NBS

PUBLICATIONS

-2393

Analysis of Thermal Comfort in A

Passive Solar Heated Residence

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NBSIR 81

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U.S. DEPARTMENT COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Washington, DC 20234

November 1 981

Prepared for Passive and Hybrid Solar Energy Division

^QQ^^^i^^^'fice of Solar Heat Technologies

le U.S. Department of Energy

ashington, DC 20545

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NBSIR 81-2393

ANALYSIS OF THERMAL COMFORT IN A

PASSIVE SOLAR HEATED RESIDENCE

S. T. Liu

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U.S. DEPARTMENT COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Washington, DC 20234

November 1 981

Prepared for Passive and Hybrid Solar Energy Division

Office of Solar Heat Technologies

The U.S. Department of Energy

Washington, DC 20545

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director
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ABSTRACT

An analytical investigation was conducted on the thermal comfort conditions in

a passive solar heated residence of the popular Trombe Wall configuration. The

National Bureau of Standards Load Determination Program (NBSLD) was used to

simulate the indoor thermal environment of an actual passive solar residence,

using the Typical Meteorological Year(TMY) weather data tape as input at three

locations of different climatic conditions. The relevant thermal comfort

parameters such as the space air temperature, mean radiant temperatures, operative temperatures, radiant temperature asymmetry, and temperature drifts of the

occupied zone, were computed for a prime heating month, a transition month, and

a prime cooling month of a typical weather year at the three locations. These

parameters were analyzed in accordance with the criteria specified in the

recently revised ASHRAE Comfort Standard 55-81. It was found that for the

specific passive solar residence analyzed, the upper boundary of the comfort

envelope can be exceeded (overheating) during a typical clear day in the transition month of April unless a change of clothing to summer wear is made during

the daytime high solar radiation hours. The upper boundary will be exceeded

during a typical clear day in the prime cooling month of August for a person

in typical summer clothing at all three locations unless the average air movement in the occupied zone is increased above the level of natural circulation,

or the thermostat setting is reduced to a lower level, or both.

Keywords: ASHRAE Standard; asymmetric heating; collector/storage wall; comfort

envelope; comfort zone; mean radiant temperature; operative temperature; passive solar; temperature drifts; thermal comfort condition;

Trombe Wall

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TABLE OF CONTENTS

Page

ABSTRACT iii

LIST OF FIGURES v

1. INTRODUCTION 1

2. ASHRAE STANDARD 55-81 2 3. THE THERMAL SIMULATION PROGRAM 4

4. WEATHER DATA 5 5. DESCRIPTION OF BUILDING MODELED 6

6. VERIFICATION OF THE COMPUTER PROGRAM 7 7. SIMULATION RESULTS AND DISCUSSIONS 8

7.1 Operative Temperature at Center of the Room 8

7.2 Operative Temperature Near the Thermal Storage Wall 9

7.3 Temperature Drifts 9

7.4 Radiant Temperature Asymmetry 9

7.5 Effects of Non-typical Conditions 10

8. CONCLUSIONS 12

9. ACKNOWLEDGMENTS 13

REFERENCES 14

APPENDIX A. LISTING OF SUBROUTINE TROMBE A-1

APPENDIX B. SELECTED HOUSE PHYSICAL DATA USED IN THE STUDY B-1

V
LIST OF FIGURES

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

Figure 10.

Figure 11.

Figure 12.

Figure 13.

Figure 14.

Figure 15.

Figure 16.

Figure 17.

Floor plan of the passive solar (Trombe Wall) house

Comparison of experimental and simulation results on the surface

temperatures of the Trombe Wall on clear days in winter

Hourly solar radiation on a horizontal surface, Albuquerque, Nil

Hourly solar radiation on a horizontal surface, Washington, DC

Hourly solar radiation on a horizontal surface, Madison, WI

Operative and air temperature at center of room on a clear day in

January (Albuquerque, MN)

Operative and air temperature at center of room on a clear day in

January (Washington, DC)

Operative and air temperature at center of room on a clear day in

January (Madison, WI)

Operative and air temperature at center of room on a clear day in

April (Albuquerque, NM)

Operative and air temperature at center of room on a clear day in

April (Washington, DC)

Operative and air temperature at center of room on a clear day in

April (Madison, WI)

Operative and air temperature at center of room on a clear day in

August (Albuquerque, NM)

Operative and air temperature at center of room on a clear day in

August (Washington, DC)

Operative and air temperature at center of room on a clear day in

August (Madison, WI)

Variation of operative temperature in the occupied zone (Albuquerque, NM)

Variation of operative temperature in the occupied zone (Washington,

DC)

Variation of operative temperature in the occupied zone (Madison,

WI)

vx
1 . INTRODUCTION

Over the past several years, the national concern with the increasing cost of

conventional energy and on energy conservation has placed great emphasis on

the utilization of solar energy for the heating and cooling of buildings.

Specifically, the design of residential buildings with passive solar heating

features has received increasing attention from both the U.S. Department of

Energy (DoE) and the general public because of the potential for large energy

savings at lower cost than for many active solar heating systems. In a passive

system, solar energy which impinges on the building is collected and stored by

the architectural elements of the building such as heavy mass walls, floor, or roof, and is distributed by natural means such as conduction, convection, and

radiation without the use of solar collectors and conventional mechanical equip

ment. However, the acceptance and growth in the number of passive solar heated

buildings will depend to a large extent on occupant comfort in such buildings.

The American Society of Heating, Refrigerating, and Air Conditioning Engineers

(ASHRAE) Standard 55-81, "Thermal Environmental Conditions for Human Occupancy,

[1]*, which defines the condition for thermal comfort in a building, has

recently been revised to include adjustments for extending the comfort zone due

to the effect of air movement. The revisions also set limits on the amount of

temperature drift within the occupied zone, and on the non-uniformity of vertical temperature distribution, radiant asymmetry, and floor temperature. All

these have a direct bearing on the level of thermal comfort existing in passive

solar buildings.

