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NBS TECHNICAL NOTE 710-4

U.S.

PARTMENT

OF

COMMERCE

BUILDING

RESEARCH TRANSLATION

Thermal Comfort Requirement

Adjacent to Cold Walls -

Application to Glazed Opening
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and

technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Computer Sciences and

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THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of

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" Located at Boulder, Colorado 80302.
«L BUREAU OP ST*«O.MB? 8 1972 X£> BUILDING RESEARCH TRANSLATION

^

6

; Thermal Comfort Requirement

73. Adjacent to Cold WallsApplication to Glazed Opening

J. Anquez and M. Croiset

Centre Scientifique et Technique du Batiment

Paris, France

Translated by the Joint Publication Research Service, U.S. Department of Commerce,

Washington, D.C. 20234

"few of

U.S. DEPARTMENT OF COMMERCE, Peter G. Peterson, Secretary

(,,$. NATIONAL BUREAU OF STANDARDS, Lawrence M. Kushner, Acting Director

>« Issued May 1972 •£• , rerhtttcoC woVe M, "(0-4.
National Bureau of Standards Technical Note 710-4

Nat. Bur. Stand. (U.S.), Tech. Note 710-4, 54 pages (May 1972)

CODEN: NBTNAE

Issued May 1972

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. C13.46:710-4). Price 55 cents.
FOREWORD

The United States/French Cooperative Program on Building

Technology entails an exchange of personnel between the

National Bureau of Standards (Building Research Division)

and the Centre Scientifique et Technique du Batiment

(CSTB) of France. The program also involves the exchange

of information between the two research organizations.

It is felt that some of the documented information can be usefully shared with the U.S. building industry; and,

therefore, certain papers were selected for reproduction

in media on sale to the public by the Government Printing

Office. It should be understood that the CSTB documents

made public through such media as this TECHNICAL NOTE

do not necessarily represent the views of the National

Bureau of Standards on either policy or technical levels.

At the same time, building researchers at the National

Bureau of Standards consider it a public service to share

with the U.S. building industry certain insights into

French building technology.

<JAMES R. WRIGHT

Chief, Building Research Division

Institute for Applied Technology

National Bureau of Standards

III

THERMAL COMFORT REQUIREMENT ADJACENT

TO COLD WALLS

Application to Glazed Openings

by

J. Anquez and M. Croiset

This paper is translated from the French original

and is published under the Building Research Division/

Centre Scientifique et Technique du Batiment information

exchange program.

The thermal comfort of an individual inside a closed room in winter is essentially a function of

the temperature of - the air with which the human body

transfers heat by convection, and also of the temperature

of the room's walls with which the human body transfers

heat by radiation. The presence of glazed openings

(windows) which in winter are generally the coldest

walls in a residence room, can thus be a source of

discomfort

.

The first part of the paper reports research

conducted with a view to determining the thermal comfort

requirement near to a cold wall. The research led to the

definition of the "air-radiation requirement" for a plane

surface element parallel to the wall, the requirement

being that, at about 1 m from the wall, this temperature

must remain above l6 or 17 °C.

The second part of the paper studies ways of satisfying

the requirement near to glazed openings in a living room

in winter. The solution to the problem will depend on numerous factors: climatic zone, average temperature of

the room, position of heat sources, dimensions of the

openings, type of glazing (single or double), presence or absence of curtains or screens.

Key words: Curtains, effect of; environmental conditions;

glazed openings; human response; thermal comfort requirement,
PART I: DEFINITION OF THE REQUIREMENT

1.1 METHOD EMPLOYED

Method Concept, Test Equipment and Facilities

In order to understand and define the requirement, subjects were

placed close to cold walls under known conditions and their responses as

to sensations of comfort or discomfort were noted.

The test facility utilized is depicted in Figure 1. It had three

rooms

:

A. The first room simulated the cold outside atmosphere.

An approximate temperature of 0°C was maintained in this

room.

B. The second room simulated a residence room with an

outside vertical wall. This wall separated room B

from room A. It contained a glazed opening consisting

of a single pane of glass covering an area of 2.7 m2 .

The remainder of the wall had a K coefficient

(coefficient of heat transmission) of 2.6 kcal/m2h°C. —

C. The third room simulated a residence room without an

outside wall.

Tests were conducted in room B where the subject remained for 10

minutes before being questioned. Room C served as a transition or

waiting room in which the subject remained for 30 minutes before entering

room B.

1/ o -lkcal/m2h°C = 0.20^8 Btu/ftTi°F
Test Environmental Conditions

The environmental conditions maintained in room B for the tests were

as follows

1. Heating was either "by radiator or by floor and ceiling

(embedded pipe coils).

With floor and ceiling heating, the temperature of the floor was not

above 2^°C and the ceiling temperature did not exceed 2

rJ°C . They were

therefore well within comfort limits.

For heating by radiator, the latter was installed in the position

indicated by the letter t in Figure 1. Screens were arranged in such a

way as to virtually eliminate all radiation transfers between radiator

and subject, and also between radiator and walls. In this way 5 heating

was almost exclusively by convection.

2. Heating was controlled so as to obtain a temperature measured

by "bulb thermometer"^/ (globe temperature) of approximately l8 , 20,

or 22°C at a height of one meter in the center of the room.

3/

3. Ventilation air flow was Ho m^/h. This means that the airchange rate was essentially equal to one. Air from cold room A was

delivered into room B through either a series of openings distributed

alongside the ceiling (when heating was by floor and ceiling) , or

through an elongated, deflector-equipped opening behind the radiator

(when a radiator provided the heating). In this way, all likelihood of

discomfort due to cold-air drafts was eliminated (see the study on this

subject, listed as item a in the Bibliography). Air velocity in the

zone occupied by the subjects was below 0.15m/s.

2T— .Translation note: bulb thermometer is used for globe thermometer ^1 m3/h = 35-3 ft^Th" Vh

3
h. Humidity of the air was not controlled. But ventilation air

came from a cold room in which, therefore, there was little variation in

absolute humidity, and furthermore, occupancy conditions were almost

always the same. Therefore, relative humidity in room B varied little.

It fluctuated between 30 and i+5 per cent.

5. The walls, floor and ceiling of the room, other than the exterior

wall (between room B and A) and those surfaces possibly used for heating

purposes, were either inside walls (between room B and C), or very highly

insulated outside walls (K coefficient was of the order of 0.2 kcal/m^h°C).

Surface temperatures of all these outside walls thus differed less than

half a degree from the normal temperatures of the inside walls

.

Temperature, humidity, and average air velocity in room C were

identical to those in room B. A radiator provided the heating. In this

room also, screens eliminated radiation transfers from the radiator.

There was no cold wall nor warm wall. All walls were inside walls or

heavily insulated as above for room B.

Test Conditions Relative to the Sub.jects

As we stated above, the subjects initially stayed in room C for 30

minutes, and then spent 10 minutes in room B. We did verify with 10

subjects during a small number of experiments, that this was sufficient

time, since sensations after 10 minutes and after 30 minutes were

practically the same. This conclusion is of course valid only within

the temperature and humidity range of our experiments. But this range

corresponds well enough to average indoor conditions in France during

cold-weather periods. The subject was seated when in either room C or B.

In room B, the subject sat in the axis of the cold wall and either faced
that wall or had his back to it. The distance to the cold wall, measured

from the vertical axis of the chair, was 3.30 m, 2.00 m, 1.00 m, or

0.50 m.

Tests were conducted on five subjects, one man and four women, all

CSTB staff personnel: a 30-year old male technician (subject A) , a kOyear old cafeteria worker (subject B) , and three secretaries ranging in

age from 20 to 25 years (subjects C, D, and E). Subjects wore their

customary indoor clothing.

Recapitulation of Study Parameters and Number of Tests

Study parameters were as follows

:

—type of heating: floor and ceiling or by convection. —average ambient temperatures: 18, 20, or 22°C

.

—distance to cold wall: 3-30 m, 2.00 m, 1.00 m or 0.50 m. —position of subject: facing the cold wall or with back

to it. —subject: A, B, C, D, or E.

If we had used all parameter values we would have had to conduct

2x3xUx2x5= 2k0 tests. Actually, because subjects were not

always readily available, there were some gaps. On the other hand, we

often had to start the tests with convection heating over again, We did

finally complete a total of 2kQ tests.

Physical Magnitudes Measured to Characterize the Environment. "AirRadiation Temperature for a Surface Element."

