A Study of a Baseboard

Convector Heating System

in a Test Bungalow

United States Department of Commerce

National Bureau of Standards

Building Materials and Structures Report BMSUS
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UNITED STATES DEPARTMENT OF COMMERCE • Charles Sawyer, Secretary NATIONAL BLTREAU OF STANDARDS • E. U. Condon. Director

A Study of a Baseboard

Convector Heating System

in a Test Bungalow

by Paul R. Achenbach and Edward M. Tierney

Building Materials and Structures Report BMS1I5

Issued August 1, 1949

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C.

Price 15 cents
Foreword

The increase in construction of small houses without basements has resulted

in efforts to provide heating systems that will produce comfort in such houses

when the heater is located on the first floor. A recently developed distribution

system that uses finned piping adjacent to all the exterior walls of a house at the

baseboard level appears to offer greater comfort near the floor of basementless

houses than some other systems now in use. The tests described in this report were made to determine the temperatures

produced at several levels above the floor with one form of baseboard heating

system and to study the characteristics of two types of room-temperature controls with that kind of heating system in a partially insulated frame house. The

project was part of the research program carried on at the National Bureau of Standards in cooperation with the Housing and Home Finance Agency and its technical staff. E. U. Condon, Director.

II
A Study of a Baseboard Convector Heating System

in a Test Bungalow

by Paul R. Achenbach and. Edward M. Tierney

The temperature distribution produced by a baseboard convector heating system was observed in a 4-room Test Bungalow on the grounds of the National Bureau of Standards. The

distribution system consisted of finned sections of iron pipe placed beneath the windows, standard

iron pipe connecting the finned elements in a continuous loop around the house at the baseboard

level, and a hot-water boiler located on the first floor. The .vertical temperature differences, roomto-room temperature differences, heat loss of the house, and the heat emission per unit length of finned pipe were observed for a range of outside air temperatures. In addition, the control of room

temperature provided by an electric room thermostat and by an outdoor-thermostat control and

modulating water-flow valve were compared for steady outside air temperatures. The characteristics of the outdoor-thermostat control and modulating water-flow valve were also studied

for transient outside air temperatures and under pick-up conditions indoors.

CONTENTS

Page Foreword II

I. Introduction 1 II. Test Equipment 3

1. The Test Bungalow ' 3

2. Insulated enclosure 3

3. Heating system 4

4. Controls 6

5. Temperature measurements 8

III. Test procedure 8

IV. Temperature distribution 8 V. Heat loss 13 VI. Room temperature controls 14 VII. Pick-up characteristics 16 VIII. Heat emission of convector 17 IX. Discussion and conclusions 17 X. References 19 XI. Glossary of selected heating terms 19

1. Introduction

The various combinations of dry-bulb temperature, relative humidity, and air motion necessary to provide comfort in homes in the United States using convection heating have been established by

the American Society of Heating and Ventilating

Engineers and are illustrated in comfort charts pre- pared by that Society. Lower room temperatures

are considered comfortable in some European

countries; for example, the living-room temperature

in British houses is seldom much above 60° F and

bedroom temperatures are often in the range from

50° to 55° F [1].^ In actual practice; however, in America many heating systems provide means for regulation of the dry-bulb temperatures only. The

relative humidity and air circulation in the living

space are partially controlled by these heating

systems.

' Figures in brackets indicate the literature references at the end of this paper.

The temperature differences in the region from

the floor to head level and from room to room are of primary importance in heated houses. The objective

in American houses is to heat all rooms uniformly

and to have a minimum temperature gradient in a

vertical direction. Uniformity of temperature is difficult, if not impossible, to attain, especially with

inexpensive heating devices or systems. In houses

with basements the heat liberated by a boiler,

furnace, or piping in the basement assists greatly in warming the floor above [2]. However, in recent

years, a great many small houses have been built

with concrete floors laid on the ground or with

floors laid over shallow crawl spaces. In such constructions, the lack of basement spaces necessitates

placing the heating plant on the first floor, which

in most cases prevents direct warming of the under

side of the floor. A Study of a Baseboard Convector Heating System in a Test Bungalow 1
A great many different heat-distribution systems

have been tried in houses in an attempt to produce

a uniform temperature in all rooms and at all levels. Warm air, hot water, and steam have been employed as media for conveying heat in various in- stallations, and it has been found that the results with each depend in part upon the size, shape, and

location of the heating elements and in part upon

the physical characteristics of the medium used.

Experiments at the University of Illinois [3] have

shown that long, low, thin, direct radiators produce

smaller floor-to-ceiling temperature differentials than high radiators, which indicates that better

temperature distribution may be provided in a room when the heat is supplied by laterally distributed heating surfaces near the floor than by tall units

concentrated over a small floor area. Further development guided by this principle has led to the

manufacture of radiant baseboard elements and

baseboard convectors. Several types of baseboard heating systems have

been developed recently. Hollow cast-iron elements,

either with or without fins [4], have been used in some types and finned steel pipe or finned copper

tubing with shields or covers partially enclosing the

heating elements in others. Such systems provide

heating surfaces near the floor by using elements

around the entire perimeter of the living space

which are not much thicker or higher than a baseboard. These heating elements are sometimes

referred to as floor-line radiation or baseboard

radiation. In addition to the advantage of low

vertical temperature differentials, this type of system occupies practically no usable living space.

A disadvantage of the baseboard heating system,

however, arises from the use of a distribution system

consisting of a continuous loop of pipe around the

inside of the house. With this arrangement, the heat

cannot be shut off in one room without shutting it off in all rooms; thus resulting in a waste of heat in

bedrooms in which windows are opened at night for ventilation. Of course, this undesirable feature can

be remedied by using two parallel piping circuits with one to heat the bedrooms and the other to heat the remainder of the house.

The continuous piping circuit also necessitates more accurate design of the individual elements for the several rooms of a house since it permits no

simple method for decreasing or increasing the heat

output of a particular convector with relation to the

others if that particular convector has too much or too little heating surface. The conventional hotwater heating system with free-standing radiators can be "balanced" by partially closing the valve on

a radiator that has too much heating surface. One type of baseboard heating system was in- stalled in the Test Bungalow at the National

Bureau of Standards to study the temperature

distribution produced in a typical four-room house

and to investigate the instaflation and operational

problems involved in its use. A photograph of the

Test Bungalow is shown in figure 1. The above-mentioned system had iron pipe with

fins under the windows and pipe without fins around the walls, partially enclosed by a perforated

sheet-metal cover. Heat was transferred primarily

by convection of air through the enclosure and over

2

Figure 1. Test Bungalow before insulated enclosure was built.

Building Materials and Structures Report BMSI15
the pipe and fin surface; hence, the system has been

termed a baseboard convector heating system in

this discussion.

Two types of controls were used for the tests; a

conventional wall-type electric room thermostat

and a modulating control system with an outdoorthermostat control and a three-way mixing valve

that blended the boiler supply and return water to control the temperature of the water entering the

system.

II. Test Equipment

1. The Test Bungalow

The Test Bungalow at the National Bureau of Standards is of conventional frame construction and

has four rooms and bath, connected by a hallway

located approximately in the center of the house.

There is a full basement under the entire house

although this feature was not a consideration in the

tests discussed herein. A floor plan of the Test

Bungalow is shown in figure 2.

26-4'

|-30"-j BOILER KITCHEN

(ir-9"jBY(,lo'-2";

LIVING ROOM

(13-7"; BY (13-6";

(I

Figure 2. Floor -plan of Test Bungalow showing the piping

circuit and the location and size of the baseboard convector

elements. The outside walls, which are without insulation,

consist of 2- by 4-in. studding with sheathing and

lap siding separated by a layer of building paper on

the outside and 3^-in. plasterboard nailed directly

to the studding on the inside. The floor consists of pine subflooring and %-in. tongue-and-grooved

pine finish flooring laid on 2- by 10-in. joists with

building paper between. The basement ceiling is 1-in. rigid insulation board nailed directly to the

underside of the floor joists. The ceiling of the living

quarters is }yi-in. plywood supported by a framework of 2- by 4-in. members and the ceiling height

in all rooms except the bathroom can be adjusted

by means of screw jacks permanently mounted in the construction. Ceihngs are insulated from the

unfinished attic space by 3^-in. rock wool batts.

All windows in the living quarters are double-hung

except one casement window in the kitchen and one

in the bathroom. The basement occupies the entire space below the living quarters. The foundation

walls are of concrete block and the floor is concrete. For the current tests, the ceiling height was 8 ft. Insulation was installed over the ceiling and under

the floor joists and the windows and doors were

weather-stripped in order to reduce the heat loss of the Test Bungalow to approximately 55 Btu/hr

(ft-) of interior floor area for an inside-outside air temperature difference of 70 deg F. This heat loss value^ is being used in some parts of the United

States at the present time as a guide for determining

the amount of insulation to be used in new construction. The computed heat losses for the several rooms of the Test Bungalow, assuming an infiltra- tion of one air change per hour, are summarized in table 1. Table 1. Computed heat loss of the Test Bungalow for an

inside-outside air temperature difference of 70° F

Room

Heat loss

Anticipated Corrected

Living room

Kitchen North bedroom

South bedroom

Bath

Hall

Total

Btu/hr

10,590 7,630

5,870

7,000

1,700 280-

Btu/hr

10,090 7,300

5,610

6,630

1,600 200

33,070 31,430

The heat losses, based upon the temperatures

anticipated in the basement and attic, were computed for each room before the tests were made.

