Steam System Balancing 

and Tuning for Multifamily 

Residential Buildings 

in Chicagoland—Second Year 

of Data Collection

Jayne Choi, Peter Ludwig, and Larry Brand

Partnership for Advanced Residential Retrofit

August 2013
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iii

Steam Balancing and Tuning for Multifamily Residential Buildings 

in Chicagoland—Second Year of Data Collection

Prepared for:

The National Renewable Energy Laboratory

On behalf of the U.S. Department of Energy’s Building America Program

Office of Energy Efficiency and Renewable Energy

15013 Denver West Parkway

Golden, CO 80401

NREL Contract No. DE-AC36-08GO28308

Prepared by: 

Jayne Choi, Peter Ludwig, and Larry Brand

Partnership for Advanced Residential Retrofit

2125 W North Avenue

Chicago, IL 60647

NREL Technical Monitor: Stacey Rothgeb

Prepared Under Subcontract No. KNDJ-0-40346-00

August 2013
iv

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v

Contents

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

List of Tables ............................................................................................................................................. vii

Definitions................................................................................................................................................. viii

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

1 Problem Statement............................................................................................................................... 1

1.1 Introduction..........................................................................................................................1

1.2 Previous Studies...................................................................................................................3

1.3 Relevance to Building America’s Goals..............................................................................3

2 Experiment ............................................................................................................................................ 5

2.1 Research Questions..............................................................................................................5

2.2 Technical Approach.............................................................................................................5

2.3 Assessment of One-Pipe Steam Heating Systems: What To Look For...............................6

2.3.1 Main Line Air Vents................................................................................................6

2.3.2 Near Boiler Piping ...................................................................................................8

2.3.3 Boiler Controls.......................................................................................................10

2.3.4 Radiator Vents .......................................................................................................10

2.3.5 Temperature ...........................................................................................................13

2.3.6 Tenant Comfort......................................................................................................14

2.4 Measurements and Equipment...........................................................................................14

3 Measure Implementation ................................................................................................................... 16

3.1 Determining a Scope of Work ...........................................................................................16

3.2 Measure Costs....................................................................................................................16

4 Analysis and Results ......................................................................................................................... 17

4.1 Temperature Control and Steam System Behavior............................................................17

4.2 Boiler Cycles......................................................................................................................20

4.3 Cost Effectiveness..............................................................................................................23

4.4 Tenant Comfort..................................................................................................................24

5 Discussion........................................................................................................................................... 25

5.1 Temperature Control and Steam System Behavior............................................................25

5.2 Cost Effectiveness..............................................................................................................26

5.3 Tenant Perceptions.............................................................................................................27

6 Conclusions and Recommendations ............................................................................................... 28

6.1 Establishing Steam Balancing Guidelines.........................................................................28

6.2 Further Recommended Studies..........................................................................................28

References................................................................................................................................................. 29

Appendix A: Test Building Details .......................................................................................................... 30

Appendix B: Sample Tenant Letter ......................................................................................................... 32

Appendix C: Sample Tenant Survey ....................................................................................................... 33

Appendix D: Detailed Measures and Costs............................................................................................ 34

Appendix E: Temperature Data ............................................................................................................... 35
vi

List of Figures

Figure 1. Schematic of single-pipe steam system................................................................................... 2

Figure 2. Two of 10 test buildings. The buildings chosen were brick three-story walk-ups, a 

common structure for multifamily housing in Chicago. See Appendix A for specifications on 

all of the test buildings. ....................................................................................................................... 6

Figure 3. At the beginning of a boiler firing cycle, the piping system and radiators are filled with air 

and quite cool, meaning that the steam must heat a large mass of piping and push air out of 

the air vents. The furthest radiators will receive heat more slowly than the closest. As shown 

in (C), in the absence of main line vents, steam may never even reach the furthest radiators if 

the boiler shuts off before it can reach them. ................................................................................... 7

Figure 4. The header piping is smaller than the boiler manufacturer’s specifications. ...................... 8

Figure 5. Specifications for how to pipe a Series 211ATM natural gas steam boiler by Peerless® ..... 9

Figure 6. Gorton No. 4 angle radiator vent. Gorton models are made in No. 4, 5, 6, C, and D, 

ranging from 4 with the smallest orifice to D with the largest....................................................... 11

Figure 7. Painting over radiator vents is a common oversight that can have a serious effect on the 

heating in an apartment. Blocked radiator vents must be cleaned or replaced. ......................... 12

Figure 8. Schematic plan of Building 1 in the study ............................................................................. 14

Figure 9. Building 10 average pre-measure logging period temperature readings by hour of the 

day........................................................................................................................................................ 18

Figure 10. Building 10 average post-measure logging period temperature readings by hour of the 

day........................................................................................................................................................ 18

Figure 11. Building 4 average pre-measure logging period temperature readings by hour of the 

day........................................................................................................................................................ 19

Figure 12. Building 4 average post-measure logging period temperature readings by hour of the 

day........................................................................................................................................................ 19

Figure 13. Weather-normalized natural gas use from utility bills during pre-balancing and postbalancing periods............................................................................................................................... 22

Figure 14. Tenant survey responses rating overall temperature comfort. The tenants were asked to 

rate the overall temperature comfort within their unit on a scale from 1 = Uncomfortable to 5 = 

Comfortable. Note: Building 7 received no survey responses pre-retrofit. ................................. 24

Figure 15. Building 3 average pre-measure logging period temperature readings by hour of the 

day........................................................................................................................................................ 26

Figure 16. Building 3 average post-measure logging period temperature readings by hour of the 

day........................................................................................................................................................ 26

Figure 17. The pre-measure heating EUI for each test building is at or above the line representing 

the median EUI for 105 similar steam-heated buildings in Chicago. This suggests that the 

buildings chosen for this study all had potential for energy savings. ......................................... 31

Unless otherwise indicated, all figures were created by PARR.
vii

List of Tables

Table 1. Logger Equipment...................................................................................................................... 13

Table 2. Measurements and Equipment ................................................................................................. 15

Table 3. Average Costs for Steam Balancing Measures....................................................................... 16

Table 4. Number of Boiler Cycles During Pre- and Post-Balancing Periods...................................... 20

Table 5. Cycle Counts per Year, Average Lengths of Boiler Cycles and Percent of Day Boiler On 21

Table 6. Measured Weather-Normalized Natural Gas Use (Heating Only) .......................................... 22

Table 7. Average Percent Natural Gas Savings,* Balancing Costs, and Simple Paybacks .............. 23

Unless otherwise indicated, all tables were created by PARR.
viii

Definitions

Btu British thermal unit 

CDD Cooling degree day

CNT Center for Neighborhood Technology 

DOE U.S. Department of Energy

EUI Energy use intensity

HDD Heating degree day

NBP Near boiler piping 
ix

Executive Summary

Of the 470,000 multifamily housing units in the Chicago region, an estimated 70,000 are steam 

heated. With these centrally metered systems, the cost of heat for tenants is reflected in the 

owners’ operating costs. Highly variable and rising energy costs have placed a heavy burden on

building owners. In the absence of well-designed and relevant efficiency efforts, increased 

operating costs would be passed on to tenants who often cannot afford those increases. 

Steam-heated buildings often suffer from uneven heating as a result of poor control of the 

amount of steam entering each radiator. In order to satisfy the heating load to the coldest units, 

other units are overheated. As a result, some tenants complain of being too hot and open their 

windows in the middle of winter, while others complain of being too cold and are compelled to 

use supplemental heat sources. 