We did not question the validity of the fact that the sensation of

thermal comfort depends exclusively on the dry-bulb temperature of the

air and the radiant temperature under the following conditions: a heated

5
room in winter, with still air and an approximately uniform humidity.

This principle allows the environment to be characterized by a single

temperature generally called "resultant dry temperature" and measured in

still air with a "bulb thermometer."

But this procedure appears a priori to be unsatisfactory for our

problem. In fact, we observed that the discomfort experienced by the

subjects—when there actually was discomfort—resulted from sensations of

cold localized on parts of the body (knees, back...) turned toward the

cold wall. Consequently, we thought that the globe temperature which

uniformly records transfers on all sides of the body, was doubtlessly

poorly suited to the problem. We thus devised a method of measurement

using a "plane thermometer" to record heat transfers on only one side of

the body, the side turned towards the cold wall. This plane thermometer

consists of a 20 cm-thick, 0.80 m by O.UO m block of good thermal

insulating material (A = 0.032 kcal/m.h°C) whose surface temperature is

measured by a thermocouple. This block was placed on a chair (see Figure

2) so that it stood vertically on end and was parallel to the cold wall.

Temperature was measured in the vertical axis of the block 0.25 m from its

top. This was tantamount to a height of 1.00 m above the floor.

Measurement was taken without the subject being present, but under the

same conditions, and with the chair in the same place.

We shall explain the significance of this measurement in detail by

means of a calculation. The heat loss from a surface element of the human

body at temperature 9 , due to transfers by convection with the air at

temperature t a , and by radiation with the cold walls, with a radiant

temperature of 6r » is represented by the following equation (per surface

6
unit)

:

Q = ac

(9 — t a

) + ar

(0 - e r

)

where a and a are the coefficients of heat transfer by convection and

radiation, respectively. This equation may he written:

Q = (a c + ar )

The ratio (a

c t a

+ ar 6r)/( ac + ar) ^ s an air-radiation temperature. We

shall call it "air-radiation temperature for a surface element" and

represent it by the symbol t are (air-radiation temperature of an element).

For the plane thermometer described above, the transfer equation

remains the same, but since no heat whatever is produced in the block

and that in practice this block is highly insulated on its rear surface

(its thermal resistance is of the order of 6.0 m2h°C/keal) , Q is null

and is equal to t are . Therefore the measurement of 9 gives the value

°f ^are This equivalence is approximate, however, for the following

reasons

:

1. First of all, it assumes that discomfort is due to a cold

sensation received on a body surface that is plane and parallel to the

cold wall. Of course, it was noted that discomfort originated essentially

from the cold sensation felt on the knees when the subject was facing the

glazed opening, and on the back in the opposite case. These are indeed

sufaces facing the cold wall, but they are neither plane, nor,

consequently, parallel to that wall.

2. It then assumes that the body surfaces to be taken into

consideration for heat transfers by convection and radiation, are the same.

This is almost true where the knees and back are concerned because there
the clothing lies quite flat against the body. But on other parts of the

body convection is greater because of the air circulating between the

body and the clothing. Moreover, that is probably the reason why

discomfort due to the cold wall is experienced to a lesser degree on those

parts

3. It also assumes that the ratio a

c /ar

is the same for the body

and the plane thermometer. Since ar

is about constant (of the order of

h.2 kcal/m h°C) , ac must be held constant. This point—a critical one

is discussed in the appendix to this paper, where it is shown that the

result depends particularly on the distance from the measuring point to

the top of the block, and that the correct distance is approximately 0.25 m

(a is then of the order of 3 kcal/m2h°C). It was this distance that was

retained.

k. And it also assumes that replacing the subject by a block does

not alter the air-temperature field in the room. It appears that this

is actually the case, to at least within half a degree.

5. Lastly, it assumes that there is little variation between the

value of the air-radiation temperature in the vertical axis of the chair

one meter above the floor, and its value at the exact point where the

discomfort is felt. Although such is nearly the case when that point is

the subject's back, it is no longer so when the knees or legs are the

point of discomfort.

Finally, the measurement made with the plane thermometer can be

considered as only the measurement of an index (indication) whose validity

can only be allowed or nullified a posteriori. Results —discussed in a

subsequent chapter of this paper—proved the retained index's value. In

8
this connection, it should he noted that the prohlem is the same when an

environment is characterized "by a temperature measured with a hulh

thermometer.

In addition to the plane thermometer measurement (t„TM„)« a measureare ment of the air temperature (t a ) and a bulb-thermometer measurement (t^)

were made for each test at the same point.

Questions Ashed the Subjects

At the end of a ten-minute stay in room B the subject was asked the

following questions: —Is the environment thermally comfortable? The subject

answered yes or no. —In the case of a negative response: Is it too cold or too

warm for you, and what part of your body feels cold or

warm?

Attempts to have the subject specify whether he or she felt slightly

cold, cold, or very cold, were abandoned.

1 . 2 RESULTS

Presentation of Results

A compilation of the results is given in Tables I, II, and III.

These tables are for tests conducted at 22°, 20°, and l8°C (average

ambient temperatures), respectively.

To facilitate evaluation of the results, they are not presented in

the order in which obtained.
Actually, in practice, each subject generally underwent four

successive tests with the same type of heating (floor and ceiling or

convective), in the same position with respect to the glazed opening

(facing it or back to it), and at four distances from that opening

(3.30 m, 2.00 m, 1.00 m, and 0.50 m). At times, even eight successive

tests were made on the same subject, by varying, first the distance to

the glazed opening, then the subject's position (facing the glass or back

to it). Of course, as stated above, the subject remained in room C for

30 minutes between two successive tests.

But in order to have the relation between the values of t-^ or t are

and the comfort reactions of the subjects show up better when tabulated

we have grouped when possible (and regardless of the subject), the results

obtained at the same distance from the glazed opening, and thus for about

the same values of t^ and t are

.

Comment on Results

The following comment can be made upon examining Tables I, II, and

III:

1. Remarks about the temperatures.

The air temperature (t a ) was almost uniform throughout room B. With

floor and ceiling heating, it was below the bulb temperature in the center

of the room. With convective heating, it was above that temperature in

the center of the room. In both cases the difference was of the order of

one degree. The bulb temperature (t-^) decreased in the vicinity of the

cold wall. The same was true, but to a greater extent, for the temperature measured with the plane thermometer facing the cold wall (t^g).

10
Variations in these different temperatures as a function of distance

to the cold wall are shown in Figures 3a and b for tests conducted at

20°C with floor and panel heating and with heating by convection,

respectively.

2. Remarks about comfort responses of the subjects.

As we have already mentioned, whenever the subjects reported feeling

cold in one part of the body, it was generally in the knees or legs when

in the face-to-the-wall position, and in the back when in the other

position. This proves that discomfort sensations do in fact result from

the radiation of the cold wall. However in a few tests at l8°C the

subject was unable to specify where he felt cold. The discomfort in that

instance perhaps resulted from a general impression of cold. In some of

the tests conducted at 22°C , one subject declared he experienced a

sensation of warmth.

Comparison between Temperatures and Responses of Subjects: Adoption of

tu as Criterion of Comfort.

are An analysis of the results reveals that there was on the whole

little dispersion in the comfort responses of the different subjects and

also in the aggregate of the comfort responses when the subject faced

the cold wall or turned his or her back to it. This being the case, we

then determined the proportion of discomfort responses as a function

solely of the following parameters

:

—average ambient temperature (22, 20, or l8°C

,

—type of heating (floor and ceiling or by convection), and —distance to the cold wall (3.30 m, 2.00 m, 1.00 m, or

0.50 m).

11
We therefore did not take the other two parameters into account

—the subject (A, B, C, D, or E), and —the position of the subject (facing wall or back to

it).

The figures obtained in this manner were grouped in Table IV.

Listed opposite the proportions of discomfort cases are the average

values of t^ and t are measured during the corresponding tests. The

discomfort cases involving a sensation of excessive heat were not

retained. Examination of this table reveals that there is a rather good

correspondence between the discomfort cases and the values of t-^ on the

one hand, and those of t are on the other, whatever the average ambient

temperature, the type of heating, and the distance to the cold wall.

This fact is highlighted by the graphs of Figure Ua and Vb. Study of

Figures ha and Ub shows that the correspondence between the proportion

of discomfort cases and temperatures t-^ or t are is more precise with t are

than with t-u. As a consequence we adopted t are as sole criterion.

Choice of Threshold. Formal Definition of the Requirement .

As often happens in matters of thermal requirement , there is no

absolute threshold for the problem considered herein, inasmuch as the

choice of threshold is in part a function of economic considerations.

