NBS BUILDING SCIENCE SERIES 116

Geographical Variation in the

Heating and Cooling Requirements

of a Typical Single-Family House,

and Correlation of These

Requirements to Degree Days /V

U.S. DEPARTMENT OF COMMERCE • NATIONAL BUREAU OF STANDARDS \ W

C:^.
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' 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 measurement 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's technical work is performed by the National Measurement Laboratory, the National Engineering Laboratory,

and the Institute for Computer Sciences and Technology.

THE NATIONAL MEASUREMENT LABORATORY provides the national system of

physical and chemical and materials measurement; coordinates the system with measurement

systems of other nations and furnishes essential services leading to accurate and uniform

physical and chemical measurement throughout the Nation's scientific community, industry,

and commerce; conducts materials research leading to improved methods of measurement,

standards, and data on the properties of materials needed by industry, commerce, educational

institutions, and Government; provides advisory and research services to other Government

Agencies; develops, produces, and distributes Standard Reference Materials; and provides

calibration services. The Laboratory consists of the following centers:

Absolute Physical Quantities^ — Radiation Research — Thermodynamics and

Molecular Science — Analytical Chemistry — Materials Science. THE NATIONAL ENGINEERING LABORATORY provides technology and technical

services to users in the public and private sectors to address national needs and to solve national problems in the public interest; conducts research in engineering and applied science

in support of objectives in these efforts; builds and maintains competence in the necessary

disciplines required to carry out this research and technical service; develops engineering data and measurement capabilities; provides engineering measurement traceability services; develops test methods and proposes engineering standards and code changes; develops and

proposes new engineering practices; and develops and improves mechanisms to transfer

results of its research to the utlimate user. The Laboratory consists of the following centers:

Applied Mathematics — Electronics and Electrical Engineering^ — Mechanical

Engineering and Process Technology^ — Building Technology — Fire Research —

Consumer Product Technology — Field Methods.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts

research and provides scientific and technical services to aid Federal Agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and

economy in Government operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives; carries out this mission by managing the Federal Information Processing Standards Program, developing Federal ADP standards

guidelines, and managing Federal participation in ADP voluntary standardization activities; provides scientific and technological advisory services and assistance to Federal Agencies; and

provides the technical foundation for computer-related policies of the Federal Government.

The Institute consists of the following divisions:

Systems and Software — Computer Systems Engineering — Information Technology.

'Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234. ^Some divisions within the center are located at Boulder, Colorado, 80303.

The National Bureau of Standards was reorganized, effective April 9, 1978.
;; onai Bureau o? Stan DEC 5 1978

NBS BUILDING SCIENCE SERIES 116

u s ^

o

Geographical Variation in the

Heating and Cooling Requirements

of a Typical Single-Family House,

and Correlation of These

Requirements to Degree Days

Edward A. Arens

William L. Carroll

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D.C. 20234

Sponsored by:

Energy Research and Development Administration

Office of Conservation

Division of Buildings and Community Systems

Washington, D.C. 20545 and

Department of Housing and Urban Development

Office of Policy Development and Research Washington, D.C. 20410

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

Issued November 1978
Library of Congress Cataloging in Publication Data

Arens, Edward A

Geographical variation in the heating and cooling requirements

of a typical single-family house, and correlation of these require- ments to degree days.

(National Bureau of Standards building science series ; 116)

Supt. of Docs, no.: Cl3.29/2:116

1. Dwellings—United States—Energy conservation. 2. United

States—Climate. 3. Degree days—United States. I. Carroll, William

Leslie, 1945- joint author. II. Title. III. Series: United States. National Bureau of Standards. Building science series ; 116. TA435.U58 no. 116 [TJ163.5.D86] 690'.021s [697] 78-606140

National Bureau of Standards Building Science Series 116

Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser. 116, 58 pages iNov. 1978) CODEN: BSSNBV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1978

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

Stock No. 003-003-01992-5—Price $2.50

(Add 25 percent additional for other than U.S. mailing)
FOREWORD

This is one of a series of reports planned to document NBS research

efforts in developing energy and cost data needed to formulate energy

budgets for Building Energy Performance Standards (BEPS). The work

described in this report was jointly supported by ERDA/NBS Modification

No. 2 of Contract E(49-l)3800 and Task Order No. A008-BCS to Interagency

Agreement No. EA-77-A-01-6010 , and by HUD/NBS Contract No. RT193-12.

Edward A. Arens and William L. Carroll

iii
SI CONVERSION UNITS

In view of the present accepted practice in this country for building

technology, common U.S. units of measurement have been used throughout

this document. In recognition of the position of the United States as

a signatory to the General Conference of Weights and Measures, which

gave official status to the metric SI system of units in 1960, assistance is given to the reader interested in making use of the coherent

system of SI units by giving conversion factors applicable to U.S.

units used in this document.

Length

1 in = 0.0254 meter (exactly)

1 ft = 0.3048 meter (exactly)

Area

1 in^ = 6.45 X 10 ^ meter^

1 ft^ = 0.09290 meter^

Volume

1 in^ = 1.639 X 10"^ meter^

1 gal (U.S. liquid) = 3.785 x 10 ^ meter^

Mass

_2

1 ounce-mass (avoirdupois) = 2.834 x 10 kilogram

1 pound-mass (avoirdupois) = 0.4536 kilogram

Pressure or Stress (Force/ Area)

1 inch of mercury (60°F) = 3.377 x 10"^ Pascal

1 pound-f orce/inch (psi) = 6.895 x 10"^ Pascal

Energy

1 foot-pound-force (ft»lb»f) = 1.356 joule

1 Btu (International Table) = 1.055 x 10"^ joule

1 kilowatt-hour (kWh) = 3.600 x 10^ joule = 3.412 x 10^ Btu

Power

1 watt = 1 joule/sec

1 Btu/hr = 0.2929 watt

Temperature

= 1.8 top

ys) + 32

(Degree daysjop = 1.8 (Degree days)o^

IV
Heat

1 (Btu*in)/(h*f t^'F) = 1.442 x lO""*- W/(m»K) (thermal conductivity)

1 Btu/lbm»°F = 4.184 x 10^ J/(kg*K) (specific heat)

1 langley = 4.184 x 10^ J/m^ = 1 cal/cm^ = 3.69 Btu/ft^

V
ABSTRACT

The report has three main purposes:

First, it assesses 'Test Reference Year' (TRY) hourly climate data tapes

to determine how well they represent long-term average climate when used

for estimating average annual heating and cooling requirements. The

report presents a method to adjust heating and cooling requirements that are computed using TRY data, in order to make them represent long-term

average heating and cooling requirements.

Second, the report quantifies the geographic variation of annual heating

and cooling requirements across the U.S. by computing the heating and

cooling requirements of a typical ranch-style residence for the 8760

hours of each of the 60 TRY tapes, and adjusting the results by the

method described above.

Third, the effectiveness of 'degree-day' data for predicting these computed annual heating and cooling requirements is examined, and the variability of heating and cooling requirements within degree-day 'zones' of

1000 degree day width is presented.

Key words: Building energy conservation; climatic effects on building

energy consumption; computer modeling of building energy consumption;

energy conservation; geographical variation of building energy consumption; residential energy consumption.

vi
TABLE OF CONTENTS

Page

Introduction 2

1. The Test Reference Year Tapes 5

1.1 Description of TRY Tapes 5

1.2 Determining the Representativeness of TRY Data 5

1.3 Results 8

2. Geographical Variation of Heating and Cooling 1^

Requirements in the U.S.