This report describes an investigation of the thermal comfort condition in a collector/storage wall (Trombe Wall) residence which is one of the more popular

configurations in passive solar heated buildings. The National Bureau of Standards (NBS) Load Determination Program, NBSLD [2], which is expanded to include

a subroutine for the simulation of the thermal interaction between the living

space and the collector/storage wall assembly, was used to simulate the indoor

thermal environment of an actual passive solar residence. The thermal comfort

parameters such as the space and surface temperatures, space mean radiant temperatures, relative humidity, and operative temperatures were computed on a dynamic, hour-by-hour basis for the heating, cooling, and transition seasons of

a typical year at three geographical locations of different climatic conditions

The Typical Meteorological Year (TMY) weather tape [3] developed by the Sandia

Laboratories for the Department of Energy and prepared by the U. S. Environmental Data Service, National Climatic Center, were used as the weather data

input to the computer program. The indoor thermal comfort conditions for the

three seasons and three locations were analyzed and discussed on the basis of

the criteria established in the ASHRAE Standard 55-81 (1981).

The thermal simulation computer program, the indoor physical environment

settings and the passive solar feature of the residence modeled, the weather

data, and the analysis of the thermal comfort conditions, are described in the

following sections.

* See references at end of text.

1
2.

ASHRAE STANDARD 55-81

The standard specifying the thermal environmental conditions in a building for

the comfort of healthy people is ASHRAE Standard 55-81, "Thermal Environmental

Conditions for Human Occupancy" [1], revised in 1981. It states in part that

at the center of, and 0.6 m (2 ft) from each exposed wall, and at the center

of the room, the following standards should be met at all times;

1. The operative temperature, Tq, measured within the occupied zone shall be

on the boundary or within the "comfort envelope". The operative temperature is defined as the uniform temperature of a radiantly black enclosure

in which an occupant would exchange the same amount of heat by radiation

plus convection as in the actual nonuniform environment. The comfort

envelope is defined as a quadrangle with the following corner coordinates

when plotted on the psychrometric chart;

Winter; Tq = 19.5-23 °C (67.1-73.4 “F) at 16.7 °C

(62 “F) dew-point temperature (DP), and

To = 20.2-24.6 °C (68.4-76.35 °F) at 1.7 °C

(35 °F) DP.

Summer; Tq = 22.6-26 °C (72.7-78.8 °F) at 16.7 ”0 DP

and

Tq = 23.3-27.2 °C (74-80.9 °F) at 1.7 °C DP.

2. The humidity as described in terms of dew-point temperature (DP) shall not

be less than 1.7 °C (35 °F) or greater than 16.7 °C (62 °F).

3. The average air movement in the occupied zone shall not exceed 0.15 m/

(30 fpm) in winter and 0.25 m/s (50 fpm) in summer. However, the comfort

zone can be extended above 26 °C (79 °F) if the average air movement is

increased 0.275 m/s for each degree C (30 fpm for each °F) of increased

temperature to a maximum temperature of 28 °C (82.5 °F) and 0.8 m/s

(160 fpm).

4. When the mean radiant temperature (defined as the uniform surface

temperature of a radiant black enclosure in which an occupant would exchange

the same amount of radiant heat as in the actual nonuniform space) differs

from the air temperature in the occupied zone, the air temperature shall be

adjusted to keep the operative temperature within the appropriate comfort

zone. For low air movement, Tq is approximately the average of the air

temperature and the mean radiant temperature.

5. Monotonic, steady, non-cyclical temperature changes (drifts) shall not

extend beyond the comfort zone by more than 0.6 °C (1 °F) and for longer

than one hour.

6. The radiant temperature asymmetry for a plane element 0.6 m (2 ft) above

the floor, shall be less than 5 °C (9 °F) in the vertical direction and

less than 10 °C (18 °F) in the horizontal direction.

2
The above criteria are specified for persons clothed in typical summer or winter ter clothing, at light, mainly sedentary, activity. The insulating

value of clothing is defined in units of Clo, where 1 Clo = 0.155 m^’K/W

(0.88 f t2 ‘h’F/Btu) . An example of typical winter clothing is given in Std.

55-81 as consisting of heavy slacks, long sleeved shirt and sweater, with an overall insulating value of 0.9 Clo, and for summer clothing, light slacks and

short sleeve shirt (0.5 Clo). In addition to the above criteria. Standard

55-81 also states the conditions for temperature cycling, nonuniformity in

vertical air temperature and floor temperature, for sedentary but nontypical

clothing, and for active persons. Details of these are contained in Reference

[!]•

For the present study, the occupants were assumed to be in typical winter

or summer clothing, at sedentary or light activity level, with normal indoor

thermostat and humidity settings, so that only the criteria 1 to 6 above are applied in the analysis.

3
3. THE THERMAL SIMULATION PROGRAM

The program NBSLD [2] is a research oriented computer program developed by

T. Kusuda of the NBS for the dynamic simulation of the building indoor thermal

environment when the building is subject to hour-by-hour randomly fluctuating

outdoor climatic conditions. The program computes, on an hourly basis, the

heat loss and heat gain within and through the building envelope, the indoor

air temperature, and all the Inside surfaces temperatures required for the

computation of the mean radiant temperature. Details of this program are given in reference [2].

The program NBSLD as described in reference [2] does not simulate the

Interaction between two zones on a simultaneous basis. For a passive solar

heated building with the Trombe wall assembly as an integral part of the building, strong thermal interaction exists between the Trombe wall assembly and

the living space, so that dynamic simulation of the two zones simultaneously

becomes a necessity. For the present study, a new subroutine called "TROMBE" was developed and integrated into the program NBSLD to accomplish this purpose.

Subroutine "TROMBE" used the same solution method and algorithm as used for the

simulation of the living space in NBSLD. The narrow space between the glazing

and the mass thermal storage wall in the Trombe wall assembly was treated as a two-surface mini-zone. The air and surface temperatures of this mini-zone were

computed on an hour-by-hour basis simultaneously with those of the living space,

where output of one zone were used as input to the other zone, and vice-versa.

In its present form, the subroutine "TROMBE" can simulate a Trombe assembly with

one or two-glazing layers, with or without thermal circulation flow between the

Trombe wall space and the living space, with or without nighttime insulation,

and vented or unvented Trombe wall space in the summertime. A listing of the

program code for subroutine "TROMBE" is given in appendix A for reference.