After the tests were completed, the heat losses were computed again using the observed temperatures

in the basement and attic. Table 1 shows that the

anticipated heat loss was 33,070 Btu/hr (equivalent

to 53.7 Btu/hr (ft-) of floor area) for an insideoutside air temperature difference of 70 deg F,

whereas the second computation shows that the

heat loss would be only 31,430 Btu/hr (equivalent

to 51.0 Btu/hr (ft-) of floor area).

2. Insulated Enclosure

Completely surrounding the Test BungaloAv, and

at a distance of approximately 5 ft from its outside

walls, is a heavily insulated enclosure without

windows. A large unit cooler, installed in the space

between the bungalow and the enclosure, makes it possible to rfiaintain the air around the bungalow

at selected temperatures down to approximately 0°

F. Air is circulated around the bungalow at a rate

of about 9,000 cfm, but the maximum air velocity

adjacent to the exterior wall is approximately 2

2 The various local offices of the Federal Housing Administration are accepting construction with heat losses ranging from 50 to 70 Btii' lirut-') of floor area at the design inside-outside air temperature difference for different sections of the country. A Study of a Baseboard Convector Heating System in a Test Bungalow 3
Figure 3. Insulated enclosure for the Test Bungalow.

mph. The outside air temperatures at the four

corners of the bungalow do not differ more than 2

deg F at the lowest temperature obtainable. The

refrigerating system and enclosure thus provide a means for studying heating systems under controlled conditions, regardless of outdoor weather

conditions or temperature. A photograph of the

insulated enclosure is shown in figure 3.

3. Heating System

The heat-distribution system selected for test consisted of lengths of finned l3^-in. black iron

pipe under each window and 1-in. standard pipe to

Figure 4. Close-up view of a finned convector element without

the sheet-metal enclosure.

form a continuous circuit around the perimeter of the house as shown on the floor plan of the Test

Bungalow in figure 2. After the hot water had left the

boiler it was pumped through the rooms in the

following order: kitchen, living room, south bedroom, and north bedroom. A close-up view of one

of the finned elements is shown in figure 4, and the

method of installing the connecting pipe is shown

in figure 5. The lengths of the finned sections in each room (shown on the floor plan in fig. 2) were chosen

so that their computed heat outputs were equal to the computed heat loss of that room. The fins were

3 3^ -in. square and were spaced M-in. apart on the

pipe. A perforated metal enclosure partially covered

the convector elements and piping as illustrated in figure 6. A cross-sectional drawing of the finned

pipe, its supports, and the metal cover is shown in

figure 7. This drawing also shows the method of installation of the convectors and their location

relative to the floor and outside wall surfaces. The

lower 10 in. of the plasterboard was removed from

the wall and a nailing strip %hy \% in. was nailed

to the studding at the bottom of the remaining

plasterboard. The pressed-steel panel forming the

back of the convector housing was then secured to the nailing strip and floor. Metal support brackets were screwed to the studding at intervals to support the convectors and piping. After placing the

heating elements on the brackets and assembling

the connecting piping, the metal cover was screwed

to the nailing strip and the studding. The metal

cover for the system used in the tests extended

33^^ in. out into the room from the wall surface and

the skirt of the cover had a clearance of 2 in. above

4 Building Materials and Structures Report BMS115
Figure 5. Baseboard convector without the sheet-metal enclosure showing the method of installing the connecting pipes.

Figure 6. Baseboard convector in the living room with the perforated metal housing in place. The warm air register near

the door has no connection with the baseboard convector system.

the floor surface to permit air circulation over the

heating elements.

Where the pipe would otherwise have obstructed an outside doorway, it passed in a downward loop

through the floor and insulation, thence under the

insulation for a distance a little greater than the

width of the door opening, and back up through the

floor and insulation on the other side of the doorway. An air valve was attached to each of these

loops adjacent to the door to permit removal of air that might accumulate at these places. The treat- ment of the piping at the exterior doors can be

observed in figure 6. PLASTERBOARD

U.S. STD,

OA. STL. No. 16

LAP SIDING

SHEATHING

Figure 7. Vertical cross section of the baseboard convector showing the method of installation and the location of the elements relative to the wall and floor. An experimental electric boiler was used to supply hot water to the system. It consisted of a

cylindrical shell 6 in. in diameter containing seven

hairpin-type immersion electric heaters with a total capacity of l-i kw. Electric energy was supplied to these heaters through calibrated watthour meters so that the heat input of the system could be accurately determined. A centrifugal pump was used to circulate the water through the boiler and the heating system. The electric energy used by the /^-hp

motor on the pump was also measured. The pump

was located in the piping circuit near the inlet of the

boiler. It circulated approximately 10 gal min of water through the heating circuit. At this rate of flow the drop in water temperature around the

circuit was 2.2 deg F for an outside air temperature

of 50° F, and increased to 5.1 deg F for an outside

A Study of a Baseboard Convector Heating System in a Test Bungalow 5
Figure 8. Experimental hol-water boiler, circulnling pump,

controls, and adjacent piping for the tests with an electric room

thermostat.

ail' temperature of 1° F. Figure 8 shows the experimental boiler, circulating pump, expansion tank, conti'ols, and adjacent piping. The manometer, shown at the right on hgiu-e 8, was used to indicate the pressure

difference between the suction and discharge connections of the pump.

The boiler and circulating pump were located in the space that would normally be the bathroom in the Test Bungalow to simulate a first-floor installa- tion in a basementless house. The heating system

was a closed system with the expansion tank placed

just below the ceiling.

4. Controls

Two types of heating-system controls were used

during these investigations. The first consisted of a commercial low-voltage electric room thermostat, a

relay, an immersion aquastat, and a temperaturelimit control. The thermostat and relay connected

and disconnected the electric heaters from the

power supply, and the immersion aquastat operated

the circulating pump intermittently in response to changes of the water temperature at the boiler

outlet. The temperature-limit control interrupted

the electriLvheater circuit when the boiler supply

water reached the maximum desired temperature.

A wiring diagram of the first type of heating system

controls is shown in figure 9. The locations of the

aquastat and temperature-limit control for this system are shown in figure 8. The thermostat had a

spiral bimetallic element approximately 14 in. long

Avith a small magnet secured to the free end. This

magnet closed the circuit in a drop of mercury by

attracting a small piece of iron attached to the contact arm. The thermostat was mounted 30 in. above the floor on the east wall of the living room

adjacent to the archway connecting the living room

and the hall. The second heating-system control consisted of an outdoor thermostat, a motorized three-way

valve, an immersion aquastat, and an electric control circuit for adjusting the three-way mixing

valve position. This system blended the boiler

supply water and the cooler water returning from

the heating system in various proportions by means

of a bypass line as determined by the temperatures

of the outside thermostat bulb and the bulb immersed in the mixed water. When rapid changes of

CIRCULATING PUMP

MAGNETIC-^

SWITCH

Figure 9. Diagram of the electric circuits for the tests with the

electric room-thermostat control system.

6 Building Materials and Structures Report BMSIIB
Figure 10. Experimental hot-water boiler and attached piping showing the three-way mixing

valve and some of the other controls used with the outdoor-thermostat control system . the mixed-water temperature were required, the

three-way valve could fully close either the bypass

line to raise the temperature or the boiler supply

line to lower the temperature of the water supplied

to the distribution system. The control system was

designed to modulate the temperature of the water

entering the distribution system in just the proper

way to rnake the heat output of the system equal

the heat loss of the house for any outside air temperature. Most of the control equipment for

this system is visible in figure 10. A diagrammatic

sketch of the wiring circuits and the piping arrangement for the modulating control system is shown in figure 11.

Figure 11. Diagram of the electric and piping circuits for the modulating-temperature control system. A Study of a Baseboard Convector Heating System in a Test Bungalow
5. Temperature Measurements

Temperatures were measured in the Test Bungalow by means of thermocouples supported bystrings attached to the ceiUng. Five strings carrying

five thermocouples each, were located in the

kitchen, living room, and the two bedrooms, with

one string suspended at the center of each room

and one midway between the center and each corner

of these rooms. Three strings of five thermocouples

each, were suspended in the bathroom. The five thermocouples on each string were permanently

installed at distances of 2, 30, 60, 78, and 94 in. above the floor. To eliminate the fluctuations of

temperature caused by the cycling of the thermostat

and any minor changes due to opening the outside

doors, these thermocouples were attached to blocks

of copper ^ in. in diameter and ^ in. long and

were enclosed in blocks of cork. Thus, the temperatures observed in all rooms could be compared, even though approximately 45 min were required to take

all the observations. The effect on the temperatures

of covering the thermocouples with cork insulation

is described in an earlier Building Materials and

Structures Report [5]. Other thermocouples were used to measure the

temperatures outside of the bungalow, on the inside

and outside surfaces of the exterior walls, on the

floor surfaces, in the basement, in the attic, and at several places on the hot-water pipes of the con- vector heating system encircling the inside walls of the house.

III. Test Procedure

The temperature distribution was observed in the Test Bungalow with an inside temperature of 70° F maintained at the 30-in. level in the living room and outside air temperatures of 50°, 32°, 20°,

and as near 0° F as could be attained. With the room

thermostat controlling the boiler, a series of tests was made for this range of outside air temperatures

with the interior doors closed to determine whether

or not the heat output of the convector elements

equaled the heat loss on a room-by-room basis. The

series was then repeated with the interior doors

open. When the modulating control with the out- door thermostat was used, temperature distributions were observed for a range of outside air temperatures from 1° to 50° F with the interior doors

closed. Before starting the tests for each set of conditions, the temperatures inside and outside the

bungalow were maintained constant for enough

time to permit the temperatures in the attic and

basement to reach a steady state. During the test period, which was usually of 24 hours duration,

hourly observations were made of the outside air temperature, the temperature at the 30-in. level

in the living room, the basement temperature, the

attic temperature, and the electric-energy con- sumption. At 4-hour intervals, temperatures were

observed at all stations on the inside and outside

of the bungalow.