2.1 Representative House I5

2.2 Annual Heating & Cooling Requirements 15

2.3 Heating and Cooling Requirements in Relation to 2.6 Energy Consumption

2.4 Geographic Variation 16

3. Correlation of Heating and Cooling Requirements With 19

Degree Days

3.1 Introduction 19

3.2 Degree Days to Base 65°F 19

3.3 Degree Days to a Base Matched to the Balance 20

Point of the Ranch House

3.4 Conclusions 23

4. Adjustment of TRY-Computed Annual Heating and Cooling 25

Requirements to Represent the Long-Term Record

4.1 Procedure 25

4.2 Results 26

4.3 Conclusions 26

5. Variation of Heating and Cooling Requirements in Climate 31

Zones Based on Degree Days

5.1 Introduction 31

5.2 Results 32

5.3 Conclusions 36

6. Conclusion 37

References 39

Appendix A. 1. List of the TRY Tapes Available May 1977 41

2. Selection Procedure for TRY Years 42

vii
TABLE OF CONTENTS (cont.)

Page

Appendix B. Design of the Representative Ranch-Style House 43

Appendix C. Description of the Heating and Cooling Load 46

Modeling Procedures Used for the Representative

Ranch House

1. Approach 46

2. Insulation Levels 46

3. Operating Conditions 47

4. Infiltration and Ventilation Rates 47

5. Floor Slab Model 49

6. Orientation and Solar Transmission of Windows 50

7. Listing of the Building Description 51

Coding of the Ranch House

We thank Candace L. Roat, Daniel Nail, and Andre Tanner, Architectural

Research Program, NBS, James Filliben, Statistical Engineering Section,

NBS, Paul R. Achenbach, Building Environment Division, NBS, and Charles

Robinson, Thermal Engineering Program, NBS, for their help in preparing

and analyzing the data presented here.

viii
INTRODUCTION

PURPOSE AND BACKGROUND

The rapidly rising cost of energy has made buildings' heating and cooling

operating costs, taken over the expected life span of the building, often

exceed the first costs of construction. Accordingly, building designers

have been increasingly considering energy conservation during design, and are attempting to determine the optimum investment of construction funds

into energy-conserving design options.

At the same time, the national energy shortage has highlighted the fact

that heating and cooling buildings consumes almost one fifth of the entire

national energy demand. This energy has, in consequence become the focus

of regulatory agencies promulgating energy conservation standards, and

of energy planners and suppliers.
This report addresses several topics that may be useful to building

designers, and to planners and regulators concerned with larger-scale

energy issues:

1. Building designers need to be able to compute accurately the average

annual energy requirements of buildings in order to optimize energy

conserving measures. The "Test Reference Year" (TRY) hourly climate

data tapes provided by National Oceanic and Atmospheric Administration (NOAA) are being used by engineers for computing building energy

requirements in a large number of U.S. locations. The tapes were

not originally selected to represent average, or long-term, climate;

the appropriateness of using TRY tapes for this purpose needs to

be determined and possible errors quantified.

2. Both designers and regulators charged with developing building energy

standards need to know the geographic variation of building heating

and cooling requirements around the U.S. The heating and cooling

variations should be attributable to climate and location alone, and

not include the effects of existing regional differences in construction practices.

3. Designers, regulators, and energy planners need to investigate the

usefulness of degree days for predicting building heating and

cooling requirements in locations with widely varying sunlight, humidity, and wind. Since the degree day to the base 65°F is the basis

of most traditional methods of energy calculation, and is also the

basis of most energy standards, e.g., ASHRAE Standard 90-75, a detailed comparison of this parameter against energy requirements

nationwide is useful. An investigation of degree days to other base

base temperatures is also needed.

4. There is a need to investigate whether geographical zones can be

identified within which building energy requirements could be considered constant with respect to climate. Regulators, energy planners, and designers are using such zones to formulate building energy

standards, priority lists for energy conserving measures, and other

such regulatory and design implements.

APPROACH

1. The report describes in detail the Test Reference Year data tapes for

computerized building energy calculations. The TRY tapes' accuracy

in representing the average long-term climate is tested by comparing

the degree days and average temperatures calculated from the TRY

tapes themselves to the National Weather Service's long-term records

for these parameters. Degree days to a wide range of different base

temperatures have also been investigated for each TRY tape.

2. The geographical variation of annual heating and cooling requirements across the U.S. is given, using one single-family ranch house as a basis for the computer simulation. The ranch house has been carefully designed to be representative of current typical house con2
struction, and the energy demands caused by the activities of a typical occupancy have been included in the simulation.

3. The correlation of heating and cooling requirements to heating and

cooling degree days is determined for degree days to two bases:

the traditional National Weather Service base of 65°F, and empirically determined bases specific to this residence. The correlation

is obtained by comparing the annual values of heating and cooling

requirements with TRY-calculated degree days for each of the 60

locations for which TRY tapes are available.

4. The heating and cooling requirements, as calculated from the TRY

tapes, are then adjusted to more closely represent the long-term

climate at each location. The percent difference between TRY-calculated degree days and long-term degree days is used to adjust the

energy values.

5. The report describes the variation in heating and cooling requirements within 1000-degree-day bands defined by degree days to the

base 65°F. Such bands have been incorporated in building energy

standards, on the assumption that energy consumption is reasonably

uniform within each band. It may be inequitable to require uniform

insulation levels across a band with a wide variation in heating

and cooling requirements, particularly if the adjacent zone with

lower insulation requirements contains locations with higher heating

and cooling requirements.

This report is the first of a series being prepared by the authors to

describe the effects of climate on heating and cooling requirements on buildings. The companion reports will use the TRY data and the NBS Loads

Determination Program (NBSLD) [7] program to define the functional relationships between heating and cooling requirements and the individual

climatic elements of temperature, humidity, solar radiation, and wind.

Additional building designs are included in the investigation. The

reports will also include a method of abbreviating climatic data for

reduced computation costs and ease of analysis, a means of increasing

the representativeness of TRY data, and a method for providing more geographically specific computerized climate data to building sites.

3
I

i
1. THE TEST REFERENCE YEAR TAPES

1.1 DESCRIPTION OF TRY TAPES

A Test Reference Year (TRY) Computer tape consists of climate data in a standardized format for use by engineers in comparing energy requirements

of various heating and cooling systems. The climate data are in hourly

form for the full reference year, as needed for computer simulation of

building heating and cooling performance. The TRY tapes are provided by

NOAA, in accordance with criteria developed by ASHRAE Technical Committee 4.2 (Engineering Weather Data). TRY tapes are now available for 60

cities. The data are generally recorded at weather stations in nearby

airports. The number of tapes is to be increased to 90 in the future

with the addition of data from military bases.

Appendix A, part 1, lists available TRY tapes. The list includes the

city, the year chosen to be the representative TRY, and the coordinates

and elevation of the weather station.

5
The tapes contain the following climatic information for each of the

8,760 hours of the year (or 8784 hours for leap years):

Dry-bulb temperature

Wet-bulb temperature

Dew-point temperature

Wind direction

Wind speed

Barometric pressure at station

Weather (consisting of precipitation, fog, haze, dust)

Total sky cover

Cloud amount of each of four cloud layers

Type of cloud for each of four cloud layers

Height of base of each of four cloud layers

Solar radiation (not currently included in the tapes)

The various building energy computer programs draw from this list whichever climatic elements they require in their calculation procedure.

