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NATIONAL BUREAU OF STANDARDS REPORT

8097

PERFORMANCE OF HOT-WATER PANEL HEATING SYSTEMS

IN HIGH-RISE APARTMENTS OF THE CHICAGO HOUSING AUTHORITY

by

Selden D. Cole and Paul R. Achenbach

Report to

Chicago Housing Authority

and

Public Housing Administration

U. S. DEPARTMENT OF COMMERCE

NATIONAL OUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

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Printing Office, Washington, D.C., 20402.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1003-30-10630 October 1, 1963 8097

Performance of Hot-Water Panel Heating Systems

in High-Rise Apartments of the Chicago Housing Authority

by

Selden D. Cole and Paul R. Achenbach

Mechanical Systems Section

Building Research Division

Report to

Chicago Housing Authority

and

Public Housing Administration

NATIONAL BUREAU OF STAN

for use within the Government. Bel and review. For this reason, the pi whole or in part, is not authorizec Bureau of Standards, Washington ; the Report has been specifically pre

IMPORTANT NOTICE

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

iccotrntmg documents intended

jjected to additional evaluation

ting of this Report, either in

iffice of the Director, National

i Government agency for which

es for its own use.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
-
PERFORMANCE OF HOT- WATER PANEL HEATING SYSTEMS

IN HIGH-RISE APARTMENTS OF THE CHICAGO HOUSING AUTHORITY

by

Selden D. Cole and Paul R. Achenbach

ABSTRACT

A field investigation of the performance of the hot-water panel

heating systems in two high-rise apartment developments of the Chicago

Housing Authority was made during a period of cold winter weather to

develop information on the effectiveness of a heated concrete slab at

each level which delivered heat both upward and downward. Of principal interest were the distribution of temperature in the heated panels

and in the living space, the adequacy of the control system and the

exhaust ventilation system, and the effect of apartment location and

room exposure on the thermal environment. The results observed indicated that this type system was able to provide adequate heating for

the Chicago climate, but that the single-zone control system utilizing

an outdoor thermostat did not provide close temperature control in the

several apartments and that most apartments were overheated by varying

amounts ranging up to about 9°F. About equal quantities of heat were

delivered from the floor and ceiling surfaces, and the floor surfaces

operated at a surface temperature in excess of 90°F during cold weather

in some cases. The exhaust ventilation system provided an adequate

amount of fresh air and was sufficient to prevent condensation on the

outside walls. Readjustment of the temperature control system and re- balancing of the room temperatures in the various apartments were

recommended for the existing buildings. A different type of balancing valve would facilitate adjustment of water flow rate in the various tube circuits. A multi-zone control system with a separate outdoor

thermostat and circulating pump for each zone was recommended for

future construction, with the outdoor thermostat designed to sense

solar radiation and wind effects as well as temperature effects. The

control system in the existing buildings could also be modified for

multi- zone control to improve temperature distribution among the various apartments, but the modifications would be quite expensive and

would be only partially effective in the Frances Cabrini Extension

Project because of the design of the individual heating circuits.

Regular cleaning of the exhaust ventilation grilles and a re-balancing

of the ventilation rate among apartments was also recommended.

PERFORMANCE OF HOT-WATER PANEL HEATING SYSTEMS

IN HIGH-RISE APARTMENTS OF THE CHICAGO HOUSING AUTHORITY

by

Selden D. Cole and Paul R. Achenbach

1.0 Introduction

The Chicago Housing Authority constructs and operates a large number

of high-rise apartment buildings for low-income families in metropolitan

Chicago. Extensive use has been made of hot water panel heating systems

in these apartment buildings with the heat being distributed from central

heating plants. Records of fuel consumption over a period of three years

indicate that some of the lower values of annual fuel consumption per

room have occurred in buildings with this type of heating system.

At the request of the Chicago Housing Authority and the Public Housing

Administration in Washington, a limited field investigation of the performance of the hot water panel heating systems in two high-rise apartment

developments in Chicago was made during a period of cold weather in February 1963. The William Green Project together with the Frances Cabrini

Extension Project were chosen for the investigation because they provided

buildings of different orientation near to each other, and because the

performance of heating systems in apartments near the middle of the buildings could be compared with that of end apartments exposed to the prevailing wind.

The broad purposes of the investigation were as follows:

(a) To evaluate the internal thermal environment for a range of outdoor

temperature

,

(b) To measure the panel temperatures and water temperatures for a range

of outdoor temperature,

(c) To investigate the adequacy of the control system,

(d) To indicate the adequacy of the ventilation with respect to condensation control,

(e) To investigate the effect of apartment location in the building and

building orientation on the thermal environment,

(f) To indicate possible improvements in operating economy and control of

the interior thermal environment in these apartments, and

(g) To evaluate the suitability of hot-water panel heating systems for

future apartment buildings for similar occupancy or for the aged.

The investigation comprised measurements of air temperatures at

several levels between floor and ceiling, indoor relative humidity, floor

and ceiling surface temperatures in the areas containing embedded hot

water tubes, wall surface temperatures on the exposed walls, unheated

globe- thermometer temperatures, the quantity of air exhausted from the

apartment through the bathroom, the temperatures of the supply and return

water in the apartment, and the outdoor temperature.

- 1

-
2.1 Description of Buildings and Apartments

Two apartment buildings were selected for detailed measurements:

one at 1160 Sedgwick Street in the Frances Cabrini Extension Project,

and the other at 1230 N. Larrabee Road in the William Green Project.

The longer dimension of both buildings was oriented in a north- south

direction. The two buildings were approximately 1200 feet apart.

The building selected from the William Green Project was one of

five buildings of identical construction, each fifteen stories in height.

The buildings were of reinforced concrete column and beam construction

with a 7 1/2-inch reinforced concrete floor at each story. The outside

curtain walls, front and back, consisted of insulating concrete spandrels 3' 10" high and 8" thick, with 4-foot high windows the entire width

of the exposed back wall, and 3'1" high windows the entire width of the

exposed front wall. The front wall had a poured concrete wall section

about 8 inches in height above the windows, made as an integral part of the

ceiling construction above. The ceiling height was 7' 10". The end

walls consisted of reinforced concrete ranging in thickness from 10

inches at the first floor to 6 inches at the top floor, backed up by

varying thicknesses of concrete block to comprise a total wall thickness

of 12 inches. There were 134 apartments in the building investigated.

