October 2013

Overheating in Hot Waterand Steam-Heated 

Multifamily Buildings

Jordan Dentz, Kapil Varshney, and 

Hugh Henderson 

ARIES Collaborative
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iii

Overheating in Hot Water- and Steam-Heated Multifamily Buildings

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:

Jordan Dentz, Kapil Varshney, and Hugh Henderson

ARIES Collaborative

The Levy Partnership, Inc.

1776 Broadway, Suite 2205

New York, NY 10019

NREL Technical Monitor: Michael Gestwick

Prepared under Subcontract No. KNDJ-0-40347-03

October 2013
iv

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v

Contents

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

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

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

Executive Summary.................................................................................................................................... x

1 Introduction........................................................................................................................................... 1

1.1 Background..........................................................................................................................3

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

1.3 Cost Effectiveness................................................................................................................3

2 Problem Description ............................................................................................................................ 4

3 Research Methods................................................................................................................................ 5

4 Results and Discussion....................................................................................................................... 9

4.1 Effect of Floor Levels........................................................................................................15

4.2 Effect of Building Height on Energy Management System Performance.........................17

4.3 Variation of Indoor Temperature Between Apartments ....................................................17

4.4 Effect of Heating System Type..........................................................................................18

5 Conclusion .......................................................................................................................................... 21

Appendix: Variations of Indoor Temperatures....................................................................................... 25
vi

List of Figures

Figure 1. Multifamily building used in the study...................................................................................... 6

Figure 2. Typical wireless temperature sensor (left) and radiator (right) ............................................. 6

Figure 3. Building 15 indoor air temperatures and outdoor air temperature with EMS off............... 14

Figure 4. Building 15 average indoor air temperatures during the 2011–2012 heating season ....... 14

Figure 5. Building 15 indoor air temperature as a function of outdoor air temperature (2010–2011 

heating season) .................................................................................................................................. 15

Figure 6. Building 1 average temperatures for apartments on the top and bottom floors of a twostory building...................................................................................................................................... 16

Figure 7. Building 16 average temperatures for apartments on four floors of a six-story building 

(1st digit is floor number) .................................................................................................................. 16

Figure 8. Building 18 average temperatures for apartments on five floors of a six-story building 17

Figure 9. Comparison between the overall average indoor temperature of the buildings and 

average indoor temperatures of overheated apartments when the EMSs were off and on ....... 19

Figure 10. Building 1 temperatures......................................................................................................... 26

Figure 11. Building 2 temperatures......................................................................................................... 27

Figure 12. Building 3 temperatures......................................................................................................... 28

Figure 13. Building 4 temperatures......................................................................................................... 29

Figure 14. Building 5 temperatures......................................................................................................... 30

Figure 15. Building 6 temperatures......................................................................................................... 31

Figure 16. Building 7 temperatures......................................................................................................... 32

Figure 17. Building 8 temperatures......................................................................................................... 33

Figure 18. Building 9 temperatures......................................................................................................... 34

Figure 19. Building 10 temperatures....................................................................................................... 35

Figure 20. Building 11 temperatures....................................................................................................... 36

Figure 21. Building 12 temperatures....................................................................................................... 37

Figure 22. Building 13 temperatures....................................................................................................... 38

Figure 23. Building 14 temperatures....................................................................................................... 39

Figure 24. Building 15 temperatures....................................................................................................... 40

Figure 25. Building 16 temperatures....................................................................................................... 41

Figure 26. Building 17 temperatures....................................................................................................... 42

Figure 27. Building 18 temperatures....................................................................................................... 43

Figure 28. Outdoor air temperature in New York City from June 2011 to May 2012.......................... 44

Figure 29. Indoor air temperature dependence on outdoor air temperature in building 1................ 44

Figure 30. Indoor air temperature dependence on outdoor air temperature in building 2................ 45

Figure 31. Indoor air temperature dependence on outdoor air temperature in building 3................ 45

Figure 32. Indoor air temperature dependence on outdoor air temperature in building 4................ 46

Figure 33. Indoor air temperature dependence on outdoor air temperature in building 5................ 46

Figure 34. Indoor air temperature dependence on outdoor air temperature in building 6................ 47

Figure 35. Indoor air temperature dependence on outdoor air temperature in building 7................ 47

Figure 36. Indoor air temperature dependence on outdoor air temperature in building 8................ 48

Figure 37. Indoor air temperature dependence on outdoor air temperature in building 9................ 48

Figure 38. Indoor air temperature dependence on outdoor air temperature in building 11.............. 49

Figure 39. Indoor air temperature dependence on outdoor air temperature in building 13.............. 49

Figure 40. Indoor air temperature dependence on outdoor air temperature in building 14.............. 50

Figure 41. Indoor air temperature dependence on outdoor air temperature in building 15.............. 50

Figure 42. Indoor air temperature dependence on outdoor air temperature in building 16.............. 51

Figure 43. Indoor air temperature dependence on outdoor air temperature in building 17.............. 51

Figure 44. Indoor air temperature dependence on outdoor air temperature in building 18.............. 52

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

List of Tables

Table 1. Building Characteristics .............................................................................................................. 5

Table 2. Difference Between TSI and EMS Temperature Readings in One Building ........................... 8

Table 3. Building Summary Data ............................................................................................................. 10

Table 4. EMS ON/OFF Time Periods by Building................................................................................... 12

Table 5 Weighted Average Differences by Building Floor EMS on Minus EMS Off........................... 17

Table 6. Variation in Overheating by Heating System Type ................................................................. 18

Table 7. Statistical Analysis of the Temperature Data .......................................................................... 20

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

Definitions

ARIES Advanced Residential Integrated Energy Solutions 

Collaborative Building America Team

EMS Energy management system

Tn Neutral temperature

To Outdoor temperature
ix

Acknowledgments

The Advanced Residential Integrated Energy Solutions (ARIES) Collaborative would like to 

recognize the support of the U.S. Department of Energy’s Building America Program and 

Michael Gestwick and Michael Heaney of the National Renewable Energy Laboratory for 

technical guidance. This project would not have been possible without the support and 

participation of David Ungar and Anthony Jabbour of U.S. Energy Corp., Daniel Carleton of 

Heat Watch, Inc., and Victor Zelmanovich of Intech 21, Inc.
x

Executive Summary

The Building America program aims to develop and prove technologies that optimize the energy 

performance of buildings—reducing energy consumption by 30%–50% without compromising 

occupant comfort. Indoor thermal climate is also an important issue affecting the health and 

productivity of building occupants. Many steam- and hydronically heated multifamily buildings 

are reportedly overheated in winter due to poor boiler system controls and uneven heat 

distribution, which result in heating energy waste and uncomfortable interior conditions. A 

rigorous study measuring the extent of overheating in these building types and associated 

building characteristics has not been previously done.