4
4. WEATHER DATA

The Typical Meteorlogical Year (TMY) weather data tape was developed by the

Sandia Laboratories under the sponsorship of DoE, and prepared for distribution

by the U.S. National Climatic Center, Asheville, N.C. [3]. It contains a com- posite year's data of solar radiation and surface meteorological data (temperatures, barometric pressure, wind, cloud cover) for 26 locations in the United

States

For each location, data for each calendar month are selected from among 23 years

(1953-1975) of data as the most representative, or typical, for the month, using

a statistical technique developed by Sandia Laboratories. Detailed information

on the tape is contained in reference [3]. For the present study, three geographical locations, covering three types of climatic conditions, are selected.

The three locations are:

1. Albuquerque, NM - 2383 °C - days (4290 °F - days) for heating,

arid climate

2. Madison, WI - 4290 °C - days (7730 °F - days) for heating,

northern climate

3. Washington, DC - 2339 °C - days (4210 °F - days) for heating,

warm and moist summer climate

The reason for the selection of Albuquerque, N.M., and Washington, D.C. which

have almost identical heating degree-days, is that they have different summer

time climate. Albuquerque has an arid climate while Washington, D.C. normally

has a warm and moist climate in summer. The effect of humidity on the indoor

thermal comfort condition can be studied with results from these two locations.

5
5. DESCRIPTION OF BUILDING MODELED

The building selected for the simulation study is the Bruce Hunn residence [4]

located at White Rock, New Mexico. It is extensively instrumented and monitored

by the Los Alamos National Laboratory (LANL) to assess the thermal performance

of a collector/storage-wall (Trombe wall) passive system under actual occupancy

conditions. The portion of the house containing the Trombe wall is a two storey

structure with the south-facing Trombe wall extending from the ground up to the

roof overhang. Figure 1 shows the floor plans of the building. Detailed con- struction data are in reference [4]. The Trombe wall is constructed of 0.3 m

(1 ft) thick open slump block completely filled with concrete. A 5 cm (2 in)

air space separates the mass storage wall from the double glazing. The wall is

equipped with operable vents for summertime venting of the wall with roof chimney vents serving as exhaust ports. The double glazings are standard 9 mm

(3/8 in) thick plate glass spaced 2.5 cm (1 in) apart. The dimension of the

Trombe wall are 3.7 m (12 ft) wide by 7 .2 m (23.5 ft) high. The outer surface

of the wall is stained a dark brown color with a measured solar absorptivity of

0.91. No vent openings are provided for thermal circulation flow between the

Trombe wall space and the living space. The heating of the living space by the

Trombe wall is by radiation and convection from the inner surface of the thermal

storage wall. All rooms of the two storey section are open in order to provide

free natural circulation paths. A description of the building variables and

the thermal physical properties of the construction materials taken from

reference [4] are given in the appendix B for reference.

For the present study, only the section of the building containing the Trombe

wall was simulated. The indoor thermostat and humidity settings for the

simulation are as follows:

a . Space Air Temperature :

20-25.6 °C (68-78 °F). Auxiliary heating is supplied to maintain

20 °C (68 °F) minimum space air temperature. Natural cooling (if

feasible, by ventilation) or air conditioning is used to maintain

25.6 °C (78 °F) maximum space air temperature. These temperature

limits are chosen so that the space temperature, when not under the

influence of the thermal storage wall surface temperature, will

stay within the comfort zone boundaries of ASHRAE Standard 55-81.

b. Indoor Relative Humidity : 20-50 percent

The 24-hour daily internal heat gain data (lighting, appliance, and occupants)

which contribute to the indoor temperature variations were taken from reference

[5] and are given here in appendix B for reference.

6
6. VERIFICATION OF THE COMPUTER PROGRAM

The computer program NBSLD has been verified by experimental work on two

separate research projects at NBS [6,7]. However, the expanded program for a building with an attached mini-zone (Trombe wall) has not been verified before.

Therefore, the expanded program was checked for its ability to predict the temperature variations in the Trombe wall assembly. The Hunn residence was simulated for a two-week period in January using the actual measured weather and

solar radiation data reported in reference [4j. The resulting computed inside

and outside thermal mass wall surface temperatures for a cloudless 48-hour

period were compared with the actual measured surface temperatures reported

in reference [4]. The results of the comparison are shown in figure 2. The

agreement is shown to be very good, especially during the period of high solar

heat gain. Since the thermal storage wall inner surface temperature is the

main driving force for the variation in the mean radiant temperature for storage wall type passive solar heated house, the computer program is considered to

be verified for use in the simulation of indoor physical environment for thermal

comfort study.

7
7. SIMULATION RESULTS AND DISCUSSIONS

The living area of the Hunn residence containing the Trombe wall section was simulated with the expanded program NBSLD, using the TMY weather data as input,

for the prime heating month of January, the transition month of April, and the

prime cooling month of August, for the three locations described in section 4

of this report. The air temperature and the surface temperatures of all interior surfaces were computed on an hour-by-hour basis, and the thermal comfort

parameters such as the mean radiant temperature, the operative temperature, the

radiant asymmetry, and the operative temperature drifts were computed from these

temperature data and evaluated on the basis of ASHRAE Std. 55-81 as discussed

below. Since the effect of solar radiation on the passive solar residence will

be most pronounced during a clear day, all the results to be shown were for a clear day chosen from the first two weeks of each of the three months mentioned

previously. The solar radiation data for the first two weeks of each month for

the three locations are shown in figures 3 to 5 where the selected days are shaded

7 . 1 Operative Temperature at Center of the Room

The hourly variations of the outdoor temperature T^jjj^, the indoor space

temperature T^, and the operative temperature Tq for a typical clear day in

each of the three months for each of the three locations are shown in figures

6 through 14. The operative temperature Tq was computed as the average of the

space air temperature and the mean radiant temperature at the center of the

living space, 0.6 m (2 ft) above the floor. The mean radiant temperature, Tgjj.^

,

was computed from the inside surface temperatures and the associated angle

factors as given by ASHRAE Std. 55-81. In equation form, the mean radiant

temperature is written as, approximately [1],

Tmrt = Fp-1 + Fp_2 T2 + . • • + Fp.^ Tfj (1)

where Tj^ = temperature of surface N,

Fp_jj = angle factor from person at location P to

surface N,

N = total number of surfaces.