Therefore in this instance we do not claim to be setting a definite

requirement, we are simply making a proposal.

We consider it reasonable to accept a percentage of discomfort cases

of the order of 20 per cent, which is tantamount to fixing l6 to 1T°C as

the minimum admissible values of t are . To be complete, the formal

12
definition of the requirement must indicate the minimum distance to the

cold wall from which comfort is desired. We view it as reasonable to

allow a distance of the order of one meter. Since discomfort is

experienced only if a person remains at rest (immobile) for a certain

time, the adoption of such a distance does not in fact appear restrictive.

PAET II: HOW TO SATISFY THE REQUIREMENT

IN THE AREA ADJACENT TO GLAZED OPENINGS

With the requirement defined, we now propose to determine what

should be done to satisfy that requirement in the vicinity of glazed

openings, inside a room in a dwelling.

Problem parameters are as follows

:

1. Outside temperature for which it is desired to satisfy the

requirement.

2. Inside temperature (more specifically that temperature measured

with a bulb thermometer in the center of the room one meter up from the

floor) that is accepted as normal.

3. The following construction and equipment characteristics and

elements

:

—dimensions of the panes of glass

,

—insulation of the panes of glass (single or

double sheets), —dimensions and insulation of outside opaque

walls

,

13
—presence of curtains

,

—type of heating and specific location of heating

units in the room.

The effects of most of these parameters can be studied by calculation.

The only exceptions are the last two parameters. For them we had to

resort to experimentation, and afterwards even to extrapolating by

calculation the experimental results obtained. For this last reason we

shall begin our account with the experimentation phase and then continue

from there with the calculations.

2.1 PRELIMINARY EXPERIMENTAL STUDY OF THE EFFECTS OF THE TYPE OF HEATING

AND OF PROTECTIVE CURTAINS OR DRAPES.

Conditions for the Experiment

For this experiment we used the same facility described in Part I

and under the same conditions as for the requirement study, with the

following differences:

1. When a radiator was used for heating it was employed either with

screens, as stated in Part I, or without screens. In the latter case,

the radiator was placed either under the glazed opening (position m in

Figure l) , or against the opposite wall (position n). In both cases it

was parallel to the opening and in its axis.

2. The glass was sometimes protected by curtains or by drapes.

Those used were made of cotton cloth of 58g/m weight. They were hung

h cm from the pane of glass.

14
3. The intended average inside temperature (temperature measured

with a bulb thermometer, in the center of the room at a height of one

meter) was always 20°C . And the intended outside temperature was always

0°C. As a matter of fact, it was not always possible to obtain exactly

20°C and 0°C. When they could not be obtained, results were corrected to

re-establish these conditions, by the method of computation which is

described in a subsequent part of this paper.

Effect of the Type of Heating. Improvement Produced by a Radiator Set

against the Wall below the Glazed Opening .

Figures 5& to 5d present variations in t-j-, and t r as a function of

the distance to the glazed opening for the following four heating

situations

:

—Figure 5a: floor and ceiling heating, —Figure 5b: heating by convection (radiator with

screens, in position V) , —Figure 5c: heating by radiator set against the

wall below the glazed opening (radiator without

screen, in position m) —Figure 5d: heating by radiator placed against the

wall opposite the glazed opening (radiator without

screen, position n) .

For the moment we will examine only those solid-line curves plotted

for the case where the glass was not protected by drapes or curtains.

The four heating modes are classified as follows in order of

increasing comfort (increasing values of t one meter from the opening):

15
1. Heating by a radiator set against the wall opposite the opening,

t = lU.3°C.

2. Heating by floor and ceiling, t are =1^.9° •

3. Heating by convection, t are

= 15.9°C

h. Heating by radiator set against the wall below the glazed

opening, t are =1T.7°C.

The results are accounted for as follows:

Heating by a radiator set against the wall below the opening gave

decidedly better results than the other heating modes owing to the fact

that the warm radiation of the radiator partially compensated for the

cold radiation of the window opening. That is the sole reason, for

because of the position of the air inlet above the radiator, the glass

was not any warmer than with the other heating modes.

Heating by floor and ceiling was less effective than by heating by

convection, for the following reason: for a same value of tv in the

center of the room, the air temperature with floor and ceiling heating

was approximately two degrees below that with convection heating.

Radiant temperature, for the bulb thermometer, was on the other hand

approximately two degrees higher in the case of floor and ceiling

heating. But for the plane thermometer which measures t are , although

there was still two degrees of difference in the air temperature, the

same was not true for the two degrees of difference in radiant temperature. Actually the plane thermometer, which is in a vertical position,

"sees" the warm floor and ceiling less than the bulb thermometer,

especially in the area adjacent to the cold wall.

16
Heating with the radiator placed against the wall opposite the

glazed opening gave the poorest result. This is due in large part to a

certain air-temperature gradient in the room and to a lesser temperature

of the glass, this second reason being a consequence of the first.

But perhaps we should somewhat qualify what we have just said. We

have admitted that the same bulb temperature prevailed in the center of

the room, thus that the air temperature was variable, with a variation on

the order of two degrees . Yet everyday experience seems to show that such

variations are rare: about the same air temperature is required with

floor heating as with radiator heating. Perhaps this is due to the fact

that the bulb thermometer ignores air movements between skin and clothing.

For closer air temperatures, there would practically no longer be any

difference between heating by convection and heating by floor and ceiling.

On the other hand, heating by a radiator set against the wall below the

glazed opening would remain decidedly better (value of t are

at one meter

from the opening, about two degrees higher), and heating by a radiator

set against the wall opposite the glazed opening would become rather

sharply, less satisfactory (value of t a one meter from the opening,

approximately one degree lower).

We made no measurements for other radiator locations , but an

approximate calculation seems to indicate that no distinctly better

result can be expected than that obtained with floor and ceiling heating

or with convective heating, unless the radiator is positioned against the

cold wall or not far from it

.

And lastly, we should like to add that the method of room ventilation

would have a certain effect and that our results are valid only for

the ventilation method we used.
Effect of Curtains and Drapes

The values of t are obtained with drapes or curtains over the glazed

opening are depicted by dotted line in Figures 5a, 5c and 5d. This

measurement was not made with convection heating. The values of t-u are

not shown. In the center of the room these values are the same as

without any drapes, within less than half a degree.

The gain in t OT.„ at one meter from the opening is nearly the same

for the three cases studied. It was approximately one degree. Drapes

or curtains are consequently less effective than the radiator set against

the wall below the opening for which the gain was close to two degrees.

It was verified that, except for the case of the radiator set against

the wall below the opening, this result was practically independent of

the interval between the drape and the glass, at least for distances

of from 2 to 10 cm. With the radiator set against the wall below the

opening, moving the drape away from the pane of glass enhanced the

result. The reason for this is that the warm air rising from the

radiator more easily enters behind the drape and heats it. Obviously

this increases heat losses, but we did not measure to what extent.

2.2 GENERAL STUDY BY CALCULATION. INFLUENCE OF VARIOUS PARAMETERS.

Calculation Principle. Equation for t are .

In Part I we saw that temperature t„„„ was expressed by the

equation:

a

c *a + a

r

e r

18
where t a

= air temperature

6 = radiant temperature

a„ = coefficient of convection

a„ = coefficient of radiation

The radiant temperature is equal to the average of the temperatures

of the walls, floor, and ceiling of the room, with each of these

temperatures being "affected" by the "form (geometry) factor" under which

it is "seen" by the surface element of the body (or plane thermometer).

Calculation of this form factor will be done under the following

assumptions

:

1. The outside wall(s) include glazed parts and opaque parts, both

having uniform temperatures, which we represent by 6 y

and 8 , respectively.

This assumption is altogether valid when there is only one outside wall.

And we shall see further on that the conclusions reached in this case

are generally valid when there are several outside walls.

2. The inside walls, floor and ceiling, have a uniform temperature

which we represent by 6^ . Obviously this assumption is false when the

room is heated by the ceiling and floor. But at least in the vicinity

of the glazed opening—the only point in the room that concerns us —the

angle under which the plane thermometer sees the floor and ceiling is so

small that the assumption can be allowed with sufficient approximation.

3. The heating units cause no perceptible radiation. This is still

true for the plane thermometer near the glazed opening, as long as there

is no heating unit against the cold wall. Calculations will be made

only in this case.