In this project, data have been collected from the archives of companies that provide energy 

management systems (EMSs) to multifamily buildings in the northeastern United States. EMSs 

typically include temperature sensors located in apartments networked to a central controller that 

modulates the heating system. The collected data have been analyzed from more than 100 

apartments in 18 buildings where EMSs were already installed to quantify the degree of 

overheating. For the purposes of this report, overheating is defined as indoor temperatures > 

70°F during periods when heating is supplied. This research attempts to answer the question, 

“What is the magnitude of apartment overheating in multifamily buildings with central hot water 

or steam heat?” This report provides valuable information to researchers, utility program 

managers, and building owners interested in controlling heating energy waste and improving 

resident comfort.

Apartment temperature data were analyzed for deviations from minimum heating requirements 

and for variations by heating system type, apartment floor level, and ambient conditions. To 

quantify overheating, temperature data for more than 10% of the apartments in each building 

were analyzed for deviation from this set point. Information on heating system type, apartment 

floor level, and ambient conditions was also collected for each building. The data show that 

overheating is significant in these multifamily buildings with both hot water and steam heating 

systems. 

When EMSs were inactive, average temperatures for all apartments were > 70°F in 15 of the 

buildings, while the other three buildings had 88% of the apartments > 70°F. Average apartment 

temperatures ranged from 71.8°F to 81°F with a mean of 76.3°F.

When EMSs were active, average temperatures for all apartments were > 70°F in seven of the 

buildings, while the other 11 buildings had 67% of the apartments > 70°F. Average apartment 

temperatures ranged from 70.5°F to 77.3°F with a mean of 74.2°F.

Based on this analysis, the estimated average increase in annual space heating energy costs for 

these buildings due to overheating is approximately 18.6% when the EMS is off, compared to a 

baseline average temperature of 70°F all the time.
1

1 Introduction

To minimize energy consumption and associated greenhouse gas emissions, researchers and 

practitioners employ various techniques to avoid excess energy consumption in residential and 

commercial buildings. In the United States, approximately 41% of all energy utilized 

(approximately 40,000 trillion Btu [11.7 trillion kWh]) is consumed in residential and 

commercial buildings (U.S. Energy Information Administration/Annual Energy Review 2010).

Of the energy consumed in U.S. buildings, approximately 50% is used for space heating. This

energy consumption increases rapidly if a building is overheated. In the Northeast and Midwest, 

many multifamily buildings are heated by common systems using hot water or steam. According 

to the 2005 American Housing Survey, there are about 3.2 million occupied hydronically heated, 

low-rise housing units in the United States (U.S. Census Bureau, 2005). Nearly 90% of these 

homes are in the Northeast or Midwest, with a large portion being rental units (40%), or 

occupied by the elderly (24%) (U.S. Census Bureau, 2005). Most hydronically heated residences 

are older, with only 1% being classified as New Construction (built within the past four years) in 

the 2005 American Housing Survey data (U.S. Census Bureau, 2005). Typically, residents of 

these buildings do not pay for heat directly (i.e., heat is not submetered). Heating fuel use for 

these systems is reputed to be higher than necessary, given the thermal properties of the 

buildings. Anecdotally, a significant number of apartments are overheated much of the time (the 

window-as-a-thermostat syndrome) (Urban Green Council, 2010). Overheating results in an 

estimated increase in annual energy consumption of approximately 1% per °F over the desired 

temperature in a dwelling for each eight hours of the day (the percentage of energy waste is 

greater in milder climates than in severe climates) (U.S. Department of Energy, 2012). This 

savings estimate does not include any increase in energy use associated with the reported 

opening of windows by residents to temper discomfort caused by overheating. In the United 

States, controlling space hydronic and steam heating systems typically involves an outdoor reset 

control algorithm, possibly with different day and night space temperature targets. 

The extent of overheating, and the variance of it in different parts of the building and on different 

days of the heating season, affects the strategy used to combat it. Generally, local laws require 

apartments to be heated to at least 68°F during the heating season. If overheating is shown to be 

similar throughout a building, reducing heat at the heating plant is a logical solution. However, 

most often overheating patterns are more complex, requiring zone- or apartment-specific 

solutions. Many older multifamily buildings, such as those addressed in this research, were built 

without effective zone-level controls (e.g., a thermostat and zone valve for each room or 

dwelling unit). Therefore, one strategy is to reduce the range between the warmest and coldest 

apartments by making distribution or radiator improvements, and then lowering the entire 

average building or zone temperature at the heating plant or zone valve. 

In order to estimate overheating in multifamily residential and commercial buildings, and to 

relate optimum indoor temperature to outdoor air temperatures, researchers in the past have 

performed several theoretical and field studies. Robinson and Haldi (Robinson & Haldi 2008) 

proposed a mathematical model for predicting overheating risk given a set of measured or 

simulated environmental conditions based on an analogy between the charging and discharging 

of human’s tolerance to overheating stimuli and that of charge in an electrical capacitor. 
2

EME Group (EME, 1994) performed a study to determine if the installation of large-capacity air 

vents at the ends of steam mains and risers would economically reduce the temperature gradient

between apartments and reduce the amount of space heating energy required. They conducted 

tests by enabling and disabling air vents biweekly in 10 multifamily buildings in New York City 

and compared the temperatures of selected apartments and total space heating energy during 

each venting regime. No difference in energy consumption between “vents on” and “vents off”

periods was found. However, there was a reduction in the maximum spread of apartment

temperatures.

Many researchers have used an adaptive approach to thermal comfort based on the findings of 

surveys of thermal comfort conducted in the field (such as those of Humphreys 1978, 

Humphreys & Nicol 2000, Nicol & Humphreys 2002, de Dear & Brager 2002). Humphreys 

established a relationship between the indoor temperatures with the outdoor mean effective 

temperature for naturally ventilated buildings (Humphreys, 1978),

Optimum indoor temperature (°C) = 18.9 + 0.255 × (outdoor mean effective temperature) (1)

He also proposed a correlation between the neutral temperatures (Tn) against outdoor mean 

monthly temperatures (To) for air-conditioned buildings:

Tn = 23.9 + 29.5(To − 22) × e− ((To−22)/ (24×√2))2 (2)

where To is the outdoor temperature (°C).