In addition to the investigation of the temperature distribution in the four rooms of the Test

Bungalow with a constant outside air temperature,

the characteristics of the modulating-valve and

outdoor-thermostat control system were observed

whpn the outside air temperature was varied between 0° F and 40° F and back as rapidly as the

refrigerating system permitted.

The pick-up characteristics of the baseboardconvector system, when controlled by the outdoorthermostat control, were also observed. The two

bedrooms were cooled down to 50° F by opening the

windows to simulate the practice of ventilating

sleeping rooms. When the temperature in the bed- rooms reached 50° F, the windows were closed and

the rise in temperature was observed with the in- terior doors closed. The temperatures in the kitchen

and living room and the supply-water temperature were also recorded during this transient condition.

IV. Temperature Distribution

The averages of the temperatures observed at each of five levels above the floor in the several rooms of the Test Bungalow are tabulated in tables

2 to 9, inclusive, for the tests using the roomthermostat control and in tables 10 to 13, inclusive,

for the tests using the outdoor-thermostat control. The maximum horizontal temperature difference

between any two rooms of the house and the vertical temperature differences between levels are also shown in these tables. An examination of tables 2 to 13 shows that comparatively small temperature differences existed

between rooms and between different levels in the same room with the baseboard convector heating

system for the range of outside air temperatures

from 50° to 0° F. The temperature differences in- creased in magnitude both horizontally and verti- cally as the outside air temperature decreased. The

vertical temperature gradient ranged from 0.3 deg

F/ft above the floor for an outside air temperature

of 50° F to 0.8 deg F/ft for an outside air temperature of 0° F. A comparison of the results obtained

with the interior doors of the bungalow open (tables

2 to 5, inclusive) with those with the doors closed

(tables 6 to 9, inclusive) shows that the temperature

differences in a vertical direction were not appreciably affected by closing the doors, but that the

maximum temperature difference between rooms was approximately doubled for the levels 2, 30, and

60 in. above the floor by closing the doors. The

8 Building Materials and Structures Report BMSI15
maximum difference between the average temperatures in the Hving zone^ of any two rooms ranged

from 0.7 deg to 1.4 deg F with the interior doors

open and from 1.4 deg to 3.1 deg F with the interior

doors closed for an outside air temperature range

from 50° to 0° F.

Table 2. Temperature distribution produced by baseboard

convector with room thermostat {inside doors open)

Outside air temperature 49.9° F. Heat input 8,650 Btu/hr.

Height above

floor

A. Average room temperature Maximum

horizontal temperature

difference between rooms"

Living room Kitchen

North

bed- room

South

bed- room Bath

in. 230

6078

94

2 to 60. .. 2 to 94. .

.

°F

69.2

70.2

70.6

70.6

71.1

Of

69.4

70.7 71.0

71.6 72.0

°F

69.

1

69.8

70. 70.6

71.0

°F

69.1

70.1 70.4 70.8

71.1

"F

72.7

74.3

75.5

77.6 78.0

Deg F

0.3

.9

.9 1.0

1.0

B. Vertical temperature difference Average

for B»

Deg F

1.4

1.9

Deg F

1.6 2.6

Deg F

1.0

1.9

Deg P

1.3 2.0

Deg F

2.8

5.3

Deg F

1.3

2.1

Average basement temperature 61.7° F

Average attic temperature 56.1° F

Floor surface temperature 68.0° F

Wall surface temperature 66.6° F

Running time of pump 58%

Running time of heater 24%

• Bathroom data not included.

Table 3. Temperature distribution produced by baseboard

convector with room thermostat {inside doors open)

Outside air temperature 31.6° F. Heat input 16,280 Btu/hr.

Height above

floor

A. Average room temperature Maximum

liorizontal temperature

difference between rooms*

Living room Kitchen

North

bed- room

South

bed- room Bath

in. 230

60

7894

2 to 60. .

.

2 to 94. ..

Of

68.2

70.1 70.4 70.5

71.6

°f

67.8

70.2

70.9

71.9

72.7

°F

67.9

69.7

69.9

70.4 71.0

°F

68.6

70.3

70.9

71.5 71.8

°p

73.4 76.0

78.4

80.8

81.8

Deg F

0.8

0.6

1.0 1.5

1.7

B. Vertical temperature difference Average

for B»

Deg F

2.2

3.4

Deg F

3.1 4.9

Deg F

2.0

3.1

Deg F

2.3 3.2

Deg F

5.0

8.4

Deg F

2.4

3.7

Average basement temperature 55.2° F

Average attic temperature 46.8 °F

Floor surface temperature 66.3° F

Wall surface temperature 64.1° F

Running time of pump 76%

Running time of heater 32%

' Bathroom data not included.

» The space between levels 2 in. and 60 in. above the floor is called the

living zone in this report.

Table 4. Temperature distrihution produced by baseboard

convector with room thermostat {inside doors open)

Outside air temperature 20.7° F. Heat input 22,410 Btu/hr.

Height above

floor

A. Average room temperature Maximum

horizontal temperature

difference between rooms"

Living room Kitchen

North

bed- room

South

bed- room Bath

in. 230

60. 78

94

2 to 60. .

.

2 to 94. .

°F

67.2 69,8

70.5

70,7

71,9

°F

66.5

70.3

71.2

72,3

73.1

"F

66.7

69 1 69.8

70,3

70.9

°F

67.1 69,5 70,2

70,8

71,8

°F

72.6 77,2

80,1 82,3

83,2

Deg F

0.7

1.2

1.4 2.0

2,2

B. Vertical temperature difference Average

for B»

Deg F

3.3

4,7

Deg F

4.7 6.6

Deg F

3.1 4,2

Deg F

3.1 4,7

Deg F

7,5

10,6

Deg F

3.6

5.1

Average basement temperature 50.7° F

Average attic temperature 40.5° F

Floor surface temperature 64.9° F

Wall surface temperature 62.9° F

Running time of pump 100%

Running time of heater 45%

' Bathroom data not included.

Table 5. Temperature distribution produced by baseboard

convector with room thermostat {inside doors open)

Outside air temperature 4.9° F. Heat input 27,970 Btu/hr.

Height above

floor

A. Average room temperature Maximiyn

horizontal

Living room Kitchen

North

bed- room

South

bed- room Bath

temperature

difference between rooms"

in. 2 °F

66.6 °F65.6 °f

65,7 °F66,0 °F72,5 Deg F

1.0 30 69.8 70.1 68.5 69,

1

78.3 1.6

60 70.6 71.2 69.6 69,8 81.6 1.6 78 70.9 72,8 70,2 70,5 84.2 2.6 94 72.4 73.6 70,7 71.4 86.7 2.9

B. Vertical temperature difference Average

for B»

2 to 60... 2 to 94 . .

.

Deg F

4.0 5.8

Deg F

5.6

8.0

Deg F

3.9 5.0

Deg F

3.8

5.4

Deg F

9.1

14.2

Deg F

4.3

6.1

Average basement temperature 45.9° F

Average attic temperature 35.7° F

Floor surface temperature 63.3° F

Wall surface temperature 60.4° F

Running time of pump ^''"^ Running time of heater 55%

' Bathroom data not included. The room temperatures for most of the tests when the doors were closed decreased in the following order: kitchen, living room, south bedroom, and

north bedroom. This was the same order in which

the piping circuit progressed through the several rooms from the boiler supply to the boiler return. This room-temperature gradient around the heating

circuit showed that the sizes of the last convectors

in the circuit were not increased sufficiently to compensate for the lower water temperature. A much

smaller gradient in room temperature was observed

around the circuit when the interior doors were A Study of a Baseboard Convector Heating System in a Test Bungalow 9
open than when they were closed, which indicated

that some equahzation of air temperature occurred

when the interior doors were open into the hall. If the convector elements had been accurately selected as to size there should have been practically no

temperature difference between rooms. A comparison of the temperature distribution

obtained with the baseboard convector system for two methods of room-temperature control is shown

in tables 6 to 9 and tables 10 to 13. The results in tables 10 to 13 indicate that the vertical temperature differences were a little greater with the out- Table 6. Temperature distribution produced by baseboard

convector with room thermostat {inside doors closed)

Outside air temperature 49.9° F. Heat input 9,220 Btu/hr.

Height above

floor

A. Average room temperature Maximum

liorizontal temperature

difference between rooms ^ Living room Kitchen

North

bed- room

South

bed- room Bath

in. 23060

7894

2 to 60. .

2 to 94 . .

op

69.2

70.

70.2

70.4

71.0

°F

69.6 70,8

71-. 0 71.5

71.9

°F

68.2

68.8

68.8

69.0

69.3

°F

69.0

69.9

70.

70.3

70.5

°F

77.3

79.8

81.

82.2

83.2

Deg F

1.4 2.0

2.2

2.5

2.6

B. Vertical temperature difference Average

for B»

Deg F

1.0

1.8

Deg F

1.4

2.3

Deg F

0.6

1.1

Deg F

1.1 1.5

Deg F

3.8

5.9

Deg F

1.0

1.7

Average basement temperature 61.3° F

Average attic temperature 55.7° F

Floor surface temperature 68.1° F

Wall surface temperature 66.6° F

Running time of pump 63%

Running time of heater 30%

* Bathroom data not included. Table 7. Temperature distribution produced by baseboard

convector with room thermostat {inside doors closed)

Outside air temperature 32.1° F. Heat input 16,530 Btu/hr.