19
This being so, let f^ , fv

, and f "be the form factors for each

series of walls defined above: inside walls, glazed outside wall,

opaque outside wall. We have

e„ = f: e. + t e + t e r 11 v v o o

Furthermore

:

f. + f + f =1

1 v o The expression t are may thus be written as:

ac t a + ar [ (l - fv

- fQ

) Q ± + fy y

+ fQ

6 Q

] tare ~ __

ac + a

r or again:

t„„„

ac + ar ac + ar

[fv

(e. - e T

) + f

o

(e. - e T )]

The first term of the expression of t is, approximatively,

the resultant dry temperature in the center of the room which we shall

henceforth designate by t-

:

The temperature differences (0. - ) and (0. - O ) are, as a first

approximation, proportional to (t^ - t e ), where t e is the outside

temperature; the proportionality coefficients, which we will represent

by the letters yv and y Q , are wall characteristics. We thus have

ar tare = *I ( fv ^v + f

o ^o^i " *e)

ac + ar By replacing a r and <x n with their values h, 2, and 3 kcal/m h°C, we

finally obtain

tare = H " °" 6 < fv ^v + f

o ^ (t i " ^

20
Value of the Parameters .

We shall see what the values of the various parameters of the equation

giving tare > may 1° e » and retain a few of these values for a subsequent

calculation.

1. Inside temperature tj_

In a dwelling that is heated normally, t^—approximately the temperature measured with a bulb thermometer in the center of the room at a

height of one meter—varies between 19 and 22°C . We shall calculate for

19, 20, 21, and 22°C

2. Outside temperature t

The choice of the outside temperature is first of all a function of

the location in which the dwelling is constructed. However, given the

rather appreciable relativity of the problem being studied—there is no

need to be as rigorous as for computations of heating capacity, for

example—we deem it sufficient to limit ourselves to a breakdown of three

climatic zones as defined in the CSTB technical report for implementation

of the regulation on construction. However we do divide zone A into two

parts , one for altitudes of above 800 meters the other part for altitudes

of below 800 meters. In selecting the temperature for each of the three

zones we will take the following considerations into account:

a. During the coldest hours, generally occurring at night, shutters

and/or curtains are closed and the cold-wall effect problem is thereby

resolved. Consequently the temperature taken into account should not be

the daily minimum, but rather the daily average.

b. In view of the rather large relativity of the problem, a certain

number of extreme days may be disregarded. We consider it reasonable to

21
ignore at least five days per year (on an average). Moreover, we feel

that it may not be unreasonable to extend this figure to 15 days.

That being so, for a certain number of localities in each zone, we

have determined the lowest average daily temperatures observed 5 and 15

days per year on the average. We obtained the following values per zone

on an average

Lowest average daily temperature

observed on an average of:

Five Days Per Year Fifteen Days Per Year

Zone A

above 800 m -12 -8

Zone A

under 800 m -8 -h

Zone B -1+

Zone C +k

The above values are those we will use in our calculations.

3. Form factors fv and fQ

.

We should remember that the form factor represents in a sort of way

the angle under which the plane thermometer "sees" the wall under

consideration.

In a standard residence room, when the opaque walls are correctly

insulated, the cold-wall effect arises essentially from the glazed

openings, in other words product f u v predominates over product fQ y .

So factor fv is the one that mainly interests us. That may not be exact,

22
however, for a room having many outside walls like a gabled room under

the roof. This special case will be examined later. For the moment we

will consider a room having only one outside wall with only one glazed

opening centered on that wall.

We shall calculate for three categories of glazed openings. We

shall call these categories "small," "rather large," and "very large."

They are illustrated in Figure 6. In each category we have depicted two

openings, each with the same form factor, but with windows of

different heights. It is noted that the less the height of the windows

the less the area of the opening. Those openings in which width

exceeds height are more propitious for our problem than those in which

height exceeds width.

In the interest of realism, whenever the opening was larger, we

sketched the overall wall proportionately larger.

The corresponding values of form factors fv and fQ (always in the

axis of the opening and one meter above the floor), computed by means of

the graph at Figure 7 are

:

Small Opening

Rather Large

Opening

Very Large

Opening

fvf

o fv f

o

fV

f

at one meter

from the opening 0.26 o.Ho 0.1+2 0.32 0.60 0.1U

at 1.50 meter 0.20 0.38 0.36 0.26 0.50 0.12

23
In addition to the values at one meter from the opening, we present

those at 1.50. We thought it would be interesting to know what the

alleviation of the requirement corresponding to this further distance

from the opening would entail

.

k. The u v

and u Q coefficients.

Let us remember that for a wall whose surface temperature is 9

,

t i - 9

u - > and

t. - t

1 e

that for walls and panes of glass without inside curtains,

K ""ST

where K = coefficient of heat transmission of the wall

h^ = coefficient of inside surface heat transfer, equal to

approximately 7kcal/m2h°C in the case of a vertical wall.

For single-sheet and double-sheet glass, with K coefficients equal

to 5 and 3 kcal/m2h°C respectively, we obtain

uv

= 0.71 for single-sheet glass

uv

= 0.U3 for double-sheet glass

The above equation is no longer applicable when the glass is covered

by curtains. In such cases y can no longer be determined by calculation.

We must resort to other measures. That is what we did by using the

results of the experiments described in paragraph 2.1. The procedure

followed is outlined in the appendix to this paper. The values obtained

for glass-wall areas with the drapes or curtains defined earlier are

Uv

= 0.51 for single-sheet glass

Mv

= 0.31 for double-sheet glass

24
In our calculations we shall use these values of y , plus those

calculated above for glass-wall areas without drapes or curtains.

As for the opaque parts of the outside wall, we shall still consider

that coefficient K is equal to 1.2 kcal/m2h°C , for which the corresponding

value of y Q is 0.l6.

Application of the Equation to an Average Case .

In actual conditions , the problem to be resolved is phrased as

follows: in a given climatic zone, what size window is admissible for

single-sheet glass, for double-sheet glass?

We shall calculate the solution to this problem by using the equation

determined earlier, and by restricting ourselves to the case in which

that equation is applicable, in other words, specifically by assuming that

there is no heating unit set against the wall below the glazed opening.

But even when we do this, the solution to the problem is still based on

a certain number of conditions that we shall provisionally establish and

call "average conditions." They are:

1. Outside temperature is equal to the lowest average daily

temperature recorded on an average of five days per year. This temperature is -12° in Zone A at an altitude above 800 meters, -8°C in the rest

of Zone A, -k°C in Zone B, and 0°C in Zone C.

2. Inside temperature is 21°C

.

3. The glazed opening has drapes or curtains.

h. The distance from the opening at which comfort is desired is

one meter

.

25
Table V gives the values obtained under these conditions , for each

climatic zone and for each category of opening defined earlier, with

single-sheet glass and with double-sheet glass. In this table, and also

on those that follow, the cases where t is below l6°C are highlighted

by shading, and where t are is between l6 and 17°C by dotted lines.

If we fix 17°C as the admissible minimum values of tare , we see that

single-sheet glass is never satisfactory in Zone A above 800 m altitude,

that it is never satisfactory in the rest of Zone A except for small

openings, that it is not satisfactory in Zone B for very large openings,

and that it is always satisfactory in Zone C.

If we fix the admissible minimum value of t OT,_ at l6°C instead of

1T°C , single-sheet glass becomes always satisfactory in Zone B, and

in Zone A below an altitude of 800 meters, it is insufficient only for

very large openings. And we see that in Zone A above 800 meters it

becomes satisfactory for the small openings.

Whatever admissible minimum value is established for t a , the

double-sheet glass is always satisfactory.

Before concluding, it is convenient to consider what occurs when

the adapted conditions are modified.

Effects of a Modification of Conditions .

We shall examine, in turn, the effect of a modification made to

each of the conditions defined in the preceding paragraph.

1. Inside temperature.

Table VI gives t are values obtained with t i of 19, 20, 21, and 22°C

and with the other conditions being average conditions.

26
Since the variations of t are are nearly equal to those of t -j_ , the

effect of a variation in t^ is evidently highly significant.

At 19°C , single-sheet glazing is never completely satisfactory,

even in Zone C. And double-sheet glass is frequently insufficient.

Conversely at 22°C single-sheet glass is really insufficient only in

Zone A above 800 meters with very large glazed openings.

2. Outside temperature.

We stated earlier that it was perhaps not unreasonable to accept

that —in the problem being studied herein—the number of discomfort days

reached a total of 15 per year.

As seen in Table VII, when instead of 5 discomfort days per year, we

use 15 days, which corresponds to an increase of i+°C in t e , t are is

thereby increased by a little more than half a degree. The conclusions

are obviously modified thereby, but to a lesser extent than if we

increased inside temperature by one degree.

