduction. The results indicate that 

support the author’s contention that residential heating and cooling equipment should be tested 

and improved as a system rather than a collection of individual components. 
26

References 

ANSI/ACCA. (2010). ANSI/ACCA Standard #5 HVAC Quality installation Specification. 

Arlington, VA: Air Conditioning Contractors of America, 

www.acca.org/industry/quality/quality-installation. 

ASHRAE 111-2008. (2008). Measurement, Testing, Adjusting, and Balancing of Building 

HVAC Systems.

ASHRAE 152-2004. (2004). Method of Test for Determining the Design and Seasonal 

Efficiencies of Residential Thermal Distribution Systems.

EIA. (2009). Residential Energy Consumption Survey. Washington, D.C.: Energy Information 

Administration.

Ueno K., Straube J. Understanding Primary/Source and Site Energy, Building Science Digest 

151, 2010 

Walker, I.S.; Modera M.P. (1998). Field Measurements of Interactions Between Furnaces and 

Forced Air Distribution Systems. Berkeley, CA: Lawrence Berkeley National Laboratory, LBNL 

40587. http://epb.lbl.gov/publications/pdf/lbl-40587.pdf. 
27

Appendix A: Supplementary Data

Appendix A contains the supporting data for the seven additional homes analyzed in the third 

part of this research that were not included in the case studies. 
28

Table 8. Supporting Data for 7 Additional Homes That Have Undergone System Tune-Ups and Equipment Replacement

Pre Post Pre Post Pre Post Pre Post Pre Post Pre Post Pre Post

AFUE % 71 93 80 89 93 93 93 93 81 81 94 94 93 93

Rated Input Btu 60000 45000 100000 52302 60000 60000 60000 60000 110000 110000 80000 80000 100000 10000

Rated output Btu 48000 42000 80000 46319 56000 56000 56000 56000 89000 89000 75000 75000 93000 93000

Total ESP i.w.c 0.57 0.73 0.85 0.5 0.56 0.49 0.74 0.55 0.5 0.5 0.5 0.5 0.5 0.5

Target ESP i.w.c 0.5 0.5 0.5 0.82 0.5 0.5 0.5 0.5 0.6 0.62 0.81 0.81 0.7 0.64

Temp rise across the equip. F 43.9 46 73.8 45.1 39.3 54.2 61 62 36 49 41 54 51 51

System Temp Rise F 33.4 28.7 56.6 35.1 28.1 39.1 46.5 58.5 26.8 46.3 33.8 51.7 37.3 50.2

Supply reg ave temp F 120.2 123.2 130.9 117.9 97.7 112.3 119 131 96.3 116.3 104.3 121.7 107.3 121.7

required fan airflow CFM 780 675 1000 900 900 900 900 900 1430 1430 1200 1200 1500 1500

recorded fan airflow CFM 1105 605 816 1045 1055 1078 852 853 1450 1450 1284 1284 1231 1450

Equip Adj Input Btu 68965 44253 86539 52302 54369 73469 85714 64286 90000 105882 81818 81818 90000 90000

Equip Delivered BTU Btu 35128 29756 56539 46319 42092 57423 56130 57117 56376 76734 56856 74883 67814 79866

Conversion Efficiency % 51% 67% 65% 89% 77% 78% 65% 89% 63% 72% 69% 92% 75% 89%

System Efficiency- test % 64 43 63 70 56 62 46 74 49 71 54 80 63 80

Equip manufactuer ComfortMaker Ruud Singer Trane Carrier Carrier Bryant Bryant Carrier Carrier Carrier Carrier Carrier Carrier

equip model GUA060A012AIN GRC - 04EMAES12100-14MPDB060A9V3VAC58MXA060-1258MXA060-12 V036060FFKA V036060FFKACTA110-12116CTA110-12116MVB080F1-120MVB080F1-120A100-F-17116A100-F-17116

Mount Vernon, IA Council Bluffs, IA 1

Test home # 7 Test home # 8 Test home #9 Test home #10

 Mount Vernon, IA Lisbon, IA Council Bluffs, IA 2 Council Bluffs, IA 3 Council Bluffs, IA 4

Test home # 4 Test home # 5 Test home #6
29

Appendix B: Topics Covered in the HVAC SAVE Training

Appendix B contains a basic outline of the topics discussed during MEEA’s HVAC SAVE 

training.