Humphreys’ equation was revised by Auliciems, who analyzed the data obtained for several 

other studies which included many other climate zones and more countries and considered only 

compatible field studies of Humphreys (Auliciems 1981, 1983). Auliciems presented the 

equation after analyzing the data for naturally ventilated building and air-conditioned buildings, 

for 53 different studies,

Tn = 0.48Ti + 0.14To + 9.22 (3)

In addition, Auliciems and de Dear (Auliciems & de Dear, Air conditioning in Australia I: 

human thermal factors, 1986) presented an equation for all types of buildings,

Tn = 17.6 + 0.31To (4) 

For the purposes of this report, overheating is defined as indoor temperatures > 70°F during 

periods when heating is supplied. Nicol and Humphreys (2002) collected data in a number of

countries and climate zones and found that the typical indoor comfort temperature range is 

67.6°–69.8°F for a wide range of outdoor air temperatures (–4°–55°F). Therefore, additional 

energy spent to raise indoor temperatures above 70°F contributes to overheating buildings.
3

1.1 Background

At the 2011 expert meeting conducted by the Advanced Residential Integrated Energy Solutions 

(ARIES) Building America team1 titled Multifamily Hydronic and Steam Heating Controls and 

Distribution Retrofits, the subject of how significant a factor overheating is (and how large a 

potential exists for energy savings by eliminating it) was debated. It was acknowledged that no 

rigorous analysis of the phenomenon is published (The Levy Partnership, Inc., 2011).

Building energy consumption can be reduced in several ways, including improving boiler control 

strategy, giving the occupant the ability to modulate the temperature according to need (instead 

of opening a window), and altering the distribution of heat within the building in ways that better 

reflect demand. ARIES currently has a project underway in this area.2 Case studies of 

multifamily buildings in New York State (Allen, 2011) have shown a pattern of excessive 

temperatures of 80°–85°F in some apartments, while building-wide averages in the mid-70s°F 

imply that overheating is typically in only part of the building, for only part of the winter.

1.2 Relevance to Building America’s Goals

The motivation to quantify and characterize overheating in multifamily buildings is driven by the 

desire to reduce overheating. Reducing overheating is relevant to Building America goals 

because it reduces the space heating energy consumption of the building and increases occupant 

comfort. Quantifying and characterizing overheating in multifamily buildings will help to reduce 

it by:

• Proving that the issue exists, if indeed it does, and measuring the savings opportunity

• Identifying the characteristics of multifamily buildings that are most closely associated 

with overheating

• Developing a baseline measurement for overheating to which improvements can be 

compared.

1.3 Cost Effectiveness

Because this project does not include the implementation of any retrofits, there is no direct cost 

analysis for this project. Indirectly, the results of this report can be used to evaluate the most 

cost-effective approach to retrofitting heating plants and distribution systems in multifamily 

buildings. Although the data currently available on the topic are largely anecdotal, they are the 

primary driver of the hydronic heating retrofit market. The determination of statistically relevant 

information would inform manufacturers and building owners on the best approach to reducing 

their heating energy expenditure.

 1 Building America is a U.S. Department of Energy research program focusing on residential energy efficiency. 

2 Hydronic Heating Control Retrofits for Low-Rise Multifamily Buildings
4

2 Problem Description

For the purposes of this report, overheating is defined as heating to a temperature > 70°F while 

heating is supplied.

3

However, it was found that indoor temperatures in many buildings were significantly higher than 

70°F while boilers were in operation. Overheating can cause discomfort for residents due to the 

heat and excessively low humidity levels, which can have negative health consequences. 

Overheating also results in higher fuel consumption than necessary and increases building fuel

expenses. Moreover, if residents find it too hot, they may open windows, which further 

exacerbates the problem. 

Reducing overheating improves occupant comfort. However, different habits and preferences 

cannot all be accounted for, and some dissatisfaction may occur. Reducing overheating should 

result in a reduction of energy use, and thus a reduction on the load on the heating system, 

increasing the equipment’s lifetime (Energystar.gov, 2013). Quantitatively understanding the 

heating patterns in multifamily buildings can assist owners in complying with local minimum 

heat ordinances and can spur owners to take action to reduce the problem. Furthermore, if it can 

be proven that a heating plant’s output can be reduced as a result of curing overheating problems, 

then when heating plants are replaced, smaller systems can be installed.

In this report, we address the following research questions: (1) what is the magnitude of

apartment overheating in multifamily buildings with central hot water or steam heat; and (2) 

what drives variation in overheating and by how much, with respect to heating system type and 

apartment location. Data have also been tabulated separately for periods when the energy 

management system (EMS) software was actively managing the energy consumption of the 

building versus when the EMS was only monitoring the temperature. These results are also 

compared. 

 3 Note that in New York City where the study buildings are located, local law requires multifamily building 

operators to maintain a minimum daytime (6:00 a.m. to 10:00 p.m.) indoor air temperature of 68°F (when the 

outside temperature is below 55°F) and a minimum nighttime indoor air temperature of 55°F (when the outside 

temperature is below 40°F) (NYC Department of Housing Preservation and Development).
5

3 Research Methods

In order to quantify overheating, data were obtained from the archives of companies that provide 

EMSs to multifamily buildings in the Northeast. EMSs typically include temperature sensors 

located in apartments networked to a central controller that modulates the heating system. In all 

buildings the data were acquired hourly and when boiler status changed. This resulted in a 

typical sampling rate of one to four temperature measurements per hour. Data were collected for

time periods when the EMS control system was disabled and for periods of time when it was

enabled. This procedure enabled us to quantify overheating in these buildings when the EMSs 

were not in operation as well as the effectiveness of the EMSs when they were in operation. Data 

were collected and analyzed for 18 multifamily buildings for deviations from the 70°F 

established above as the desired temperature. Data have been analyzed for enough apartments (a 

minimum of 11%, and an average of 20% per building) so that the data are representative of the 

entire building. Table 1 shows characteristics of the buildings considered in this study. Figure 1

shows one of the buildings in the study.