Each TRY tape consists of one year's climate records chosen from a population of 27 years of records on U.S. National Weather Service 1440

series data tapes. The year chosen as the TRY year varies with location.

The TRY selection procedure is described in Appendix A, part 2.'- ^ The

TRY data were not intended to be sufficiently typical of long-term climate to yield reliable estimates of average energy requirements. However,

since they are currently the only publicly available hourly data tapes

which are representative of the long-term temperature record,* they have

come to be used for energy calculations by the engineering and research

communities. It is therefore desirable to determine how representative

each TRY tape is of the long-term average climate.

1.2 DETERMINING THE REPRESENTATIVENESS OF TRY DATA

It is possible to check the representativeness of each TRY tape by com- paring the number of heating and cooling degree days in the TRY tape data

with those established from long-term climatic records. This method was

was chosen here after initial results showed a well defined correlation

between annual degree days and calculated annual heating and cooling

requirements.

The number of heating degree days for a particular day is calculated from

the following:

Another nationwide data tape series is in preparation at time of

writing. This is the Typical Meteorological Year (TMY) , prepared by

the Department of Energy in NOAA' s SOLMET format. The years are primarily intended for use in designing solar systems. Each year is a composite of the most typical months from 2 3 years of record. The

criteria for typicalness are weighted toward solar radiation, but also

include temperature, humidity, and wind velocity.

6
where: is a specified "base temperature"

"^max daily maximum temperature**

T . is the daily minimum temperature**

1/2CTjjj^^ + Tjij-^j^) is the NOAA definition of daily average

temperature.

N is set to zero if the calculated value is negative. The expression for

cooling degree days is:

N = [l/2(T^ax + T^in) " Tfe]

•

The daily calculated degree-day values are then summed for monthly and

annual periods to give a measure of accumulated temperature difference.

The National Weather Service uses a method devised by H.C.S. Thom [2, 3,

4] to calculate monthly heating and cooling degree days from monthly

average temperature and the standard deviation of daily average temperatures about the monthly average. Both heating and cooling degree days

to the base 65°F are calculated by NOAA as described above from long-term

temperature records for a large number of locations in the U.S. [5].

The base temperature should be a daily average temperature above which

(in the case of heating degree days) there is, on the average, no heating

load or below which (in the case of cooling degree days) there is, on the

average, no air conditioning load. If the base temperatures do correspond to these thresholds, and if heating and cooling requirements are basically proportional to temperature, the degree-day total for a given

period will then be basically proportional to the heating and cooling

quired for that period. This proportionality relates climate to energy

use

.

The results presented in Chapter 3 show that annual heating and cooling

requirements of the ranch-style test house used in this study are basically proportional to heating and cooling degree days, when the base

temperature for heating degree days is 53°F, and for cooling degree days

is 68°F. Thus the preferred test of each TRY tapes' representativeness

of predicting the annual heating requirements of this test house would

be a comparison of its number of heating degree days, base 53°F, with a long-term record of heating degree days, base 53°F. In order to test

the TRY tapes' representativeness for predicting annual cooling of this

test house, a similar comparison would be made with cooling degree days,

base 68°F. This approach is taken in Chapter 4.

** There is a small difference between the procedure used here and that

used by NOAA in calculating degree days. NOAA uses actual extreme

temperatures, taken from continuous records, while the TRY tapes provide only the maximum and minimum hourly values for T^^^ and T^^^,

respectively, for each day. This should cause only insignificant

differences in determining the daily average, and thus the calculated

degree days.

7
The traditional base for both types of degree days, however, is 65°F.

Since nearly all the published climatic data and building energy use data

are expressed in terms of degree days to this base, the general comparison

of TRY and long-term degree days presented in Table 1.1 uses degree days

to this base. Table 1.1 contains:

a. The number of 65°F base heating and cooling degree days for each

reported location computed from the tapes.

b. The NOAA National Weather Service's long-term degree-day totals calculated for the same locations.

c. A similar comparison of the annual mean temperatures in the TRY to

those in the long-term record.

d. A similar comparison of the annual mean temperatures in the TRY to

those in the long-term record.

The relationship between the number of 65°F base degree-days and the

number with other bases may be determined by computing and plotting of

the numbers of degree days to a wide range of degree-day bases. An

example of such output is presented in Figure 1.3, a frequency distribution of degree days versus degree-day base temperature.

Figure 1.3 reveals that this relationship is nearly linear for inland

stations, within the ranges of interest: 65°F to 53°F for heating degree

degree days, and 65°F to 68°F for cooling degree days. Coastal locations, which have fewer cold days and a higher proportion of their total

days in the range 53°F to 65°F than inland stations, exhibit a more significant curve in their heating degree-day frequency distributions in

in this range. San Francisco has the most extreme curvature of all the

TRY locations.

1.3 RESULTS

Figures 1.1 and 1.2 give an indication of the accuracy of the whole population of TRY tapes at predicting actual long-term heating and cooling

degree-day data to base 65°F. The relevant statistics are:

8
a) CO

ao 3 Q. C C B

o c 01 ^ H

>> ,-{ u

as CO 0) H 3 O. c a

H H

> kJ

01 I

a ><

at

M 00 CO

K 00

0) o

00 CO c >^

•H lO

4-» Q LO

CO

0) OJ X 0) 0)

t4 Cfl 00

Dci 0) H Q

oommvor^'^r^oo>un-vj-m^mi rnrHfor^r--rnoovorN.<j-co^DcN-Hfsioo^ocN<r

cocslcN^c^J<fo^O'^u-lcoa^coo^cNf^Otnoo<ro^c^IO<^^^<T»o^a^<roolnooo^

•<tcNCN^^^oo<fc^OOO'^<|lncvJ'^O^ln^^^X)r-^^o.H^Htn^---.H'^

CN iH -H <N r-i

l + l I t+ + -fl I I I I I++I I I I I l + l I I I ( I

ln^^^ooocNCOlH•J^^^fn<T^^^c^J^sloOr^^o<^^Ha^oo^^cooor~^cNO^c^^^

cNu^oo<7^<fooa^-<^lHOoo^^ooc^r-^OLn^^^£)^oa^<^^cg.Hc^lLnr^ o^<^u-lvOlnc^<fr^u^o^^r^o>H<^r~^ooocsllnOcn<^<^Ovx)<^J^^<^lOo^

rH .H rH .H en .H CNJ CS >H Csl «H rH

inr^o><rr~--iJ^rnr^u^ooooinr~^Ocsr^-*<trHrvj<NrHrHincnr^c^

u~lOOtnOLncvJcO<^OC^^^^JtHr^CsJ^^)CNJM^OOOOOM.Hu-^<tr^lHO^roOM<^

ooc^^^oln<^<rcOr^or^'X)^Ln^--<r^coo^^o(X)r^lOcN<f^^cor^^^ooc^ oo<T^oo<T'<^<^cnc^lOCNr~^<fLncs|<ru~)l^^H<^^^cnu^Lnror^ln^ ^ <js r-^ <t- <t cn oocNtHOooooo'*o\£)a>oOrHrsjrHcOiHO<ro^oo^vO<rLncNrnrH<rco'X>Lnr^o>