The building selected from the Frances Cabrini Extension Project

was one of six buildings of identical construction, each nineteen stories in height. The buildings were of reinforced concrete column and

beam construction with a 6-inch reinforced concrete floor at each story.

The outside curtain walls consisted of 4 inches of brick on the outside

separated by a 2-inch air space from 4-inch concrete block on the inside. Weep holes were provided in the brick masonry at 3-foot spacings.

Windows, 4’ 3" high, were used in the front and back walls. There were

262 apartments in the building investigated.

All interior partitions in both buildings were made of 4-inch concrete blocks, and asphalt tile was used as floor coverings in all buildings. The interior surfaces of the walls and the ceilings were covered

with latex paint.

The apartments were accessible from outside galleries at each floor

level. One exterior elevator serviced the even-numbered stories and

another the odd-numbered stories. Two interior unheated stairways serviced all of the galleries.

Each apartment consisted of living room, dining room, kitchen,

bathroom, storage room, hallway, and from one to five bedrooms. In

some cases, the kitchen and dining area were integrated and in others

- 2-
the kitchen, dining area, and living room were an integrated space with

only partial partitions between the different functional areas. All

bathrooms were interior rooms ventilated by a central exhaust blower on

the roof.

One apartment was selected at about mid- length of each building

and near midheight, and a corner apartment was selected on the end of

each building at another floor level. Each center apartment had outside exposures principally on opposite sides of the building.

One corner apartment had exposures principally on adjacent sides

of the building, and the other corner apartment had significant exposure in four directions. Descriptive data on the location, size, number

of rooms, and heat transmission characteristics of each of the four

apartments investigated are summarized in Table 1.

-3

-
TABLE 1 Description of Four Apartments Investigated

Frances Cabrini

Extension Project William Green Project

Descriptive Item 1160 Sedgwick St. 1230 N. Larrabee Road

Apartment Number 707 1405 601 906

Floor Level 7 14 6 9

Location in Building Corner of

West Wing

Center East WingSouth End

Center

Exposures North, West

& East

East, West

& South

North, South

,

East & West

East &

West

Floor Area, ft^ 710 720 818 734

Exterior Wall Area, net, ft^ 407 302 584 174

o Window & Door Area, ft^ 124 140 176 188

Ceiling Height, ft 7.83 7.83 7.83 7.83

Number of Bedrooms 3 2 3 2

Integrated Spaces Kitchen, LR

& DR

Kitchen, LR

& DR

Kitchen, LR

& DR

Kitchen,

Dining Room

Observed Exhaust Ventilation Rate,

Air Changes per Hour

1.47 3.19 0.75 0.89

a/ Computed Design Unit Heat Loss,—'

Btu/hr (ft^ floor area)

46.8 66.0 43.4 39.4

Computed Design Unit Heat Loss,—

Btu/hr (ft^ floor area)

41.4 41.3 46.2 40.9

Computed Unit Heat Loss,—

/

416 595 444 362

Btu/hr (°F temp, diff.)

a / —Based on observed exhaust ventilation rate.

—^Based on an infiltration rate of 1 air change per hour.

- 4

-
2.2 Description of Heating Systems

The William Green and Frances Cabrini Extension Projects were both

supplied with heat from the same central heating plant. The heating

plant contained five boilers fired with oil or gas, and four boilers

operating on oil alone connected in parallel to furnish low temperature

hot water to the underground heat distribution system. Boilers were

fired up manually in sequence as needed to maintain a predetermined re- lation between the supply water temperature and the outdoor temperature

Each boiler could be operated at a low or high firing condition.

Each apartment building was equipped with a shell -and- tube heat

exchanger in the basement. The boiler water was circulated through the

primary side of the heat exchanger and two pumps circulated water

through the secondary side of the heat exchanger and the various apartments in the building. A bypass line was provided between the supply

and return lines on the secondary side of the heat exchanger. This

bypass line was fitted with a modulating three-way valve whose position

was controlled by an outdoor thermostat mounted on a shaded wall of the

exterior elevator shaft on each building. The modulating control system was preset to vary the temperature of the water supplied to the

apartments in the building in a fixed relation to the outdoor temperature .

The heating system in both projects consisted of copper tubes em- bedded in the concrete slabs between floor levels. The tubes were

placed underneath the reinforcing bars and located 2 inches above the

ceiling surface. The heating system for each apartment consisted of

several tube circuits in parallel. Each parallel tube circuit contained a plug-type valve which was used to provide initial adjustment

of the heat supplied to the various rooms and the various apartments.

However, since each apartment was partially heated from the floor and

partially from the ceiling, an independent adjustment of water flow

and heat output could not be made for each apartment.

In the William Green Project the heating tubes were spaced 18

inches apart for a distance of 9 feet from the exterior perimeter of

the building, with the first tube about 6 inches from the exterior wall

There were no heating tubes in the central area of each apartment ex- cept for the supply and return lines which connected to risers near

the centerline of the building.

In the Frances Cabrini Extension Project the heating tubes were

distributed over the entire apartment area. Generally, the tubes in

the dining room and kitchen and in an exterior border 54 inches wide

in the living room were spaced 6 inches apart, whereas the tubes were

- 5-
12 inches apart for the rest of the ceiling area in the living room.

The tube spacing in the bedroom with two exposures was 12 inches. In

one of the bedrooms with one exposure the spacing ranged from 12 to

24 inches, and in the other it ranged from 12 to 30 inches. In each

apartment, regardless of size, a perimeter tube circuit was spaced

three inches from the enclosing outside walls.

3.0 Test Equipment and Procedure

Temperatures were determined in each of the four apartments using

thermocouples made of thirty-gage copper and constantan wire, a Rubicon

portable potentiometer, and an ice bath. An unheated 8-inch black globe

was used to investigate the mean radiant temperature. The rate of air

exhaust through the bathroom grilles was measured with a vane-type anemometer and stop watch. The wet- and dry-bulb temperatures were determined with a sling psychrometer

.

In each apartment, temperature values were recorded at twenty to

thirty different stations. These stations were similarly located in

the living room of each of the four apartments investigated, as follows:

(1) six stations on the ceiling, along a line perpendicular to the outside wall toward the center of the room and placed alternately underneath the tubes and between the tubes; (2) four stations on the floor

located exactly below the four nearest to the exterior wall on the ceiling; (3) three stations in the air at room center, located 3 inches from

the floor, 30 inches from the floor, and 3 inches from the ceiling, respectively; (4) a black globe 30 inches from the floor and adjacent to

the station at room center thirty inches above the floor; (5) a position

on the exterior wall between floor and window in the living room, usually

30 inches above the floor; (6) a station on the supply manifold tube

for the several heating circuits; and (7) a station on the return manifold tube for the several heating circuits.