DAY ONE

SECTION ONE – Introduction to Performance Testing 

Review Typical Installation Practices and Effects on Performance

Introduce Appropriate Standards for Sizing Equipment and Ductwork 

Review a Typical Service Call

Review Performance Studies

Explore BTU Measurements and Formulas Used Throughout Training 

Introduce CommonCents Software 

SECTION TWO – Measure and Interpret Static Pressure 

Static Pressure Basics – Why Check? 

Static Pressure Units of Measurement and Tools Required

How to Test Static Pressure in a System

Plotting Airflow Using Static Pressure

Static Pressure Drops

Top 10 Static Pressure Repairs

SECTION THREE – Identify and Plot Fan Airflow 

Interpreting Manufacturer’s Model Numbers/Nomenclature

Gathering Information about Equipment Potential Performance 

Calculating Required System Airflow

Plotting Fan Airflow

Equipment Setup

The Impact of Airflow on Efficiency
30

SECTION FOUR – Airflow Measurement Methods 

Tools and Specifications Necessary to Properly Measure Airflow

Introduce Air Balancing Hood 

Basic Airflow Traverse Tools and Procedures

Complete Hand-On Airflow Measurements

Calculate Airflow Impacts on Efficient Performance

SECTION FIVE – Temperature Measurement and Diagnostics 

Temperature Measurement Tools and Accessories

Measuring Temperature Change

Understanding Duct Loss / Gain Impacts 

Temperature Profiling

Temperature Measurement Type 

Combustion Efficiency 

Common System Temperature Defects and Repairs

DAY TWO

SECTION SIX – Pressure Diagnostics and Duct Design 

Benefits of Quality Installation Practices – Fixing the Whole System 

Identify Common Pressure Problems Throughout the System

Complete a Total System Static Pressure Profile

Using the NCI Duct Tables for Redesigning Existing Duct Systems 

Manual D Review for New Duct Systems

Typical System Repairs

Duct Requirements 

SECTION SEVEN – Equipment Replacement & Commissioning 

Common Load Calculation Procedures 

Blower Selection Process
31 

Determining Room by Room Airflow Requirements 

Air Balancing and Proportional Air Balancing

Final Commissioning of System and Reporting 

SECTION EIGHT – Putting it All Together (Sales and Service) 

Discuss the Performance-Based Sales and Service Approach

Review Required Test Instruments and Accuracy Ranges

Review People, Roles, and Process Flow in the Performance-Based Process

Practical Pricing Strategies and Proposals
32

Appendix C: Data Collected During the Test-In and Test-Out 

Procedures 

Appendix C shows a list of the data that is typically collected during the test-in and test-out 

process described in Section 3. 

• Type of house

• Year house was built

• Total Sq Ft of the house

• Time of testing

• Altitude of the test location

• Typical thermostat setting for heating

• Outdoor conditions

• Manufacturers recommended CFM

• Type of heating equipment

• Furnace manufacturer

• Furnace model number

• Furnace serial number

• Furnace AHRI reference number

• CEE air handling ratio

• AFUE

• Rated input

• Rated output

• Furnace age

• Type of fuel

• Type of furnace

• Equipment’s maximum rated total ESP

• Type of blower motor 

• Blower motor size

• Blower speed setting

• Condition of the blower motor

• Location of filter

• Pressure before the air enters the filter

• Pressure after the air exits the filter

• Pressure where air enters equipment

• Pressure before the air exists 

equipment/enters the coil

• Pressure after the air exits the coil

• Return dry bulb temperature of the 

equipment

• Supply dry bulb temperature of the 

equipment

• Equipment airflow & method used

• Supply dry bulb temps at supply register(s)

• Return dry bulb temps register(s)

• Gas meter dial size and number of seconds 

per revolution

• % of supply ducts located in unconditioned 

space

• % of return ducts located in unconditioned 

space
DOE/GO-102013-4164 ▪ August 2013

Printed with a renewable-source ink on paper containing at 

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