For the purpose of discussion, the thermal comfort zone boundaries for a person

clothed in typical winter and/or summer clothing at light activity specified

in the comfort envelope of the ASHRAE Std. 55-81 are also shown in figures 6

through 14. Figures 6, 7, and 8 show the variation of the operative temperature, Tq, for a typical clear day in January in the three locations. It is seen

that, except in Madison, Tq stays within or close to the lower comfort boundary

of ASHRAE Std. 55-81 for a person in typical winter clothing (Clo = 0.9) during

the nonsleeping hours. The low operative temperature in Madison was caused

mainly by the low outside temperature which caused the not well insulated Trombe

wall surface temperature to drop below the space air temperature. The upper

comfort boundary will not be exceeded in Albuquerque if a change of clothing to

summer wear (Clo = 0.5) is made during the high solar radiation daytime hours.

8
The high operative temperature in Albuquerque is caused mainly by the higher

outdoor temperature in the daytime hours. Figures 9, 10, 11 show the results

for a typical clear day in April. For all three locations, the operative

temperature stays within the comfort boundaries if a change of clothing from

winter to summer wear is made during the daytime hours.

Figures 12, 13, and 14 show the results for a typical clear day in August.

The comfort boundaries for Albuquerque were based on a 1.7 °C (35 °F) dew point

(DP) temperature due to its arid climate, while the boundaries for Madison and

Washington, DC were based on 16.7 °C (62 °F) DP (50 percent relative humidity).

It is seen that the operative temperature exceeded the upper comfort boundary

for all 3 locations by the amount of 0.6 °C (1 °F) in Albuquerque to near

1.7 “C (3 “F) in Madison, WI and Washington, DC.

7 .

Operative Temperature Near the Thermal Storage Wall

The occupied zone is defined in ASHRAE Std. 55-81 as the region within a space

between the floor and 1.8 m (6 ft) above the floor, and more than 0.6 m (2 ft)

from the walls. Since the higher operative temperature was caused by the higher

surface temperature of the Trombe wall, the operative temperature for a person

0.6 m (2 ft) away from the Trombe wall and 0.6 m above the floor level was also

computed. The results are shown in figures 15, 16, and 17 where, for comparison, the operative temperatures at the center of the space are also shown. It

is seen that for all three geographical locations, the maximum difference in

operative temperature between the two locations was less than 0.6 °C (1 °F)

during the period when the comfort boundary was exceeded, with the location

near the Trombe wall having the higher value most of the time as expected.

7 .

Temperature Drifts

As stated in section 2 of this report, the ASHRAE Std. 55-81 specifies that the

drift of the operative temperature shall not extend beyond the comfort zone by more than 0.6 °C (1 °F) and for longer than one hour. It is seen from figures

6 through 17 that the excursion of the operative temperature over the upper

comfort boundary for Madison and Washington, DC lasted over a period of more

than 10 hours and exceeded the boundary by nearly 1.7 °C (3 °F) at the center

of the room, and by nearly 2.2 °C (4 °F) at a point 0.6 m (2 ft) from the

Trombe wall.

7

.4

Radiant Temperature Asymmetry

The plane radiant temperature for an environment, Tp^ , is defined as the

uniform temperature of an enclosure in which the incident radiant flux on

one side of a small plane element within the enclosure is the same as in the

existing environment. In equation form, it can be written approximately as [1]:

Tpr “ ^e-1 '^1 ^e-2 ^2 + ••• + Fe-N % (2)

where Tj^ is the temperature of surface N. Fe-N angle factor from the

plane element to surface N, where the N surfaces form a hemisphere or open box

enclosing the element. The values of Fg_jg are given in Reference [!]• The

9
radiant temperature asyimnetry in the horizontal (vertical) direction is the

difference in plane radiant temperatures in opposite directions with respect

to a small vertical (horizontal) plane element 0.6 m (2 ft) above the floor.

It is an indication of the asymmetric radiant heating from surfaces with

different temperatures. In equation form, it is defined as [1]:

ATpr - Tp^]_ - Tp^2

For the present study, ATpj- in the horizontal direction for a vertical plane

element 0.6 m (2 ft) from the Trombe wall was computed. The maximum values of

ATpr attained during a typical clear day are shown below:

LOCATION MAX. ATpr^ °C

JAN APR AUG

Albuquerque, NM 4.5 3.0 2.5

Washington, DC 2.0 2.2 2.4

Madison, WI 1.0 2.8 2.8

The above table shows that the maximum values of ATp-j- reached were far below

the 10 °C maximum allowable value specified in the Std. 55-81.

7 . 5 Effects of Nontyplcal Conditions

1. Air movement: In the present study, natural circulation was assumed to

exist within the living space where the air movement in the occupied zone was less than 0.15 m/s (30 fpm) . ASHRAE Std. 55-81 specifies that the

upper boundary of the comfot zone can be extended to above 26 °C (79 °F)

if the average air movement is increased 0.275 m/s for each 1 °C of

increased temperature (30 fpm for each 1 °F) to a maximum temperature of

28 °C (82.5 °F) and air movement of 0.8 m/s (160 fpm). Therefore, if some mechanical means were used to increase the air movement to 0.8 m/s during

high operative temperature periods, the occupied zone would stay within

the extended upper comfort boundary.

2. Thermostat setting: The simulation was run for a normal thermostat setting

of 20 °C - 25.6 °C (68 °F - 78 °F) as described in section 5. Since the

operative temperature is approximately the average of the air temperature

and the mean radiant temperature, and a decrease of 1 to 2 °C of the air

temperature is not expected to materially affect the value of the mean

radiant temperature which is a function of the wall surface temperatures,

the operative temperature could be reduced to within the comfort zone boundary for most of the time if the upper thermostat setting was reduced

10
to a lower setting of 24 °C (75 °F). This would, however, increase the

mechanical cooling energy requirement.

3. Nontypical clothing: ASHRAE Std. 55-81 specifies that for each 0.1

decrease or increase in Clo value, the comfort zone boundary operative

temperature can be increased or decreased respectively by 0.6 °C. With a minimal clothing of 0.05 Clo, the upper boundary can be extended to 29 °C

(84 °F). Therefore, if the occupants would adjust (reduce) the clothing

to below the typical summer clothing’s value of 0.5 Clo during the high

operative temperature period of the day, the length of the time period when

the comfort criteria was exceeded would be reduced or eliminated.