Thermocouples were placed at corresponding locations on the ceiling, floor, exterior wall, and in the air in one of the bedrooms in each

apartment. Temperatures were observed at one or two miscellaneous stations in some of the apartments.

The positions for the thermocouple stations on the ceiling were

determined by exploring the ceiling surface temperature at close intervals with a thermocouple and pyrometer. The high temperature spots indicated the location of the tubes and the low temperature spots indicated

the midpoint between the tubes. This exploration indicated that the tubes

were not always located in accordance with the drawings.

Temperature readings were taken in each of the four apartments in

the forenoon and sometime in the late afternoon. Each one of the twenty

to thirty thermocouple indications in each apartment was obtained with

- 6-
the poteniometer and recorded. The living room thermocouple used to

measure air temperature 3 inches from the floor was inserted in the

black globe immediately upon entering the apartment for a set of readings, inasmuch as the globe was transported from unit to unit and

required time to come to room temperature conditions. After reading

the globe temperature, the thermocouple was returned to its position

3 inches above the floor and observed as the last reading of the group.

During several of the visits to the different apartments, the wet- and

dry-bulb temperatures were determined in the living room and recorded,

before the thermocouple readings were obtained.

Wet- and dry-bulb temperatures were obtained in several apartments

in one of the buildings in the William Green Project that was not instrumented with thermocouples. Temperatures were taken on the fifteenth

floor, the seventh floor, and on the ground floor in two apartments on

each floor; one unit near the center of the building and one unit at

the end of the building. Wet- and dry-bulb temperatures were also re- corded in several apartments in the buildings at 1160 Sedgwick Street

and 1230 N. Larrabee Road other than the four principal apartments

under investigation.

A short duct, about 8 inches long, was fitted over the bathroom

exhaust grilles to improve the conditions for measuring the air flow

rate through these grilles. A vane-type anemometer was placed in each

of several increments of area inside these ducts to obtain an average

air flow rate. Readings were taken with interior doors open and shut,

and with some windows open and all windows closed to evaluate the

effect of these restrictions on the exhaust air flow rate.

4.0 Results and Discussion

Figure 1 is a graph of the outdoor temperatures that occurred during the time of the investigation based on hourly weather data reported

for Chicago. Except for the first day, when but one apartment had been

instrumented, the outdoor temperature did not rise above 25 °F, and at

three different times fell below zero. Figure 1 shows that the outdoor

temperature decreased from 35°F to -6°F in about 38 hours from 6:00 p.m

on February 19 to 8:00 a.m. on February 21. Thereafter the diurnal tem

perature change was in the range from 10 to 20 degrees in most instances. The average rate of change of outdoor temperature was less

than 1 degree per hour during the 40 hours from 3:00 p.m. on February

24 to 7:00 a.m. on February 26, and was in excess of 7 degrees per hour

during the two hours from 7:00 a.m. to 9:00 a.m. on February 23. The

changes in outdoor temperature were great enough to require manual adjustments in Supply water temperature at the heating plant and to cause

automatic change in the supply water temperature for the several apartments.

- 7-
During most of the period of observation the prevailing winds came

from the west or northwest with velocities ranging from 10 to 25 mph.

However, on February 23 and 27 the prevailing winds were southerly in

direction, but in the same velocity range.

The temperatures observed on ceiling, floor, and wall surfaces,

on the supply and return headers to the tube circuits, and at selected

levels in the air at the center of the living room and one bedroom of

the four apartments are summarized in Tables 2-5, inclusive, for the

duration of the field study. The data from two apartments in the

building at 1230 N. Larrabee Road in the William Green Project are

shown in Tables 2 and 3, and the data for two apartments in the building at 1160 Sedgwick Street in the Frances Cabrini Extension Project

are shown in Tables 4 and 5.

Only apartment 906 at 1230 N. Larrabee Road had been instrumented

in time to show the effect of the long steady decline in outdoor temperature from February 19 to February 21 on the indoor temperatures

and the heating system temperatures. Table 2 shows that a decrease in

outdoor temperature from 35°F at 5:00 p.m. on February 19 to -5°F at

9:15 a.m. on February 21 caused the following temperature changes in

apartment 906:

(a) a rise in supply water temperature from 113°F to 144°F,

(b) a rise in return water temperature from 101°F to 119°F,

(c) a rise in ceiling surface temperature underneath the tubes in the

living room from 100°F to 117°F, and only a small change in ceiling

surface temperature between tube centers,

(d) a decrease in air temperature at the 30-inch level in the living

room from 83°F to 78°F,

(e) a decrease in exterior wall surface temperature 30 inches above the

floor in the living room from 67°F to 54°F,

(f) changes in the ceiling surface temperatures in the bedroom similar

to those in the living room,

(g) decreases in the air temperature at the 30-inch level and of the

exterior wall surface temperature in the bedroom nearly twice as great as those observed in the living room. The lower wall temperature and more variable air temperature in the bedroom may have

been caused by the prevailing westerly winds to which the exterior

wall was exposed, and

(h) the floor surface temperatures changed much less in both rooms than

the ceiling surface temperatures. The temperatures on the floor

were higher at the stations identified as being between tubes than

at those over the tubes. This suggests that the tube locations

were not the same distances from the exterior wall in the floor and

ceiling of this particular apartment, and that the identification

of the tube locations in the floor was inaccurate.

- 8-
Assuming that the outdoor thermostat on this building modulated the

supply water temperature in an inverse linear relation to the outdoor

temperature in accordance with the design concept employed, the supply

water temperature would range from 90°F to 148°F for a range of outdoor

temperature from 65°F to -10°F, based on the observed data cited above.

The temperature data observed in apartment 906 from 8:45 a.m. on

September 22 to 9:40 a.m. on September 26 were taken either between 8:45

a.m. and 9:40 a.m. during a steep rise in outdoor temperature two or three hours after the daily minimum, or in the late afternoon a few

hours after the daily maximum. The outdoor temperature ranged from 0°F

to 16°F at the times of these observations. Thus the temperatures observed inside the apartment are not representative of a steady state

heat transfer or temperature distribution. During the entire period of

observation in this apartment, the air temperature at the 30-inch level

in the living room ranged from 78°F to 83°F, whereas the corresponding

temperature in the bedroom ranged from 71°F to 83°F. With a few exceptions, the temperature of the unheated black globe was 2 to 3 degrees

higher than the air temperature at the 30-inch level in the living room.