Building on previous research, the Center for Neighborhood Technology identified 10 test 

buildings in Chicago and conducted a study to identify best practices for the methodology, 

typical costs, and energy savings associated with steam system balancing. A package of common 

steam balancing measures was assembled and data were collected on the buildings before and 

after these retrofits were installed to investigate the process, challenges, and the cost

effectiveness of improving steam systems through improved venting and control systems. The 

test buildings that received venting upgrades and new control systems showed 10.2% savings on 

their natural gas heating loads, with a simple payback of 5.1 years. The methodologies for and

findings from this study are presented in detail in this report. This report has been updated from a 

version published in August 2012 to include natural gas usage information from the 2012 heating 

season and updated natural gas savings calculations. 
1

1 Problem Statement

1.1 Introduction

The majority of Chicago’s multifamily housing stock (five or more units) was built between 

1910 and 1939 and uses gas-fired heating with central boilers and single-pipe steam distribution 

systems (Biederman and Katrakis 1986). Single-pipe steam heating was the best option for 

buildings constructed in the first few decades of the 20th century; only after 1928, when the first 

circulating pump was invented, did hydronic systems become the standard in modern apartment 

buildings (Peterson 1985; Holohan 2011). Though these original steam systems have been 

converted from coal to gas and many have undergone boiler replacement or other small 

upgrades, the distribution systems remain largely the same as when they were first installed. 

Single-pipe steam systems were designed for longevity but not for energy efficiency (Peterson 

1985). Steam system efficiency is limited by the fact that a steam boiler cannot have a rated 

efficiency of greater than 83%.

Old one-pipe steam systems are often controlled by a timer or by a single thermostat. When the

thermostat or timer calls for heat, the boiler comes on, heats the water, and generates steam. The 

steam moves through the piping that is initially full of air, heating the metal and pushing the air 

out through vents on the main distribution lines and radiators. As steam reaches each vent, the 

vents close so no steam escapes. Within each radiator, the steam condenses and releases latent 

heat, allowing more steam to enter. The water that has condensed inside the radiators runs back 

(through the same pipes that carry the steam) to the return lines and down to the boiler. When 

the building has been heated according to the thermostat or timer’s specifications, the boiler 

shuts off. 

The boiler can also be regulated by a pressuretrol that will shut the boiler off if the pressure in 

the boiler builds to greater than the allotted amount. One-pipe steam systems should typically 

operate at 1⁄2–11⁄2 psig of pressure. It is important to adjust pressuretrols to these settings. 

Incorrect pressure settings can result in short boiler cycles and distribution problems. 

As the radiators cool, the air vents open and allow air to re-enter the system. A schematic of this 

entire system is shown in Figure 1. The system shown in Figure 1 is a gravity return system, 

meaning that the return condensate relies on gravity to return from the radiator through the 

piping back down to the boiler.
2

Figure 1. Schematic of single-pipe steam system 

(adapted and used with permission from Peterson 1985)

These buildings often suffer from significant temperature gradients, with differences between

units often reaching up to 15°F. As a result, some tenants complain of being too hot and others 

too cold.

With insufficient air venting of the radiators and main lines, air can become trapped in the 

system and block steam from entering radiators. Radiators may partly heat as air is compressed 

within the system, but the system must be properly vented in order for the radiators to fully fill 

with steam. If the thermostat for the boiler is located in an area of the building that heats more 

slowly than others, the thermostat will keep calling for heat until that area reaches the desired 

temperature. This setup has the problem of overheating units that receive steam more quickly 

and wasting heating fuel. Alternatively, if the thermostat is located in a section of the building 

that heats quickly, the boiler cycle will end before steam is able to reach and release its latent 

heat to units that are further from the boiler or vented more slowly. Systems with multiple indoor 

sensors that are able to calculate an average temperature to determine when to call for heat can 

help to avoid these issues.
3

Insufficient venting, large differences in steam arrival times, excessively short boiler cycles, lack 

of zone control or temperature averaging, and variable steam main lengths can all contribute to 

uneven heating in a building (Peterson 1985).

Providing a balanced building, where adequate heat is provided to all of the apartments at the 

times that the heat is needed, minimizes wasted heating fuel and is therefore an opportunity for

cost savings. Additionally, a balanced building improves tenant comfort. This study explored

whether steam balancing can be an efficiency measure that building owners and utility 

companies can implement as a cost-effective and beneficial retrofit.

More specifically, this study examined the effects of installing large-capacity air vents on steam 

main lines, replacing radiator vents, and upgrading boiler controls from thermostats or timers to 

indoor averaging systems. All of the test buildings in this study were low-rise multifamily 

buildings in Chicago with centrally metered boilers with single-pipe steam distribution systems. 

1.2 Previous Studies

Previous research performed by the Minneapolis Energy Office, the Center for Neighborhood 

Technology (CNT) in Chicago, and New York State Energy Research and Development 

Authority in New York City documented techniques and savings associated with steam 

balancing. Improved venting and controlling the steam cycle were identified as important

measures for ensuring even temperatures throughout a building and increasing tenant comfort. 

These findings were taken into consideration when assessments were done and measures selected 

for this study (Peterson 1985; Biederman and Katrakis 1986; Karins 1994).

Biederman and Katrakis (1986) also determined that ensuring tenant awareness in advance of 

and during the project increases its success and facilitates a smoother experiment. This project 

took this into consideration as a part of its technical approach. 

Although the costs and savings associated with upgraded venting and control systems will vary

depending on the pre-retrofit conditions of a building as well as the specific scope of work

administered, previous studies have shown these to be cost-effective measures. Katrakis et al.

(2010) reported energy savings of 5%–10% with a payback of 0–2 years for installing larger 

main line air vents and savings of 3%–5% with a payback of 0–3 years for utilizing control 

systems to reduce boiler short-cycling. Peterson (1985) reported that rebalancing a steam heated 

building can reduce space heating costs by as much as 15%–25%.

1.3 Relevance to Building America’s Goals

The U.S. Department of Energy’s (DOE) Building America program is designed to “reduce the 

home energy use by 30-50% (compared to 2009 energy codes for new homes and pre-retrofit 

energy use for existing homes).” To this end, the program looks to conduct research to “develop 

market-ready energy solutions that improve efficiency of new and existing homes in each U.S. 

climate zone, while increasing comfort, safety, and durability” (DOE 2011). 

This project looked at multifamily residential buildings in Chicago. As a colder humid 

continental climate, Chicago has an average of 6,500 heating degree days (HDDs) and 800 

cooling degree days (CDDs) per year; heating is therefore the focus of residential energy use.

Since the majority of Chicago’s multifamily housing stock (five or more units) was built between 
4

1910 and 1939 and uses gas-fired heating with central boilers and single-pipe steam distribution 

systems, it is important to address any common issues with these heating systems (Biederman 

and Katrakis 1986). When the distribution of steam is not properly balanced in steam systems, 

certain units become overheated. In a study conducted in Minneapolis, which has a climate 

similar to that of Chicago, it was estimated that the cost of overheating is 3% of space heating 

costs per 1°F of overheating (Peterson 1985). By this estimate, imbalances in steam distribution

and the resulting overheating can be very costly for a building owner. Therefore, finding 

methods to streamline and improve the process of balancing steam systems has the potential to 

contribute an effective energy solution to the marketplace.
5

2 Experiment

2.1 Research Questions

• How do steam balancing measures affect the temperature variations within buildings?

• Will steam balancing affect the average length and frequency of boiler cycles?

• How will steam balancing affect the amount of natural gas used for heating?

• How cost effective are steam balancing measures?