Table 1. Building Characteristics

No. Number 

of Floors

Total Number 

of Apartments Heating System* Ownership Type

1 3 60 1-pipe steam Rental

2 3 48 Hot water Rental

3 4 36 1-pipe steam Rental

4 4 16 1-pipe steam Rental

5 4 12 1-pipe steam Rental

6 4 39 1-pipe steam Rental

7 5 21 Hot water Rental

8 5 77 1-pipe steam Rental

9 5 77 1-pipe steam Co-op

10 5 202 1-pipe steam Rental/co-op

11 6 71 Hot water Rental

12 6 74 1-pipe steam Rental

13 6 56 Hot water Rental

14 6 48 1-pipe steam Rental

15 6 26 1-pipe steam Rental

16 6 22 1-pipe steam Rental

17 6 34 1-pipe steam Rental

18 6 44 1-pipe steam Rental

* All are single zone with no apartment level controls)
6

Figure 1. Multifamily building used in the study

Researchers visited each building to collect information on boiler type, heater type, exposures, 

sensor locations, and other building characteristics. All apartments were heated with radiators 

(Figure 2).

Figure 2. Typical wireless temperature sensor (left) and radiator (right)

Following is a list of potential uncertainties that could affect the results and how they were 

addressed in the study:

• Data are from buildings with EMSs: Buildings with EMSs may be more efficient (i.e.,

have less overheating) than buildings without such a system due to the function of the EMS 

itself. These systems are sometimes run in passive mode after installation to obtain baseline 

temperature data before actively modulating the heating system, or during periods when the 

controls are overridden by building staff. Data recorded during these periods have been 

analyzed separately and compared to the data recorded during active system management.
7

• Variance in reset controls settings: While the indoor temperature averaging and cutoff 

function of EMSs are not designed to reduce temperature variations within a building, in a 

steam-heated building, its effect on shortening boiler cycles may reduce steam delivery to 

distant apartments in some cases. Also, because the EMSs used in these buildings had 

different outdoor reset control settings than the original outdoor reset boiler controllers, the 

comparison between EMS on and EMS off includes effects of these different control settings.

• Sensor location within building: Most EMSs don’t require temperature sensors to be 

installed in every apartment. The EMS vendors from which the data have been collected 

typically install sensors in top floor apartments so that the building staff can confirm that all 

heating risers are operating properly for the full height of the building. However, a number of 

buildings had sensors on lower floors as well. An analysis of data by floor level shows that 

average temperature was not a function of floor level during the periods observed in these 

buildings. This is presented in more detail later in this report. Sensors located in apartments 

that are a long horizontal distance from the boiler room as well as the overheating of 

apartments directly above the boiler room could also influence these results.

• Sensor location within apartment: The location of the sensor within the apartment should 

be representative of the overall climate in the apartment. Radiation from windows and 

proximity to radiators and ovens can influence local temperatures. Data have been collected 

from buildings where sensors were in a central location distant from these conditions. 

Sensors were typically installed approximately 5 ft above the floor and at least 10 ft away 

from any window or kitchen appliances (Figure 2).

• Local effects: Opening windows to relieve overheating would depress temperatures and 

cause overheating to be underestimated, while local solar gain or the use of space heaters or 

other heat generating devices (electronics) near the sensors would increase apartment 

temperatures, potentially causing overheating to be overestimated. 

• Sensor calibration: Best practices would call for commissioning of new EMSs by 

calibrating each sensor with a hand-held temperature sensor and adding adjustments to each 

sensor reading prior to factoring that reading into the algorithm that controls boiler operation. 

Temperature readings in a sample of units in each building (about 10%) were measured to 

confirm readings were within acceptable limits (± 1°F). In cases where the hand-held sensors 

varied by more than 1°F from the EMS sensor, the EMS data were adjusted (offset) 

accordingly. 
8

Table 2 shows the difference between the temperatures measured by the EMS sensors and a

handheld temperature sensor (TSI, model 8345) at the same time in various apartments of one 

building. The difference in temperature (TSI – EMS) for each apartment was added to all 

temperature data for that location considered in this analysis. In some apartments with EMS 

sensors, TSI temperature readings could not be made because of lack of access. The EMS 

readings in those apartments were adjusted by the average difference in temperature readings 

between the TSI and EMS readings for the other apartments in that building. This approach was 

used for all buildings.

Table 2. Difference Between TSI and EMS Temperature Readings in One Building

Apartments 1 2 3 4 5 6 Average

TSI Temperature Reading 80.3 85.3 84.3 78.4 77.5 84.7 –

EMS Temperature Reading 79 83 81 76 79 82 –

Delta (TSI – EMS) 1.3 2.3 3.3 2.4 –1.5 2.7 1.75
9

4 Results and Discussion

A summary of the data for the 18 buildings is provided in Table 3. The number of floors, sensor 

location by floor, and number of sensors in each building are provided along with average 

temperatures during periods when the EMS is ON and OFF. 

Overheating is significant in nearly every building, even with the use of an EMS. Note that 

minimum temperatures in few buildings were low but for a short duration, perhaps due to open 

windows or vacancies. The average temperature was > 70°F in all the buildings when the EMSs 

were OFF. In 15 of the 18 buildings, average temperatures in all the apartments when EMSs 

were not in operation ranged from 70.7°F to 87.4°F and in three buildings, average temperatures

in more than 88% of apartments ranged from 70.3°F to 85.2°F. Likewise, when the EMSs were 

on, in seven of 18 buildings, average temperatures in all the apartments were > 70°F, ranging 

from 70.3°F to 81.1°F. In the remaining 11 buildings, average temperatures in more than 67% of 

apartments were also > 70°F, ranging from 70.0°F to 81.2°F. The average temperature in 

overheated apartments was > 75°F in 61% of the buildings when EMSs were off and > 75°F in 

33% of the building when EMSs were on.
10

Table 3. Building Summary Data

Building 

Number

Number of

Floors

Number 

of Apartments

Sensor

Location

(by 

Floor)

Number of 

Apartments 

With

Sensors

EMS Status

Range of 

Instantaneous 

Temperature

(°F)

Average 

Temperature in 

All Apartments

(°F)

Apartments

Overheated

(> 70°F)

Average 

Temperature in 

Overheated 

Apartments (°F)