u^rsi<xioo<toor^a>r^'-OrnOfHiHOa^ogO'0<nr^rn\DO>LnLn.Hu^

cNJror^^o^ool^^o<X)<^cOoc^r^.HO^lOcsIlOcn'^^nv£)lnlnc^

^^-<r^cvJcsICT^mu~l 'X>co<^r~^^<t'^L^'^^<Nc\jf^Jr^'HLncNiiHiOiH>H<r<^r^<*

O <

"to -

oj « - X i-i OS

, . -U 01 0) H 3 O

Oj" |h < . §

3 o e

cr « CO " o ho - j: j>i M

0) rH CO 00 O

3 rH U C U -

CO 3 IH CO B < S3 -I <

rH C/1 -H W O MH

•H -H O O V4 3

pp m pq pa cq

H HH X 2

> O OH H

CO tu g M « X CO >i •H rH C c M •H s >^H < rH rH rH o o 4J a j-> u rH O

4H 0) CO c CO •rl " »-i CO a >

00 Cfi c O c CO H 4-> U O O C CO C c

c 01 c 00 c rH CO 3 o o c o o

•H rH 01 CO •H 0) o 0) CO c U CO to to rH U >^ o o > u 00 CL, 4-1 CO CO CO •rl U CO 0) H c 0) rH 4J U OJ 01 3 13 u (J 3 •H rH o OJ O rH o o C CO to (O u u u u u a Q U o 3: M ->

w u c > o o »^

to 0) 5^

< to o to o

tH J2 -H MH 3 J2 -O O 3 to 0) rJ J S S

9
f-l ^ u

CO <u c c e

^OLnu~l<JCOfno-)0^lrl^Ofn<^OvOr^CX>f^O^OOO(T^CT^^ogCNm

r^lOiHOmOOOr^i—lmcnO-^O^U~^^£>QOrnm-^C^JO^

•H H

>

HI I <^r^^ou-la^ocoro^-^IHO^-^a^ 00cncy>rsiiHcsiLr)O\£)cNmminr^cN00vDmm<j-^(^fn\£)iHLo

I++IIIP++II++IIIII + IIIIII +

a^oor^<^moOf-^voa^-^^'oo^--r^lO<J^ocT^Lr^^^-*cslooo^o^m c^lfnc^JO^o<^<^^^<roo<^u-^oo^lnml^rsl0^cNOO^-<3I^

oou~lvo^^o<looa^r^u~l^c^J^ncoo^I—^<to^a^^^'—^c^l^oo^<r

Csl<f t-HcNiHt—IrH t—Ifn T-HiHtH-H CM cniHrH

ooa^<rr^o^^ooc^J^^.^<^cN^^IoOlrl^o-)Ocooooo-d^sJa^I-^ mooa\oomcNir)cx30ooncno>-<fmcor^o\Ln^o<7^cnmiHON QOMOO<fvOOcnaOOOfOI^CN<NCOCNO^cnO^OOv£) rHtHr^^

rH-^t rHCSlrHtHi—IrHiHrO rHiH r-t (SI fniHrH

> H

(U iJ O I

oocMi—l<r^Hr^(Nr^or^^ot^u~l^^cNI^oo<^o^m^£>aor^I—fr—

r^^o^lOO^oomo^mcMOooc^J<to^mo^oor^cNmooo^ ^^lO.Ha^^£>ococ:^<3-^omfna^a^r^o-)-^lrlco^^o<J'OOr^cOr^ cNCNfn^D<^CT^<^^ocOLOCT^<J^^tr1a^co^-^<T^mLnOr^r^\Oc^l

(^JCNImfO<JCT^Or-^r^cN^£)^^^rsIl00oo^Dm^m-<^•<J<r^Or^<J

Lnu~lOmr-^^^•<^<^Jcoo^^HI—^oo^.o<^o^^^N<^co-crcr^oor^<r^

cMI^<^>J~l^^mfna^c^II—^Ln^^\Da^vou~^a^^^I^slcoog^o<J-<^vDT-^

J rH D to - "feO-HO)^ - CO

CO CX i-H tH ^1 ^ e H " (0 -H ^-1 O iH O

j::-H (i)>o>-i oj=:

J= <C £

a 00 -

01 X 3 C

- C X

to 00 . „ _

-H a to 3 3 (0^r-<ai4-l4J4J(UXVJ fO'HO^-'VjJ-'iHOCJ

3 <: 3

- X < >, H "to U O 4-1 < O B S -H » U CJ O U O CO o O * -H - -H to

* 4-) CO 0) C O O H

C ••^ o 00 C I aj 3 to -u dj CO OJ O iJ C 'H U t-l <; Q fc, 4-1

' ^ C C C to

to to -H

Q. CO ^

B i-H «

I -n vu to (0 to to d) to -J lcc;wc/3coc/:icoc/3c/3HH

10
Heating

:

Best-fit regression equation: I^Drjij^y ~ 0.99 DD^^-p + 115

Residual standard deviation: 298 degree days

Correlation coefficient*: 0.99

Cooling :

Best-fit regression equation: ^^^XRY ~ 1«03 DDj^,j, + 40

Residual standard deviation: 137 degree days

Correlation coefficient: 0.99

These results do not determine the tape's representativeness on a monthly

basis. The differences between the TRY and long-term monthly degree days

tend to be considerably larger than for the annual values. The same observation holds for the differences between the TRY and long term

monthly average temperatures, as compared to the differences in the

annual values given in Table 1.1.

* The correlation coefficient is a measure of dependence between two

variables and is defined as

where x and y are respectively the mean of all the x values and the

mean of all the y values, ay respectively the standard

deviations of all the x values and all the y values, and N is the

number of x,y observations. 1.0 represents perfect dependence between

the two variables.

11
TRY HEATING DEGREE DAYS ( BASE 65°F )

9m- 3125 I- >-

625 -

• •

1250 2500

TRY COOLING DEGREE DAYS ( BASE 65°F )

3750 5000

FIGURE 1.2

12
13

2. GEOGRAPHICAL VARIATION OF HEATING AND COOLING REQUIREMENTS IN THE

U.S.

2.1 REPRESENTATIVE HOUSE

A 1200 square-foot single-story ranch-style house with a slab-on-grade

floor was selected as representative of new construction in the U.S.

based on 1974 statistics collected by the NAHB Research Foundation.'- ^

A ranch house based on these statistics was designed by S.R. Hastings of

NBS, as representative of current house design. This design is being

used for research on the energy effectiveness of various insulation

levels and building design features at NBS. A detailed description of

the design, with drawings, is given in Appendix B. The ranch-house envelope parameters and operational data were encoded to permit heating and

cooling load calculations by the NBS Loads Determination (NBSLD) com- puter program*-^^. A listing of the building description as input to

NBSLD is attached in Appendix C.

15
2.2 ANNUAL HEATING AND COOLING REQUIREMENTS

The annual heating and cooling requirements of the representative ranch

house, as calculated from the 60 TRY tapes, are presented in Table 2.1

and Figure 2.1. The range of the values is: heating requirements, 0.2

to 64.5 million Btu; cooling requirements, 0.9 to 33.7 million Btu; and

total, 3.6 to 68.9 million Btu. The average heating requirement is 21.8

million Btu and the average cooling requirement, 10.4 million Btu.

2.3 HEATING AND COOLING REQUIREMENTS IN RELATION TO ENERGY CONSUMPTION

The heating and cooling requirements are accumulated loads, or heating

and cooling energy deficits, that need to be met by the heating and

cooling equipment. The energy conversion efficiencies of heating and

cooling equipment are not included in the table and figure. In order to

obtain the energy needed to meet these heating and cooling requirements,

one must first make an assumption about the types of heating and cooling

systems in the house. Second, one must divide the heating and cooling

requirements given here by the seasonal coefficients of performance

(COPs) of the heating and cooling equipment, respectively. This gives

the energy required at the house ("metered load"). If one is interested

in source energy, which is the generally accepted way to put different

types of energy or fuel on a common energy denominator, one must multiply

connected load by a resource utilization factor.'-

The "total" heating plus cooling requirement given here is useful as an indicator of climate stresses only; since the COPs of heating and cooling

equipment are rarely the same, the combined energy needed to meet the

"total" requirement will vary with the proportions of heating and cooling

requirements making up the total.