• What further research is needed to conclusively determine the efficacy of steam 

balancing measures?

2.2 Technical Approach

A package of common steam balancing measures (replacing radiator vents, installing highcapacity air vents on main lines, and installing indoor averaging boiler controls) was assembled 

and data were collected on 10 buildings before and after these retrofits were installed. This 

project built on the relationships between building owners and contractors and the CNT Energy 

Savers Program.

1

All the building owners involved in this project had previously worked with the CNT Energy 

Savers Program, so all the potential test buildings had already received energy assessments. An 

initial pool of candidate buildings was identified according to the following criteria:

• Single-pipe steam heating system

• Around 15–30 units

• Non-uniform temperatures throughout the building (based on qualitative observations 

from the auditor, building manager, and/or tenants)

• Well-maintained boiler.

Boiler replacement was not tested in this study, so the boiler had to be well maintained and 

appear to produce dry steam for a building to participate. This was assessed both from 

information collected during the previous energy audit and from the steam heating contractor

about the boiler condition and its regular maintenance. 

The previous assessment data and reports were reviewed and candidate buildings were revisited 

by a CNT energy analyst. The buildings were then examined by a Chicago steam heating 

contractor who diagnosed the building’s problems and submitted a scope of work for each 

building. Final test buildings were chosen based on, among other criteria, potential for energy 

savings and building type (see Figure 2). 

 1 Energy Savers is a program run by CNT Energy that works with multifamily building owners in Chicago to 

identify cost-effective energy efficiency measures and connect them with resources to implement these upgrades 

(Evens et al. 2008). Since 2007, the Energy Savers program has retrofitted more than 10,000 units for efficiency.
6

Figure 2. Two of 10 test buildings. The buildings chosen were brick three-story walk-ups, a 

common structure for multifamily housing in Chicago. See Appendix A for specifications on all of 

the test buildings.

(used with permission from CNT Energy 2011)

Access to units and the boiler room is an important factor for assessing and fine-tuning a 

building’s steam heating system, so the relationships and communication between the building 

owners and tenants were also considered in choosing buildings. Regular communication with 

tenants (both to ensure minimal tampering with the data collection and for ready access to the 

apartments) was necessary for project success. Tenants were given notice by their building 

managers before each visit and letters explaining the project (a sample of which can be seen in 

Appendix B) were distributed during the data collection periods. 

2.3 Assessment of One-Pipe Steam Heating Systems: What To Look For

After the test buildings were selected, their boilers and distribution systems were assessed to 

determine their current effectiveness. Monitoring of the buildings was conducted before and after 

the packages of steam balancing measures were installed. The following sections detail what was

examined in this study. They are divided into subsections to indicate which system components 

particular data relate to and outline the guidelines for studying the following components:

• Main line air vents

• Near boiler piping

• Boiler controls

• Radiator vents

• Unit temperatures

• Tenant comfort.

2.3.1 Main Line Air Vents

2.3.1.1 Guidelines

The purpose of main line air vents is to rapidly vent the large amounts of air in the steam lines. 

These vents lower the back pressure during the fill part of a boiler cycle and aid the flow of 

steam down the main distribution pipes. Without main line air vents, all the air in the lines must 

be purged at the radiators, in which case steam would fill the radiators closest to the boilers much 

faster than those furthest away. This can cause uneven heating, particularly if the boiler shuts off 
7

before the whole system is full (see Figure 3). As such, there should be at least one main line air 

vent per steam main line. Proper air venting can be used to control the relative speed of steam 

delivery to radiators in various parts of a building. Main line air vents should be installed on the 

main distribution lines after the last riser and before the dry return drops into the wet return. The 

valve is open until the steam reaches it, at which point it shuts and prevents steam from escaping 

through it (Peterson 1985).

Figure 3. At the beginning of a boiler firing cycle, the piping system and radiators are filled with air 

and quite cool, meaning that the steam must heat a large mass of piping and push air out of the 

air vents. The furthest radiators will receive heat more slowly than the closest. As shown in (C), in 

the absence of main line vents, steam may never even reach the furthest radiators if the boiler 

shuts off before it can reach them. 

(adapted and used with permission from Peterson 1985)

2.3.1.2 Measurements

Measurements for the main line piping consisted of: 

• A census of all the main lines in the building

• The approximate length of each main line

• Varying thickness of pipe for each main line

• Pipe insulation for each main line

• Positions of vents on each main line

• Sizing and condition of main line vents.
8

Vents are often hidden in unused basements or storage facilities, and a thorough inspection was 

conducted to assess the current efficacy of the venting. This information was then either 

confirmed by or relayed to the heating contractor for determination of which vents needed to be 

replaced or whether vents needed to be added to the distribution lines. The e-booklet “Balancing 

Steam Systems Using a Venting Capacity Chart” by Gerry Gill and Steve Pajek (2005) includes 

resources for determining the required amount of venting.

2.3.2 Near Boiler Piping

2.3.2.1 Guidelines

The size and configuration of the near boiler piping (NBP) are important for producing dry steam

(Holohan 1992). As steam boilers are replaced, their accompanying piping is often incorrectly 

configured to be either too large or too small. Figure 4 shows an example of an insufficiently 

sized replacement header.

Figure 4. The header piping is smaller than the boiler manufacturer’s specifications.

(used with permission from CNT Energy 2011)

As shown in Figure 5, the risers leading from the boiler takeoff to the header piping should be at 

least 24 in. The supply line leading from the header should not be directly aligned vertically with 

any of the risers or with the equalizer. This configuration ensures that wet steam, which 

decreases the amount of latent heat available from the steam and therefore decreases the 

efficiency of the system, will not collect in the header piping or supply lines. The steam must be 

dry to reach the furthest radiators. The boiler manufacturer’s specifications provide instructions

about how to correctly pipe a boiler (see Figure 5 for an example). 
9

Figure 5. Specifications for how to pipe a Series 211ATM natural gas steam boiler by Peerless®

As shown in the diagram, the boiler risers should always be at least 24 in. long and the steam 

supply should always be piped between the last boiler riser and the equalizer.

(used with permission from Peerless® Boilers)

The NBP should also include a Hartford Loop, which consists of an equalizing pipe connecting 

the steam header to the condensate inlet at the bottom of the boiler. It acts as a backup safety 

measure to the low-water cutoff by allowing steam pressure to build in the boiler without forcing 

water into the return line and protecting the boiler against low water in the event of a return line 

leak (Ahlgren 1994). If there is a leak in a return line, water can only back out of the boiler to the 

point where the wet return line connects into the equalizer. The loop acts as a siphon that runs 

out of water, stopping the boiler from emptying completely, which allows for additional time to 

notice a leak and have it fixed (Holohan 2010a). This reduces the chance of a boiler dry-firing, 

which can be extremely dangerous as well as cause damage to the equipment. Local codes 

should always be consulted when considering boiler repiping.

2.3.2.2 Measurements

Measurements for the NBP consisted of: 

• Height of the header piping

• Width of risers and header

• Descriptive geometry of the NBP. 
10

The NBP was examined at each test building and, if necessary, corrected before the data logging 

period or before any other steam balancing measures were installed. One of the 10 buildings had 

incorrectly installed NBP that had to be corrected.

2.3.3 Boiler Controls

2.3.3.1 Guidelines

Steam heating systems are often controlled by a single thermostat, or an aquastat and time clock. 