1 3 60 1, 3 16 OFF

ON

59.0–82.0

53.0–85.0

71.8

72.3

88%

94%

72.3

72.5

2 3 48 3 16 OFF

N/A

57.2–90.2

–

76.8

–

100%

–

76.8

–

3 4 36 4 5 OFF

ON

63.4–87.6

66.0–88.4

78.7

77.3

100%

100%

78.7

77.3

4 4 16 3, 4 12 OFF

ON

60.0–91.0

46.0–88.0

73.7

71.3

100%

83%

73.7

72.0

5 4 12 3, 4 3 OFF

ON

69.1–87.1

69.1–95.1

75.5

75.8

100%

100%

75.5

76.1

6 4 39 3 9 OFF

ON

62.0–84.0

59.0–82.0

72.3

70.5

89%

67%

72.7

71.7

7 5 21 4, 5 5

OFF 69.2–83.7 75.5 80% 76.5

ON 65.7–90.2 74.6 100% 74.6

8 6 77 6 9 OFF

ON

65.0–84.0

59.0–83.0

76.2

73.6

100%

89%

76.2

74.2

9 5 77 1, 4 12 OFF

ON

54.0–86.0

61.0–83.0

77.9

75.0

92%

92%

78.5

75.8
11

Building 

Number

Number of

Floors

Number 

of Apartments

Sensor

Location

(by 

Floor)

Number of 

Apartments 

With

Sensors

EMS Status

Range of 

Instantaneous 

Temperature

(°F)

Average 

Temperature in 

All Apartments

(°F)

Apartments

Overheated

(> 70°F)

Average 

Temperature in 

Overheated 

Apartments (°F)

10 5 202 5 20 N/A

ON

–

64.8–82.8

–

76.8

–

100%

–

75.2

11 6 71 6 8 OFF

ON

65.5–87.5

62.5–93.5

74.3

75.9

100%

100%

74.3

75.9

12 6 74 6 10 N/A

ON

–

59.0–83.0

–

72.9

–

80%

–

74.1

13 6 56 6 6 OFF

ON

62.1–100

57.0–91.0

77.7

75.1

100%

83%

77.7

76.8

14 6 48 5, 6 12 OFF

ON

62.8–94.7

48.8–95.7

81.0

75.1

100%

92%

81.0

75.2

15 6 26 2, 3, 4, 5 10 OFF

ON

65.0–88.0

54.0–82.0

76.3

70.6

100%

70%

76.3

72.1

16 6 22 1, 2, 3, 5 13 OFF

ON

59.4–89.6

62.8–95.4

79.7

75.1

100%

100%

79.2

75.0

17 6 34 6 11 OFF

ON

61.0–87.0

55.0–87.0

76.7

75.4

100%

73%

76.6

73.4

18 6 44 1, 2, 3, 

5, 6 15 OFFON

66.5–86.5

63.3–90.5

77.8

75.8

100%

100%

77.6

74.1
12

Table 4 shows the time periods from which the temperature data were gathered for each building. 

The EMSs were turned on and off more than one time in some buildings. Periods of less than 

two days were excluded. The average temperatures in Table 4 are the averages of the average 

apartment temperatures within each building. The maximum, minimum, and standard deviations 

are the averages of those values for all apartments in the respective building. 

Table 4. EMS ON/OFF Time Periods by Building 

Bldg.

No.

EMS

Status Time Periods No. Days Average Max Min Std.Dev.

1 ON

OFF

10/27/2011 to 04/30/2012

10/06/2011 to 10/27/2011

186

21

72.3

71.8

79.4

76.3

65.1

68.1

2.0

1.7

2 ON

OFF

–

01/22/12 to 04/30/2012

0

99

–

76.8

–

87.6

–

65.7

–

3.1

3

ON

OFF

10/02/2011 to 02/09/2012

and 03/12/2012 to 

04/30/2012

02/09/2012 to 03/12/2012

179

32

77.3

78.7

85.1

84.7

68.7

68.8

2.5

3.0

4 ON

OFF

11/17/2011 to 04/21/2012

04/22/2012 to 04/28/2012

156

6

71.3

73.7

83.4

84.8

60.8

60.3

2.8

4.7

5 ON

OFF

03/02/2012 to 05/04/2012

02/26/2012 to 03/02/2012

63

5

75.8

75.5

84.4

82.1

66.1

70.8

2.8

2.5

6 ON

OFF

10/31/2011 to 04/30/2012

10/21/2011 to 10/31/2011

182

10

70.5

72.3

79.3

80.7

62.2

65.3

2.1

3.7

7 ON

OFF

01/31/2012 to 04/30/2012

01/28/2012 to 01/30/2012

90

2

74.6

75.5

87.1

78.9

67.1

72.9

2.3

1.5

8 ON

OFF

03/24/2012 to 04/30/2012

02/11/2012 to 03/19/2012

37

37

73.5

76.2

80.2

81.4

67.9

68.8

2.0

2.4

9 ON

OFF

01/25/2011 to 04/23/2011

12/19/2010 to 01/25/2011

88

37

75.0

77.9

81.9

83.8

68.6

71.1

1.9

2.3

10 ON

OFF

03/05/2012 to 04/18/2012

–

44

–

76.8

–

79.9

–

69.5

–

1.9

–

11 ON

OFF

03/03/2012 to 04/30/2012

02/27/2012 to 03/02/2012

58

4

75.9

74.3

85.9

79.2

69.0

70.2

2.7

1.9

12 ON

OFF

12/01/2011 to 03/31/2012

–

121

–

72.9

–

78.8

–

65.9

–

1.7

–

13 ON

OFF

12/27/2011 to 01/04/2012

01/04/2012 to 04/30/2012

8

117

75.1

77.8

84.8

94.3

66.8

65.7

4.0

4.4
13

Bldg.

No.

EMS

Status Time Periods No. Days Average Max Min Std.Dev.

14 ON

OFF

01/17/2012 to 03/31/2012

01/10/2012 to 01/17/2012

74

7

75.1

81.0

81.9

87.2

66.6

70.6

2.6

4.0

15 ON

OFF

12/01/2011 to 01/26/2012

01/27/2012 to 02/03/2012

56

7

70.6

76.3

77.2

82.0

64.2

69.6

1.9

3.2

16 ON

OFF

01/18/2012 to 04/30/2012

01/03/2012 to 01/18/2012

103

15

75.1

79.7

85.5

86.5

65.9

71.4

2.6

3.0

17

ON

OFF

12/01/2011 to 02/02/2012

and 02/22/2012 to 

04/30/2012

02/02/2012 to 02/22/2012

131

20

75.4

76.7

83.7

84.5

67.4

65.9

2.9

3.6

18

ON

12/01/2011 to 01/10/2012 

and 02/11/2012 to 

04/30/2012

119 75.8 83.9 67.8 2.9

OFF

02/05/2012 to 02/10/2012 

and 01/11/2012 to 

01/17/2012

11 78.0 82.1 72.5 2.2

Figure 3 through Figure 5 show data from a typical building (building 15) in the study for