3. Absence of drapes or curtains.

The "average conditions" assume that the glazed openings are

protected by drapes or curtains, at least in cold weather. Table VIII

shows what would result from an absence of such protection.

With single-sheet glass, t are would be lessened by approximately

2°C , and with double-sheet glass, by a little more than one degree, at

least for the most unfavorable cases. This is obviously significant

and it would very often be probably preferable to close the drapes or

curtains , rather than to raise the heat in the room by an additional one

or two degrees.

27
It should "be noted, however, that single-sheet glass with drapes or

curtains is less effective than double-sheet glass.

h. Moving comfort "line" away from the opening.

Asking that comfort be provided at a distance of one meter from the

glazed opening is perhaps a severe requirement. At a distance of 1.5

meters, the value of t are for single-sheet glazing with drapes/curtains,

is approximately one degree higher than that at a distance of one meter,

as shown in Table IX, or equal to its value at one meter for an opening

twice as small.

Thus by being satisfied with the comfort "line" at 1.50 meters from

the opening instead of at one meter, it is possible, for an opening of

any given size, to heat the room at one degree less, or- for the same room

heating to accept an opening that is twice as large.

Special Case of a Radiator Set against the Wall below the Glazed Opening .

The equation for t a determined above is not valid when the

radiator is set against the wall below the glazed opening. Moreover,

calculation in this case is uncertain and we shall not attempt it. But

we can extrapolate experimental results by assuming, as a first approximation, that the difference t± - t are is, as in the general case,

proportional to t± - te and furthermore, that it depends little upon the

size of the opening because the size of the radiator is proportioned

to the size of the opening.

Under these circumstances, the values of tare for each of the

climatic zones under "average" out side-temperature conditions are those

given in Table X. 28
We see that when there are drapes or curtains, there is practically

never any likelihood of discomfort, and that even -without such protection,

there is likelihood of discomfort only when the heating is mediocre (19°C),

Case of Several Glazed Openings or Several Outside Walls

Calculations in the case of several openings or several outside

walls present no difficulties. We have calculated for a few such cases.

The conclusions reached are approximately as follows, with the reasoning

"based as always on an equal "resultant dry-bulb temperature" in the

center of the room.

1. When there is only one opening but several outside walls, the

preceding conclusions remain valid.

2. When there are several openings very close together, the

preceding conclusions are still valid, providing the group of openings

are considered as a single opening.

3. When there are several openings quite separated from each other,

the preceding conclusions are valid on condition that they are applied

separately to each one of the openings.

29
2.3 CONCLUSION

The satisfaction given by an opening of certain dimensions and with

certain types of installed glass panes, depends considerably upon the

values accepted for the requirement, the outside factors and inside

temperature, and whether or not the presence of drapes /curtains are

considered.

We consider it reasonable to accept the following:

1. The requirement is that t ov,„ must be at least l6/lT°C one meter

away from the opening.

2. Outside temperature is the average daily temperature recorded on

an average of five days per year.

3. Inside temperature is 20-21°C, measured with a bulb thermometer

in the center of the room at a height of one meter.

h. The glazed opening is covered by drapes or curtains in cold

weather.

Under these conditions, we reach the following conclusions;

1. When there is a radiator of sufficient size set against the wall

below the opening, there is no likelihood of discomfort or cold radiation.

2. When there is no radiator set against the wall below the opening

or any other heating unit producing an equivalent effect, it seems

reasonable to provide double-sheet glass as follows: —in Zone A above 800 meters, regardless of the size of the opening,

30
—in the rest of Zone A, whenever the openings are rather

large, i.e. of the, order of 3m, —in Zone B, for very large openings, i.e. of the order of 6 i .

Whenever these specifications are not followed, it may at times be

possible to avoid discomfort by heating better, thus in Zone B if heating

is maintained at 22_ 23°C , there is never any need of double-pane glass.

And lastly, to get back to a -point examined in Chapter 2.1, we

should like to add that specifications must be made even more severe

whenever the heating is particularly nonhomogeneous , for example when

radiators are placed against partitions opposite outside walls.

As an overall conclusion it may be said that large glazed openings

necessitate good heating, i.e. sufficient temperature, highly uniform

temperature throughout the room, and, still better, heating units set

against the wall below the glazed openings.

APPENDIX

1. COEFFICIENT OF HEAT TRANSFER BY CONVECTION

The problem is to have coefficient a be the same for the human body

and for the plane thermometer. To accomplish this it is first of all

necessary to know the value of a for the human body.

Knowing this value is not a simple matter. The value of ac is not

the same along all the body for various reasons: height above the floor,

general geometric shape of the body, geometric shape of each part of the

body... But when there is discomfort due to cold walls, it is localized

in certain points: back, knees, and legs. This fact seems a priori to

31
simplify the problem. But unfortunately it is practically impossible to

determine the value of ac on these parts of the body. Any measurements

require use of a device or apparatus , and that equipment alters the heat

transfer conditions.

Several investigators give c^ values. But either because they are

for problems that differ from the one we are examining, or because they

are rather questionable determinations , no specific value can be drawn

from them. The best approach seems to be to refer to those experiments

during which it has been possible to compare the relative value of

transfers by convection and by radiation (Bibliography) . By hypothesizing

on the relation of transfer surfaces by convection and by radiation,

since the coefficient of transfer by radiation is well known, the value

of a

Q may be deduced therefrom. In this manner, we find a value of the

order of 3 kcal/m2h°C .-'

But we reiterate, the coefficient of convection etc has quite different

values depending on the various parts of the body. Consequently

3 kcal/m h°C is only an order of magnitude, no more.

How can this value be obtained with the plane thermometer? Here

,

since the measurement of surface temperature is accurate, and that,

moreover, all other elements of the problem can be calculated effectively

(particularly the form factors pertaining to the various walls, of the

room and to its floor and ceiling), a can be accurately determined.

c Coefficient ac is not the same over all the block. It is higher in

its upper part than in its lower part, in the case that concerns us,

that is to say when the temperature of the block is below that of the air.

Coefficient a varies also with the temperature of the block; the more

—'See footnote 1, page 2.
the latter differs from the air temperature, i.e. the greater the cold

radiations, the higher the coefficient a . c A few tests showed us that a value of 3 kcal/m2h°C is obtained

for a temperature differential "between the air and the block, thus

approximately between t^ and t are , of the order of 3 to h °C , which

corresponds to the requirement threshold, when the measurement is made

at about 25 cm from the top of the block.

2. VALUES OF COEFFICIENT u^ WHEN THE GLAZED OPENING HAS A DRAPE OR

CURTAIN

.

1. With single-sheet glass.

The value of coefficient yvis determined experimentally. But

instead of directly measuring the temperature of the drape or curtain

a difficult operation for several reasons—we preferred the following

procedure

:

All things being equal, let t are be the value of the temperature

measured with the plane thermometer when the pane of glass has no

curtain or drape, and t are the same temperature when the glass is

protected by drapes or curtains. And let uvand \i^ be the coefficients

corresponding to each of these cases . By applying the equation for

t determined in the beginning of Chapter 2.2:

f - t = o.6 (u - y) f (t. - t ) are are v ^v Kv ' v l e

In this equation all terms are known except u' which can therefore

be calculated.

33
2. With double-sheet glass.

We calculated as follows:

Let t- and t' be the outside temperatures leading to the same

temperature of glass 8 for a same inside temperature tj (therefore also

for a same drape/curtain temperature 8vo ), on the one hand, for singlesheet glass with drapes or curtains, and on the other hand, for doublesheet glass also drapes or curtains. The flow leaving the room or area

is then the same, i.e. we have

V - t

e =

ev

- t

e l/he l/h

e + r

where r = thermal resistance of double-sheet glass (thermal resistance

of single-sheet glass is negligible).

Having measured for a given t

e during tests on single-sheet

glass, and with he and r being known, we deduce tg therefrom.

If yv if the value of y corresponding to single-sheet glass with

drapes or curtains, and Uy the value for double-sheet glass with drapes

or curtains , we have

*i " 6vo

y.v t. - t

i e

and K =

t i " v°

therefore y v

= yv

ti " tg

ti " t

e

ti _ t e

34
uvie , t. and t are known,' t' has just been calculated, we thus e u >

deduce the value of y' from it.