2.4 GEOGRAPHIC VARIATION

In comparison with the real population of housing, the heating and cooling

requirements in Figure 2,1 are expected to be overestimated in the colder

northern locations and underestimated in the hotter southern locations.

This is because the ranch house used in the study is kept uniform across

the country. It is relatively less insulated than many existing northern

houses and more insulated than most southern houses. However, as noted

in Appendix C, the insulation levels assumed in the ranch house are now commonly used in construction in all regions of the country.

Figure 2.1 would be most useful if the relative heating and cooling

requirements it presents are valid proportionally for other types of

buildings and other insulation levels. At present, several other singlefamily residences have been modeled at NBS, using a selected group of TRY

stations. This research was not complete at time of writing, but the

house types, insulation levels, and variations in assumed operating con- ditions that have been tested to date have shown geographic variations

proportional to those given in Figure 2.1.

16
TABLE 2.1

ANNUAL HEATING AND COOLING REQUIREMENTS OF TEST

HOUSE AT 60 TRY STATIONS, IN MILLIONS OF BTU

Station Heating Cooling Total

Albany, NY 41.7 3.2 44.9 Albuquerque, NM 15.8 10.1 25.9 Amarillo, TX 19.8 10.1 29.9

Atlanta, GA 9.6 11.4 21.0 Birmingham, AL 9.3 12.5 21.8 Bismarck, ND 64.5 4.4 68.9

Boise, ID 29.7 5.5 35.2

Boston, MA 34.0 3.2 37.2 Brownsville, TX 1.1 32.4 33.5 Buffalo, NY 41.3 1.9 43.2 Burlington, VT 48.6 2.1 50.7 Charleston, SC 8.1 14.0 22.1 Cheyenne , WY 42.7 2.1 44.8 Chicago, IL 33.4 4.3 37,7

Cincinnati, OH 27.2 6.1 33.3 Cleveland, OH 37.6 4.1 41,7

Columbia, MO 28.4 8.7 37.1 Detroit, MI 38.4 4.5 42.9 Dodge City, KS 30.1 9.0 39.1

El Paso, TX 8.1 17.3 25.4 Fort Worth, TX 7.1 21.9 29.0

Fresno, CA 7.1 16.4 23.5 Great Falls, MT 53.5 2.0 55.5 Houston, TX 4.5 22.9 27.4 Indianapolis, IN 33.8 5.9 39,7

Jackson, MS 8.1 18,4 26,5

Jacksonville, FL 2.3 22.7 25,0 Kansas City, MO 27.0 10.1 37.1 Lake Charles, LA 4.9 21.8 26.7 Los Angeles, CA 1.2 2.4 3.6 Louisville, KY 22.0 8.4 30.4 Lubbock, TX 16.1 12.9 29.0 Madison, WI 43.3 2.9 46.2 Medford, OR 16.2 5.4 21.6 Memphis, TN 12.8 14.6 27.4 Miami , FL .2 33.7 33.9 Minneapolis, MN 55.3 5.5 60.8 Nashville, TN 14.9 10.7 25.6 New Orleans, LA 4.9 21.0 25.9 New York, NY 24.8 4.7 29.5 Norfolk, VA 14.3 8.5 22.8 Oklahoma City, OK 21.1 14.3 35.4 Omaha , NE 35.5 7.6 43.1 Philadelphia, PA 28.3 6.4 34.7 Phoenix, AZ 3.0 29.9 32.9 Pittsburgh, PA 33.1 3.9 37.0 Portland, ME 41.7 1.8 43.5 Portland, OR 24.0 1.9 25.9 Raleigh, NC 13.9 9.8 23.7 Richmond, VA 20.6 8.8 29.4 Sacramento, CA 8.3 9.7 18.0

St. Louis, MO 27.7 10.0 37.7

Salt Lake City, DT 33.8 6.6 40.4

San Antonio, TX 6.0 22.1 28.1 San Diego, CA .6 3.7 4.3 San Francisco, CA 5.7 .9 6.6 Seattle-Tacoma, WA 25.5 1.1 26.8 Tampa, FL .7 24.9 25.6 Tulsa, OK 15.7 13.9 29.6 Washington, DC 19.7 9.0 28.7

17

Heating, cooling, and t

station against average |g_|gpj^j|y i^Q^jg ^jj^g ^gg^ reference year data

Q AVERAGE OF ALL STATIONS

STATION VALUE

Healing, coolino, and total load for

station against average for all stations Based on the simulated consumption of a characteristic single-family tiouse using test reference year data
I
3. CORRELATION OF HEATING AND COOLING REQUIREMENTS WITH DEGREE DAYS

3.1 INTRODUCTION

The heating and cooling requirements calculated for 60 U.S. locations

provide a useful test of the predictive accuracy of the degree day.

Both heating and cooling degree days are considered here. The traditional NOAA degree days to the base 65°F are considered first, and degree

days to an empirically determined base appropriate for the representative

ranch house are considered second, both for heating and for cooling.

3.2 DEGREE DAYS TO BASE 65 °F

The 65 °F base heating degree day has been in steady use for over 40 years

by utilities and fuel suppliers as a measure to predict the demand of the

average population of buildings. It is also used by the building design

profession to estimate monthly and annual heating requirements. It has

evidently been satisfactory for this purpose, although the base tempera19
ture is high for most buildings except those with no insulation and

smaller internal loads than are common today.

The cooling degree day, also with base 65°F, is published by the NOAA for

all stations, but has not gained as wide acceptance in the design professions as the heating degree day.

Figure 3.1 compares heating requirements with the number of heating

degree days, base 65°F, for each of the 60 TRY stations calculated. The

degree-day numbers are calculated from the TRY tapes themselves. The

regression lines do not pass through the origin; the equation Qjj = 0.007 X DDj^^^ - 9.0; Q^^ is the annual heating requirement in millions

of Btu, and DD^^^ is the number of heating degree days, base 65°F. The

residual standard deviation is 3.5 x 10 Btu, and the correlation coefficient, 0.97.

Figure 3.2 compares cooling requirements with number of cooling degree

days, base 65°F, for each station. As with the heating degree days, the

cooling degree-day numbers are calculated from the TRY tapes themselves.

The regression line does not pass through the origin, the equation being

= 0.009 X DDq^^ - 1.3, where is the annual cooling requirement and

C65 number of cooling degree days to the base 65°F. The residual standard deviation is 1.3 x 10 Btu, and the correlation coefficient,

0.98.

3.3 DEGREE DAYS TO A BASE MATCHED TO THE BALANCE POINT OF THE RANCH

HOUSE

In theory the degree-day base temperature should equal the "balance

point" of the building being predicted: the temperatures above which, or below which, the heating or cooling system is not needed, respectively.

The balance points of the ranch house were found empirically from a detailed analysis of the hours in which there were heating and cooling

loads in the house. They were also found by an iteration of plots such

as Figures 3.3 and 3.4 at different base temperatures.