4. Active Persons: The comfort zone boundary values stated in section 2 are

for a sedentary or slightly active person. If the activity level of the

occupants are increased, the standard requires a decrease in the upper

boundary value. For example, for a person doing domestic work (medium

activity) and wearing clothes with a Clo value of 0.35, the reduction in

the upper boundary temperature would be by 3.2 °C (5.8 °F). This would

cause the operative temperature at the center to exceed the allowable

boundary value by 3.8 °C (6.8 °F) in Albuquerque and by 5 °C (9 °F) in

Madison and Washington, DC.

11
8 . CONCLUSIONS

Based on the preliminary study described in this report, the following

conclusions can be drawn:

1. The occupied zone of a collector/storage wall (Trombe wall) type, well

insulated residence will stay close to or within the recently revised

ASHRAE thermal comfort standard (Std. 55-81) during the prime heating

months without overheating if a change of clothing from winter to summer

wear, when necessary, is made during the high solar radiation hours. The

exception is in a northern climate zone where the lower boundary of the

comfort zone specified in Std. 55-81 will be exceeded. This is caused by

the low outside temperature which reduces the poorly Insulated Trombe wall

surface temperature to the uncomfortable region. Night time insulation

of the Trombe wall should help in alleviating this condition.

2. The occupied zone will stay within the comfort zone during the transition

months (in-between heating and cooling season) for all three climatic

regions studied, if a change of clothing to summer wear is made during the

daytime high solar radiation hours.

3. The operative temperature in the occupied zone will exceed the upper

comfort boundary for all three climatic regions studied during the prime

cooling months. However, an increase in the average air movement within

the occupied zone by some means, a reduction of clothing below the typical

summer wear's value of 0.5 Clo, or a reduction of the thermostat setting to

a lower value, will reduce or eliminate the period of time when overheating

occurs. Shading of the Trombe wall from outside by additional or longer

overhang projections should also help in reducing the overheating problem.

A note of caution should be made about applying these results. The results of

this report apply in detail only to the building modeled here along with the

operating assumptions (e.g., internal heat gain schedules, summer venting and

overhang size, no convective flow between the Trombe wall space and the living

space, etc.). While the results should apply in general to similar buildings,

additional study on the variations of the building design and operating conditions on indoor comfort conditions, through computer simulation as is done in

the present study and through analysis of data from actual thermal performance

test results, is also indicated and recommended.

12
9 . ACKNOWLEDGMENT

The author wishes to acknowledge the advice of Dr. T. Kusuda of NBS in the

development of the computer subroutine TROMBE for the predicting of the thermal

performance of the Trome-wall space. J. Barnett of NBS provided great help in

the coding and de-bugging stage of the development. The author also would like

to express his appreciation to Dr. Larry Berglund of the Pierce Foundation

Laboratory of the Yale University for his suggestions and comments on this

project

The work reported here was sponsored by the Passive and Hybrid Solar Energy

Division, Office of Solar Heat Technologies, U.S. Department of Energy,

Washington, D.C. 20545, under Interagency Agreement No. EA-7 7A-01-6010

13
REFERENCES

1. ASHRAE Standard 55-81, "Thermal Environmental Conditions for Human

Occupancy "

, ASHRAE, 345 East 47th Street, New York, New York 10017, 1981.

2 . Kusuda , T . , "NBSLD, The Computer Program for Heating and Cooling Loads

Buildings" , BSS 69, U.S. Department of Commerce, National Bureau of

Standards, Washington, DC 20234, 1976.

3. "SOLMET, Hourly Solar Radiation-Surface Meteorological Observations" , Volume 1 - User’s Manual, TD-9724, Chapter 6, U.S. National Climatic

Center, Ashville, NC 28801, 1978.

4 . "Performance Data for Passive Systems - The Bruce Hunn House" , SERI Report

TR-0924-6, Solar Energy Research Institute, Golden, Colorado 80401, June

1980.

5. Barnett, J. P., "Energy Analysis of a Prototype Single-Family Detached

Residence: The Effects of Climate, House Size, Orientation, Internal Heat

Release, and Natural Cooling" , NBSIR 80-2184, U.S. Department of Commerce,

National Bureau of Standards, Washington, DC 20234, 1981.

6. Peavy, B. A., Burch, D. M., and Powell, F. J., "Thermal Performance of an Experimental Masonry Building" , NBS Building Science Series 45, 1973.

7. Peavy, B. A., Burch, D. M., Powell, F. J., and Hunt, C. M., "Comparison of

Measured and Computer-Predicted Thermal Performance of a Four Bedroom

Wood-Frame Townhouse" , BSS 57, U.S. Department of Commerce, National Bureau

of Standards, Washington, DC 20234, 1975.

14
mmm

indicates

slump

block

15

Figure

1.

Floor

Plan

of

the

Passive

Solar

(Trombe

Wall)

House
16

SIMULATION,

OUTER

SURFACE

HOUR

x

—

TEST,

OUTER

SI

RFACE
JANUARY 1-14

APRIL 1-14

AUGUST 1-14

Figure 3. Hourly Solar Radiation on a Horizontal Surface, Albuquerque, NM.

17
Figure A.

JANUARY 1-14

APRIL 1-14

AUGUST -1-14

Hourly Solar Radiation on a Horizontal Surface, Washington, DC,

18
JANUARY 1-14

IN

S0

LA

T

I0N

U

P

E

R

SQn

IN

S0

LA

T

I0

N

UP

ER

S

t}R

IN

S0

LA

T

I0

N

U

P

E

R

SQR

Figure

HOUR

HOUR

APRIL 1-14

AUGUST 1-14

5. Hourly Solar Radiation on a Horizontal Surface, Madison, WI.

19
20

HOUR

AFTER

MIDNIGHT
UJ E Q- UJ O' fr- 3 Q: LiJ O

tac

oeo

o

OS

4-1 o

S) . Uic u

<U Q

CJ

egU eg

0) (U C. -H O U

OJa

ao

•H

21

HOUR

AFTER

MIDNIGHT
f- uj z: Q. uj q: <x f- Z3 u o

22

HOUR

AFTER

MIDNIGHT
t- U E Ql LlI Ck: 3 Ci: Ul o

23

HOUR

AFTER

MIDNIGHT
24

HOUR

AFTER

MIDNIGHT
)