This indicates a substantial impingement of radiant heat on the globe,

and a mean radiant temperature 3 to 4 degrees above the air temperature.

Intermittent measurements of the wet-bulb and dry-bulb temperatures

in apartment 906 showed that the interior relative humidity ranged from

17 to 31 percent during the period of observation. Thus, the effective

temperature in the living room ranged from about 74°F on February 19 to

about 69 °F on February 26, based on dry-bulb temperature and relative

humidity only. If the mean radiant temperature in the living room is

taken into account, the effective temperatures would be 3 to 4 degrees

higher than the above values, based on data reported in the 1961 ASHRAE

Guide and Data Book. Thus, the effective temperature in the living room

of apartment 906 was probably in the range from 72°F to 78°F, whereas

the generally accepted value for optimum winter comfort is about 68 °F.

The data in Table 2 taken after 10:00 a.m. on February 20 indicate

that the surface temperature of the heated portion of the floor averaged

about 15 degrees higher than the air temperature 3 inches above the

floor in the living room, whereas the corresponding temperature difference in the bedroom was about 9 degrees. Thus, the floor panel output

in the living room was about 29 Btu/hr(ft^), whereas that for the bedroom was about 17 Btu/hr(ft2) based on data reported in the ASHRAE Guide

and Data Book. For the same period, the surface temperature of the

heated portion of the ceiling averaged about 22 degrees higher than the

air temperature at the 30-inch level in the living room, whereas the

corresponding temperature difference was about 24 degrees in the bedroom.

Thus, the gross ceiling panel output in the living room was about

22 Btu/hr(ft2), whereas that for the bedroom was about 24 Btu/hr(ft^)

based on data reported in the ASHRAE Guide and Data Book.

- 9

-
SUMMARY

OF

OBSERVATIONS

Apartment

906-

1230

N.

Larrabee

Road

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Based

on

Dry-Bulb

Temperature

and

Relative

Humidity

Only.
For the average of the conditions observed in apartment 906 between

5:00 p.m. on February 20 and 9:40 a.m. on February 26, the difference in

temperature between indoor air at the 30-inch level and the outdoors was

71 degrees F. Based on the materials of construction shown in the blueprints for the William Green Project, the corresponding calculated heat

loss would be 25,700 Btu/hr. On the assumption that the results in the

one bedroom represented the performance of the three rooms with a west

exposure, and that the results in the living room represented the performance of the room with an east exposure, the calculated combined heat

output of the floor and ceiling panels was about 23,400 Btu/hr with the

heat output of the ceiling panels comprising about 53% of the total.

Apartment 601 in the building at 1230 N. Larrabee Road had its

principal exposure toward the east with lesser areas of exterior wall

facing north, south, and west. Temperatures were measured on the floor

and ceiling panels along lines perpendicular to the east wall in the

living room and to the south wall in one of the bedrooms. The temperature data from this apartment are summarized in Table 3.

A comparison of the data in Tables 2 and 3 shows that the supply

and return water temperatures were nearly the same in the two apartments

for corresponding times of observation. The ceiling surface temperatures

over tube centers were about 4 degrees cooler in apartment 601 than for

apartment 906 for both living room and bedroom. This could have been

caused by a greater thermal resistance in the materials covering the

tubes in apartment 601, or it may have been the result of having two ex- terior walls in each of the rooms in apartment 601 as compared to one

exterior wall in each room in apartment 906. The room air temperature

at the 30-inch level in the living room varied only 3.3 degrees F during

the observation period with an average of 82.3°F. The corresponding

variation in temperature and average temperature in the bedroom were

7.7 degrees F and 79.9 degrees F, respectively, during the same period.

The wall temperature 30 inches above the floor was much lower in

the living room than in the bedroom. Since the heat transmission factors

of the two walls were approximately equal, both were exposed to sunshine

from the outside at different times of the day, and neither faced the

prevailing wind; these factors probably do not account for the average

difference in temperature of about 13 degrees. The wall thermocouple in

the living room was located about 16 inches below the sill of the window

directly above, whereas the corresponding station on the south wall was

not beneath a window. It is probable that the cold air falling from the

window surface above caused the low wall temperatures in the living room.

- 11 -
The temperature of a window pane in the east wall of the living

room was measured with a thermocouple secured to the glass with transparent cellophane tape. The temperature of the window pane approximated

the midpoint value between indoor and outdoor temperature, but was

usually a few degrees lower than the midpoint value. It will be noted

in Table 3 that the dewpoint temperature of the air in the living room

was several degrees above the window pane temperature for each observation of the relative humidity in the apartment. This accounts for the

frequent sweating of the living room windows. However, the dewpoint

temperature was always a few degrees below the wall surface temperature

at the 30-inch level in the living room, thus precluding sweating of

the wall at this station of measurement. The occupants of this apartment did considerable cooking on the gas range during the day which

probably accounts for the somewhat higher dewpoint.

The unheated globe thermometer temperature was higher than the air

temperature at the 30-inch level in the living room by amounts ranging

from 1 to 4 degrees in all but two cases. This indicates that the mean

radiant temperature at this station exceeded the air temperature by

somewhat greater margins and that the probable effective temperature

in the living room of apartment 601 was also in the range from 72°F to

78°F.

The data in Table 3 for apartment 601 indicate that the surface

temperature of the heated portion of the floor averaged 9 degrees higher

than the air temperature 3 inches above the floor in the living room,

whereas the corresponding temperature difference in the bedroom was 5.6

degrees. Thus, the floor panel output in the living room was about 17.5

Btu/hr(ft^), whereas that for the bedroom was about 9.5 Btu/hr(ft2)

based on data reported in the ASHRAE Guide and Data Book. For the same

period, the surface temperature of the heated portion of the ceiling

averaged about 17.8 degrees higher than the air temperature at the 30-

inch level in the living room, whereas the corresp 9nding temperature

difference in the bedroom was 18.4 degrees. Thus, 'the ceiling panel

output in the living room was determined to be about 19.5 Btu/hr(ft2)

including the effect of infiltration, and that in the bedroom was

determined to be 18 Btu/hr(ft^) without adjustment for infiltration.