Figure 3.3 compares heating requirements with the number of heating

degree days, base 53°F, for each of the 60 TRY stations calculated. The

degree day numbers are calculated from the TRY tapes themselves. The

regression line passes quite close to the origin, the equation being:^

= 0.01 X 00^1^2 ~ 0.4. The residual standard deviation is 2.0 x 10

Btu, and the correlation coefficient is 0.99. The accuracy of fit is

considerably improved over the equation using the 65°F base heating

degree day.

Figure 3.4 compares cooling requirements with the number of cooling

degree days, base 68°F, for each of the 60 TRY stations calculated. The

regression equation is: = .01 X DD^^g + .08. The residual standard

deviation is 1.3 x 10 Btu and the correlation coefficient is 0.99. The

accuracy of fit is improved over the equation using the 65° base cooling

degree day.

20
2500 5000 7500 10000

TRY HEATING DEGREE DAYS ( BASE 65°F ) FIGURE 3.1

• a

1250 2500

TRY COOLING DEGREE DAYS ( BASE 65°F )

3750 5000

FIGURE 3.2

21
2000 4000

TRY HEATtNG DEGREE DAYS ( BASE 53°F )

6000 8000

FIGURE 3.3

4000

TRY COOLING DEGREE DAYS ( BASE 68°F )

22

FIGURE 3.4
3.4 CONCLUSIONS

With the newer building stock better insulated, with greater appliance

usage releasing more heat in the house than in the past, and with occupants using lower thermostat settings as their energy consciousness

increases, the use of heating degree days calculated to a lower base

temperature becomes desirable. The 53° base temperature given here

applies only to the design and simulated operation of this ranch house.

Although the results show a good correlation between cooling degree days

and annual cooling requirements, they do not prove the utility of cooling

degree days for design purposes. This is because these results use the same house with the same internal heat release, and window orientation

and size, in all cases. Since solar gain and internal heat release make

up a large proportion of the total cooling requirements, any variation

in these parameters makes the determination of cooling requirements based

on cooling degree days less accurate than has been found here. In design

practice, where there is a significant variation in solar gain or internal heat loads between design alternatives, cooling degree days are con- sidered less useful than other methods such as cooling degree hours for

estimating cooling requirements.

Cooling degree days have been shown to have value in comparing the energy

requirements of a prototype across geographic regions. In this way, they

may be useful for energy regulatory purposes.

23

I

4. ADJUSTMENT OF TRY-COMPUTED ANNUAL HEATING AND COOLING REQUIREMENTS

TO REPRESENT THE LONG-TERM RECORD

4.1 PROCEDURE

It is possible to adjust or "correct" the heating and cooling requirements calculated from the TRY years and presented in Table 2.1 to make

them approximate the long-term record. The procedure used here is specific to the test ranch house:

Using the calculated annual heating and cooling requirements, Q^p^y for

each location (Table 2.1 and Figure 2.1) corrected requirements are calculated from:

Qlt

=^

DDj,

Qtry

RY

25
where Q-^r^ is the annual heating (cooling) requirement corrected to

be representative of the long-term climate at the location.

^TRY annual heating (cooling) requirement calculated from the

TRY tape.

DDj^rjn is the number of long-term heating (cooling) degree days calculated to a base temperature equal to the balance point of the ranch

house, using the procedure developed by Thom'-^-'.

DD-pj^Y is the number of heating (cooling) degree days to the appropriate base temperature, as obtained from the TRY data by the procedure discussed in Chapter 1.

Table 4.1 presents DDlt ^^^^ DIij,-^Y the base temperatures 53° and 68°,

equal to the balance points of the ranch house, for all 60 stations.

4.2 RESULTS

Table 4.2 presents the adjusted heating and cooling requirements for the

representative house at the 60 TRY stations. These values differ from

those in Table 2.1 and Figure 2.1 in that they represent long-term average climate rather than just the TRY year itself.

The mean adjusted annual heating requirement for the 60 locations is

21.56 xlO° Btu, and for cooling, 11.10 x 10° Btu. The adjusted heating

value for each city is higher than the TRY value for that city in 28

cases, lower in 29 cases, and the same in 3 cases. The population of TRY

tapes predicts slightly more heating requirements on the average than the

long-term climate. The difference is 0.2 x 10^ Btu. The TRY tapes have

on the average 45 more heating degree days, base 53°F, than the long-term

climate. This difference is on the order of 2 per cent of the average

number of degree days.

The TRY tapes are warmer than the long-term climate in the cooling season

as well. The adjusted cooling value is higher than the TRY value in 39

cases, lower in 17 cases, and the same in 4. The average cooling load is

0.7 X 10 Btu lower for the TRY tapes than for the long-term climate.

The TRY tapes have on the average 36 less cooling degree days, base 68°F,

than the long-term climate; the difference is on the order of 4 per cent

of the average number of degree days.

The percentage heating or cooling error for individual stations is mostly

a function of the size of the heating and cooling requirements. TRY stations with larger requirements tend to have lower error percentages.

4.3 CONCLUSIONS

A method is proposed here to adjust the annual heating and cooling

requirements predicted by the TRY weather data. The method is based on

the relationships found between heating and cooling requirements and the

26
TABLE 4.1

COMPARISON OF TRY AND LONG-TERM HEATING(BASE 53°F) AND COOLING (BASE 68°F) DEGREE DAYS

S 1 3. t ion Heating Degree Days ^' <!A S3**F'i VrfUUX X Llg

TRY Long ie Liii % deviation

TRY iKI —TLiT -. ^„ ^ 200

LT

TRY Lo ng~Te rrn % devia

TRY-LT

LT

Albany 4326 4034 7.2 285 348 -18.1

Al buquercj ue 2007 2003 0.2 950 923 2.9 Amarillo 1942 1964 -1.1 876 1047 -16.3 Atlanta 1110 1225 -9.4 988 1132 -12.7

Bi rm i ng ham 1096 1118 -2.0 1142 1420 -19.6

Bi smarck 6495 5967 8.9 328 307 6.8 Boise 2896 2994 -3.3 462 461 0.2

Bos ton 3108 2930 6.1 439 397 1.1 Brown svi lie 101 -5.0 2999 3042 46.9 Buffalo 3936 4002 -1.7 203 239 -15.1

Burl ing ton 4940 4822 2.5 211 225 -6.2

Cha r 1 e s t on 716 699 2.4 1407 1518 -7.3 Cheyenne 3965 4143 -4.3 135 176 -23.3 Chicago 3442 3536 -2.7 461 622 -25.9

Ci nc i nna t i 2562 2663 -3.8 757 731 3.6

CI eve land 3761 3422 10 .0 415 361 15.0

C^^\^ V>U X 1LUll im ViU T a 2 729 4 .