Height above

floor

A. Average room temperature Maximum

horizontal temperature

difference between rooms*

Living room Kitchen

North

bed- room

South

bed- room Bath

in. 230

60

78

94

2 to 60. .

2 to 94. .

°F

67.9 69.9

70.3

70.7

71.7

°f

68.1 70,7

71.1 72,0

72.6

op

67,3 69,0 69,2

69,8

70.1

op

67.6

69.3 69.8

70.2

70.6

op

81.7

87.7 90.0

92.2 93.5

Deg F

0.8

1.7 1.9 2.2

2.5

B. Vertical temperature difference Average

for B»

Deg F

2.4

3.8

Deg F

3.0 4.5

Deg F

1.9 2.8

Deg F

2.2 3.0

Deg F

8.3

11.8

Deg F

2.4

3.5

Average basement temperature 54.0° F

Average attic temperature 46.6° F

Floor surface temperature 66.2° F

Wall surface temperature 64.5° F

Running time of pump 81%

Running time of heater 34%

' Bathroom data not included.

10

door-thermostat control than with the roomthermostat control except for the lowest outside air temperature. This probably resulted from the

higher heat input and higher room temperatures

maintained by the outdoor-thermostat control for outside air temperatures of 50°, 32°, and 20° F. The maximum temperature difference between rooms was also slightly greater for the outdoorthermostat control than for the room-thermostat

control.

Table 8. Temperature distribution produced by baseboard

convector with room thermostat {inside doors closed)

Outside air temperature 20.1° F. Heat input 23,020 Btu/hr.

Height above

floor

A. Average room temperature Maximum

horizontal temperature

difference between rooms"

Living room Kitchen

North

bed- room

South

bed- room Bath

in. 23060

78

94

2 to 60 . .

2 to 94 . .

op

67.4

70,

70,8

71,1 72,8

°F

67.3

71.0

71.6 72.8

73.5

op

66.5

68.9

69.6 70.2

70.7

op

66.4

68.5

69.0

69.6

70.1

op

84.2

91,4 94,4

97,3

98.3

Deg F

1.0 2.5

2.6

3.2 3.4

B. Vertical temperature difference Average

for

Deg F

3.4

5.4

Deg F

4,3

6.2

Deg F

3.1 4.2

Deg F

2.6

3.7

Deg F

10.2

14.1

Deg F

3.4

4.9

Average basement temperature 49.3° F

Average attic temperature 40.9° F

Floor surface temperature 64.5° F, Wall surface temperature 62.8° F

Running time of pump 100%

Running time of heater 47%

' Bathroom data not included.

Table 9. Teniperature distribution produced by baseboard

convector with room thermostat {inside doors closed)

Outside air temperature 0.8° F. Heat input 32,260 Btu/hr.

Height above

floor

A. Average room temperature Maximum

horizontal

Living room Kitchen

North

bed- room

South

bed- room Bath

temperature

difference between rooms ^

in. 230

60

7894

2 to 60. .

2 to 94. .

op

65.8

69.4

70.0

70.9 72.5

op

65.4

70,4

71,2 72,9

73.2

op

64.0

66.8

67.8

68.6 69.5

op

64.0

66.9 67.2

68.6

68.9

op

85.4

95.

99.3

102.7

104.9

Deg F

1.8 3.6 4.0

4.3 4.3

B. Vertical temperature difference Average

for B"

Deg F

4.2

6.7

Deg F

5.8

7.8

Deg F

3.8 5.5

Deg F

3.2 4.9

Deg F

13.9 19.5

Deg F

4.3

' 6.2

Average basement temperature 42.9° F

Average attic temperature 32.9° F

. Floor surface temperature 62.2° F

Wall surface temperature 60.3° F

Running time of pump 100%

Running time of heater 66%

* Bathroom data not included.

Building Materials and Structures Report BMS115
Table 10. Temperature distribution produced by baseboard

convector with outdoor-thermostat control and modulating

valve {inside doors closed)

Outside air temperature 50.1° F, Heat input 12,600 Btu/hr.

Height above

floor

A. Average room temperature i\/r »« ivxaximuiii hori zon tal

Living room Kitchen

North

bed- room

South

bed- room Bath

temperature

difference between rooms"

in. 2 °F

71.1 °F

71.

i

°p

71.

1

op

71.0 op

84.5 Deg F

0.4

30 73.1 73.8 72.9 72.2 90.1 1.6 60 73.4 74.2 72.9 72.4 93.3 1.8 78 73.6 74.6 73.2 72.6 96.6 2.0 94 74.2 75.0 73.4 73.0 97.9 2.0

B. Vertical temperature difference Average

for B''

2 to 60 . .

.

2 to 94. .

Deg F

2.3

3.1

Deg F

2.8 3.6

Deg F

1.8 2.3

Deg F

1.4 2.0

Deg F

8.8

13.4

Deg F

2.1 2.8

Average basement temperature 52.2° F

Average attic temperature . . .-. 57.3° F

Floor surface temperature 69.3° F

Wall surface temperature 69.4° F

Average water temperature 128.2° F

Temperature drop in system 2.2 deg F

Bathroom data not included.

Table 12. Temperature distribution produced by baseboard

convector with outdoor-thermostat control and modulating

valve {inside doors closed)

Outside air temperature 20.5° F. Heat input 24,750 Btu/hr.

Height above

floor

A. Average room temperature Maximum

horizontal temperature

diflerence between lyoms'

Living room Kitchen

North

bed- room

South

bed- room Bath

tn. 230

60

78

94

2 to 60 . .

.

2 to 94 . . .

°F

69.3

72.6

73.3 73.8

75.2

°F

69.5

72.5

74.1 75.5

75.8

°F

67.0

69.

1

69.5 70.0

70.6

°p

68.0

70.5

71.2

71.9 72.5

°F

86.6 94.8

98.5

100.9

102.6

Deg F

2.5 3.5

4.6 5.5

5.2

B. Vertical temperature difference Average

for B»

Deg F

4.0

5.9

Deg F

4.6

6.3

Deg F

2.5

3.6

Deg F

3.2 4.5

Deg F

11.9

16.0

Deg F

3.6

5.1

Average basement temperature 45.3° F

Average attic temperature 41.2° F

Floor surface temperature 65.6° F

Wall surface temperature 64.3° F

Average water temperature 178.8° F

Temperature drop in system 4.6 deg F

* Bathroom data not included.

The temperatures observed in the bathroom were

not taken into consideration in evaluating the

maximum temperature difference between rooms

or the average vertical temperature difference for the house, inasmuch as the temperatures were not

controllable in this space since it was being used as a utility room for the boiler and circulating pump.

The horizontal temperature differences within

each room were small with the baseboard-convector

Table 11. Temperature distribution produced by baseboard

convector with outdoor-thermostat control and modulating

valve {inside doors closed)

Outside air temperature 32.0° F. Heat input 19,520 Btu/hr.

Height above

floor

A. Average room temperature Maximum

horizontal temperature

difference between rooms*

Living room Kitchen

North

bed- room

South

bed- room Bath

in. 23060

7894

2 to 60 . .

.

2 to 94. .

°F

70.8

73.5

73.9

74.3 75.4

°F

70.6

73.7

74.3 75.2

75.6

°F

69.9

71.7 72.2

72.7 73.2

op

69.3

70.7

71.

1

71.2 71.8

°F

86.2 93.3 96.8

99.3

100.3

Deg F

1.5 3.0

3.2 4.0

3.8

B. Vertical temperature difference Average

for B*

Deg F

3.1 4.6

Deg F

3.7 5.0

Deg F

2.3

3.3

Deg F

1.8 2.5

Deg F

10.6

14.

1

Deg F

2.7

3.9

Average basement temperature 48.9° F

Average attic temperature 47.9° F

Floor surface temperature 67.7° F

Wall surface temperature 66.6° F

Average water temperatvire 159.2° F

Temperature drop in system 3.6 deg F

' Bathroom data not included. A Study of a Baseboard Convector Heating System in

method of heating. The maximum difference between any two of the five stations in each room

ranged from 0.8 deg to 2.1 deg F for the different

tests. The temperature variation within the rooms

increased slightly as the outside air temperature was

lowered. The average of the maximum within-room

variations for the four rooms ranged from 0.9 deg F

for an outside air temperature of 50° F to 1.7 deg F

for an outside air temperature of 0° F. No particular

Table 13. Temperature distribution produced by baseboard

convector with outdoor-thermostat control and modulating

valve {inside doors closed)

Outside air temperature 0.9° F. Heat input 29,480 Btu/hr.

Height above

floor

A. Average room temperature Maximum

horizontal

Living room Kitchen

North

bed- room

South

bed- room Bath

temperature

difference between rooms"

in. 2 op

66.6 op

66.2 op64.6 op

64.0 "F84.4 Deg F2.6

30 70.2 70.9 67.2 66.2 94.1 4.7

60 70.8 71.9 68.2 66.8 97.8 5.1 78 71.4 73.3 68.6 67.5 100.2 5.8 94 73.0 74.0 69.4 67.9 102.2 6.1

B. Vertical temperature difference Average

for B"

2 to 60 . .

.

2 to 94 . . .

Deg F

4.2

6.4

Deg F

5.7 7.8

Deg F

3.6 4.8

Deg F

2.8

3.9

Deg F

13.4

17.8

Deg F

4.1 5.7

Average basement temperature 42.4° F

Average attic temperature 33.5° F

Floor suriace temperature 62.5° F

Wall surface temperature 59.5° F

Average water temperature 191.9° F

Temperature drop in system 5.1 deg F

* Bathroom data not included.