Since someone slept during the day in the bedroom selected for

temperature measurement, the door to this room was closed during the

day. Thus, it was assumed that the ventilation air exhausted through

the bathroom grille had little opportunity to affect the heat transfer

in that room. Assuming that the heat transfer rates determined for the

bedroom apply only to the bedroom and that those determined for the

living room apply to all the remainder of the 710 sq ft of heated panel,

the combined heat transfer of the floor and ceiling panels in the apartment was calculated to be about 25,000 Btu/hr during the period of

- 12 -
Date

and

Time

of

Observation

Feb.

20

Feb.

20

Feb.

21

Feb.

21

Feb.

22

Feb.

22

Feb.

23

Feb.

25

Feb.

26

Feb.

27

Observation

Station

11:05AM

5:30PM

8:45AM

5:35PM

8:45AM

7:00FM

9:00AM

2:10FM

9:15AM

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QJ QJ CQ O - 13 '-

CO ©

Based

on

Dry-Bulb

Temperature

and

Relative

Humidity

Only
observation. The computed heat loss of the apartment based on the materials of construction shown in the blueprints and the averaged observed

temperature difference between inside and outside was about 32,000 Btu/hr

A comparison of the results summarized in Tables 4 and 5 for the

two apartments in the building at 1160 Sedgwick Street in the Frances

Cabrini Extension Project with those already discussed in Tables 2 and 3

indicates the following conclusions for the observation period from February 22 to February 26:

(a) The supply water temperature was about 20 degrees F lower for the

building at 1160 Sedgwick Street.

(b) The temperature decrease between supply and return water was considerably lower in the building at 1160 Sedgwick Street.

(c) The average ceiling surface temperatures under the four tube circuits nearest the outside wall were only slightly lower in the

building at 1160 Sedgwick Street, perhaps because the tube spacing

was closer in the building at 1160 Sedgwick Street.

(d) The air temperatures at the 30-inch level in apartment 707 were 5

to 6 degrees lower and those in apartment 1405 about 2 degrees

lower than those observed at the corresponding stations in apartments 601 and 906 in the building at 1230 N. Larrabee Road of the

William Green Project. However, some windows were partly opened

in apartment 707 at the time of observation on February 23, 25,

and 26, which may account for the lower air temperatures.

(e) Despite a measured exhaust ventilation rate in excess of 3 air

changes per hour in apartment 1405, the relative humidity was a little higher than that in apartment 707, and was quite comparable

with that in apartments 601 and 906 having much lower ventilation

rates

.

(f) Except for the conditions on February 25 and 26 in apartment 707

when some windows were partly open, the effective temperatures in

the living room were only slightly lower in the building at 1160

Sedgwick Street than in the building at 1230 N. Larrabee Road.

The ceiling and floor surface temperatures observed in the two

apartments at 1160 Sedgwick Street do not serve as a good basis for computing the total panel output because: (1) the thermocouple stations

covered only a part of the heated panel in the two rooms used for observation, (2) the tube spacing was not constant in some of the rooms,

and (3) the tube spacing was different in the various rooms. Consequently, no comparisons are made between calculated panel heat output

and computed heat loss.

The range of temperatures observed in the four apartments instrumented with thermocouples are summarized in Table 6 for the period

between February 22 and February 26 when observations were being taken

- 14-
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Measured

18

inches

from

exterior

wall

Based

on

dry-bulb

temperature

and

relative

humidity

only

On

ceiling

surface

On

floor

surface
SUMMARY

OF

OBSERVATIONS

Apartment

1405-

1160

Sedgwick

Street co

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ft a O Eh C/3 CD CD •H 4-1 CD •H Pi H H H <D 4-1 O 0 H W rH £ • O • i-M 43 CO CD 5 C •H 60 O - 60 «-l Pi P4 Pi O pH mm o Pi •H a> > rH > CO •H •H rH CD mm Pi •H » z > CJ < Eh <c £2 < < < o ft ft TO < •H CD J ft & ft a a ft

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rH rH Pi H

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CO 43

Measured

at

room

center

Based

on

dry-bulb

temperature

and

relative

humidity

only
at all four locations. It should be noted that an equal range of temperatures in two apartments does not necessarily indicate equal averages

in the two cases. Table 6 provides a ready comparison of data in various apartments, but it does not cover a very wide range of outdoor temperatures . Wet-bulb and dry-bulb temperatures were observed in a number of

additional apartments to obtain a broader picture of dry-bulb temperature and relative humidity levels than was afforded by the detailed

instrumentation of four apartments. These wet-bulb and dry-bulb temperatures and the corresponding values of relative humidity are summarized in Table 7 together with the outdoor temperature at the time of

observation. It will be noted that the relative humidity was below 20

%

in seven apartments, was between 20 and 30% in seven apartments, and

exceeded 30% in only one apartment. The corresponding dewpoint temperatures ranged from 27°F to 48°F. An exterior wall temperature of 43°F

was observed in apartment 906 on February 21 when the outdoor temperature

was -5°F, but the dewpoint was lower than 43°F during this period. The

lowest wall temperatures were observed beneath windows where the cold

downdraft from the window cooled the wall. At the same time this stream

of cool air would have been in contact with the cold window surface and

thereby dehumidified somewhat in marginal situations. Whereas, it appears

that condensation could be produced on the exterior walls in these apartments by excessive use of the kitchen range for boiling liquids, none

was observed during the tests, and the likelihood of any serious condensation problems seemed small.

Table 7 shows that the dry-bulb temperature in the building at 624

West Division Street ranged from 79°F in apartment 1505 to 84°F in apartment 1510 for an outdoor temperature of 15°F. In six apartments in the

building at 1160 Sedgwick Street the dry-bulb temperature varied from

75°F to 80.5°F and in three apartments in the building at 1230 N. Larrabee

Road the dry-bulb temperature varied from 79 °F to 83°F at outdoor temperatures in the range from I0°F to 17° F. The low and high values of room

temperature do not appear to be associated with particular locations in

the buildings, or With particular exposures of the rooms in which the

measurements were made.

The effective temperature, based on dry-bulb temperature and relative humidity only, ranged from 67°F in apartment 1905 in the building

at 1160 Sedgwick Street to 72.5°F in apartment 1510 in the building at

624 West Division Street. Assuming that the mean radiant temperature

was at least 2 to 3 degrees above the air temperature in all of the

apartments listed in Table 7, as was observed in the four instrumented

apartments, it is safe to conclude that none of the apartments listed

in Table 7 was too cool and that most of them were somewhat too warm for

optimum comfort.