Boilers are also often switched on and off manually by building maintenance staff, depending on 

tenant feedback. All 10 test buildings were controlled by either a thermostat or time clock and 

aquastat setup with building staff frequently manually adjusting controls. These controls do not 

consider temperature variations within a building and frequently contribute to the problems of 

unbalanced temperatures in a building. If a thermostat is located in a warmer area of the building, 

the boiler cycle might end before the colder units are satisfied. If a thermostat is in a cooler area 

of the building, certain areas of the building will be overheated as the boiler will not shut off 

until this cooler area reaches the temperature set point. Control systems that have indoor 

temperature sensors and cycle the boiler on and off according to an average building temperature 

can help prevent these issues.

2.3.3.2 Measurements and Data

Information collected for the boiler and boiler controls consisted of: 

• Rated boiler capacity (Btu/h)

• Boiler annual fuel utilization efficiency

• Boiler size (number of sections)

• Burner condition

• Boiler firing pattern

• Combustion analysis (steady state efficiency, carbon monoxide, carbon dioxide, oxygen)

• Description of control type

• Daytime and nighttime set points

• Observation of how controls are being operated by maintenance staff.

A boiler runtime sensor and a data logger were wired to the boiler in each test building to assess 

and monitor the patterns of the current boiler controls. The monitors logged the activity of the 

boiler to determine the boiler cycling patterns. Using the cycling patterns and the boiler 

efficiency, the fuel consumption of each boiler was determined. 

2.3.4 Radiator Vents

2.3.4.1 Guidelines

Just as the distribution of steam heating is affected by the condition of the main line air vents, it 

is also affected by the condition of the radiator air vents. If an apartment unit is too cold, the heat 

input must be increased or the heat loss decreased; often this can be achieved by replacing

radiator vents that are blocked or not functioning properly (Peterson 1985).
11

If no steam ever reaches a radiator, the radiator valve should be checked to see if it is open and 

operating properly. Radiator valves should always be completely open or completely closed and 

were not designed to be frequently throttled. Tenants should be informed that these valves should 

typically not be tampered with. If the valve does not completely open or shut, it may need to be 

replaced. Having a partially open valve will not allow the condensate to properly drain out of the 

radiator, which will obstruct steam from entering the radiator.

If the vent is loudly whistling when the radiator fills with steam, its orifice may be too small and 

in this case, the vent should be replaced. A whistling vent could also be indicative of debris 

clogging the opening or the boiler operating pressure being higher than necessary. Alternatively, 

if an apartment is too hot, the steam reaching the radiators can be slowed by a smaller vent or

controlled by a thermostatic radiator valve. Though studies have shown that there is a point at 

which an increased orifice size has little influence on fill time (Peterson and Otterson 1985), 

proper air venting can be an effective way to largely control the relative speed of steam delivery 

to various radiators. Figure 6 shows an example of a radiator vent that comes in different models 

of varying orifice size.

Figure 6. Gorton No. 4 angle radiator vent. Gorton models are made in No. 4, 5, 6, C, and D, 

ranging from 4 with the smallest orifice to D with the largest.

(used with permission from CNT Energy 2011)

The size of the radiator is also important when considering the appropriate vent size. Large

radiators contain more air than small ones, so larger radiators need larger air vents to fill with 

steam more quickly. Two vents can be used on larger radiators; a second vent can be positioned a 

few inches lower than the first and the two vents will work together to vent the air. Once the 

steam reaches the first vent and closes, the second air vent will continue to vent air. The larger
12

radiator will thus heat more completely (Holohan 2010b). The e-booklet “Balancing Steam 

Systems Using a Venting Capacity Chart” by Gerry Gill and Steve Pajek (2005) includes 

resources for determining the amount of air in a radiator and the venting capacities of different 

air vents. 

2.3.4.2 Measurements

Information collected about the radiator vents consisted of: 

• Sizes of radiators in the building

• The size and condition of radiator vents. 

The radiator air vent should be removed and tested; if it is not passing air, it should be cleaned or 

replaced. Figure 7 shows the common problem of a radiator vent that has been painted over and 

no longer works. 

Figure 7. Painting over radiator vents is a common oversight that can have a serious effect on the 

heating in an apartment. Blocked radiator vents must be cleaned or replaced.

(used with permission from CNT Energy 2011)

For this study, the condition of the radiator vents in a sample number of units was examined and 

an assessment was made about whether to replace some or all of the vents. Adjustable air vents 

can be considerably more expensive and subject to tampering by tenants (negating their 

usefulness of being able to adjust to the location and size of the radiator); therefore, they were

not used in this study. Removing, rearranging, or replacing radiators can be difficult and 

expensive and were also not considered in this study. 
13

2.3.5 Temperature

2.3.5.1 Guidelines

Many factors influence the temperature of an apartment unit; for example, tenants often open 

windows to cool their overheated apartments, even during winter months. Temperature

measurements over the heating season are important for studying the distribution of heat in a 

steam-heated, multifamily building. Identifying the patterns of temperature change over these 

time periods can help researchers infer exactly how the heating distribution is failing. 

2.3.5.2 Method

Temperature data loggers were placed in six units in each building and recorded the temperature 

every 5 min for 4 weeks. Both the pre- and post-balancing logging periods were during the 

2011–2012 heating season. The loggers were placed in units directly above the boiler (predicted 

to be the most overheated) and in units that were furthest from the boiler (predicted to be 

receiving the least heat) on at least two floors to capture the different unit temperatures. The 

loggers were installed on the walls at approximately 5 ft from the ground, and were not placed on 

external walls, above radiators, or in kitchens or bathrooms. The buildings used in this study 

were low-rise brick walk-ups. (For a detailed description of the buildings used, refer to 

Appendix A.)

Temperature loggers and boiler runtime loggers were also placed in the boiler rooms. Table 1

lists the logger equipment that was used for this study. Figure 8 depicts a test building and a 

typical setup for the data logger placement.

Table 1. Logger Equipment

Measurement Model Description Accuracy*

Outdoor Air Temperature HOBO U23 

Pro v2

Outdoor 

temperature/relative 

humidity data logger

± 0.38°F from 

32° to 122°F

Indoor Air Temperature HOBO 

U10-003

Indoor 

temperature/relative 

humidity data logger

± 0.95°F from 

32° to 122°F

Boiler Firing Pattern HOBO 

U9-001 State logger

Approximately 

± 1 min/month 

at 77°F

AC Current/Boiler State 

(On/Off) CSV-A8 AC current 

switch/sensor –

*Logger specifications from manufacturer: www.onsetcomp.com/products
14

Figure 8. Schematic plan of Building 1 in the study

Temperature loggers were placed in units in each of three sections: directly above the boiler, in 

the north wing, and in the south wing.

2.3.6 Tenant Comfort

2.3.6.1 Guidelines

Interviewing the tenants and building manager enables a comparison of temperature data to the 

residents’ perceptions of the unit temperature. It may also be useful in explaining abnormalities 

in the temperature data. If a unit far from the boiler, and therefore predicted to be cold, shows 

higher than average or expected temperature readings, the tenants may be using space heaters or 

the oven to additionally heat their unit. If a unit close to the boiler, and therefore predicted to be 

warm, shows lower than average or expected temperature readings, the tenants may be opening 

their windows. Also, surveying the tenants is useful in determining which parts of the building 

are too cold and which are too hot, especially in the absence of sensors.

2.3.6.2 Method

A tenant survey is an inexpensive method of understanding tenants’ perceptions of the heating in 

their apartments and information about how the system operates (Peterson 1986). A tenant 

comfort survey was conducted in this study when the pre-measure temperature data were 

collected (before any steam balancing measures were done) and when the post-measure 

temperature data were collected (after the steam balancing measures were completed by the 

contractor). (A copy of this survey is shown in Appendix C.) The survey was administered and 

the responses were recorded in the field. 