njC

o

Ba

o

cd

U_(o

(Uc

0) o

<u <u a. r-| o u

0)3

CO •H

i-uz:Q.ijjQ:^i-3a:uj o

25

HOUR

AFTER

MIDNIGHT
c:

o

S

oo

es

4-1o

CJ

cu 2

u

!-( ci3 OJ 0) O- O CJ

CN

4) a

ao

*H

P4

K LU z: CL ui q: <X E~ =3 q: UJ o

26

HOUR

AFTER

niDNIGHT
35.0

L/) OJ 0) coeoo

ecS

U-lo

(U

J-l • c

0)

u

U

Q

)-i eg

0) (U fX rH o u

lU

00

pi4

27

HOUR

AFTER

MIDNIGHT
28

HOUR

AFTER

MIDNIGHT
8S.S

T ZB.9

E

N

P

E 27.5

RA

T

u 27.

E

® 26.5

26.9

25.

• 5 1® , 15 29 25

HOUR AFTER HIDNICHT T AT CENTER OF ROOM

o

- T 0.6 m FROM TROMBE WALL

o

Figure 15. Variation of Operative Temperature in the Occupied Zone

(Albuquerque, NM)

29
e 5 Id 15 2« 25

HOUR AFTER niOHlGHT

T AT CENTER OF ROOM

o T 0.6 m FROM TROMBE

o Figure 16. Variation of Operative Temperature in the Occupied Zone

(Washington, DC).

!

30
N.6

9 5 1« 15 89 2S HOUR AFTER NIBMIQHT

T AT CENTER OF ROOM

o T 0.6 m FROM TROMBE WALL

o Figure 17. Variation of Operative Temperature in the Occupied Zone

(Madison, WI)

31
i

I

N
APPENDIX A. LISTING OF SUBROUTINE "TRONBE"

The following list defines the input and output variables in the Subroutine

TROMBE

Inputs

X,Y,Z

CR

NT

UT

DAT(l)

DAT(2)

DAT(3)

DAT(4)

DAT(5)

DAT(6)

DAT(7)

DAT(S)

DAT(9)

DAT (10)

DAT (11)

DAT (12)

DAT(13)

DAT(14) -

DAT(15)

TI

TA

TEi

DB

PB

FO

SO

SHGW

QLS

Response factors for the mass storage wall

Response factors common ratio

Number of terms of the response factors

U-value of the Trombe wall assembly

Solar absorptivity of glazing

Solar absorptivity of mass wall outer surface

Emissivity of glazing surface

Emissivity of mass wall outer surface

Number of glazing layers

Glazing area Mass wall surface area

Thermal circulation vents area ( inlet=outlet

)

Gross-sectional area of summer vent opening

Height of Trombe wall

Width of Trombe wall

Trombe wall space gap width

Vent opening indicator

= 0 - no opening

= 1 - with opening

Night-time insulation indicator

= 0 no night-time insulation

= 1 with night-time insulation

Therma resistance value (R-value) of the night-time insulation

Surface temperature of mass wall facing the living space

Air temperature of the living space

A reference temperature

Outside dry bulb temperature

Barometric pressure

Coefficient of heat transfer for surface facing outside

Total insolation normal to Trombe wall surface

Solar heat gain through Trombe wall glazings

Sensible (hourly) load of the building

Outputs

QO

Ql

qc

TO

TWA

TG

Convective heat transferred between Trombe wall air space and mass wall outer surface

Convective heat transferred between room air and mass wall inner

surface

Heat transferred by thermal circulation from Trombe wall air space to

living space through vents

Temperature of mass wall outer surface

Trombe wall air space temperature

Average temperature of the Trombe wall glazings

A-1
SUBROUTINE

TROMBE(X.

<

»—o

<

3

00

00'T

I

I

I ra to 'T O -I —

t- o — A • - 3

cj or t- o =: • • O CO — X ®

o z ^ UJ

• - «*«' H- 0X0 0 1-3 q:

• Z I- 3

*- o • c S —

Q - m a

- 3 T o • • I- a - a CO O X M UJ 1 fO

• to • ~ o • —

CO o a H- 2 O 03 CO 3 UJ o CO • • CO ^ •• CO o

rr —*- X CD CO o

u o > - ^ CO

. u- • ^ • •w - -- o O 03 \ ISI • — UJ O < • 00

• CD 03 CO o z 3 O ^ O • CO

>- Q. <!T

. ^ 00

CD X - Q . m n

t- 00

<t —

o < z z

o o >

— — <

to to Q

Z Z II lU UJ > S S < — « Q Q O »

(Dso

tr

< a h- II CM * If) o > Ui o • 3 o \ * «T ^ < o CO < II •*—

a • o o 3 o o o »-< o o < 3 X - X O o h- I—

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tn • o> in H- — •w W h- h- — q: O • < o CO o H- > —k •— > —»» m Wr + z M z » •» « 3 o 3 O 'W 03 < < a

UJ < CM w - cx CO z w • w' 3 3 + CM - * UI <t UJ + ^

a w> —

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< o h~ - o 1— CN -D > N| W W CD -1 •w^ • a

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—k 3 X > ISJ > 3 3 cu UI 03 GQ • < Cl < CO * o

< O z o o n i/i >- >- < < 11 n *— Mt z • + + X z > z z < < o o (J V u • H

a o M II H < < CO < < < CO < o o o o M o M Owl' o o X > ISI CO •—

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/o o

Cl OCO

OS — cMco'Tifi<oc*oooiO-— o'ico«»’ir)tof^cDO)0 — cNro»rmiot~CDa>0’-c<fo«Tincoc*ODO>o*-cioo<rincot^cDcT>o — cico'O’in Z o<cicic(cicNCNCNcic'ifOcocococooooorocooo«T«T^'T'J’’T'i’'T'T<Tuoif)inmmui

k-2
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— ~ o

o o 1— Z o o

> o * 05 o * o Ui —UJ 4- <D -> O 1- s CO I U C*5 a • —

V X o -f w < o — Ui M • 3 CM n

a: <t H- 3 < fsi o z u. o ^

o •- LU 3 O cr H- \ + < ^ u. X —« cr H- o o ^ h- CD \ h- UJ > CO 44 —

—

o 3 w in w < 4 UI O 3 3 O CQ - o • < —

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tn U5 3 o CN 3 X 1- X X U5 1- 2 UJ ^ * in cr < 3 O