- 17 -
RANGE

OF

TEMPERATURES

IN

FOUR

APARTMENTS

for

the

Period

February

22

-

26,

1963

m

o

NO CN tH nO NO 00 O m n- O

rH NO rH CN CN LO rH 00 CO 00 tH

CN o o o on 00 00 00 00 NO r-' 00 00

I—

1

rH rH rH O o o on in r-'- in 00 in o o CO m

ON o o NO ON on ON NO m 00 CN CN m

o o o on 00 NO r- oo r>> NO 0- 00

NO CO o o ON co 00 rH co NO CO

I-"- vf NO NO m 1 NO o CN CN r"> 00 ON CO 1 rH O o ON ON 1 00 ON 00 NO o- 00 1 rH rH rH 1 1 r''- 1 1 O i i i 1 1 1 I l | 1 1 i i 1 1 r^- 1 1 u rH C'. m o m 1 rH o 00 CO m NO CO CN 1 a t • • • •

1 • • • 1 -O ON ON ON rH rH 1 00 co NO m o cn <r o

0 o ON ON ON 00 NO o- 00 O' m n- n- 00 a tH

iz

4Jaa

B

4-1 a ON Nt CO NO o CN 00 o CN CN CO ON o I"" <r a • • • • a m ON 00 CN o CO in in ON 00 CO 00 CN

<3 CO iH o ON 00 ON 00 00 ON 00 m oo 00 r»

rH iH tH

rHo | i i 1 1 | 1 1 | 1 I i 1 1 I NO

NO NO <d" NO NO CN CN CO CN rH m f"~ LO m

ON ON <r rH St o CO o O co CO o NO ON

CN o o ON 00 ON 00 ON 00 in n- 00 00 NO

ON o NO NO O'- CN CN o CN in r-~ rH m ON

NO NO <t CO o NO ON CO o vt ON tH CO o tH

CO tH rH ON ON ON r-' oo ON 00 m 00 00 ON NO

tH rH rH

CO 00 tH rH vf o m uo CN NO r^- o m UO

00 CO i-" ON NO CN CO 00 NO ON 00 ON CO CO

CN o o 00 00 ON 00 n- m 00 LO

Eh Eh Eh Eh El, Eh

o o © o o o

Eh Eh fa Eh Eh o o o o o

Eh Eh Eh En o o o o

CO r\ cu •i a

co O co o

a a <u o

a X> H - rO i—

t

o a co a tH •H H a CU H

4-1 a -o r CU

03 u <u a a W) > 60 M <u H CU r a O r\ a

CO 'O •u <u u •H -Q a •H a cu u > o tH a o i—

i

e D PQ (U 4-1 o - •H o z •r4 o > OJ rH cu z t—

i

a

•H r\ 6 PQ Eh o o Eh u

4-4 cu CO

tO B

r CU a &

> a cu > o « — > o r H 6 = o - rH a. a o = rH cu

QJ * r Q> rO <D B B UQ Q) 0

CO o- cu a H a X) <u cu a rO a

-D 0 B co o H H H

o a a u co <U z z z. z z z H H CO 4-1 r o CO O cn • CU CO o cn a Q u cfl CO B o co o U M a 4-1 = ft a a a

ai a g CO 9% CU IW 4-1 r* 4H

4J 4J o a a_ -a u a cu u

« CO o 00 CO z H a Q 0 = z a

£5 IS OS a § CO a CO

•H M H <U g H

C CK rH z O = I—

1

o tH

1—1 Ul a •H O M o 1—

1

o rH

cu a •1-1 0) rH •H — z rH a u •H — z a

CU 4J > CJ f-H <3 o -o <

a <D •H a

CO os J PQ
1505

1505

1510

1510

710

710

704

704

107

107

1905

1902

1405

805

101

103

906

701

601

°F

15

15

15

15

15

15

15

15

15

15

12

12

17

10

10

10

16

16

15

TABLE 7 OBSERVED RELATIVE HUMIDITY IN SELECTED APARTMENTS

iOcation in Dry- Bulb Wet-Bulb Relative

Building Temperature Temperature Humidity

°F °F %

624 West Division Street

Center 79 57 23

it 80 57 21.5

!.E. Corner 83.5 56 13.5

II II 84 56.5 14

! . E . Corner 80 56 19

ii ii 80 56 19

Center 81.5 55 14

ii 82 55 13.5

Center 80 57.5 23

it 80 57 21.5

1160 Sedgwick Street

Center 75 52 16

End 78 55 19

Center 80 57.5 23

Center 80.5 57.5 22

End 78 59 31

End 77 57 27

1230 N. Larrabee Road

Center 79.5 55 17

End 79 59 29

End 83 62 29

- 19 -
The observed exhaust ventilation rates measured at the bathroom

grilles in four apartments are summarized in Table 8 for various conditions of window and door closure. The results show that the exhaust

ventilation rate was affected very little by closing the bathroom door

or by opening a few windows. This indicates that the provision for air

flow beneath the bathroom door was adequate and that the resistance to

air infiltration from outside the apartment was small compared to the

other resistances in the exhaust duct system. The exhaust air flow

rate was quite variable in apartment 707, presumably due to variations

in wind velocity.

It was observed that the exhaust grilles in all four of the apartments where air flow rates were measured had a considerable accumulation

of dust and lint in the grille openings. The grilles and the exhaust

duct immediately behind the grilles were cleaned before the air flow

measurements were made.

The drawings for the William Green Project indicate a design ex- haust ventilation rate of 55 cfm for apartment 601 and 50 cfm for apartment 906. The drawings for the Frances Cabrini Extension Project indicate

design exhaust ventilation rates of 70 cfm and 85 cfm in different groups

of apartments. The observed ventilation rates were 50 to 60% in excess

of the design values in apartments 601 and 906 and from 50 to 250% in

excess of the design values in apartments 707 and 1405. If all of the

exhaust grilles were obstructed with lint and dust like the four involved

in this study, cleaning these particular four grilles may have caused

abnormally high exhaust ventilation rates because of the high resistance

at the other grilles.

5.0 Conclusions

The measurements and observations made in the apartment buildings

of the William Green and Frances Cabrini Extension Projects of the Chicago

Housing Authority indicated the following conclusions:

(a) The hot water panel heating systems provided ample heat for the design weather conditions in Chicago.