January and February 2012. The figures show the variations of indoor air temperature, average 

indoor air temperatures, and the variations of indoor air temperatures as functions of outdoor air 

temperature. For nearly the entire time and for a wide range of outdoor air temperatures, indoor 

air temperatures in all apartments were > 70°F. Likewise, the average indoor air temperatures in 

all apartments for this period were > 70°F.
14

Figure 3. Building 15 indoor air temperatures and outdoor air temperature with EMS off

Figure 4. Building 15 average indoor air temperatures during the 2011–2012 heating season
15

Figure 5. Building 15 indoor air temperature as a function of outdoor air temperature

(2010–2011 heating season)

Note that the temperature data presented in Figure 3 and Figure 4 represent temperatures in the 

buildings for only a portion of the 2011–2012 winter because the EMS was installed partway 

through the heating season. The green line in Figure 4 shows the desired indoor air temperature 

of 70°F. As can be seen in Table 3 and Figure 3, average space temperatures in all the buildings 

were significantly higher than desired space temperatures, especially when the EMSs were 

disabled.

In this building, the sensors were located in 10 different apartments on various floors. The 

average temperatures in all the apartments were > 70°F, ranging from 73.8°F to 79.6°F (average

of 76.3°F). Apartments located on the fourth floor were overheated the most (Figure 4). The 

average temperature of the top floor apartments was 75.0°F, which was lower than the average 

temperature of the entire building. 

It can also be seen in Figure 5 that indoor temperature increases as outdoor air temperature 

decreases. Histograms are presented in the appendix showing the impact of outdoor temperature 

on the apartment temperatures when the EMSs were off in these buildings (Figure 29 to Figure 

45). It can be noted in these graphs that for some buildings the average building temperature 

increased with increasing outdoor temperature; for some the average building temperature 

decreased with increasing outdoor temperature; and for others the average building temperature 

barely changed with increasing outdoor air temperature. This information may be useful in 

tuning the outdoor reset boiler control parameters for each building.

4.1 Effect of Floor Levels

Temperature variation by floor was examined in four buildings. Figure 4 through Figure 8 show 

average temperature by apartment for apartments on various floors. In these figures average 

temperature is not a function of floor level. These were low-rise buildings and therefore stack 

effect did not play a major role. Based on these results, it is concluded that for buildings in which 
16 

sensors were located only at the top floors, the average of top floor temperature sensors closely 

represents the average temperature of the entire building.

Figure 6. Building 1 average temperatures for apartments on the 

top and bottom floors of a two-story building 

Figure 7. Building 16 average temperatures for apartments on

four floors of a six-story building

(1st digit is floor number)

70

72

74

76

78

80

82

84

1E 1H 2D 2E 2G 3B 3E 3G 3H 3I 5A 5B 5C

Temperature (F)

Apartments
17

Figure 8. Building 18 average temperatures for apartments on 

five floors of a six-story building

4.2 Effect of Building Height on Energy Management System Performance

The effectiveness of the EMS appears to increase with the height of the building. Average 

temperature data were weighted by number of apartments with sensors for steam-heated 

buildings of four and six floors high that have both EMS off and EMS on data (there was only 

one such five-story building and one such three-story building). The temperature differences 

were calculated as follows: average apartment temperature with EMS off minus average 

apartment temperature with EMS on. The weighted average differences by building floor are 

shown in Table 5.

Table 5 Weighted Average Differences by Building Floor EMS on Minus EMS Off

Number of 

Floors

Number of 

Buildings

Weighted Average 

Temperature 

Difference

4 4 1.77

6 6 3.65

4.3 Variation of Indoor Temperature Between Apartments

Figure 3 shows the variations of indoor air temperature in various apartments in building 15 and 

the outdoor air temperatures. It can be seen that for nearly the entire time and for a wide range of 

outdoor air temperatures, indoor air temperatures in all apartments were above 70°F. In this 

building, temperature sensors were located in apartments at four different floors. In all the 

apartments, indoor air temperatures were > 70°F. The appendix shows similar graphs for all 

remaining buildings. The pattern is similar: nearly all apartments are heated to > 70°F for nearly 

the entire time when the EMS is off. However, there is a wide spread of apartment temperatures 

70

72

74

76

78

80

82

84

1D 2G 3C 3E 3G 5A 5C 5D 5E 5F 5G 6A 6C 6E 6G

Temperatures

Apartments
18

with the warmest and coolest apartments being separated by about 10°F on average and the 

coolest apartment being close to 70°F much of the time. This indicates that while there is some 

room to reduce heating building wide, an individual zone (by apartment or by section of 

building) is necessary to achieve the full extent of available savings.

4.4 Effect of Heating System Type

Table 6 shows the effects of different types of heating distribution systems on overheating. Of 

the 18 buildings, four were heated by hot water and the remainder by one-pipe steam. When the 

EMSs were off, the average temperature in the hot water-heated buildings was slightly lower

than that of the steam buildings. When the EMSs were on, the average temperature in the hot 

water buildings was nearly 2°F higher than that of the steam buildings. Table 4 includes only the 

15 buildings for which both EMS on and EMS off data are available. 

Table 6. Variation in Overheating by Heating System Type

Heating 

Type

Number

of 

Buildings

EMS OFF EMS ON

Range Average

T

Average T 

in 

Overheated 

(> 70°F) 

Apartments

Range Average

T

Average T in 

Overheated 

(> 70°F) 

Apartments

Hot 

Water 3 74.3–

77.7 75.9 76.3 74.6–75.9 75.2 76.3

Steam 12 71.8–

81.0 76.6 76.7 70.5–77.3 74.1 74.7

Figure 9 (a and b) compares the overall average indoor temperature of the buildings and average 

indoor temperatures of overheated apartments when the EMSs were off and on. As stated, the 

data were collected for the 2011–2012 winter season except building 9, for which data were

collected from the 2010–2011 season.
19

Figure 9. Comparison between the overall average indoor temperature of the buildings and 

average indoor temperatures of overheated apartments when the EMSs were off and on

Table 6 presents a statistical analysis of the temperature data collected in the buildings. The

average lowest temperature of all apartments was 72.6°F when the EMS was off.