BIBLIOGRAPHY

a. Croiset , M. and Bizebard, H. , Les entrees d'air de ventilation

(Ventilation Air-Inlets), Cahier du CSTB Vol. i+78 , Issue 59-

bMissenard, A., Mise au point sur les echanges thermiques entre le

corps humain et 1 'ambiance (Restatement of the nature of heat

transfers between the human body and its immediate environment),

Industries Thermiques , No. 12, 1957-

c. Dupuy, R. , Les taches presentes du conditionnement climatique

(Climate Condition's Current Tasks), Chaleur et Climate (Heat and

Climate) , No. 291.

d. Cours superieur de chauffage , ventilation et conditionnement de l'air

(Advanced Course in Heating, Ventilation, and Air Conditionning 'ome k,

Miscellaneous supplementary data by A. Missenard , Tome h.

e. Yaglou, C.P. and Houghten, F.C., Various articles and papers (see

Bibliography, ASHRAE, Guide and Data Book, Section II, Chapter VII ).

Conversion Factors

1 ft = 0.305 m = 30.U8 cm

1 m = 39.^ in = 3.28 ft = 1. 1 yd

1 cm = 0.39 in = 0.033 ft = 0.011 yd

1 m

2 =10.8 ft 2 =1.20 yd2 1 ft 2 = 0.09 m

2 =0.11 yd2 1 yd2 = 0.8U m

2 = 9.0 ft 2 1 m

3 =35.3 ft 3 = 1.31 yd3 1 yd3 =27.0 ft 3 = 0.76 m

3

2 Pa = Pascal, Newton/m

1 Pa = 0.00^01^7^ in water gauge pressure

°C = (F -32)/1.8

1 kcal/m2h°C = 0.20^8 Btu/ft 2 h°F

1 m3 /h = 35-3 ft 3 /h

35
Layout

Room A

Outside atmosphere

T-T

_ J _air in letRoom B

test area

air outlet

Room C

Waiting area

~U

[ IF Ceiling air inlet

Air inlet above radiator

WMuL

: r. 2 20 , O^SQ

'

1

1

1

Vertical view A- B Vertical view C-D

Figure 1. Test facility

Thermcouple

_Z 'Constantan Copper 0.2 mm /

Polystyrene

' L

Q20

Figure 2.

Device for measuring

air radiation temperature

of a surface element

36
Figure 3. Variation of ^ and tg re as a function of distance to glazed opening

— . .

" r —

p

". ><•

- c

01

(0

a>E

i1

l are

i

10 Distance to opening in meters

3 a) With floor and ceiling heating

Distance to opening in meters

3 6) With heating by convection

37
Figure 4. Variation of the percentage of cases of discomfort

Test at : 22 »C 20 "C 18 °C

Floor and ceiling heating • A

Heating by convection o A

90

1 ! J

!

. :•

i

1 '1

60

50

40

iO

1 *

; &

(

1

<

1 \m;.

| ..t,

v -| 7

10

It

3 1

1 T ip t

o

i -«-! 1 22 21 20 19 18 17 16 15 14 13 12 11 10

t„ in°C

4 a) As a function of th

100

i 90 o

8. 80

* r~i

|

1

1

1 ;^

v |/;l^ - --FEES

" n

'I—

7

' .' '. — *r- 1-

» I' m I ri .. . 1 m I 1 1 1 1 . 22 21 20 19 18 1? 16 15 14 13 12 11 10

4/>) as a function of t„ 38
Figure 5. Variation of *b and Was a function of distance to glazed opening, with single

glass, without drapes { ) and with drapes ( ). for various types of heating

Distance to opening in meters

5a) Floor and ceiling heating

P 2

ID

'b 3

(UQ. —

E r

01

tore

1

i

1 1

Distance to opening in meters

5 b) Heating by convection

39
Figure 5. (Cont'd)

-

c

ID

r -=T=

^t "^r^— , ' 3 ""

a

E© IS htore

Distance to opening in meters

5 c) Heating by radiator sefagainst wall below glazed opening

J-^"c ^\

^^*g-

'

•b ,J-Z

„.^ """"Zf^^^

"\ "s^

Distance to opening in meters 5d) Heating by radiator set against wall opposite glazed

opening

40
Table I. Results of tests at 22 °C (average ambient temperature)

Room B

Type of Distance

to glazed Position Subject's

heating opening

(in m)

'. fi t„. Subject of subject

comfort response

Floor 3,30 20.5 21.5 21.0 A Facing and 20.5

20.0 21.0

21.0

20.5

20.0 BC wall Ch ceiling 20.5 21.5 20.5 D Ch

2.00 21.0 22.0 19.5 A

20.5 21.5 19.0 B

20.0 20.0 19.0 C

21.0 21.0 19,5 D Ch

1.00 20.5 21.0 16.5 A

19.5 21.0 16.5 B

19.5 20.5 16.0 C

20.0 21.5 17.0 D Ch

0.50 21.0 20.5 15.0 A

19.0 19.5 14.5 B F 18.5 19.5 14.0 C

20.5 20.5 15.0 D O

3.30 20.5 21.5 20.5 A back

20.5 21.5 21.0 B to 20.0 21.0 20.5 C Ch

21.0 22.0 21.0 D wall

2.00 21.0 22.0 19.5 A

21.0 22.0 19.5 B

20,5 22.0 19.0 C Ch

21.5 22.5 19.5 D

1.00 20.5 21.0 16.5 A

20,5 20.5 16.0 B

20,0 20.5 16.0 C Ch

21.0 21.5 17.0 D

0.50 21,0 20.0 14.0 A F 20,5 19.5 14.0 B F

20,0 19.5 14.5 C Ch

21.0 20.0 14.5 D

3.30 22,5 20.5 18.5 A Facing

22.5 22.5 20.0 B Ch Convection 21.5 21.0 18.0 C wall F (1st series) 24.5 21.5 19.5 D O

23.0 21,0 19.0 E

2.00 24,5 20.5 18.0 A

23.5 21.0 19.0 B Ch

23.5 20.5 18.5 C F 25.0 21.0 19.0 D

24,0 21.0 18.5 E

1.00 22,5 20.0 16,0 A

23.5 21.0 17.0 B

23,0 20,5 16.5 C F 24.5 21.0 17.0 D

22.5 20.5 16,5 E

0.50 22,5 19.5 14.5 A F 22.5 20.0 15.5 B

23.5 19.5 15.0 C F 24.5 21.0 15.0 D F 23.5 20.0 15,5 E

41
Table I (conclusion)

Room B

Type of heating

Distance to glazed f» f» t„. Subject Position of Subject's comfort opening (in m) subject response

3.30 24,0 21.5 19.5 A back

23.0 21.0 18.5 B

to 23.0 21.0 18.5 C

23.5 21.0 19.0 D wall

23.5 21.5 19.5 E

2.00 25.0 21.0 19.0 A

24.0 20.5 18.5 B

24.0 20.5 18.5 C

24.5 21.0 18.5 D F 25.5 21.0 18.5 E

1.00 23.5 21.0 16.5 A

23.5 20.5 16.0 B

22.5 20.0 16.0 C

22.5 20.0 16.0 D F 23.5 21.0 16.5 E

0.50 23.5 19.5 15.0 A F 23.5 20.0 14.0 B F 23.0 19.5 14.5 C F 23.5 20.0 14.5 D F 23.5 20.0 15.0 E

Convection 3.30 23.0 21.5 20.0 A Facing Ch (2nd series) 22.5

22.5

21.5 22.0

19.5

21.0 BC wal I Ch

2.00 23.0 21.5 19.5 A Ch

22.5 21.5 19.5 B

23.0 22.0 20.0 C Ch

1.00 23.0 21.0 17.0 A Ch

22.5 20.5 16.5 B O

22.5 21.5 17.5 C Ch

0.50 22.5 21.0 15.5 A

C2.5 20.5 15.0 B

22.0 21.0 15.5 C

3.30 23.0 22.0 20.5 A back

24.0 22.5 21.0 B to Ch

22.0 21.5 20.0 C wal I O 2.00 23.5 22.0 20.0 A

24.0 22.5 20.5 B

22,5 21.5 19.5 C

1.00 23.0 21.5 17.0 A

23.5 22.0 17.0 B

22.0 21.5 16.5 C Ch

0.50 23.5 21.0 15.0 A O

24.0 21.5 15.0 B

22.0 20.5 15.0 C

Temperature terms: Resporise terms:

r„ : air temperature O : neither warm nor cold

h ' bulb—thermometer emperature Ch: sensation of warmth

r ar. : plane -thermometer temperature F : sensation o r cold

h2
Table II: Results of tests at 20 C C (average ambient temperature)