7

843 902 -6.5

De troit 3731 3672 1.6 431 398 8.3 Dodge City 2905 2758 5.3 960 992 -3.2

El Paso 1001 934 7.2 1448 1576 -8.1

Fort Worth 795 805 -1.2 1938 2031 -4.6

Fr esno 761 771 -1.3 1193 1221 -2.3

Great Falls 4474 4583 -2.4 190 187 1.6 Hous ton 459 357 28.6 2091 2235 -6.4 Indianapolis 3326 3075 8.2 591 590 0.2

•Ja c k. s on 839 813 3.2 1787 1747 2.3 Jacksonville 225 321 -29.9 2042 1934 5.6 Kansas City 2782 2816 -1.2 1084 1043 3.9 Lake Charles 466 382 22.0 1996 2098 -4.9

Los Angeles 37 174 -78.7 117 309 -62.1

Loui sville 2295 2353 -2,5 829 884 -6.2 Lubbock 1524 1534 -0.7 1106 1198 -7.7

Mad i son 4438 4759 -6.8 243 267 -9.0

Med ford 1847 2103 -12 .2 252 337 -25.2 Memphi s 1373 1382 -0.7 1391 1534 -9.3 Miami 12 5 140.0 3190 3113 2.5 Minnea polls 5556 5264 5.6 601 366 64.2

Na s hV i 1 1 e 1539 1694 -9.2 1034 1250 -17.3

New Orleans 482 377 27.9 2028 2064 -1.7

New Yo rk 2135 2457 -13.1 670 698 -4.0 Norfolk 1322 1445 -8.5 943 1011 -6.7 Oklahoma City 1826 1691 9.0 1455 1421 2.4 Omaha 3600 3553 1.3 702 840 -16.4

Ph iladelphia 2758 2439 13.1 731 747 -2.1

253 321 -21 .2 2735 2957 -7 .5 Pi ttsburgh 3096 3245 -4.6 428 384 11.5

ruj, LJ-diiu J

l ull 4431 4305 2.9 146 125 16.8 Portland, OR 1972 1841 7.1 125 152 -17.8 Raleigh 1559 1474 5.8 934 974 -4.1

Richmond 2275 17 71 28.5 849 944 -10.1 Sacramento 914 797 14.7 606 755 -19.7

St. Louis 2892 2476 16.8 1008 1085 -7.1

Salt Lake City 3530 3237 9.1 644 645 -0.2

San Antonio 583 395 47.6 2220 2358 -5.9

San Diego 21 116 -81.9 251 371 -32.4

San Francisco 507 537 -5.6 33 21 57.1 Seattle 2061 1517 35.9 72 85 -15.3 Tampa 36 97 -62.9 2318 2568 -9.7 Tulsa 1671 1676 -0.3 1265 1487 -14.9 Washington, DC 1857 1976 -6.0 1084 1006 7.8

27
TABLE 4.2

ANNUAL HEATING AND COOLING REQUIREMENTS OF TEST HOUSE AT 60 TRY STATIONS CORRECTED TO REPRESENT THE LONG-TERM CLIMATE

IN MILLIONS OF Btu

Station Heating Cooling Total

Albany , NY 38.8 3.9 42.7 Albuquerque, NM 15.8 9.8 25.6 Amarillo, TX 20.0 12.1 32,1

Atlanta GA 10.6 13 .1 23,7

Birmingham, AL 9.5 15.5 25,0

Bismarck, ND 59.3 4.1 63,5

Boise, ID 30.6 5.5 36.1

Boston, MA 32.0 2.9 34.8 Brownsville, TX 2.2 32.7 34.9 Buffalo NY 42.1 2.2 44,4

Burlington, VT 47.6 2.3 49.9 Charleston, SC 7.9 15 .1 23.1 Cheyenne , WY 44.4 2.7 47.1 Chicago, IL 34.4 5.8 40,2

Cincinnati, OH 28.3 6,2 34,5

Cleveland, OH 34.2 3.6 37,8

Columbia, MO 27.3 9.3 36,6

De t r 0 i t , MI 37.6 4,1 41.8 Dodge City, KS 28.6 9,3 37.9

El Paso, TX 7.5 18.9 26.4

Fort Worth, TX 7.2 23.0 30.2

Fresno, CA 7.2 16.7 23,9

Great Falls, MT 54.6 2.0 56,5

Houston, TX 3.5 24.5 28,0

Indianapolis, IN 31.1 5.9 37.0

Jackson, MS 7,9 18.0 25,9

Jacksonville, FL 3.3 21 .5 24,8

Kpnc^Aq ri tv MO 27.3 9.7 37,0

Lake Charles, LA 4.0 22.9 26,9

Los Angeles, CA 5.6 6.3 12 ,0

T niii '?vi lie KY 22.7 9.0 31,7

Lubbock, TX 16.3 13.9 30,2

MalictUX H n o(JI.I cnn y WTW X 46.3 3 .2 49.5 MpHfnrH OR 18 .

7.2 25.7

MpTTinhi L iC 111 L 1 X OQ J TNX Li 12 .9 16.1 29.0

Ml am 1 FT 0.1 33,0 33.1

M"innpanr^l liXLlLlCa.lJ<^XXO i q MM J

L ill 52,5 3 ,4 55.9

Np Qhvi lip TN 16 .4 13 ,0 29 .

Mpi.t ilCW OTlpanc; V-/i.XCdLio TA ] J_if\ 3.8 21 ,4 25.2 Npu iNt; W YnlULIVj rV IsTY I'll 28 .5 4,9 33.4 Norfolk, VA 15.6 9.1 24.7

Oklahrtma Ti fv OK 19 .6 14 ,0 33.6

Oma Via MP 35,2 9.1 44 .3 Philadelphia, PA 24.9 6.5 31.4

PViripniY IT LtUtrLlX A A 7 , t\Aj 3.8 32.3 36.1 Pittsburgh, PA 34,8 3.5 38.3 Portland, ME 40.5 1.6 42.0 Portland, OR 22.3 2.3 24.6 Raleigh, NC 13.2 10.2 23.4 Richmond, VA 16.1 9.8 25.8 Sacramento, CA 7.2 12,1 19,4

St. Louis, MO 23.8 10,8 34,6

Salt Lake City, UT 31.1 6,6 37,7

San Antonio, TX 4.1 23,4 27,5 San Diego, CA 3.3 5,5 8,8

San Francisco, CA 6.0 0,6 6,6

Seattle-Tacoma , WA 18.8 1.3 26,8

Tampa, FL 1.9 27.6 29,5

Tulsa, OK 15.7 16.4 32,1

Washington, DC 20.9 8.4 29,3

28
heating and cooling degree days to a base appropriate to the test ranch

house.

On the whole, the 60 TRY tapes contain somewhat warmer temperatures than

the long-term average climate record. This is reflected in the slightly

lower heating requirements and higher cooling requirements predicted by

the TRY tapes.

29

5. VARIATION OF HEATING AND COOLING BIEQUIREMENTS IN CLIMATE ZONES BASED

ON DEGREE DAYS

5.1 INTRODUCTION

The initial purpose of this investigation was to develop climate zones

for building energy standards. The zones, based on climatic parameters,

would define areas of relatively uniform heating and cooling requirements. With such zones, various requirements of building energy standards might be applied equitably across the different climates of the

country

.

The research on the geographic distribution of loads described above

yields some information on one common type of climate classification, in

which the zones are defined as bands of annual degree days, base 65°F, one thousand degree days in width. The calculations done here allow the

range of heating and cooling requirements to be determined for each of

these zones.

31
The 60 stations were classified into nine heating degree-day bands and

five cooling degree-day bands, based on their long-term annual degree-day

totals. The heating and cooling requirements for each station, as adjusted to represent the long-term record (Table 4.2), were then collected into each band.

5.2 RESULTS

Tables 5.1 and 5.2 show the variability of heating and cooling requirements with each band. The range of the values within each band and the

overlap between bands are seen to be substantial. The non-uniformity

may have serious implications for the equitability of climate zones based on degree days to the base 65°F.

A large part of the observed heating variability within these zones is

due to the difference between 65°F and the 53°F balance point of the

house, which has the effect of causing coastal locations, particularly

west coast locations, to have low heating requirements in relation to

their degree days. The coastal locations have a larger proportion of

daily average temperatures in the range between 65°F and 53°F than the

inland locations. Consequently, the representative house in these locations will accumulate numerous degree days without any heating energy

being required. This characteristic of coastal cities may be seen in

Figure 1.3, where San Francisco displays considerable curvature in the

cumulative degree day distribution between 53°F and 65°F.