2.4 Measurements and Equipment

Although most of the building information (other than the temperature data and boiler runtime

data) were collected by observation during the site visits, some additional equipment was 

necessary for the study. Table 2 outlines the additional equipment needed. 
15

Table 2. Measurements and Equipment

Measurement Equipment Needed

Census of Radiators Observation

Radiator Vent Size Observation

Radiator Vent Condition Observation

Census of Main Lines Observation

Main Line Lengths Laser distance meter

Thickness of Main Lines Calipers

Vertical Tier Position Laser distance meter

Position of Vents Laser distance meter

Main Vent Size Observation

Main Vent Condition Observation

Main Line Steam Time Infrared camera

Rated Boiler Capacity (Btu/h) Observation

Boiler Size (sections) Observation

Burner Condition Observation

Boiler Efficiency Combustion analyzer

Header Piping Height Laser distance meter

Riser and Header Width Calipers

NBP Geometry Camera

Return Line Condition Observation

Description of Boiler Controls Observation

Number of Functioning Sensors Observation

Daytime/Nighttime Set Points Observation

Current Boiler Operation Observation
16

3 Measure Implementation

3.1 Determining a Scope of Work

CNT Energy worked with a steam heating contractor to develop a final scope of work for each 

test building. These scopes were highly detailed. It was decided that one contractor would do all 

the work, as this would minimize variability in installation methods, techniques, materials, and 

cost, and thus enable a consistent analysis of the effects of the main measures for a steam 

balancing package. The contractor proposals included itemized costs and descriptions of each 

steam balancing measure, informing the analysis on cost effectiveness. 

3.2 Measure Costs

When examining the scopes of work for balancing the steam systems of the test buildings, the 

measures most frequently recommended by the steam heating contractor were: 

• Adding or replacing the main line air vents

• Replacing the radiator vents

• Upgrading or adjusting the boiler control system. 

Table 3 summarizes the average costs for each measure, including equipment and installation. 

Table 3. Average Costs for Steam Balancing Measures

Measure Average Cost

Adding or Upgrading to High-Capacity Main 

Line Air Vents (With New Risers) $1,800 ($200–$250/vent)

Replacing Radiator Vents $3,680 ($38–$52/vent)

Upgrading Boiler Control System $5,060 ($3,900–$6,995)

For a detailed breakdown of all of the measures completed on each building (between December 

2011 and January 2012) as well as their cost breakdowns, see Appendix D.
17

4 Analysis and Results

4.1 Temperature Control and Steam System Behavior

The air temperature data provided useful insights to the building steam delivery system 

performance. More uniform air temperatures will theoretically lower energy bills and improve

tenant comfort, as there is no longer a need to overheat apartments close to the boiler to ensure 

that there is adequate heat for distant apartments. It was indicated in a previous study that gas 

consumption for heating can be reduced on the order of 16% by reducing a temperature spread 

through balancing a system (Biederman and Katrakis 1986). As described in the Technical 

Approach, six units in each building were fitted with temperature data loggers that recorded 

readings every 5 min for 1 month before the steam balancing, and for 1 month afterward.

Unfortunately, in a couple of instances, tenants removed loggers from the walls or moved them. 

The data recorded by these loggers were therefore not accurate depictions of what the in-unit 

temperatures were. These instances are noted in Appendix E.

The temperature data were analyzed by looking at the average temperature of each logger at each 

hour of the day over the pre- and post-balancing logging periods. Buildings 2, 4, 8, and 9 showed 

decreases in temperature differentials between units. Buildings 1, 3, 5, 6, and 10 did not show 

decreases in temperature differentials. Data for Building 7 were inconclusive because data from 

two of the loggers were unavailable and a third logger had been dropped to the floor and 

therefore recorded much lower temperatures.

Figure 9 through Figure 12 show samples of the temperature data. These represent the 

fluctuations during a day and the temperature differentials between units. The rest of the 

temperature data graphs are included in Appendix E.

Building 10, whose temperatures are shown in Figure 9 and Figure 10, showed an increase in 

overall temperature across all units. The post-retrofit oversight visit revealed that the owner had 

increased the set point temperature on the new boiler controls. This explains the uniform 

temperature increase, because the distribution of temperatures remained the same. The operation 

and settings of the boiler controls were important factors in this project. Although the building 

owner or manager should decide how to set the controls (based on feedback from his or her 

tenants), this will be an important factor in whether the building can save on energy costs after 

balancing work is done. Proper building manager education on operating more complicated 

boiler controls is a very important step to steam balancing. Since Building 10 was using less 

natural gas over the course of its continued monitoring (shown in Table 6), this suggests that the 

increased main line venting and upgraded radiator vents are allowing the steam to reach the 

apartments more quickly and efficiently. This enables the building owner to save natural gas and 

money, even though the temperature set points on the controls are higher. 
18

Figure 9. Building 10 average pre-measure logging period 

temperature readings by hour of the day

Figure 10. Building 10 average post-measure logging 

period temperature readings by hour of the day

In Building 4 (see Figure 11 and Figure 12 for temperature data), the two coldest units (Units 2 

and 4) pre-retrofit showed an increase in temperature by about 2° overall post-retrofit. The 

temperature differential between the hottest and coldest units was therefore decreased, 

suggesting a more even distribution of heat throughout the building. The manager also reported 

that heat seemed to be reaching the extreme ends of the building more quickly and evenly.

60

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 10 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

60

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 10 Post-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6
19

Figure 11. Building 4 average pre-measure logging period

temperature readings by hour of the day

Figure 12. Building 4 average post-measure logging period

temperature readings by hour of the day

The information collected from the tenant surveys and building owners revealed that some

tenants in the coldest units were using space heaters or their ovens for additional heat on the 

coldest days of the logging periods, which could raise the average temperatures of units. 

60

62

64

66

68

70

72

74

76

78

80

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 4 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

60

62

64

66

68

70

72

74

76

78

80

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 4 Post-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6
20

4.2 Boiler Cycles

The number of times that the boiler cycled on at each building over the pre- and post-balancing 

logging periods is shown in Table 4. Since this value is dependent on weather, it was weathernormalized using HDDs (see Table 5). Also shown for each building are the average lengths of 

the boiler cycles and the weather-normalized percent of time each boiler was on per day. Data 

for building 10 were unavailable because of a problem with the logger.

According to the weather-normalized data, four of nine buildings showed less frequent boiler 

cycles and seven showed shorter boiler cycles post-retrofit.

Table 4. Number of Boiler Cycles During Pre- and Post-Balancing Periods

Building

Pre-Balancing Post-Balancing

Number of 

Days Counted

Boiler on Cycle 

Count

Number of 

Days Counted

Boiler on 

Cycle Count

1 36 193 29 257

2 36 210 55 272

3 37 214 59 548

4 37 174 42 249

5 32 42 41 306

6 34 71 45 201

7 44 72 34 146

8 38 226 69 507

9 39 197 49 487

10 Data 

unavailable

Data 

unavailable

Data 

unavailable

Data 

unavailable
21

Table 5. Cycle Counts per Year, Average Lengths of Boiler Cycles and Percent of Day Boiler On

Building

Average Boiler on Cycle 

Count per Year*

Average Length of 

Boiler Cycle 

(min)

Average % of Time Boiler 

on per Day 

(per HDD)

PreBalancingPostBalancingPreBalancingPostBalancingPreBalancingPostBalancing

1 1265.4 1699.3 68.9 59.6 0.0098 0.0112

2 1972.7 1030.1 68.9 75.3 0.0134 0.0085

3 2015.1 1902.0 72.0 46.5 0.0137 0.0099

4 1638.3 1142.9 52.6 61.5 0.0095 0.0078

5 381.9 1509.7 163.3 44.1 0.0062 0.0074

6 700.4 854.6 68.0 55.1 0.0052 0.0051

7 540.5 885.0 143.5 64.5 0.008 0.0063

8 1623.3 1458.5 78.6 78.1 0.0142 0.0124

9 1615.6 1994.8 75.6 54.0 0.011 0.0118

10 Data 

unavailable

Data 

unavailable

Data 

unavailable

Data

unavailable

Data 

unavailable

Data 

unavailable

* The number of boiler cycles per year was weather normalized and calculated by dividing the average number of cycles per 

day during the four-week logging periods by the actual number of HDDs each day, then taking an average and extrapolating to 

a year’s worth of cycles by multiplying by the (30-year average for the) total number of HDDs in a year.