Room B

Type of Distance to Subject Position of Subject's

Heating glazed f„ f» for. subject comfort opening (in m) response

floor 3.30 18,0 19.0 18.5 A facing and 19.5 20.0 19.0 B wall 18.5 19,5 18.5 C ceiling 19.0 20.0 19.0 D

2.00 18.5 19,5 17.5 A

19.0 20.0 18.0 B 18.5 20.0 17,5 C

19,5 20.5 18,0 D F

1.00 18,0 18.5 14.5 A

18.5 19.0 15.5 B

18.0 19,0 15.0 C

19.0 19,5 15.5 D F

0.50 18.0 18.0 13,0 A F 18.5 18.5 13,5 B F 18.5 18.0 13.0 C

19.0 18.5 14,0 D F

3.30 19.0 20.5 19.0 A back

18.5 19.5 18.5 B to

18.5 19.5 18.5 C

18.5 19.5 18.5 D wall

2.00 19.5 20.5 18.0 A

19.0 20.0 17.5 B

18.5 19,5 17.0 C

18.5 19.5 17.5 D

1.00 19,0 19.0 15.0 A

18,5 18.5 14.5 B F 18.5 18.5 14.0 C

18,5 18.5 14.5 D

0.50 19.0 18.0 14.5 A

19.0 18,0 13.0 B F 18,5 17.5 12.5 C

18,5 17.5 12.5 D 0/F

Convection 3.30 21.0 20.0 ^9.0 A Facing

20,5 20.0 19,0 B o

(2nd series) 20.0 19,0 18,0 C

Well I

2,00 21,5 20,0 18.5 A

20,5 20.0 18.0 B

20.0 19.0 17.5 C

1.00 21.0 19.5 15.5 A

20.0 19.5 15.5 B Q

20.0 19.0 15.0 c

0.50 21.0 19.5 14.0 A F 20.0 19.0 13.5 B c 19.5 18.5 13.5 C b

3.30 21,0 20.0 18.5 A back

19,0 18.5 17.0 B to

20.5 19.5 17.5 C wall

2.00 21,0 20,0 17.5 A

19.5 18.5 16.5 B F 21.0 19.0 17.0 C

1,00 20.5 19.5 15.0 A

19.5 18.0 140 B F 20.5 19,0 15,0 C

0,50 21.0 19,0 13.5 A F 19.5 17.5 12,5 B F 21.0 19.0 13.0 C

43
Table II (conclusion)

Room B

Type of heating

Convection

(2nd series)

Distance to glazed

' opening (in m)

3.30 2.00

1.00 0.50

3.30 2.00

1.00

0.50

21.5 22.0

20.5 2V0

21.5

22.0 21.0

20.5

19.5

19.0

19.0 18.5

19.5

19.0

18.5 18.0

17.5

17.5

15.5 14.0

17.5

17.5 15.0

13.0

[Position of Subject's

Subject subject comfort response

facing

wall

back

towall

Temperature terms:

fa : air temperature

'<• ' bulb—thermometer temperature

r„, . plane—thermometer

temperature

Response terms: O : neither warm nor cold Ch: sensation of warmth

F : sensation of cold

Table III Results of tests at 18 C (average ambient temperature)

Room B

Type of heating

Distance to glazed

opening (in m)

t,, fa,. Subject

Position of subject

Subject's comfort response

floor 3.30 16.5 17.5 17.0 A facing and 16.0 17.0 16.0 B F 16.0 16.0 16.0 C wall

ceiling 16 5 17.5 16.5 D F

2.00 17.0 18.0 16.0 A F 16.5 17,5 15.5 B F 16.0 17.0 15.0 C

16.5 17.5 15.5 D F

1.00 16.5 17.0 13.5 A F 16.0 16.5 13.0 B F 15.5 16.5 13.0 C F 16.0 17,0 13.5 D F

0.50 16.5 16.5 12.0 A F 16.5 16.0 11,5 B F 16.0 15.5 11.5 C F 16.5 16.0 11.5 D F

3.30 16.5 17.0 16.0 A

back F 16.0 17.5 15.5 B O

15.5 16.5 15.5 C to

16.0 16.5 15.5 D wall

F

2.00 16.0 17.0 15.0 A F 16.5 17.0 15.0 B

16.0 17.0 14.5 C

16.0 17,0 14.5 D F

1.00 16.0 16.0 12.0 A F 16.0 16.0 12.5 B F 15.5 15.5 12.0 C

15.5 17.5 12,0 D F

0.50 16.0 15.5 10,5 A F 16.0 15.0 10.5 B F 15.5 14.5 10.5 C

15,5 15.0 10.0 D F u
Table III (conclusion)

Room B

Distance Position Subject's

Type of to glazed t. t» t„. Subject

of comfort heating opening

(in m) subject response

Convection 3.30 19.0 18.0 16.0 B facing

(1 st series)

20.0

20.0 18.018.0

16.5 16.0 C

D wall F

F 20.0 18,0 16.5 E

2.00 20.5 17.5 15.5 B

20.5 18.0 16.5 C F 20.5 17.5 16.0 D

20.5 18.0 16.0 E

1.00 19.0 17.5 14.0 B F 19.5 18.0 14.5 C F 19.0 17.5 14.0 D F 19.0 17.5 14.5 E F

0.50 19.5 16.5 12.5 B F 18.5 17.0 13.0 C F 20.0 16.5 12.5 D F

19,5 17.0 13.0 E F

3,30 19.0 17.5 15.0 A back

19.5 18.0 16.5 C O

21.5 18.5 16.5 D to

18.0 17.5 16,0 E wall

2.00 20.5 18.0 16.0 B

20,0 17.5 16.0 C F 21.0 18.0 16.0 D F 18.5 17.0 15.5 E F

1 00 19.5 17.0 15.0 B

18.5 17.5 13.5 C F 19,0 17.5 13.5 D F 18.0 16.5 13.0 E F 0.50 20.0 16.5 12.0 B F 19.5 16.5 12.0 C

19.5 16.5 12.0 D F 17.5 15.5 11.5 E F

Convection 3.30 19,0 18.0 16.5 A facing

(2nd series)

19,5

19.5 19.0

18.5 17,5

17.5 BC wall

2.00 19.0 18.0 16.0 A

20,0 18.5 17.0 B

19,5 18.5 17.0 C

1.00 19,0 17.5 14.0 A F 19.5 18.5 15.0 B

19.5 18,0 14.5 C

0.50 19,0 17.0 12.5 A F 19,5 18.0 13.5 B F 19,0 18.0 13.0 C

3.30 19.0 18.0 16.5 A back

19.5 18.5 17.5 B

19.0 18,0 16.5 C to

2.00 19.5 18.0 16.0 A wall

19.5 18.5 16.0 B

19.5 18.0 16,0 C

1.00 19.0 17.5 13.5 A

19,0 18.0 13.5 B

19,0 17,5 13,5 C

0.50 19.5 18.0 12.0 A

19.0 17.5 12,0 B F 19.0 17.5 12,0 C F

Temperature terms: Respimse terms:

t

. air temperature O : neither wann nor cold

t, : bulb—tnermometer i emperature F : Sensation ol' cold

r„r. : plane- 'hermometer temperature h5
Table IV Proportion of Discomfort Cases

as a function of average ambient temperature, type of heating, and

distance to cold wall, and corresponding values of temperatures l b and l are

Test conditions

Temperature (T>) in center of room

approximately 22 C

approximately 20 C

Type of heating

Floor and

ceiling

By convection

Floor and

ceiling

By convection

Floor and

ceiling

aoDroximately 1 8°C

By convection

Distance to cold wall (in m)

3.00 2.00

1.00 0.50

3.30

2.00

1.00 0.50

3,30

2.00

1.00 0.50

3.30

2.00

1.00 0,50

3,30

2,00

1,00 0,50

3,30 2,00

1.00 0,50

Temperatures measured

With bulbthermometer b

21.5 22

2120

21,5

21

2120

19,5 20

19

18

19.5

19.5 19

18,5

17

17,5 16

15.5

18

18

17.5 17

With plane thermometer are

20,5

19.5

16,5 14.5

19,5 19

16.5 15

18,5

17,5 15

13.5

18

17,5 15

13.5

16

15

12.5

11

16.5 16

14

12,5

Proportion of discomfort cases expressed in numbers of cases and, within parentheses,

in percentage.