o < CK (/> CN r5 > > H- (T O cr + a o o + in 05 * < > a o \ f- Ui CN £ o in « 3 3 O X X X o X X X o + < to > O UJ O • + «- •w w

o O 1- o CD O o O UJ X 1 1 * u. t 1 1 XX* CN U) Z o • o UJ 4- 4- • to in

• CO UI m in o cr m O -t 3 II II II II II U II 11 II o o • M O z o II CO CN V 3 II II O * 03 CQ < • O u o U. u. Z «k XXk J—«k J—

o m o — 4 in CN 'W < CD CD Z UJ UJ 10 u < 4 3 O 3 M o II o m < II > 11 o > H CM cn »- CM n CM n II II u o. 1- - w - o o o o o 1-4 u u ^ q: II H

M a. 3 3 t- o M > 3 3 1-3 3 »- < to -i II 11 u < < H X < < W s O O w > O O O O z CN CN CM n n 3 1 2 3 L 3 Z -1 O II < — o Z 0. a > II o o

u. O o O -1 o u. > o -J O 1^ O 0 0 4 3 a 30 u.oaoom (/) 4 o: H- — > u U. (J O i-i < > U. u. o u. u. U «x < A A A 4 < < A B B B S UJ U U H* o « O 1- H. o o: X t- X o o

(S3O 05

• 05 o o — II n 3 o

cn I— H C5 o O

• I X o

o o o

(O

U5

CD m o O iD <T 'T 3 0

”” - M O O O O t- I- X X

o o

a o o O _ I- . . . . < o •» Q UJ UJ

a> 1 _j o a o ^ . . . . h- UJ < < a • o o • »-

»— t— (D > O O O ~

Oi < <

<- o o

3 0 0 0

0 u. Ik 1 — «

o

«T m to O

in u o o

o

03 O

o o ® — (J u u u

o(7)0»-iNO»Tin<op»fflo>0'«-c'((n^intop'00)0 — fN(*5^min^oo>o«-(N<*5viniof^ootf50 — f'jo'Tinop'ffloo — <xf^<Tin

mif)(0(0(0(0(0(a(0(0(0(Of,p.tvt't~r»r'f»r»r»cDeooofflfflcoffl(aooo)0>05a)0)o»o)0>05a>oooooooooo —

A-3

VOLUME

FLOW

RATE

THRU

TROMBE

WALL

CHANNEL

BASED

ON

EQUATION

USED

IN

THE

PROGRAM

PASOLE

OF

LASL

o 3u

»- o o o Uu

i/)

a o a o o

t—

< a »- o - • o • o •-H o - o < 1—

H- • • • o o 3 3 o

(£)

O2 <2 «

t- 2 + o »- . < o - o < 3 n < I—

H- 3 • *

•.-r o - o cr t- • a Z)

00^

O H- o o < o o 1— • X

*- I- > o - CD z 1 » CD O • o < 0-^ O • cr o 3 0—^ in • 3 >

H* • o + -*— 3 O o o + > O X -

-1- CD o V < UJ

X cn >•

a »-

N < o O cn • < ^ UJ X + O o z • a o 0—ft to • •—O' < < cr H O It > m o cr 2 CM

H- - 3 »- z> > < >- < cr 3 - —

o > q: »— • o < \ < o X O XO

— •—

a ^ < I o 0— o z o o X >- 4-

•—O' tn \ 3 —

o s IX . z il. o o a « CD I'- o s s o cr - > o —ft 3 a o Q. «T M •-ft + 0-lft o o > < 2 • ^- o ft * CN o H- 1— J— ro o < Q « 0-. < CN in 3 + •f o < • lO o —ft o

-D < - CD

OO o o o-ft 0—

< « o 0-ftu 0—

—

CM • O CM -J LU lU —

\ ft-l ill UJ CM O O rft CM u. o •—OO • »- CM n u- 3 •—

—

(/) o > _j • O (» - O I 3 LU Nl O >- -j <• • •» O o o o M ^ 1 < X a • o - 4- CO ft- 4- - 3 1 • o • GO q: X X 3 3 O w o < V UJ CO CO CO •—

W' •—

z X o • < —'CM 3 3 II H- H H o z z o < —

ft— - M o u CD 3 O II O O o II H It o II Q cr UJ O UJ UJ < < <

-D - O 2 Q - u 3 O I X cr ••

—

u. 3 N > s > Z z »- s 2 2 z II o <-ir .0 -J O H ft-o X o 1-4 to U cr < w> < wo M cr q: cr

OOO -< u. u.

O -J CJ u. u. o 3 3 —1 - >- o o u. u. cr o crOO o U O U. M »« > u- O 1 1- o a £ z — *-• 3 O 2 3 il. u. il. o . in CM O

<o

U

U rft

Oz

UJ

ira

•T in (O CD CDO

— CO CO in CD pft CO ID o — CM CO in CD CD O) o ft- CM (O

CD

O GO <D CO CO CO CD CO 00 CD CD 0> CD CD CD CD D) O) o o o o o CO sc

CM CM CM CM CM z o

UJ

O

-io

Appendix B. Selected House Physical Data Used in the Study

A. Building Variables

1) Interior Dimensions:

2) Glazing Area:

(Values include wood framing

Glazing thickness is 1/4 in.

except for 3/8 in. thick

glazing of Trombe Wall)

3) Glazing Transmittance:

4) Glazing U-value:

5) Total Mass:

6) Estimated Mass Heat Capacity:

7) Mass Surface Area:

8) Solar Absorptance of Mass:

9) Building Heat Load Factor:

10) Infiltration:

11) Ventilation:

Refer to construction drawings [4]

South - 9.58m^ (103.2 ft^) Direct Gain

24.04m2 (258.8 ft^) Trombe Wall.

North - 0.66m2 (7.1 ft2)

East - 3.51m2 37.7 ft^)

West - 2.79m2 (30 ft2)

Skylights - 1.5m2(16 ft2) 45° South Tilt

0.9m^(9.6ft2) 20° North Tilt

0.87 * (Per 3/16 in. pane)

2.84 w/m^°C (0.50 BTUH/ft^°F)*

double pane glass with 2.54 cm air space.