(b) Two features of the building design used in these two projects contributed to the economy of heating: first, the use of exterior galleries, stairways, and elevator shafts reduced significantly the

amount of volume to be heated and, second, the use of a continuous

concrete slab construction at each floor level together with the

exterior stairways and elevators virtually eliminated air movement

from floor to floor and caused each floor level to act as a onestory structure insofar as infiltration was concerned.

- 20 -
TABLE 8

OBSERVED EXHAUST VENTILATION RATE IN BATHROOMS

OF FOUR APARTMENTS

Exhaust

Apartment Avg. Exhaust Ventilation Window and Interior Door

Number Velocity Rate Positions

f pm cfm

906 395 85 Windows closed - all doors open

392 84 Windows closed - bathroom door closed

403 86 3 windows open - all doors open

601 403 86 Windows closed - all doors open

373 80 Windows closed - bathroom door closed

415 89 2 windows open - all doors open

707 590 - 825 a 127 - 177a Windows closed all doors open

569 122 Windows closed - bathroom door closed

637 136 2 windows open - all doors open

1405 1379 295 Windows closed - all doors open

1450 311 Windows closed - bathroom door closed

1380 296 2 windows open - all doors closed

a. Exhaust air flow rate varied with wind velocity outdoors.

- 21 -
(c) The observed ventilation rates ranging from 0.75 to 1.47 air changes

per hour in three apartments were ample to provide fresh air and

prevent condensation on the walls. The ventilation rate of 3.19

air changes per hour in apartment 1405 was excessive and should be

reduced. The ventilation rate was almost independent of the position of interior doors.

(d) A regular schedule of cleaning for the exhaust air grilles should

be instituted to maintain the desired ventilation rates and to

maintain the proper balance between apartments.

(e) A high percentage of the apartments was overheated. Air temperatures from 80°F to 83°F at the 30-inch level were not uncommon in

the living rooms and bedrooms. Considering the typical elevation

of the mean radiant temperature of 2 or 3 degrees F above air temperature in these apartments, a dry-bulb temperature of 75°F would

be adequate for optimum winter comfort even at relative humidities

in the range from 20 to 30%.

(f) The regularly spaced heating tubes 18 inches apart in the apartments

of the William Green Project produced about the same average ceiling

panel temperature with a supply water temperature of 140°F as the

non-uniformly spaced tubes 6 to 12 inches apart in the apartments

of the Frances Cabrini Extension Project with a supply water temperature about 20 degrees cooler. The measurements did not indicate

a significant difference in adequacy or comfort for the two tube

arrangements, but considerably less heating tube was used in the

William Green apartments.

(g) With a very few exceptions, each tube circuit in the buildings of

the William Green Project was confined to the floor or ceiling area

of one room, whereas many of the tube circuits in the buildings of

the Frances Cabrini Extension Project extended into the floor or ceiling area of two or more rooms. In the latter project one tube

circuit encircled the entire perimeter of the apartment near the

outside wall and was used as an antifreeze protection since it

could not be shut off by the tenant. It is obvious that the circuit pattern used in the Frances Cabrini Extension Project offered

less opportunity for balancing the temperature among the several

rooms in a given apartment by adjustment of flow valves in the individual circuits.

(h) The one-zone distribution system utilizing a three-way valve to

modulate the supply water temperature identically in all tube circuits in each building in response to an outdoor thermostat did not

provide sufficiently uniform air temperatures in the various apartments nor did it provide sufficiently uniform air temperature in a given apartment as the weather changed. In five or six apartments

in each of two buildings the air temperature varied 5 degrees in

each group. In the eight rooms instrumented for detailed study in

four apartments, the air temperatures at the 30-inch level varied

3.3 to 4.8 degrees in four of the rooms and from 6.0 to 12.3 degrees

in the other four rooms during the seven days of observations during

which the outdoor temperature ranged from 37 °F to -6°F.

- 22 -
(i) There was no direct evidence that the control of temperature and

degree of comfort was less satisfactory in the rooms with two outside exposures than for those with one outside exposure.

(j) Exterior wall surface temperatures of about 50°F were observed in

three rooms and a wall surface temperature of 43°F was observed

in one room as a result of the large window areas used and the

lack of insulation in the walls.

(k) Some floor panel surface temperatures in excess of 90°F were observed, but such occurrences would have been rare if the room air

temperature had been maintained in the vicinity of 75°F.

6.0 Recommendations on Existing Buildings

The following recommendations are made with a view to improving

the comfort and economy of heating in these two projects:

(l) Room dry-bulb temperature levels should be reduced to about 75°F

to improve the comfort and to save fuel. The effective temperature in most apartments was considerably in excess of the 68°F

level considered to represent optimum winter comfort conditions.

Lowering the dry-bulb temperatures would entail resetting the

proportioning control between the outdoor thermostat and the temperature-sensitive element in the main supply water main.

(2) The distribution of heat to the various apartments should be re- balanced. Steps to be taken in balancing hot-water heating systems in large buildings are listed on page 136 of the 1962

Applications Volume of the ASHRAE Guide and Data Book. It is

especially important to perform this operation when the outdoor

conditions are reasonably constant, such as during cloudy, rainy

weather. The balancing operation should include checking the

room temperatures in a given building at two outdoor temperature

levels, considerably separated, in order to determine whether the

correct slope of the curve representing the relation of supply

water temperature to outdoor temperature has been achieved. When

the optimum setting of the proportioning control has been obtained

with respect to temperature level and slope, the only opportunity

for balancing the temperature among the various apartments in a given building or among the several rooms in an apartment is to

use the plug valves in the return tubes of the piping circuits to

restrict the water flow to circuits serving rooms that are too

warm. The plug-type valves used in the heating circuits of the

William Green and Frances Cabrini Extension Projects are not wellsuited to adjustment of flow since a quarter turn or less changes

the valve from fully open to fully closed position. Another type

of adjustable valve could be installed that provided better choice

of intermediate positions between fully open and fully closed positions.

- 23 -
( 3 ) The exhaust grille in each apartment should be cleaned at regular

intervals and the exhaust ventilation rate at various floor levels

should be measured after the first cleaning operation is completed

to determine that the ventilation rate is approximately the same

at each floor level.