Test Bungalow 11
corner of a room was consistently colder at all levels than the other corners and none of the rooms consistently showed greater temperature variation

than the others. These observations suggest that

the temperature variations that were noted were somewhat random in nature and probably depended in part upon the activities within the rooms

during the tests. The smallest horizontal variation

in room temperature occurred at the level 30 in. above the floor, but otherwise there was no consistent relation between the uniformity of temperature around the room and the elevation above the

floor. The heat input to the house is recorded in tables

2 to 13 as are also the basement and attic temperatures and the floor- and wall-surface temperatures

for the several test conditions. The effect on these

temperatures, on the heat loss of the house, and on

the vertical temperature differences, of decreasing

the outside air temperature is shown by a series of curves in figures 12 and 13 for the tests with roomthermostat control and outdoor-thermostat control,

respectively.

These figures also show that the vertical temperature differences between the 2- and 60-in. levels and

between the 2- and 94-in. levels increased as the

inside-outside air temperature difference increased,

2" TO 94" ^BOVE FLOO R

2" TC 60" tiBOVE FLOO R

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40

I O 30

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I cc20

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20 25 30 35 40 45 50 55 60 65 INDOOR-OUTDOOR TEMPERATURE DIFFERENCE 'F 70

Figure 12. Graphs showing the relation of heat loss, vertical temperature differences, basement temperature, wall-surface temperature, and floor-surface temperature to the indoor- outdoor temperature difference for the baseboard-convector system with room-thermostat control.

130"

AV ; TEW P OF WATE R IN £ YSTE

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I 15 20 25 30 35 40 45 50 55 60 65 70

INDOOR -OUTDOOR TEMPERATURE DIFFERENCE 'F Figure 13. Graphs showing the relation of heat loss, vertical temperature differences, basement temperature, wall-surface temperature, floor-surface temperature, and average water temperature in the system to the indoor-outdoor temperature

difference for the baseboard-convector system with outdoorthermostat and modulating-valve control system.

but that they were not directly proportional. That

is, the curves showing this relationship are not

straight lines. The slopes of the curves in both

figures 12 and 13 are greater for inside-outside air temperature differences in the range from 35 deg

to 50 deg F than for either higher or lower values of the temperature difference. In figure 12, the curves approach a zero value of the vertical temperature

difference for a zero value of inside-outside air temperature difference whereas in figure 13 the curves indicate that there would still be a vertical

temperature gradient with a zero inside-outside air temperature difference. Actually, there probably

would be a small vertical temperature difference in the house with an outside air temperature of 70° F

because of the effect of the earth and basement

temperatures on the floor above. The temperature

differences between levels were the same whether

the inside doors were open or closed, as is shown in figure 12. In figure 12, the data obtained with the

interior doors open were plotted with open circles,

whereas those obtained with the interior doors

closed were plotted with solid circles. The curves in figure 12 show that the floor-surface temperature, the average of the wall-surface temperatures 30- and 60-in. above the floor, and the

12 Building Materials and Structures Report BMS115
basement air temperature all decreased uniformly

as the inside-outside air temperature difference in- creased when an electric room thermostat controlled

the heating system. No significant differences in floor-surface or wall-surface temperatures were observed with the interior doors open and closed. The

basement air temperature was slightly colder for the

tests with the interior doors closed, but this result

is attributed to greater cooling of the earth around

and beneath the house since these tests followed

those made with the doors open. It will be noted

that the wall-surface temperatures averaged about

2 deg F lower than the floor-surface temperatures

during these tests. In figure 13, the curves show

that the floor-surface temperature and wall-surface

temperature decreased as the outside air temperature decreased. The slopes of these curves are greater at low outside air temperatures than at high

outside air temperatures. This probably occurred

because the outdoor thermostat and modulatingcontrol circuit were so adjusted that the average room temperatures at the 30-in. level decreased

from 73.0° F for an outside air temperature of 50°

F to 68.6° F for an outside air temperature of 1° F.

. V. Heat Loss

The heat loss of the Test Bungalow observed at the different outside air temperatures is plotted

againgt inside-outside air-temperature difference in figures 12 and 13 for the two methods of heatingsystem control. In figure 12, the heat loss of the

structure is shown to be directly proportional to the

difference in temperature between the inside air and the outside air, although the heat loss averaged

about 5 percent more when the interior doors were

closed than when they were opened. This increase

in heat loss when the doors were closed was due

primarily to the overheating of the bathroom (used

15 2 0 25 3 0 35 4 0 45 5 0 5 5 6 0 65 70 INDOOR-OUTDOOR TEMPERATURE DIFFERENCE °F FiGUBE 14. Graphs showing the relation of the temperature dif- ferences across various building-construction elements of the Test Bungalow to the indoor-outdoor temperature difference for the baseboard-convector system with room-thermostat control.

as a utility room) as shown in tables 6 to 9. For the

tests with the outdoor-thermostat control, the

heat-loss rate of the house is shown in figure 13 to be a linear function of the inside-outside air- temperature difference for outside air temperatures

down to about 15° F and then to increase at a lesser rate for outside air temperatures below 15° F. The temperature differences across the several

construction elements of the house were plotted

against inside-outside temperature difference in figures 14 and 15 to determine whether or not they were directly proportional to the inside-outside

^ 55

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15 20 25 30 35 40 45 50 55 60 65 70 INDOOR-OUTDOOR TEMPERATURE DIFFERENCE °F Figure 15. Graphs showing the relation of the temperature dif- ferences across various building construction elements of the Test Bungalow to the indoor-outdoor temperature difference for the baseboard-convector system with the outdoor-thermostat

control. A Study of a Baseboard Convedor Heating System in a Test Bungalow 13
temperature difference. These curves show that the

temperature differences from the wall surface to the

outside air and from the bathroom air to the outside

air were proportional to the inside-outside temperature difference, but those across the ceiling and floor construction did not remain proportional to the

inside-outside temperature difference at the lowest

outside air temperatures observed. The heat loss through the floor and ceiling was proportionately

less for low outside air temperatures, apparently

because steady state conditions were not attained

as discussed later. This explains why the heat-loss curve for the entire house shown in figure 13

deviated from a straight line and suggests that a

similar, but less pronounced, deviation should have

occurred in the heat-loss curve in figure 12. The departure of the heat-loss curve from a

straight line at the lowest outside air temperatures

probably resulted at least in part from the fact that the lowest outside air temperatures could only

be maintained for 6 to 8 hr,with the refrigerating

unit, after which the tests were ended. The basement and attic air temperatures were decreasing at the rate of 0.2 deg to 0.5 deg F/hr after this length

of time and undoubtedly would have leveled off at values lower than those observed. Thus, steady

state temperature conditions were not fully attained

in either the basement or the attic. Figure 14 shows that the temperature difference

between bathroom air and outside air was considerably greater when the interior doors were closed and

that the temperature difference between floor sur- face and basement air was slightly greater with the

interior doors closed than with the doors open.

These two deviations probably account for the additional 5-percent heat loss observed for the house as a whole with the interior doors closed. Figures 12 and 13 show that the heat loss from

the Test Bungalow for outside air temperatures

above 20° F was greater with the outdoor-thermostat control than with the room-thermostat control. This was accounted for by the following conditions

which existed during the tests: first, higher room

temperatures were maintained; second, more^heat was liberated in the bathroom or utility room ; and

third, the basement air temperature was lower with

the outdoor-thermostat control than with the roomthermostat control. The first two conditions were

characteristic of the outdoor-thermostat control

system while the third condition occurred because

the house had been kept at a low outside air temperature for 2 weeks prior to the tests with the outdoorthermostat control.

VI. Room-Temperature Controls

The room thermostat used during these tests operated on the principle that a bimetallic element

will open and close a low-voltage circuit by deflec- tion caused by changing temperature of the ele- ment. Perhaps the only significant difference between the particular type used and other thermostats with bimetallic elements was that the spiral

element had a length of approximately 14 in., whereas some other room thermostats have ele- ments 2 or 3 inches long. Some air-temperature

change is required around the bimetallic element to open and close the contacts since heat must be

transferred to and from the element to deflect it. Therefore, the temperature of the air must change more than the change required in the temperature

of the element to open and close the contacts. The

change in air temperature required to open and

close the contacts of the thermostat depends upon

(1) the sensitivity of the thermostat mechanism,

(2) the heat capacity of the bimetallic element, (3) the degree of shielding and heat capacity of the

enclosing case, and (4) the rate of change of the air temperature. If the air-temperature change re- quired to operate the thermostat is too great, the

air becomes alternately overheated and overcooled

during every thermostat cycle. Usually the overcooling is more readily detected by the occupant

than is the overheating. This overcooling of a room, because of the thermostat-response characteristics, has come to be known as the "cold seventies" whereby a person might be too cool for comfort for a time just before the thermostat circuit is

closed, even though the thermostat is set at a comfortable temperature.

The change in air temperatures required to operate the room thermostat for three outside air temperatures is shown in table 14. The air temperatures were observed at the centers of three of the rooms

at the 30-in. level, whereas the thermostat was

located at the same level on the living room wall

adjacent to the archway between the living room

and hall. It will be noted that the change in air temperature due to the thermostat action became

less as the outside air temperature decreased. This

result was to be expected as the rate of rise of air temperature with time was lower at low outside

air temperatures when the heat loss of the house more nearly approached the capacity of the heating

system, than at high outside air temperatures, thus

Table 14. Room air-temperature differential produced by

electric room thermostat

Outside

air temperature

Temperature

during cycle Living room Kitchen North bedroom Average

°F

32.1 (Average maximum. . .\ Average minimum . . .