16,600KG (36,660 lbs) Trombe wall

directly behind glazing

2,710KG (5,980 lbs) Bedroom #2

3865 whr/°C (7330 BTU/°F) Trombe

wall directly behind glazing

633 whr/°C (1200 BTU/°F) bedroom #2

26. 2m^ (282 ft^) Trombe wall directly

behind glazing

6.4m2 (69 ft^) Bedroom #2

0.91 Trombe wall, measured

40.9 whr/m^*Cday(7.2 BTU/ft^/°Fday)

standard ASHRAE methods using 0.5 air

exchange per hour

0.4 - 0.5 air exchange per hour.

Estimated using measured data for

June 1979 of 0.26 air exchange per

hour. in closed condition.

Operable windows only

*Standard values taken from ASHRAE "Handbook of Fundamentals," 1977 manual.

B-l
B. THERMAL PROPERTIES OF EXTERIOR SURFACES

MATERIAL

THICKNESS

CM

(IN.)

RESISTANCE

m2hR°C/KJ

(FT^HR°F/BTU)

DENSITY

KG/M^

(Ib/FT^)

SPECIFIC

HEAT

KJ/KG°C

(BTU/lb°F)

GYPSUM BOARD 1.27 (M 0.02 (0.45) 801 (50) 0.84 (0.20)

FIBERGLASS BATT 8.89 {3h) 0.55 (11.00) 24 (1.5) 0.75 (0.18)

INSULATION 13.97 iSh) 0.95 (19.00) 24 (1.5) 0.75 (0.18)

INSULATING

SHEATHING 1.27 M 0.09 (2.00) 29 (1.8) 1.21 (0.29)

PLYWOOD 1.27 (1,) 0.03 (0.62) 545 (34) 1.21 (0.29)

1.59 (5/8) 0.04 (0.78) 545 (34) 1.21 (0.29)

15 # FELT 0.64 ih) 0.01 (0.12) N/A N/A

235 # ASPHALT

SHINGLES 0.64 ih) 0.02 (0.44) 1121 (70) 1.47 (0.35)

STUCCO 1.91 (3/4) 0.01 (0.15) 1858 (116) 0.84 (0.20)

CARPET 0.06 (1.23) N/A 1.42 (0.34)

B-2
C. Internal Heat Gain Data

Lighting:

24-Hour Profile

1. 0.0 7. 1.0 13. 0.023 19. 0.023

2. 0.0 8. 1.0 14. 0.023 20. 0.5

3. 0.0 9. 0.023 15. 0.023 21. 0.5

4. 0.0 10. 0.023 16. 0.023 22. 1.0

5. 0.0 11. 0.023 17. 0.023 23. 0.0

6. 0-0 12. 0.023 18. 0.023 24. 0.0

Normalization Factor =0.38 vatts/sq. ft

Equipment/Appliance

24-Hour Profile

1. 0.25 7. 0.33 13. 0.42 19. 0.92

2. 0.25 8. 0.46 14. 0.25 20. 0.68

3. 0.25 9. 0.63 15. 0.25 21. 0.68

4. 0.25 10. 0.88 16. 0.58 22. 0.68

5. 0.25 11. 0.35 17. 0.58 23. 0.51

6. 0.25 12. 0.88 18. 1.0 24. 0.23

Normalization Factor =0.75 watts/sq. ft

Occupants

24-Hour Profile

1. 1.0 7. 1.0 13. 0.4 19. 1.0

2. 1.0 8. 1.0 14. 0.4 20. 1.0

3. 1.0 9. 0.4 15. 0.4 21. 1.0

4. 1.0 10. 0.4 16. 0.69 22. 1.0

5. 1.0 11. 0.4 17. 0.69 23. 1.0

6. 1.0 12. 0.4 18. 1.0 24. 1.0

Normalization Factor = 2 adults emd 2 children

B-3

NBS»114A (REV. 2*80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET fSee instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 81 2393

2. Performing Organ. Report NoJ 3. Publication Date

November 1981

4. TITLE AND SUBTITLE

ANALYSIS OF THERMAL COMFORT IN A PASSIVE SOLAR HEATED RESIDENCE

5. AUTHOR(S)

S. Liu

6. PERFORMING ORGANIZATION (If joint or other than N BS, see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

NBS and DEPARTMENT OF ENERGY, Passive and Hybrid Solar Energy Division

Office of Solar Heat Technologies

Washington, DC 20545

10.

SUPPLEMENTARY NOTES

r I Document describes a computer program/, SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bliography or literature survey, mention it here)

An analytical investigation was conducted on the thermal comfort conditions in a passive

solar heated residence of the popular Trombe Wall configuration. The National Bureau

of Standards Load Determination Program (NBSLD) was used to simulate the indoor thermal

environment of an actual passive solar residence, using the Typical Meteorological Year

(TMY) weather data tape as input at three locations of different climatic conditions.

The relevant thermal comfort parameters such as the space air temperature, mean radiant

temperature^ , operative temperatures, radiant temperature asymmetry, and temperature

drifts of the occupied zone, were computed for a prime heating month, a transition month

and a prime cooling month of a typical weather year at the three locations. These parameters were analyzed in accordance with the criteria specified in the recently revised

ASHRAE Comfort Standard 55-81. It was found that for the specific passive solar residence analyzed, the upper boundary of the comfort envelope can be exceeded (overheating)

during a typical clear day in the transition month of April unless a change of clothing

to summer wear is made during the daytime high solar radiation house. The upper boundary will be exceeded during a typical clear day in the prime cooling month of August for

a person in typical summer clothing at all three locations unless the average air movement in the occupied zone is increased above the level of natural circulation, or the

thermostat setting is reduced to a lower level, or both.

12.

KEY WORDS ("Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon sj ASHRAE Standard; asymmetric heating; collector/storage wall; comfort envelope; comfort

zone; mean radiant temperature; operative temperature; passive solar; temperature drifts

thermal comfort condition; Trombe Wall

13'. AVAILABILITY

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Order From National Technical Information Service (NTIS), Springfield, VA. 22161

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PRINTED PAGES

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