The weather-normalized natural gas use of each boiler for the pre-balancing and post-balancing

periods (in kBtu) is depicted in Figure 13. The numbers of months used for analysis are shown in

Table 6.
22

Figure 13. Weather-normalized natural gas use from utility bills during pre-balancing and postbalancing periods

Table 6. Measured Weather-Normalized Natural Gas Use (Heating Only)

Building

Natural Gas Use From EUI*

(kBtu)

Pre-Balancing Post-Balancing # of Months in 

Analysis Periods % Savings

1 703,119 621,371 8 11.63%

2 1,971,622 1,394,456 9 29.27%

3 1,280,991 1,388,438 11 -8.39%

4 578,751 514,142 11 11.16%

5 873,111 640,519 9 26.64%

6 990,039 995,768 11 –0.58%

7 972,393 633,350 10 34.87%

8 972,476 844,398 8 13.17%

9 1,578,954 1,420,073 10 10.06%

10 1,027,457 977,787 10 4.83%

* Energy use intensity

All buildings except Buildings 3 and 6 used less natural gas for heating after the measures were 

completed.

0

500,000

1,000,000

1,500,000

2,000,000

1 2 3 4 5 6 7 8 9 10

kBtu

Building

Natural Gas Use

Pre (kBtu)

Post (kBtu)
23

4.3 Cost Effectiveness

In order to determine the cost effectiveness of the installed measures, analysis was conducted 

using measure costs and measured natural gas savings. The pre- and post-balancing energy use 

was compared via utility bill analysis. These are shown in Table 7.

Table 7. Average Percent Natural Gas Savings,* Balancing Costs, and Simple Paybacks

Savings

(kBtu) % Savings

Balancing 

Cost

($)

Simple 

Payback 

(yrs)***

Measured (All Buildings) 27,428 13.3% 9,434 3.4

Measured (Buildings Without 

Additional Measures Installed)** 13,606 10.2% 9,875 5.1

*

The percent natural gas savings shown in this table are for heating load only. **Some of the buildings (2, 3, 5 and 7) had additional measures installed after the balancing work and data logging 

periods. These buildings were excluded from this average value calculation. ***The simple payback was calculated using an estimate of $1/therm natural gas.

The EUI analysis, which uses actual billed natural gas use, was calculated and weather

normalized for each building using CNT Energy’s Standard Operating Procedure for energy use 

calculations. To calculate a weather-normalized heating load EUI, the actual period heating load 

usage per square foot is multiplied by a ratio of the 30-year average number of HDDs to the 

actual number of heating degree days in that period (Equation 1).

Actual HDD

Yr HDD

Building Heating SF

Actual Period Heating Load Usage EUI Heating Load

30 = * (1)

The EUI analyses showed that all except Buildings 3 and 6 reduced their natural gas usage. 

Buildings 2, 3, 5, and 7 had additional measures (air sealing and insulation in the roof cavity and 

heating pipe insulation) installed after the data logging periods were over. In Building 3, which 

had additional energy efficiency measures installed but saw an increase in measured natural gas 

usage, it is likely that the temperature set points were increased after the post-balancing logging 

period. A summary of the natural gas savings are shown in Table 7. 

The total cost effectiveness of the steam balancing package tested (upgrading or replacing 

controls, installing main line vents, replacing radiator vents) was evaluated by calculating simple 

paybacks from projected yearly financial savings and measure costs. The average measure cost 

and simple payback are shown in Table 7.

Long-term monitoring of building performance would be an interesting study to examine 

whether a building owner would see sustained savings from steam balancing measures. This 

would be accomplished by doing utility bill analyses for at least two years following 

construction. 
24

4.4 Tenant Comfort

Tenants of the units where loggers were placed were surveyed about their temperature comfort 

and whether they opened their windows or used additional heat sources during the heating season 

before and after the retrofits were done. (A sample survey is provided in Appendix C.) The 

response rate was 44% pre-retrofit and 56% post-retrofit (this translates to an average response 

rate of 12% of an entire building’s tenants pre-retrofit and 17% post-retrofit). 

Figure 14 shows the average survey responses when tenants were asked to rate their overall 

temperature comfort on a scale from 1 = Uncomfortable to 5 = Comfortable. All the buildings 

except Buildings 1 and 6 saw improvements in rated comfort post-retrofit.

Figure 14. Tenant survey responses rating overall temperature comfort. The tenants were asked to 

rate the overall temperature comfort within their unit on a scale from 1 = Uncomfortable to 5 = 

Comfortable. Note: Building 7 received no survey responses pre-retrofit. 

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

1 2 3 4 5 6 7 8 9 10

Average Survey Response

Building

Tenant Survey Responses—Overall Temperature Comfort

Average PreBalancing Response

Average PostBalancing Response
25

5 Discussion

5.1 Temperature Control and Steam System Behavior

Each test building responded differently to the steam balancing measures. Their pre-measure 

conditions were drastically different, so this was expected. However, some of the differences in 

the pre- and post-balancing temperature data were:

• Changes in the diurnal temperature patterns within units (different schedules of when the 

units were warmest and when they were coolest)

• Smaller temperature differentials between the hottest and coldest units in some buildings.

The changes in heating schedules (observed in Building 5) should provide heat at appropriate 

times and increase resident comfort. Because this change was determined by the type of controls

in place, newly installed boiler controls seem to have contributed significantly to more 

comfortable temperature settings. The indoor averaging system and the more advanced 

temperature set point control (allowing for nighttime, daytime, and differential set points) seem 

to have more tightly regulated the heating schedules. Since these controls have the added 

advantage of allowing building owners to monitor unit temperatures from a central control box in 

the boiler room, building owners are able to make more informed decisions about their set 

points.

A decrease in the temperature differential between the hottest and coldest units was also seen in 

some buildings. This suggests that heat was being more evenly distributed, reaching units that 

previously received less heat. This could have been because the indoor averaging temperature 

controls regulated the boiler to stay on longer, until heat reached the further units, or because the 

increased venting allowed steam to travel faster through the mains and to the radiators. Buildings 

2 and 4 showed increases in their average boiler cycle lengths, suggesting that longer cycles were 

needed for heat to reach the further tiers in the buildings. This more even heat distribution is also 

expected to increase resident comfort. 

The balancing work had varying effects on the lengths and frequency of boiler cycles (shown in 

Table 5). Some buildings saw shorter cycles post-retrofit and some saw much longer cycles. 