[ Differential [Average maximum. . .

< Average minimum . . .

t Differential [Average maximum. .

I Average minimum . . .

[ Differential

°F

72.2 68.2

4.0

71.7 69.6

2.1 70.1 69.0

1.1

"F

72.7

68.9 3.8

71.8 69.8

2.0 70.0

69.8

. 0.2

"F

71.2

67.2

4.0 71.2

69.0 2.2

66.9 66.0

0.9

°F

20.6

3.9

0.8

2.1

0.7

14 Building Materials and Structures Report BMSI15
allowing the element more time to follow the air temperature closely. The air-temperature differential ranged from 4.0 deg to 1.1 deg F in the living room for outside air temperatures ranging from 32° to

1° F. The temperatures recorded in table 14 were

observed with mercury-in-glass thermometers with

bulbs approximately in. in diameter and ^ in. long. The air temperatures at the observation sta- tions undoubtedly changed somewhat more than the

thermometers indicated.

The modulating heating-system control operated on the principle that changes in temperature of an

outdoor bulb could be relayed to a motor-operated

three-way valve at the boiler outlet through a potentiometer circuit in such a way as to change

the temperatures of the water entering the heating

system just the right amoimt to maintain a constant

room-air temperature at all times. The rate of change of supply-water temperature with outside

air temperature was adjustable as the range of supply-water temperature required for a given

house depends upon the amount of heating surface

provided in its heating system. For the baseboard

convector system in the Test Bungalow, a range of water temperature from about 80° to 205° F was

required for a range of outside air temperature

from 65° to 0° F. Because this range of Avater temperature was not obtainable with the control

system supplied for the tests, the manufacturer's

representative adjusted the controls to supply water

to the baseboard convoctors at a temp(^raturo of about 130° F for an outside air tcunperaturo of 50°

F and at a temperature of 195° F for an outside air temperature of 0° F. An approximate adjustment was made by using tabulated information furnished

with the control system. The final adjustment was made by repeated trials over a period of several

days observation.

The room temperatures maintained by the modulating control under steady state conditions are summarized in tables 10 to 13. The average water

temperatures in the baseboard-convector circuit are plotted against inside-outside air-temperature dif- ferences in figure 13. This relationship was one of direct proportion for outside hir temperatures

above 20° F. The actual control of water temperature provided by the modulating valve for inside- * outside air-temperature differences above 50° F is indicated by the dotted line A, B, C in figure* 13

because the control reached the limit of its modulating range at an outside air temperature of 12° F. For outside air temperatures lower than 12° F the

supply-water temperature remained constant. Tables 10 to 13 show that the room temperature

at the 30-in. level in the house averaged 73.0° F

for an outside air temperature of 50.1° F and gradually decreased as the outside air temperature

decreased until the room temperature averaged

200|

180

160

140

80r

0- GO*-

TEMPERATURE OF AIR AT CENTER OF LIVING ROOM

30 IN ABOVE FLOOR

>

) OUTSIDl : AIR EMPER iTURE

1 1 12 16 20 24 28 32 TIME , HOURS

36 40 44 48 52 56

FiGUBFi 16. Variation of living-room air temperature and boiler-outlet water temperature for transient outside temperatures with the outdoor-thermostat and modulating-valve control sysietn. A Study of a Baseboard Convector Heating System in a Test Bungalow 15
71.2° F for an outside air temperature of 20.5° F. This gradual decrease of room temperature shows

that the rate of change of supply-water temperature

with outside air temperature was a little too low to maintain constant room temperatures and that the

control mechanism was not quite properly adjusted.

It indicates that very careful adjustment by ex- perienced persons would be required to obtain

uniform room temperatures with the modulatingcontrol system. In table 13, the average room

temperature at the 30-in. level is shown to have

been 68.6° F for an outside air temperature of 0.9° F. This decrease in room temperature is attributed

primarily to the lack of sufficient modulating range

by the controller, since it could not raise the supplywater temperature above 195° F. During the tests with constant outside air temperatures, when the outdoor thermostat controlled

the heating system, there was no cycle in the room

temperature similar to that observed with the room

thermostat. The maximum change in room temperature occurring during any one test with the

outdoor-thermostat control was less than 1 deg F. The control of room temperature by the outdoor

thermostat and modulating valve for rapidly changing outside air temperature is shown in figure 16. The curve for the air temperature at the center of the living room shows that some overheating of the

house occurred during periods of rapidly falling

outside air temperature and that some underheating occurred during periods of rapidly rising outside

air temperature. This result was to be expected

because a counter change in the temperature of the

supply water occurred immediately in response to a change in outside air temperature whereas the

inside air temperatures did not indicate the effect of the outside air-temperature change for an hour

or more because of the thermal time lag of the

exterior walls. This characteristic of the outdoorthermostat and modulating-control system caused

air-temperature changes inside the house as great

as 5 deg F for the pattern of outside air temperatures used during the tests in which the outside air temperature was varied at rates up to 13 deg F/hr.

Outside air temperatures rarely increase or de- crease at such a rapid rate as this under natural

conditions so that the observed effects are probably

of greater magnitude than would occur in actual use of this control. This characteristic of overanticipating the

changes in the heat requirements of a house could

be corrected by insulating the outdoor-thermostat

bulb sufficiently to provide a thermal time lag in its response equivalent to that of the exterior walls of the house with which it was being used. With such

a provision, the heat requirements of the house and

the heat supply to the house could be kept more

nearly equal during changing outside air temperature conditions than with an uninsulated thermostat bulb.

VII. Pick-Up Characteristics

The pick-up of the bedroom temperature after night cooling was observed with the outdoor-thermostat control because consideration of the operating principle of this control suggested that it would provide slower pick-up than conventional

room-thermostat control. The results of this test are plotted in figure 17. During the test, the bedroom

windows were opened and left open for 6 hr until the room temperature had decreased to 50° F and

leveled off at 52° F. The interior doors of the house were closed during the 6-hr period and the re- mainder of the rooms were maintained at approximately 70° F by the outdoor-thermostat and modulating control. After cooling the bedrooms for 6 hr,

the windows were closed simulating the conditions

in a house when the occupants arise and wish to warm the bedrooms. The temperatures were observed in each room of the house and at the supply

to the baseboard convector system during the

pick-up period while the interior doors remained

closed. Seven hours elapsed before the temperature in the north bedroom reached 70° F and the temperature in the south bedroom did not approach a

steady value of 68° F for at least 9 hr after closing

the windows. The temperature of the water supplied to the baseboard convector did not change

appreciably when the windows were opened or

during the pick-up period. A change in supplywater temperature was not to be expected with the

outdoor-thermostat control system, however, since

the outside air temperature remained constant.

If the interior doors had been opened when the

windows were closed, the temperatures of the

several rooms would have tended to equalize but

the water temperature of the heating system would

not have been increased and about the same length

of time would have been required to raise the air temperature of the whole house to 70° F. That is, the outdoor-thermostat control pr(Tvided no additional heat for raising the temperature in rooms

that had been cooled during the night by opening

the windows.

With the baseboard convector system, a room

thermostat located in the living room would pro- vide the same type of pick-up as that shown in figure 17 if the interior doors were left closed after night cooling of the bedroom. However, if the in- terior doors were opened, the living-room air would

be cooled, whereupon the full capacity of the heating plant would become available for warming the

entire house to 70° F. The time reqvnred to accomplish the pick-up would then depend upon the margin

of heat emitted by the furnace operating at full capacity above the heat loss occurring at the time.

16 Building Materials and Structures Report BMSI15
190

180

170

160

150

u.

ft 80

UJ

a:= 70

BOILER OUTLET WATER

KITCHEN AND, LIVING ROOM AVERAGE

a 10 12 14 TIME , HOURS

Figure 17. Pick-up of bedroom temperature after night cooling with outdoor-thermostat and modulating-valve control system.

VIII. Heat Emission of Convector

The heat output per unit length of the finned

convector element was computed for the four tests employing the outdoor-thermostat control for which the average water temperature in the system was observed. The results of these computations are shown in table 15. The gross heat input to the Test

Bungalow was diminished by the heat equivalent of the electric energy used by lights, motors, and in- struments and by the heat emission of the unfinned

1-in. pipe used to connect the finned elements.

There were approximately 85 ft of unfinned pipe

in the system including that used adjacent to the

pump and boiler. The heat emission of the bare pipe was computed by using the factors tabulated in the

Guide of the American Society of Heating and

Ventilating Engineers for horizontal bare steel pipe. These factors may be slightly different for bare pipe enclosed in a housing such as that used

for the baseboard convector. The total heat output

of the finned convector elements was divided by the

total length of finned pipe installed Avhich was 19.33

ft. Table 15 shows that the heat output per linear

foot of convector element ranged frojn 382 Btu/hr

for a temperature difference of 57 deg F between

water and room air to 957 Btu/hr for a temperature

difference of 126.6 deg F. Table 15. Heat emission of baseboard convector

Outside air temperature °F. . 50.1 32.0 20.5 0.9 Average water temperature in system op 128.2 159.2 178.8 191.9 Temperature difference, water to inlet air Deg F. . 57.0 89.0 110.3 126.6

Gross heat input to Test Bungalow Btu/hr.

.

12,600 19,520 24,750 29,480 Heat equivalent of

lights, motors, etc.. . . Btu/hr .

.

1,820 1,820 1,830 1,830

Gross heat output of

boiler Btu/hr .

.

10,780 17,700 22,920 27,650 Heat output of bare pipe .Btu/hr.

.