(4) The balance of temperature in the several apartments in each building could probably be improved by using a multi-zone control system

that took into account differences in solar exposure, the direction

of the prevailing wind, the number of exposed walls per room, and

the room function. Such a change could probably be accomplished

in the existing buildings by grouping the supply and return lines

in the basement for apartments or rooms with similar load characteristics, and providing separate pumps, three-way valves and outdoor thermostats for each zone. This modification would be quite

expensive and might not be economically justified from a fuelsaving standpoint. The desirability of making such a modification

to improve the temperature distribution should be evaluated on the

basis of the effectiveness of the preceding three recommendations.

It should be noted that the tube circuit patterns used in the

Frances Cabrini Extension Project are not conducive to adjustment

of the temperature on an individual room basis since many of the

circuits cover two or more rooms.

7.0 Recommendations for Future Construction

This field study of the performance of hot-water panel heating systems in multi-story buildings for public housing purposes indicated that

such systems are capable of providing adequate heating in cold climates.

The records of fuel use of the Chicago Housing Authority indicates that

this type system is economical. However, in our opinion, further use

of this type system should be carried out in conjunction with and be

contingent upon a better system of temperature control for individual

apartments and rooms. Additional economy achieved with a better control

system would pay for a part or all of the cost of the better control

system.

All available published information on control systems for hotwater panel heating systems agrees that a modulation of the supply water

temperature in response to an outdoor thermostat (and perhaps modified

by an indoor compensator as a supplementary reset device) is essential

for heating coils embedded in concrete slabs. Zoning control is frequently employed where a single heating system is used to heat a large

number of areas or living units which do not have identical internal

heating loads or identical exposure to outdoor conditions. For zoning

- 24-
purposes all spaces or units having the same internal load pattern and

external response are grouped together on the same distribution circuit

and controlled by a single control system. In our opinion, large multistory apartment buildings of the type investigated in this field study

in Chicago should be zoned. The significant features of this application that indicates the need for zoning are:

(a) High winds in the range from 15 to 25 mph are prevalent in the

Chicago area during the winter as indicated by the data collected

during this field study.

(b) No shading from solar radiation was provided on the sides of the

buildings opposite the galleries.

(c) Apartments in the center of the building typically have one ex- posure per room, but these are on opposite sides of the building;

e.g., a north exposure would be exposed frequently to strong winds

and receive no sunshine, whereas a south exposure in the same

apartment would not receive the impact of the wind but would be

unshaded from the sun

(d) Apartments at the end of a building would typically have two ex- posures per room, one of which would often be exposed to the prevailing wind, and one of which would receive solar radiation.

(e) The kitchen, dining room, and living room were typically not

separated by partitions so the heat and moisture release from

cooking functions would tend to make this part of the apartment

warmer than the bedrooms. Nearly all of the apartment designs

incorporated a hallway between the bedrooms and the living-roomdining-room area, thus inhibiting heat exchange between these

areas to a large degree.

Taking the building at 1230 N. Larrabee Road in the William Green

Project to illustrate the possibilities of zoning, most of the bedrooms

are located on the west side of the building and are exposed to the prevailing wind, and most of the living rooms, dining rooms, and kitchens

have an east exposure adjacent to the galleries. In this building all

of the rooms on the north and west sides of the building, including the

bedroom on the southeast corner, could be placed in one zone with the

supply water temperature controlled by an outdoor thermostat designed

to compensate for the effect of wind velocity. All of the rooms on the

south and east sides of the building, including the living room-dining

room combinations in apartments 1 and 8 on the 3rd through 6th floors

and in apartments 1 and 10 on the 7th through 12th floors could be

placed in a second zone with the supply water temperature controlled by

an outdoor thermostat located on the east side of the building. Neither

of these outdoor thermostats would have to compensate for solar radiation since the quantity and duration of solar irradiation on east and

west walls is small during the winter months in the latitude of Chicago.

In this building only the living room-dining room area of apartment 2

has a significant glass exposure in a south wall.

- 25 -
In a building whose principal center line was in an east-west direction, such as those on Division Street, a somewhat different grouping of

rooms would be required and the control system would have to take into

account the effect of solar radiation on the many rooms with a south

exposure. Adjustment for solar effect on the south exposure could be

made with an indoor compensator overriding an outdoor thermostat if a representative indoor location could be found for the indoor compensator,

or an outdoor thermostat designed to suitably integrate solar effect and

outdoor temperature could be used by itself to modulate the supply water

temperature.

In our opinion, no less than two zones should be used in apartment

buildings such as those in the William Green and Frances Cabrini Extension Projects and, in some cases, three or four zones might be preferable

depending on building orientation, amount of glass area in a given ex- posure, and the arrangement of bedroom areas and kitchen, living room,

dining room areas in the buildings. In a zoned system, separate circulating pumps, three-way modulating valves, and outdoor thermostats would

be required for each zone together with any indoor compensators that

might be used to provide for solar or wind effects on room temperature.

In general, it would be preferable to have solar and wind effects sensed

outside the building because of the inherent lag in a panel heating system utilizing concrete slabs.

In our opinion, the use of one or more separate heating tube circuits in each room is preferable to a design which causes the circuits

to overlap two or more rooms because it facilitates balancing the room

temperatures with respect to each other. The use of one perimeter tube

around an entire apartment, which cannot be shut off, to prevent freezing

when the apartment is unoccupied would not ordinarily inhibit balancing

to any appreciable extent. The need for such a perimeter circuit would

depend on the duration of vacancies and the building management policy

regarding the heating of unoccupied apartments.

Balancing valves with more gradual modulation and some means for

knowing the degree of closure should be used in this type of building

since balancing of temperatures among rooms and apartments is inevitable.

In any new construction, consideration should be given to lowering

the heat transmission factor of the exterior walls, to the use of double

glass for fixed windows, and to a reduction in the percentage of the

total heat output to be delivered from the floor. Double glass should

not be used without improving the insulating qualities of the exterior

walls because of the possibility of condensation on the walls. A reduction in the heat output required from the floor would reduce the

significance of the greater lag of the floor panel as compared to the

- 26 -
ceiling panel and improve the quality of temperature control with changing

outdoor temperature. A cost study would have to be made in any particular

case to determine whether or not these improvements were economically feasible.

In our opinion, interior hallways, stairs, and elevators should be

considered in any similar apartment buildings for the aged, even though

such a design would increase the total heat requirement, because of the

greater sensitivity of the aged to cold weather.

USCOMM-NBS-DC



U. S. DEPARTMENT OF COMMERCE

Luther H. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS

A.'V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

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