Some saw more boiler cycles and some saw fewer. As previously stated, this was expected 

because each building had unique pre-retrofit conditions. It was difficult to predict exactly how 

the balancing work, especially the increased or upgraded venting, would change temperatures

and boiler behavior. What is evident, however, is that several trips and adjustments are often 

needed after the initial round of balancing work is done. Building 3 (see Figure 15 and Figure 

16) showed an example of a building where the midrange temperature units were more uniformly 

heated to a comfortable temperature, but the outliers remained after the balancing work was 

done. This suggests that the venting and control systems did not affect the hottest and coldest 

units and that there may have been some other reasons that these units were so different in 

temperature from the others. This represents an example of a building where issues with 

controlling the heat to the hottest and coldest units need to be investigated and addressed further

in subsequent heating seasons.
26

Figure 15. Building 3 average pre-measure logging period

temperature readings by hour of the day

Figure 16. Building 3 average post-measure logging period 

temperature readings by hour of the day

5.2 Cost Effectiveness 

The natural gas used for heating before and after the balancing work was calculated by looking at 

the actual heating bills for the buildings. The measured natural gas usage values (shown in Table 

7) showed that the test buildings saved an average of 13.3% with an average simple payback of 

3.4 years. However, since some of the building had additional measures installed (air sealing and 

insulation of the roof cavity and heating pipe insulation), the average for the buildings that had

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 3 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 3 Post-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6
27

only steam balancing measures was also calculated. This value was found to be 10.2% and the 

average simple payback for these buildings was 5.1 years. These results are fairly consistent with 

previous studies. The benefit of tenant comfort (which would begin immediately after a building 

is properly balanced) should also be considered as an important added value. 

5.3 Tenant Perceptions

Records of tenant complaints about the heat should be used in conjunction with logger data when 

determining how to balance a building. These often indicate where heat is not reaching. 

Though five of the buildings (1, 3, 5, 6, and 10) did not see a decrease in temperature 

differentials, it is important to note that all of the buildings except Buildings 1 and 6 saw 

improvements in average rated temperature comfort according to the tenant surveys. Tenant 

comfort can be a very important factor when deciding to do energy efficiency measures. Along 

with keeping tenants happy, it can also assist building owners with tenant retention. The one 

building that did not see improvements in temperature differentials, natural gas usage, or tenant 

comfort (Building 6) will require additional assessments to see how and why the heating system 

is failing. 

Building owners often stopped overheating their buildings because of the new controls or 

adjusted venting, so major heating imbalances became more obvious. Some units that received

heat more slowly may have initially received even less heat after the temperature set points were 

turned down or adjusted, so tenants were more likely to notice heating deficiencies caused by

imbalances. Also, many tenants were used to having their units overheated (often up to 80°–

85°F), so they were more likely to complain once set points were adjusted properly and they

were receiving less heat than before. Tenants in the two buildings that did not show 

improvements in average rated temperature comfort (Buildings 1 and 6) were either experiencing

this phenomenon post-retrofit, or they were still being overheated. Though the venting was 

adjusted, these buildings may require more follow-up visits to further assess the distribution and 

control systems.
28

6 Conclusions and Recommendations

6.1 Establishing Steam Balancing Guidelines

Several additional points are important to consider when deciding to balance a building:

• Balancing is a multistage process. All the information in the Experiment section should 

first be collected on a building thought to need balancing. Once a building has initially 

had the steam balancing measure package installed, the effectiveness of the retrofits 

should be assessed based on conversations with the building manager and tenants and on 

temperature data. The building may need to be rebalanced, reassessed, and perhaps 

further adjusted.

• Unit locations and building layout are important to consider when assessing and 

balancing a building. Each building will have different hot and cold spots and will 

require different venting configurations and placement of control sensors.

• Tenants and building managers need to be informed about the balancing process 

and that its success will require time and cooperation. The balancing work will be

most effective when tenants and building managers cooperate. Tenants should be 

informed that the work will require occasional access to their units and asked not to 

tamper with monitoring equipment. Tenants should also be informed that using space 

heaters drives up the temperature that indoor averaging systems use to control the boiler. 

This means that the boiler will not come on in a building even if some units are 

substantially below the set point. This must be communicated to tenants, and building 

managers should be properly instructed on how to use the newly installed controls.

6.2 Further Recommended Studies

Though the results of this project are generally positive, further studies should be done to more 

conclusively determine the effects of steam balancing. Variables were monitored as closely as 

possible, but the test buildings were occupied and thus subject to unpredictable tenant behavior. 

This caused uncertainties in the physical meaning of some temperature measurements collected. 

More controlled studies could be done to conclusively determine the effect of balancing on 

temperatures within units. 

The effectiveness of the three separate measures considered as a package in this project could be 

examined by installing them individually and assessing the temperature distributions and natural 

gas uses in a new set of test buildings. Measures such as thermostatic radiator valves could also 

be evaluated. 

Taking temperature readings at more frequent intervals in every unit would also help shed light 

on how the balancing work affects the time to heat a unit. The data could be matched with the 

boiler runtime data to see how long it takes to heat a unit after a boiler cycles on. This would 

require either remotely monitored data loggers or entering into units more frequently to collect

more data. The windows could also be monitored to see if tenants were cooling their apartments, 

and stoves could be monitored to see if tenants were using them as supplemental heat sources.

This type of study would require much more stringent cooperation from tenants.
29

References

Ahlgren, R. (1994). “Low Pressure Steam Heating Systems.” ASHRAE Journal, Sept 2009. 

www.nxtbook.com/nxtbooks/ashrae/ashraejournal_200909/index.php?startid=58#/58.

Biederman, N.; Katrakis, J. (1986). Space Heating Efficiency Improvements in Multifamily 

Buildings. GRI 88/0111. Chicago: Gas Research Institute. 

DOE. (2011.) Building America: Program Goals. Washington, D.C.: U.S. Department of Energy. 

www1.eere.energy.gov/buildings/building_america/program_goals.html. 

Evens, A.; Ludwig, P.; Kotewa, L. (2008). “Cook County Energy Savers: How Energy 

Efficiency in Chicago’s Multi-Family Buildings Has Evolved to Meet New Challenges from the 

1980’s to the Present Day.” ACEEE Summer Study on Energy Efficiency in Buildings. 2-197.

Gill, G.; Pajek, S. (2005). “Balancing Steam Systems Using a Venting Capacity Chart.” Gerry 

Gill and Steve Pajek. 

Gorton Heating Corporation. (2006). Gorton Heating. www.gorton-valves.com. 

Holohan, D. (1992). The Lost Art of Steam Heating. D. Holohan.

Holohan, D. (2010a). Greening Steam How to Bring 19th-Century Heating Systems into the 21st

Century (and save lots of green!). Daniel Holohan Associates, Inc.

Holohan, D. (2010b). Balancing One Pipe Steam Systems. www.heatinghelp.com/article/11/HotTech-Tips/138/Balancing-One-Pipe-Steam-Systems. 

Holohan, D. (2011). Classic Hydronics. D. Holohan.

Karins, N. (1994). “Energy Savings in One-Pipe Steam Heating Systems Fitted with HighCapacity Air Vents.” EME Group. www.osti.gov/bridge/servlets/purl/10191625-

8qJZ5M/webviewable/.

Katrakis, J.; Lobenstein, M.; Hewett, M. (2010). “Cost-Effective Boiler System Retrofits.” 

Consulting-Specifying Engineer. 

http://m.csemag.com/index.php?id=2832&tx_ttnews[tt_news]=22127&cHash=3b07e71e00. 

Peerless® Boilers. (1996). Series 211ATM – Gas Boilers – Steam – Installation, Operation & 

Maintenance Manual. Bally, PA: PB Heat, LLC.