3,400 5,820 7,650 9,150

Total heat output of finned pipe Btu/hr . . 7,380 11,880 15,270 18,500

Unit heat output of finned pipe B(u/hr/ft. . 382 614 790 957

IX. Discussion and Conclusions

The comparison of the two methods of heating

system control in this report shows that the principal advantages of the outdoor thermostat and

modulating-valve control was that it eliminated the

fluctuating room temperature caused by the differ- ential of the electric room thermostat. These fluc- tuations are sometimes excessive and may give rise to the uncomfortable condition known as the cold

seventies. The outdoor thermostat and modulatingvalve control system would be considerably more

expensive initially than the room thermostat and

would probably entail the use of more electrical energy for the circulating pump except in the coldest weather since the circulating pump runs constantly with the former control system.

A disadvantage of the particular outdoorthermostat control system used was that it provides no additional heat output for picking up the temA Study of a Baseboard Convector Heating System in a Test Bungalow 17
perature of a house in the morning as well as no means for lowering the temperature at night. This

feature would be a source of inconvenience to some

families who desire to lower the temperature of the

house at night and would prevent conservation of

fuel by reduction of room temperatures.

The results of this investigation showed that the

specimen baseboard convector system produced

smaller vertical temperature gradients in the Test

Bungalow than any other system or device that had

been tested heretofore. For equal outside air temperatures of 20° F, a temperature difference of 3.5

deg F was observed between the 2- and 60-in. levels with the baseboard convector, whereas a temperature difference of 8 deg F was observed between the same levels for a gravity hot-water heating system

with conventional thin tube radiators and a boiler

in the basement. However, the Test Bungalow was

better insulated for tests with the baseboard con- vector than for the tests with the hot-water heating

system used in this comparison. For this reason the

heat loss at an outside air -temperature of 0° F during the present tests was equivalent to the heat loss observed at an outside air temperature of 20° F

when the gravity hot-water heating system was

installed in the Test Bungalow. For this condition

of equivalent heat loss, the vertical temperature

difference was 8 deg F for the gravity hot-water

heating system and 4.2 deg F for the baseboard con- vector system in the living zone for a heat loss of approximately 32,000 Btu/hr.

The low vertical temperature differences obtainable with the. baseboard convector are attributed to the extended distribution of the elements around

the perimeter of the house and to the strategic location, from a thermal standpoint, of the convectors

at the bottom of the cold exterior walls. Analysis of the heat transmission from the interior to the exterior of the Test Bungalow reveals that about 82

percent of the total heat loss of the structure occurred through the exterior walls, the windows

and doors, and by infiltration. This 82 percent of the heat loss is largely of a nature that produces

downward currents of cold air along the exterior

walls. With heating elements distributed around

the entire perimeter of the house at the base of the

exterior walls, such as the baseboard convectors,

these cold currents of air are warmed at the perimeter of the house and are thus prevented from flowing across the floor as they otherwise would do. Measurements in a research house at Purdue

University [6] indicate that vertical temperature

gradients as low as or lower than those observed

with the baseboard convectors can be obtained

with a floor-panel heating system. However, such a system has not yet been installed in the Test Bungalow for comparison. Lower temperature gradients were observed with radiant baseboard heating in the IBR Research Home [4] than were observed in

the Test Bungalow with baseboard convectors. This

difference is attributed primarily to the more ex- tensive insulation of the former structure which was

built with 3^-in. rock-wool insulation in all exterior walls and ceiling, with all windows and

doors weatherstripped and with storm doors.

Architecturally, the baseboard heating systems

present the problem of cutting the baseboard ele- ments to fit the perimeter of the house since the

interior dimensions of houses are not standardized.

This problem is readily surmounted by the system

used in these tests since standard pipe and fittings are used to connect the finned elements and the

pipe lengths can be cut during installation. The

sheet-metal convector housing can also be shortened

during installation without great difficulty. The

installation of a baseboard heating system would

be somewhat more diflScult in a house with exterior

walls of masonry unless they were furred on the

inside. In that case the baseboard elements could

be supported on the furring strips.

The heat loss of the Test Bungalow could probably have been decreased measurably during the

tests by placing loose insulation in the stud spaces

back of the baseboard elements to a height of about

1 foot. As shown in figure 7, the pressed-steel rear housing panel for the baseboard convector adjoined

the stud space and could, therefore, transmit considerable heat into the stud spaces at the bottom

of the walls. The particular design of convector elements and

sheet-metal housing used for these tests Avas considered somewhat conspicuous and unattractive by

most observers. Many people were also of the

opinion that the type used in the Test Bungalow

projected too far from the wall. However, the rela- tively high heat output per linear foot of convector

obtained with the test specimens suggests that

smaller pipe and narrower fins might be employed

together with longer elements to improve the appearance without any sacrifice in total capacity.

The use of longer finned elements with lower heat

emission per linear foot might even decrease the

vertical gradient and increase the comfort. The

convectors could thus be redesigned to occupy less floor space at the baseboard and have a distinct

advantage over frecrstanding radiators in that

respect.

Not every design of baseboard heating element

has sufficient heat output per unit of length to heat a house without any insulation even though it is installed around all of the exterior walls. Anyone

contemplating the .use of baseboard heating should

investigate the particular design under consideration

to determine whether or not its capacity is adequate

for heating the house to which it is to be applied.

The type of element tested would heat any con- ventional house without insulation since the observed maximum heat emission was approximately 1,000 Btu/hr per hnear foot of finned pipe. A

total of 85 linear feet of finned pipe could have been

installed in the Test Bungalow. The resulting heat

output of 85,000 Btu/hr is eq,uivalent to 130 Btu/hr

for each square foot of floor area for the structure,

18 Building Materials and Structures Report BMS115
which is considerably in excess of the average design

heat loss of uninsulated houses in the United States. The baseboard heating system is well suited for application to basementless houses because it is in- stalled above the floor level except for the special

loops below the exterior doors and because it provides better comfort than most other systems at the floor level. However, this type system can also

be used in houses with basements with the boiler

located below the floor. In spite of the disadvantage

of fitting the system to the variable dimensions of conventional houses and its inability to control the

heat output to the rooms on an individual basis,

the baseboard heating system offers a means for providing more comfortable conditions in dwelling

houses than many of the systems now in use.

X. References

1. References Cited in Text

[1] Richard Eve and J. C. Weston, The economics of house

heating, J. Roy. Inst. Brit. Arch. (Nov. 1948).

[2] Richard S. Dill and Paul R. Achenbach, Temperature dis- tribution in a Test Bungalow with various heating

devices, NBS Building Materials and Structures Report

BMS108 (1947).

[3] A. P. Kratz and M. Fahnestock, Steam condensation an

inverse index of heating effect. Trans. Am. Soc. Heating

Ventilating Engrs. (1931).

[4] A. P. Kratz and W. S. Harris, A study of radiant base- board heating in the IBR research home, Univ. 111. Eng.

Expt. Sta. Bui. 358 (Aug. 30, 1945).

[5] Paul R. Achenbach, Temperature distribution in a Test Bungalow with radiant and jacketed space heaters, NBS

Building Materials and Structures Report BMS114

(1949).

[6] J. M. Ayres and B. W. Levy, Air temperature gradients in a panel heated room, Heating, Piping and Air Conditioning Mag. (Oct. 1947).

2. Additional References

A. P. Kratz and S. Konzo, Investigation of oil-fuel forced-air furnace systems in the research residence. Univ. lU. Eng.

Expt. Sta. Bui. 318 (Nov 7,' 1939).

XI. Glossary of Selected Heating Terms

This glossary was compiled to assist the reader

with definitions and explanations of a selected

number of terms used in this report. Another list of heating, ventilating, and air-conditioning terms

will be found in the current issue of the guide

published by the American Society of Heating and

Ventilating Engineers.

Air change.—An air change is a volume of air equivalent to the interior volume of the occupied

portion of a house.

Baseboard convedor.—A heating element used in the position normally occupied by the baseboard in a house and designed to transfer heat to a room

primarily by convection.

Bimetallic element. —A temperature-sensitive ele- ment that is deflected by a temperature change be- cause of the unequal expansion of the two different

metals of which it is composed.

Comfort charts. —Charts published by the American Society of Heating and Ventilating Engineers

showing the relation between an index of comfort

called "effective temperature" based on experiments with human subjects and the dry-bulb temperature, relative humidity, and air motion.

Convection.—The transfer of heat by the move- ment of a liquid or gas over a heating or cooling

surface. Crawl space.—A shallow space beneath the floor inside the foundation walls of a house.

Dry-bulb temperature.—The temperature of air indicated by an accurate thermometer suitably

shielded from radiation.

Electric room thermostat.—A temperature-sensitive device located within a heated space that automatically controls the heat delivery to that space

by opening and closing an electrical circuit.

Immersion aquastat.—A thermostat installed in a pipe or tank to control the temperature of the

fluid therein by actuating suitable controls.

Infiltration. —The leakage of air into a house

through cracks and small openings in floor, ceiling,

and exterior walls. Manometer.—An instrument usually filled with

water, mercury, or light oil used for measuring

small pressure differences.

Modulating control system.—A control or group

of controls that adjusts the heat delivery of a heating system either smoothly or in small steps between the minimum and maximum values as re- quired to offset the heat loss of a house for any

outdoor temperature likely to occur. Outside-thermostat control.—A temperature-sensitive device located outdoors that increases the heat

delivery to a house when the outside air temperature

decreases.

Pick-up conditions. —Any condition for which the

heating plant must raise the temperature in all or a

part of the living space. Radiant baseboard element.—A heating element

which emits a considerable portion of its heat to the

living space by radiation placed in the position

normally occupied by the baseboard.

Radiation.—The transfer of heat by a wave

motion similar to that by which light is transmitted.