60

65

70

75

80

85

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Average Apartment T (F)

Building Number

(a) 

EMS ON

EMS OFF

All Apartments

60

65

70

75

80

85

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Average Apt Temperature (F)

Building Number 

(b)

EMS ON

EMS OFF

Overheated Apartments
20

Table 7. Statistical Analysis of the Temperature Data 

EMS 

Status

Mean 

T (°F)

Standard 

Deviation

Minimum 

T (°F)

Maximum 

T (°F)

Range 

T (°F)

ON

Overall average T 

in apartments 74.2 2.1 70.5 77.3 6.8

Average T in the 

overheating 

apartments

74.4 1.8 71.7 77.3 5.6

OFF

Overall average T 

in apartments 76.3 2.5 71.8 81 9.2

Average T in the 

overheating 

apartments

76.5 2.6 72.3 81 8.7

Based on a U.S. Department of Energy report (U.S. Department of Energy, 2012), overheating 

results in an increase in annual energy consumption of approximately 1% per °F over the desired 

temperature in a dwelling for each eight hours of the day. In all the buildings studied, the average 

temperatures were well above 70°F, ranging from 75.2°F to 81.0°F. It was also found that most 

apartments’ average temperature during heating operation was well above 70°F. Average 

temperature of all the buildings when the EMS system was off was 76.2°F, whereas when the 

EMS was on, the average temperature of all the buildings was 74.4°F. Based on this analysis, the 

estimated average increase in annual space heating energy cost for these buildings (when the 

EMS is inactive) due to overheating is approximately 18.6% based on 70°F target temperature, 

or 24.6% based on the 68°F legal daytime temperature. In addition, nighttime setback can be 

used, reducing the legally required temperature to 55°F during the night (in New York City), 

possibly increasing savings. Saving assumptions will vary with envelope characteristics and 

climate conditions.

In a year with average winter temperatures, fuel bills for a typical 80–100 unit apartment 

building can run $50,000–$60,000. Therefore, annual overheating waste for this typical building 

and overheating profile is approximately $11,160 based on a desired temperature of 70°F, or

$14,760 based on the legal limit of 68°F.
21 

5 Conclusion

This study presents an analysis of the data collected from multiple buildings to develop 

conclusions on the magnitude of apartment overheating for buildings heated by single-zone 

steam and hot water heating systems. Eighteen sites were selected where EMSs were already 

installed and the data were analyzed for several apartments in each building. 

The primary research question addressed by this report was: What was the observed temperature 

range above comfort level (70°F) for the 18 buildings measured when the EMS was operating 

and when it was inactive, and what is the impact of overheating on operational energy 

consumption? 

The answer to this question is that overheating was found in all 18 buildings. In all 18 buildings, 

average temperature was well above 70°F when the EMSs were not in operation (Table 3). In 15 

of the 18 buildings, average temperatures in all the apartments when EMSs were not in operation 

were 70.7° to 87.4°F and in three buildings, average temperatures in more than 88% of 

apartments ranged from 70.3°F to 85.2°F. Likewise, when the EMSs were on in seven of 18 

buildings, average temperatures in all the apartments were > 70°F, ranging from 70.3°F to 

81.1°F. In the remaining 11 buildings, average temperatures in more than 67% of apartments 

were also > 70°F, ranging from 70.0°F to 81.2°F. 

Based on this analysis, estimated average increase in annual energy cost for these buildings due 

to overheating was approximately 18.6% based on a 70°F target temperature. This does not 

account for potential under- or overestimating of overheating due to occupants opening windows 

to relieve overheating or using space heaters to supplement the central heat.

Nearly all apartments were heated to > 70°F for nearly the entire time when the EMSs were off; 

however, there is a wide variation in temperatures among apartments in the same building. 

Therefore, to achieve the full potential of possible savings, individual zone or apartment control 

would be necessary. 

A secondary research question was whether apartment floor level or heating system type was 

correlated to degree of overheating. No correlation was found with these factors.

Another secondary research question was whether EMSs reduced overheating and average 

apartment temperatures. We found that EMSs did reduce overheating; however, in many 

buildings average indoor temperatures were still > 70°F for much of the time. EMSs were 

slightly more successful in reducing average temperatures in steam-heated buildings than in hot 

water-heated buildings, and in taller buildings compared to shorter buildings. 
22

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25

Appendix: Variations of Indoor Temperatures

The following graphs show the variation of indoor temperature in various apartments in all the 

buildings. Note that the data are truncated when the outdoor temperature > 55°F because that is 

the warm weather boiler shutdown temperature for these buildings.

The histograms show the variation in average indoor temperature with outdoor temperature by 

building, as well as the range in indoor temperature for each outdoor temperature bin. 
26

Figure 10. Building 1 temperatures

20

30

40

50

60

70

80

Jan-12 Jan-12 Feb-12 Feb-12 Feb-12 Mar-12 Mar-12

Temperature (F)

52-1A 52-1C 64-1A 64-1C 65-1A

65-1B 52-3B 52-3C 53-3A 64-3A

64-3B 64-3C 65-3A 65-3B 65-3C

Average Outside Temp. Desired Indoor T
27

Figure 11. Building 2 temperatures

20

30

40

50

60

70

80

90

Jan-12 Feb-12 Feb-12 Feb-12 Mar-12 Mar-12 Mar-12 Apr-12 Apr-12 Apr-12 May-12

Temperature (F)

64-3A 64-3B 64-3C 66-3D 66-3E

66-3F 66-3H 72-3J 72-3K 72-3L

72-3M 72-3N 74-3P 74-3R 74-3S

Average Outside Temp. Desired Indoor T
28

Figure 12. Building 3 temperatures

30

40

50

60

70

80

90

Feb-12 Feb-12 Feb-12 Feb-12 Mar-12 Mar-12 Mar-12

Temperature (F)

4D 4E 4F 4G

4I Average Outside Temp. Desired Indoor T
29

Figure 13. Building 4 temperatures

10

20

30

40

50

60

70

80

90

Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12

Temperature (F)

5A 5B 5F 5G 6A

6B 6C 6D 6E 6F

6G 6H Average Outside Temp. Desired Indoor T
30

Figure 14. Building 5 temperatures

30

40

50

60

70

80

Feb-12 Feb-12 Feb-12 Feb-12 Mar-12 Mar-12 Mar-12

Temperature (F)

3A 3B 4B

Average Outside Temp. Desired Indoor T
31

Figure 15. Building 6 temperatures

30

40

50

60

70

80

Oct-11 Oct-11 Oct-11 Oct-11 Oct-11 Oct-11 Oct-11 Oct-11 Oct-11

Temperature (F)