0/8

0/8

0/8

3/8

1/16

2/16

2/16

7/16

0/8

1/8

2/8 5/8

0/8

1/8

2/8

6/8

(0%)

(0 %)

(0 %)

(37 %)

(6 %)

(12%)

(12%)

(44%)

(0 %)

(12%)

(25 %)

(62 %)

(0 %)

(12%)

(25 %)

(75%)

4/8 (50%)

5/8 (62%)

7/8 (87 %)

7/8 (87 %)

2/14 (14%)

3/14 (21 %)

8/14 (57%)

11/14 (59%)

k6
Figure 6

1,75 n —\~

'Small" openings

150 m* +

"Rather Large" openings

3 m' +

o "Very La "9 i" openings o

7 m' +6 m" +

o

o

=t 4 00 1 3,00 -

U">

1 4.50 4,50 o"

Table V- Values of tare under "average conditions"

Single—sheet glass Double—sheet glass

Small opening

Rather

large opening

Very

large opening

Small opening

Rather

large opening

Very

large opening

Zone A

above

800 m

16,9 18.1 17,5 17,0

Zone A

below

800 m

17,4 16.6

16,4

18,5 17,9 17.5

Zone B 17,9 17.2 18,8 18,4 18.0

Zone C 18,4 17,8 17,1 19,2 18.8 18.5

47
n

w o o o c3" N |2 r-( ^2

< CM

II

f > •«*' j a

- .O^

"si

1 \\

o

ID

Lf> O

CNo

CLEo

O

CO

CD~ CMo"

ino

COCD

CD s CD

CD~ OO

ID

CD

CD so

CD

LDO

Jojoej uijoj

48
oO

0)

IS

CO >

>

-1 &*a •SB

u —

J

CM

(0 3 D

ce — o

01c IsV)

o>c

• m 0. > -2 o o

CN i 01 o

« w a

cc - o

0)c

1! £ w o

CDc

> 5 o o> o £ 01 ®

co 3 a c —

a

c

to © E a

0) o

c > 2, c o

U Ol m

® * a > ^ o 3£ o

D

° acr>

Ol E^

a I?* ccS o

i0) Ol "O _ .£ 11 (0 "c

10 o

CO

CD*

i

a)

r~"

cx>

r-" oCO

CD

CO*

CO

r^* CO00

°°.

CO* CO

co" r~~*

CD

to

CN

r^*

CO

r~-*

en

CO* r~" ct

co"

CO

cd'

tit? ' CO

CO*

cr> co"

co" COCO o

r^"

r;: " . j ? ;

' .,?-:, -£

1 :iO co"

CN

CD* CO"

Zone

A

above 800

m < g E £-2 o

o £ ©

CD

cuc

o

(J

CDcoN

oQ

C) «* CO <* r< CO CO cr>

*"~ "" *—

«cr CT> CO h*. CD CO CD CD

"" 1 *"" 'l_ o <* r^ T_

o> a} a> o "~ *~~ CM o LD o in

r^ r- CO CO

*~" *"" *""

LO CD <fr CO

r-- r-. co CO

,— ,— *"" 1

,_ LD CO ^J CO CO CO CD

' 1 *""

CM CD r. CD

CO .CD [-— r^

"l— *"" *~ *~

CD ^_ LD CD

CD I"*-*. r-- r-*- *"" ^~ *" *""

CM CD . en CO

r-. r^- rs CO

*"" ^~ T~

.r> . CM r--

• . ur>' •-.. CD CD

<"~ t— fCM CD o

CD CD r-

*"" T—

co CD o CO

CO CD r-. r*-. T— *~ *~~ *"

< E <S E

CD a

"" > --> CD O CD CD cog c- ©

o £ © o CO o

N CD °° NJ.O 00 N N

49
5 days of discomfort

per year

15 days of di per year

scomfort

Small opening

Rather

large opening

Very

large openinc

Small opening

Rather

large opening

Rather

large opening Zone A

above

800 m

16.9 17.4 16.6

Zone A

below 800 m

17.4 16.6 17.9 17.2 16.4

Zone B 17.9 17.2 16.4 18.4 17.8 17.2

Zone C 18.4 17.8 17.1 18.9 18.4 18.0

Table VII. Values of tare for various Outside Temperatures (with Sinjle-sheet glass), under "Average"

Conditions

r„„ below 76°C

f„, equal to or about 16?C but below 17°C

t.„ equal to or about 17°C

Table vni. Values of tare for opening with or without

drapes, under "average" conditions

With drapes

Small \"atherI Ve'V opening'""96

l lar9e |Openingjopening

Without drapes

Small :,' ar9e

• opening

Very

large opening

Single—sheet glass

Zone A

above

800 m

16.9 15.9 14.9 16.1 14.3

Zone A

below

800 m

17.4 16.6

17.2

16.7 15.1 13.6

Zone B 17,9 16.4 17.3 15.S 14.6

Zone C 18.4 17.8 17.1 17.9 16.7 HSS

Double— sheet glass

Zone A

above 800 m18.1 17.5 17.0 17.5 ,,e

I ,„

Zone A

below

800 m

18.5 17.9 17.5 18.0 17.1 16.3

Zone B 18.8 18.4 18.0 18.4 17.6 16.9

Zone C 19.2 18.8 18.5 18.8 18.2 17.6

50
Table IX Values of tare at 1 m and at 1.50 m from the opening (single-), sheet glass), under "average" conditions

Zone A

above

800 m

Zone A

below

800 m

Zone B

Zone C

at 1 m from opening

Small opening

16.9

17,4

17.9

18,4

15.9

16,6

1 7.2

17.8

Very

large opening

14,9'

1.5.6

16.4

17.1

at 1.50 m from opening

; large

K ope nine:

18.4

I 8.7

19,1

19.4

17,2

17.7

18.6

Very

large opening

16,2

16,8

17,4

18,0

Table X Values of t„, when there is a radiator set against wall below opening, under "average" outside temperature conditions

Inside Temperature :

19 »C 20 °C 21 °C 22 »C

Single-sheet glass with drapes

Zone A

above

800 m

16,7 17,6 18.5 19,4

Zone A

below

800

17,0 17,9 18,8 19,7

Zone B 17,3 18,2 19,1 20,0

Zone C 17,6 18.5 19,4 20.3

t, r . below 76 C

r„, equal to or above 16°C but below 17°C

f„,. equal to or above 17°C

Single-sheet glass without drapes

Zone A

above

' de 800 m

. 15.4 16,3 17.2 17.1

Zone A

below

de 800 m

15.9 16.8 17.7 18,6

Zone B 16.4 17.2

17.7

18,1 19,0

Zone C 16,8 18.6 19.5

U.S. GOVERNMENT PRINTING OFFICE: 1972 — 481-333 {2kk) 51
roRM NBS-114A (1-71) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS-TN-710-4

2. Gov't Accession No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE BUILDING RESEARCH TRANSLATION

Thermal Comfort Requirement Adjacent to Cold Walls —

Application to Glazed Openings

5. Publication Date May 197 2

6. Performing Organization Code

7. AUTHOR(S)

J. Anque z and M. Croiset

8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. Project/Taslc'Work Unit No. NATIONAL BUREAU OF STANDARDS DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

11. Contract/Grant No.

12. Sponsoring Organization Name and Address Building Research Division

National Bureau of Standards

Washington, D.C. 2023*+

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

C.S.T.B. No. 96, Jan/Feb 1969 , Cahier 833

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography or literature survey, mention it here.) This paper is translated from the French original and is published under the Building

Research Division/Centre Scientifique et Technique du B^timent information exchange progi

The thermal comfort of an individual inside a closed room in winter is essentially a function of the temperature of the air with which the human body transfers heat by

convection, and also of the temperature of the room's walls with which the human body

transfers heat by radiation. The presence of glazed openings (windows) which in winter

are generally the coldest walls in a residence room, can thus be a source of discomfort.;

The first part of the paper reports research conducted with a view to determining

the thermal comfort requirement near to a cold wall. The research led to the definition

of the "air-radiation requirement" for a plane surface element parallel to the wall, the

requirement being that, at about 1 m from the wall, this temperature must remain above

16 or 17°C.

The second part of the paper studies ways of satisfying the requirement near to glaze

openings in a living room in winter. The solution to the problem will depend on numerous factors: climatic zone, average temperature of the room, position of heat sources, dimensions of the openings, type of glazing (single or double), presence or absence of

curtains or screens.

17. KEY WORDS (Alphabetical order, separated by semicolons) Curtains, effect Of ; environmental

conditions; glazed openings; human response; thermal comfort requirement.

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