Relative humidity.—Approximately, the ratio of the weight of moisture in a quantity of air to the

weight of moisture in the same quantity of air at the same temperature when saturated.

Steady state.—A temperature distribution that

does not change with time.

Temperature-limit control.—A temperature-sensitive element, installed in the hot-water supply line A Study of a Baseboard Convector Heating System in a Test Bungalow 19
of a boiler or the bonnet of a furnace, that shuts off the burner or retards the rate of heat generation

when a selected maximum outlet temperature has

been reached.

Thermal time lag. —The time required for heat to pass through a material or combination of materials

used in walls, floors, or other construction elements.

Three-way mixing valve. —A valve, with two inlets and one outlet, which blends two streams of water

at different temperatures in varying proportions by- means of a double-faced disk to produce the outlet

temperature required by its control mechanism.

Washington, March 4, 1949.

20 Building Materials and Structures Report BMS116

"ii U. S. GOVERNMENT PRINTING OFFICE: 1949 831473


BUILDING MATERIALS AND STRUCTURES REPORTS

[Continued from cover page n]

BMS32 Structural Properties of Two Briclc-Concrete-Block Wall Constructions and a Concrete- Block Wall Construction Sponsored by the National Concrete Masonry Association 15j5 BMS33 Plastic Calking Materials 15^ BMS34 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 1 15i

BMS35 Stability of Sheathing Papers as Determined by Accelerated Aging * BMS36 Structural Properties of Wood-Frame Wall, Partition, Floor, and Roof Constructions With

"Red Stripe" Lath Sponsored by The Weston Paper and Manufacturing Co lOfS BMS37 Structural Properties of "Palisade Homes" Constructions for Walls, Partitions, and Floors, Sponsored by Palisade Homes * BMS38 Structural Properties of Two "Dunstone" Wall Constructions Sponsored by the W. E. Duim Manufacturing Co 10{5

BMS39 Structural Properties of a Wall Construction of "Pfeifer Units" Sponsored by the Wisconsin

Units Co m

BMS40 Structural Properties of a Wall Construction of "Knap Concrete Wall Units" Sponsored

by Knap America, Inc 15j5 BMS41 Effect of Heating and Cooling on the Permeability of Masonry Walls * BMS42 Structural Properties of Wood-Frame Wall and Partition Constructions with "Celotex"

Insulating Boards Sponsored by The Celotex Corporation 15)4 BMS43 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 2 15fi BMS44 Surface Treatment of Steel Prior to Painting lOfS BMS45 Air Infiltration Through Windows 15^ BMS46 Structural Properties of "Scott-Bilt" Prefabricated Sheet-Steel Constructions for Walls,

Floors, and Roofs Sponsored by The Globe-Wernicke Co lOfi BMS47 Structural Properties of Prefabricated Wood-Frame Constructions for Walls, Partitions,

and Floors Sponsored by American Houses, Inc 20(4 BMS48 Structural Properties of "Precision-Built" Frame Wall and Partition Constructions Sponsored by the Homasote Co 15ff BMS49 Metallic Roofing for Low-Cost House Construction 20^ BMS50 Stabihty of Fiber Building Boards as Determined by Accelerated Aging 10^ BMS51 Structural Properties of "Tilecrete Type A" Floor Construction Sponsored by the Tilecrete Co m

BMS52 Effect of Ceiling Insulation Upon Summer Comfort lOjd BMS53 Structural Properties of a Masonry Wall Construction of "Munlock Dry Wall Brick" Sponsored by the Munlock Engineering Co 10^ BMS54 Effect of Soot on the Rating of an Oil-Fired Heating Boiler IGi BMS55 Effects of Wetting and Drying on the Permeability of Masonry Walls 10(4 BMS56 A Survey of Humidities in Residences 10(4 BMS57 Roofing in the United States—Results of a Questionnaire * BMS58 Strengthof Soft-Soldered Joints in Copper Tubing... 10(4 BMS59 Properties of Adhesives for Floor Coverings 15(4 BMS60 Strength, Absorption, and Resistance to Laboratory Freezing and Thawing of Building

Bricks Produced in the United States 15(4 BMS61 Structural Properties of Two Nonreinforced MonoUthic Concrete Wall Constructions. ... 10(4 BMS62 Structural Properties of a Precast Joist Concrete Floor Construction Sponsored by the Port- land Cement Association 10(4 BMS63 Moisture Condensation in Building Walls 15)4 BMS64 Solar Heating of Various Surfaces lOff BMS65 Methods of Estimating Loads in Plumbing Systems 15(4 BMS66 Plumbing Manual 35(4 BMS67 Structural Properties of "Mu-Steel" Prefabricated Sheet-Steel Constructions for Walls,

Partitions, Floor, and Roofs, Sponsored by Herman A. Mugler 15(4 BMS68 Performance Test for Floor Coverings for Use in Low-Cost Housing: Part 3 20(4 BMS69 Stability of Fiber Sheathing Boards as Determined by Accelerated Aging 10(4 BMS70 Asphalt-Prepared Roll Roofings and Shingles 20^ BMS71 Fire Tests of Wood- and Metal-Framed Partitions 20f4 BMS72 Structural Properties of "Precision-Built, Jr." Prefabricated Wood-Frame Wall Construction Sponsored by the Homasote Co 10(4 BMS73 Indentation Characteristics of Floor Coverings 10j4 BMS74 Structural and Heat-Transfer Properties of "U. S. S. Panelbilt" Prefabricated Sheet-Steel Constructions for Walls, Partitions, and Roofs Sponsored by the Tennessee Coal, Iron & Railroad Co 15(4 BMS75 Survey of Roofing Materials in the North Central States 15(4 BMS76 Effect of Outdoor Exposure on the Water PermeabiUty of Masonry Walls 15^ BMS77 Properties and Performance of Fiber Tile Boards 10(4 BMS78 Structural, Heat-Transfer, and Water-Permeability Properties of Five Earth-Wall Constructions 25(4 BMS79 Water-Distributing Systems for Buildings 20)4 BMS80 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 4 15^ BMS81 Field Inspectors' Check List for Building Constructions (cloth cover, 5 x 7^ inches) 20^

Out of print. [List continued on cover page iv]
BUILDING MATERIALS AND STRUCTURES REPORTS

[Continued from cover page m]

BMS82 Water Permeability of Walls Built of Masonry Units 25?; BMS83 Strength of Sleeve Joints in Copper Tubing Made With Various Lead-Base Solders 10^ BMS84 Survey of Roofing Materials in the South Central States 15i

BMS85 Dimensional Changes of Floor Coverings With Changes in Relative Humidity and Temperature 10(i BMS86 Structural, Heat-Transfer, and Water-PermeabiUty Properties of "Speedbrik" Wall Construction Sponsored by the General Shale Products Corporation 15|4

BMS87 A Method for Developing Specifications for Building Construction—Report of Subcommittee

on Specifications of the Central Housing Committee on Research, Design, and Construction 15fS BMS88 Recommended Building Code Requirements for New DweUing Construction With Special Reference to War Housing * BMS89 Structural Properties of "Precision-Built, Jr." (Second Construction) Prefabricated WoodFrame Wall Construction Sponsored by the Homasote Co 15(i BMS90 Structural Properties of "PHC" Prefabricated Wood-Frame Constructions for Walls, Floors, and Roofs Sponsored by the PHC Housing Corporation 15jS BMS91 A Glossary of Housing Terms 15^ BMS92 Fire-Resistance Classifications of Building Constructions 30jf BMS93 Accumulation of Moisture in Walls of Frame Construction During Winter Exposure 10^ BMS94 Water PermeabiUty and Weathering Resistance of Stucco-Faced, Gunite-Faced, and "Knap

Concrete-Unit" Walls lOfi BMS95 Tests of Cement-Water Paints and Other Waterproofings for Unit-Masonry Walls. 25 BMS96 Properties of a Porous Concrete of Cement and Uniform-Sized Gravel lOjS BMS97 Experimental Dry-Wall Construction With Fiber Insulating Board 10^ BMS98 Physical Properties of Terrazza Aggregates 15i

BMS99 Stractural and Heat-Transfer Properties of "Multiple Box-Girder Plywood Panels" for WaUs,

Floors, and Roofs 15fS BMSlOO Relative Slipperiness of Floor and Deck Surfaces 10^ BMSlOl Strength and Resistance to Corrosion of Ties for Cavity WaUs 10^ BMS102 Painting Steel lOi BMS103 Measurements of Heat Losses From Slab Floors 15i

BMS104 Structural Properties of Prefabricated Plywood Lightweight Constructions for Walls, Partitions, Floors, and Roofs Sponsored by the Douglas Fir Plywood Association ZOi

BMS105 Paint Manual with particular reference to Federal Specifications $1 .00 BMS106 Laboratory Observations of Condensation in Wall Specimens * BMS107 Building Code P^equirements for New DwelUng Construction * BMS108 Temperature Distribution in a Test Bungalow With Various Heating Devices lOjS BMS109 Strength of Houses: AppMcation of Engineering Principles to Structural Design .$1 .50 BMSUO Paints for Exterior Masonry Walls 15ji BMSlll Performance of a Coal-Fired Boiler Converted to Oil 15(4 BMS112 Properties of Some Lightweight-Aggregate Concretes With and Without an Air-entraining

Admixture 10^ BMS113 Fire Resistance of Structural Clay Tile Partitions 15fS BMS114 Temperature in a Test Bungalow With Some Radiant and Jacketed Space Heaters 25^ BMS115 A Study of a Baseboard Convector Heating System in a Test Bungalow 15^

•Out of print.