3A 3B 3C 3D

3E 3F 3G 3H

3I Average Outside Temp. Desired Indoor T
32

Figure 16. Building 7 temperatures

30

40

50

60

70

80

Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12

Temperature (F)

4A 4D 5A

5B 5C Average

Outside Temp. Desired Indoor T
33

Figure 17. Building 8 temperatures

30

40

50

60

70

80

Feb-12 Feb-12 Feb-12 Feb-12 Mar-12 Mar-12

Temperature (F)

6A 6B 6C 6F

6H 6J 6K 6L

6M Average Outside Temp. Desired Indoor T
34

Figure 18. Building 9 temperatures

20

30

40

50

60

70

80

90

Dec-10 Dec-10 Dec-10 Jan-11 Jan-11 Jan-11 Jan-11 Jan-11 Jan-11

Temperature (F)

1U 4A 4B 4C

4F 4H 4J 4K

4L 4M 4N 4O

4R Average Outside Temp. Desired Indoor T
35

Figure 19. Building 10 temperatures

30

40

50

60

70

80

Mar-12 Mar-12 Apr-12 Apr-12 Apr-12 Apr-12 Apr-12

Temperature (F)

A52 A53 A54 A55 A56 B52

B53 B54 B56 C46 C51 C53

C55 C56 C57 D51 D53 D54

D56 D57 Average Outside Temp. Desired Indoor T
36

Figure 20. Building 11 temperatures

30

40

50

60

70

80

90

Feb-12 Feb-12 Feb-12 Feb-12 Feb-12 Mar-12 Mar-12 Mar-12 Mar-12

Temperature (F)

6A 6D 6F 6I

6J 6K 6L 6M

Average Outside Temp. Desired Indoor T
37

Figure 21. Building 12 temperatures

30

40

50

60

70

80

Nov-11 Dec-11 Feb-12 Mar-12 Apr-12

Temperature (F)

6B 6C 6D 6E 6F

6G 6H 6I 6K 6L

6L Average Outside Temp. Desired Indoor T
38

Figure 22. Building 13 temperatures

30

40

50

60

70

80

90

Dec-11 Jan-12 Feb-12 Feb-12 Mar-12 Apr-12 Apr-12 May-12

Temperature (F)

6AB 6BB 6BC

6CC 6CD 6DB

Average Outdoor Air T Desired Indoor T
39

Figure 23. Building 14 temperatures

15

25

35

45

55

65

75

85

95

Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12

Temperature (F)

5A 5B 5F 5G

6A 6B 6C 6D

6E 6F 6G 6H

Average Outside Temp. Desired Indoor T
40

Figure 24. Building 15 temperatures

35

45

55

65

75

85

Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Feb-12 Feb-12 Feb-12 Feb-12

Temperature (F)

2D 3A 4A 4B

4C 4D 5A 5B

5C 5D Average Outside Temp.

Desired Indoor Air T
41

Figure 25. Building 16 temperatures

18

28

38

48

58

68

78

88

Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12

Temperature (F)

1H 2D 2E 2G 3B

3E 3G 3H 3I 5A

5B 5C Average Outside Temp. Desired Indoor T
42

Figure 26. Building 17 temperatures

30

40

50

60

70

80

90

Feb-12 Feb-12 Feb-12 Feb-12 Feb-12

Temperature (F)

6A-774 6A-784 6B-784 6C-774 6C-784

6D-774 6D-784 6E-774 6E-784 6F-774

6G-784 Average Outside Temp. Desired Indoor T
43

Figure 27. Building 18 temperatures

20

30

40

50

60

70

80

90

Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12 Jan-12

Temperature (F)

3G 5A 5C 5D 5E

5F 5G 6C 6E 6G

Average Outside Temp. Desired Indoor T
44

Figure 28. Outdoor air temperature in New York City from June 2011 to May 2012

Figure 29. Indoor air temperature dependence on outdoor air temperature in building 1

0

200

400

600

800

1000

1200

0 20 40 60 80 100 120

Number of Hours

Oudoor Air Temperature (F)

50

60

70

80

90

35-40 40-45 45-50 50-55

Average Building T (F)

Outdoor Air Temperature (F)
45

Figure 30. Indoor air temperature dependence on outdoor air temperature in building 2

Figure 31. Indoor air temperature dependence on outdoor air temperature in building 3

50

60

70

80

90

20-25 26-30 31-35 36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)

50

60

70

80

90

15-20 20-25 26-30 31-35 36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)
46

Figure 32. Indoor air temperature dependence on outdoor air temperature in building 4

Figure 33. Indoor air temperature dependence on outdoor air temperature in building 5

50

60

70

80

90

15-20 20-25 26-30 31-35 36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)

50

60

70

80

90

36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)
47

Figure 34. Indoor air temperature dependence on outdoor air temperature in building 6

Figure 35. Indoor air temperature dependence on outdoor air temperature in building 7

50

60

70

80

90

31-35 36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)

50

60

70

80

90

36-40 41-45 46-50

Average Building T (F)

Outdoor Air Temperature (F)
48

Figure 36. Indoor air temperature dependence on outdoor air temperature in building 8

Figure 37. Indoor air temperature dependence on outdoor air temperature in building 9

50

60

70

80

90

20-25 26-30 31-35 36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)

50

60

70

80

90

10.-15 16-20 21-25 26-30 31-35 36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)
49

Figure 38. Indoor air temperature dependence on outdoor air temperature in building 11

Figure 39. Indoor air temperature dependence on outdoor air temperature in building 13

50

60

70

80

90

36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)

50

60

70

80

90

20-25 26-30 31-35 36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)
50

Figure 40. Indoor air temperature dependence on outdoor air temperature in building 14

Figure 41. Indoor air temperature dependence on outdoor air temperature in building 15

50

60

70

80

90

16-20 21-25 26-30 31-35 36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)

50

60

70

80

90

36-40 41-45 46-50 51-55 56-60 61-65

Temperature (F)

Apartments
51

Figure 42. Indoor air temperature dependence on outdoor air temperature in building 16

Figure 43. Indoor air temperature dependence on outdoor air temperature in building 17

50

60

70

80

90

15-20 20-25 26-30 31-35 36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)

50

60

70

80

90

26-30 31-35 36-40 41-45 46-50 51-55

Average Building T (F)

Outdoor Air Temperature (F)
52

Figure 44. Indoor air temperature dependence on outdoor air temperature in building 18

50

60

70

80

90

20-25 26-30 31-35 36-40 41-45

Average Building T (F)

Outdoor Air Temperature (F)
buildingamerica.gov

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