Peterson, G. (1985). Achieving Even Space Heating in Single Pipe Steam Buildings. CEE TR85-

8-MF. Minneapolis: Center for Energy and Environment. www.mncee.org/. 

Peterson, G. (1986). Multifamily Pilot Project: Single Pipe Steam Balancing & Hot Water 

Outdoor Reset. Minneapolis Energy Office. www.mncee.org/pdf/tech_pubs/86-5.pdf. 

Peterson, G.; Otterson, S. (1985). Single Pipe Steam Air Venting. CEE TR85-3-MF. 

Minneapolis: Center for Energy & Environment. www.mncee.org/. 
30

Appendix A: Test Building Details

Building Type # Units

Cond.

Square

Feet

Original 

Control 

Strategy

Natural Gas Heating Load

(kBtu)

PreBalancingPostBalancing

# of Months 

in Analysis 

Periods

1

3-story brick 

courtyard building, 

flat roof

33 24,570 Timeclock/

aquastat 703,119 621,371 8

2

3-story brick 

courtyard building, 

flat roof

30 30,050

RD SF 201 

(Nonfunctional, 

so was 

controlled 

manually)

1,971,622 1,394,456 9

3

3-story brick 

courtyard building, 

flat roof

16 18,000 Timeclock/

aquastat 1,280,991 1,388,438 11

4

3-story brick walkup, 

flat roof

6,

converted 

to 20

8,600 Thermostat

on 3rd floor 578,751 514,142 11

5

3-story brick 

courtyard building, 

flat roof

15 12,600 Timeclock/

aquastat 873,111 640,519 9

6

3-story brick walkup, 

flat roof

18 15,760 Timeclock/

aquastat 990,039 995,768 11

7

3-story brick 

courtyard building, 

flat roof

16 12,360 Timeclock/

aquastat 972,393 633,350 10

8

3-story brick 

courtyard building, 

flat roof

24 17,640 Timeclock/

aquastat 972,476 844,398 8

9

3-story brick walkup, 

flat roof

21 16,600 Timeclock/

aquastat 1,578,954 1,420,073 10

10

3-story brick walkup, 

flat roof

32 18,300 Timeclock/

aquastat 1,027,457 977,787 10
31

Figure 17. The pre-measure heating EUI for each test building is at or above the line representing 

the median EUI for 105 similar steam-heated buildings in Chicago. This suggests that the 

buildings chosen for this study all had potential for energy savings.

0

20

40

60

80

100

120

140

160

180

1 2 3 4 5 6 7 8 9 10

Energy Use Intensity 

(kBtu/ft2 ft/yr)

Buildings

Pre-Balancing Natural Gas Use (for Heating) in Test Buildings
32

Appendix B: Sample Tenant Letter
33

Appendix C: Sample Tenant Survey
34

Appendix D: Detailed Measures and Costs

Building Measures Completed

Individual 

Measure 

Costs 

($)

Total 

Cost ($)

1

Main line vents (3 Gorton (2006) #1; 6 Gorton #2)

Radiator vents (150)

Boiler controls (RD AH207 – 6 indoor sensors, 1 outdoor sensor)

4,695

5,842

6,995

17,532

2

Main line vents (5 Gorton #1; 3 Gorton #2)

Radiator vents (120)

Boiler controls (RD AH207 – 6 indoor sensors, 1 outdoor sensor)

1,560

5,200

6,995

13,755

3

Main line vents (5 Gorton #2)

Radiator vents (70)

Boiler controls (RD 1404T – 4 indoor sensors, 1 outdoor sensor)

1,540

2,820

4,500

8,860

4

Main line vents (2 Gorton #1; 2 Gorton #2)

Radiator vents (48)

Boiler controls (RD 1404T – 4 indoor sensors, 1 outdoor sensor)

895

2,195

4,698

7,788

5

Main line vents (2 Gorton #1; 4 Gorton #2)

Radiator vents (51)

Boiler controls (RD RF207 – 6 indoor sensors, 1 outdoor sensor)

1,295

2,295

3,900

7,490

6

Main line vents (3 Gorton #1; 3 Gorton #2)

Radiator vents (135)

Boiler controls (RD 1206 – 6 indoor sensors, 1 outdoor sensor)

1,570

5,500

4,500 (est)*

11,570

7

Main line vents (1 Gorton #1; 2 Gorton #2)

Radiator vents (54)

Boiler controls (RD RF207 – 6 indoor sensors, 1 outdoor sensor)

1,495

2,395

3,900

7,790

8

Main line vents (3 Gorton #1; 4 Gorton #2)

Radiator vents (72)

Boiler controls (RD 1204 – 4 indoor sensors, 1 outdoor sensor)

1,798

3,589

4,000

9,387

9

Main line vents (2 Gorton #1; 4 Gorton #2)

Radiator vents (90)

Boiler controls (RD 1404T – 4 indoor sensors, 1 outdoor sensor)

1,500

3,295

4,500

9,295

10

Main line vents (3 Gorton #1; 4 Gorton #2)

Radiator vents (71)

Boiler controls (RD 1206 – 6 indoor sensors, 1 outdoor sensor)

1,678

3,695

4,000 (est)*

9,373

*The boiler control costs for Buildings 6 and 10 are estimated costs because the owner had installed these prior to 

the start of the project and CNT Energy did not receive the formal proposals for these installations. The buildings 

were run on their original timers/thermostats during the prelogging period to simulate “pre” boiler control 

conditions.

Note: New risers were installed for the main line vents as needed. The costs for these are included in the costs for 

the main line vents. All radiator vents were Gorton radiator air vents.
35

Appendix E: Temperature Data

Building 1

Note: Access was only granted for 5 units in this building so only 5 temperature loggers were installed.

74

76

78

80

82

84

86

88

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 1 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

74

76

78

80

82

84

86

88

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 1 Post-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5
36

Building 2

Note: Pre-measure data for Unit 6 were unavailable because of limited access to the unit.

66

68

70

72

74

76

78

80

82

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 2 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

66

68

70

72

74

76

78

80

82

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 2 Post-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6
37

Building 3

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 3 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 3 Post-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6
38

Building 4

60

62

64

66

68

70

72

74

76

78

80

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 4 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

60

62

64

66

68

70

72

74

76

78

80

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 4 Post-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6
39

Building 5

60

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 5 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

60

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 5 Post-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6
40

Building 6

60

64

68

72

76

80

84

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 6 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

60

64

68

72

76

80

84

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 6 Post-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6
41

Building 7

Note: Post-measure data for Units 4 and 5 were unavailable because of limited access to the units. The logger for 

Unit 3 had been moved from where it was installed to the floor and therefore showed very low temperatures. 

54

58

62

66

70

74

78

82

86

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 7 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

54

58

62

66

70

74

78

82

86

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 7 Post-Measure Temperature Readings 

Unit 1

Unit 2

Unit 3

Unit 6
42

Building 8

Note: Post-measure data for Unit 1 were unavailable because of limited access to the unit. 

64

66

68

70

72

74

76

78

80

82

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 8 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

64

66

68

70

72

74

76

78

80

82

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 8 Post-Measure Temperature Readings

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6
43

Building 9

60

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 9 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

60

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 9 Post-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6
44

Building 10

60

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 10 Pre-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6

60

65

70

75

80

85

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

°F

Hour of the day

Building 10 Post-Measure Temperature Readings

Unit 1

Unit 2

Unit 3

Unit 4

Unit 5

Unit 6
DOE/GO-102013-4238 ▪ August 2013

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