The resulting poor fit of coastal cities in heating zones based on 65°F

degree days may be seen in Table 5.1. Two cities in particular appear

as low points in their heating zones, overlapping the adjacent lower

degree-day zone. These are San Francisco (6.0 million Btu) and Seattle

(18.8).

The positions of these coastal cities improve when arranged in zones based on 53°F based heating degree days. Table 5.3 presents such zones for comparison. The zone widths are reduced to 600 degree days, since

the numbers of 53°F based degree days are inherently lower, and it is

desirable to divide the country into ten zones to permit comparison with

the ten 65°F-based degree-day zones.

The positions of the coastal cities are now more evenly distributed

throughout the zones, and the overlapping has largely disappeared. San

Francisco and Seattle have each dropped down three zones, reflecting

their relatively small numbers of degree days to base 53°F.

A second part of the variability in both heating and cooling requirements

is due to the different levels of sunlight in the various locations. The

low heating requirements for Albuquerque (15.8 in Table 5.1) are a result

of the high sunlight level there. Since a degree-day-based zone system

does not take solar radiation into account, the solar variability will

weaken the relationship between any heating or cooling degree days.

Changing the degree-day base does not erase this variability. Albuquerque also has low heating requirements for its zone in Table 5.3. Solar

32
TABLE 5.1

ANNUAL HEATING REQUIREMENTS WITHIN ZONES DEFINED BY 1000 DEGREE DAY BANDS.*

In million of Btu

Degree Days 0- 1000- 2000- 3000- 4000- 5000- 6000- 7000- 8000- 9000- (Heating) 999 1999 2999 3999 4999 5999 6999 7999 8999 9999

Base 65°F

0.1 3.3 7.2 6.0 15.8 18.8 34.2 40.5

1.9 3.3 7.2 10.6 18.5 27.3 34.4 44.4

2.2 3.5 7.2 12.9 20.0 27.3 35.2 46.3

3.8 7.5 13.2 20.9 28.6 37.6 47.6

3.8 7.9 15.6 22.3 30.6 38.8 54.6

4.0 7.9 15.7 22.7 31.1 42.1

4.1 9.5 16.1 23.8 31.1

5.6 16.3 24.9 32.0

52.5 59.3

16.4 28.3 34.8

19.6 28.5

* Long-term heating degree days to base 65° (Table 1.1) and adjusted heating requirements

(Table 4.2) used.

TABLE 5.2

ANNUAL COOLING REQUIREMENTS WITHIN ZONES DEFINED BY 1000 DEGREE DAY BANDS.*

In million of Btu

Degree Days 0- 1000- 2000- 3000- 4000-

(Cooling) 999 1999 2999 3999 4999

Base 65°F

0.6 4.9 15.1 27.6

1.3 6.2 16.1 32.3 1.6 6.5 18.0 32.7 2.0 8.4 18.9

2.2 9.0 21.4 2.3 9,1 21.5

2.3 9.3 22.9

2.7 9.3 23.0 2.9 9.7 23.4

3.2 9,8 24.5

3.5 9,8

3.4 10,2 3.6 10,8

3.9 12.1 4.1 12.1

4.1 13.0

5.5 13.1

5.5 13.9

5.8 14.0

5.9 15.5

6.3 16.4

6.6 16.7

7.2 9.1

* Long-term cooling degree days to base 65° (Table 1.1) and adjusted cooling

requirements (Table 4.2) used.

33
TABLE 5.3

ANNUAL HEATING REQUIREMENTS DIVIDED INTO 10 ZONES

OF 53 °F - BASED HEATING DEGREE DAYS.*

In millions of Btu

Degree Days 0- 600- 1200- 1800- 2400- 3000- 3600- 4200- 4800- 5400-

(Heating) 599 1199 1799 2399 2999 3599 4199 4799 5399 5999

Base 53°F

0.1 7.2 10.6 15.8

1.9 7.2 12.9 18.5

2.2 7.2 13.2 20.0

3.3 7.5 15.6 20.9

3.3 7.9 15.7 22.3

3.5 7.9 16.1 22.7 3.8 9.5 16.3

3.8 16.4 4.0 18.8

4.1 19.6 5.6

6.0

Long-term heating degree days (Table 4. (Table 4.2) used.

23.8 31.1 37.6 40.5 47.6

24.9 31.1 38.8 46.3 52.5 27.3 34.2 42.1 54.6 27.3 34.4 44.4 28.3 34.8

28.5 35.2

28.6

30.6 32.0

1) and adjusted heating requirements

TABLE 5.4

ANNUAL COOLING REQUIREMENTS DIVIDED INTO 6 ZONES

OF 68°F - BASED COOLING DEGREE DAYS.*

In millions of Btu

Degree Days 0- 600- 1200- 1800- 2400- 3000-

(Cooling) 600 1199 1799 2399 2999 3599 Base 68°F

0.6 4.9 13.0 21.4

1.3 5.8 14.0 21.5

1.6 6.2 15.1 22.9

2.0 6.5 15.5 23.0

2.2 6.6 16.1 23.4

2.3 8.4 16.4 24.5

2.3 9.0 16.7

2.7 9.1 18.0

2.9 9.1 18.9

3.2 9.3

3.4 9.3

3.5 9.7 3.6 9.8

3.9 9.8 4.1 10.2

4.1 10.8

5.5 12.1

5.5 12.1

5.9 13.1

6.3 13.9

7.2

* Long-term cooling degree days (Table 4.1) and adjusted cooling requirements

(Table 4.2) used.

34
variability causes a great deal

in Tables 5.2 and 5.4. Cooling

to solar gains are than heating

of the spread in

requirements are requirements.

the cooling requirements

generally more sensitive

A third part of the variability in the cooling zones can be traced to the

effect of the daily range of temperature, a climatic characteristic which

is suppressed by daily average temperature and degree-day data. A day

with an average temperature of 65°F but with a large daily range might

require heating by night and cooling by day, accumulating energy requirements without accumulating either type of degree day. Thus the house in

this climate will seem to have high energy demands in relation to its

degree-days zone.

To illustrate this, the two points in Figure 3.2 showing high cooling

loads in relation to their degree day totals are Sacramento and Fresno,

both in the central valley of California. During the summer, sea breeze

penetration of the valley causes a sharp temperature drop at night, which

accounts for an unusually large daily range at these locations. In

Fresno, the daily average temperature in July and August is 80°F, meaning

that cooling degree days accumulate at only 15 per day. The daytime

temperature, however, will have reached an average daily maximum of 99°F,

which will have required considerable cooling.

The daily range in these months averages 38°F, the highest of the 60 TRY

locations[10] . Sacramento, with an average temperature in these months

of 75°F and an average daily maximum of 93°F, has the second highest

daily range.

A fourth source of variability in energy consumption within degree-daybased zones is atmospheric humidity. Humidity influences the latent heat

requirements of maintaining acceptable indoor humidity. The variation of

this influence geographically depends on the humidity limits being maintained in the building. The influence is more significant during

cooling

.

In this study, latent load was found to constitute between 0 and 13% of

the cooling energy requirements in the 60 locations. The extreme variation in latent loads between locations with similar degree day numbers is

between 1.5% in Phoenix (3334 TRY degree days) and 12% in Brownsville

(3851 TRY degree days). Brownsville is adjacent to the humid Gulf of

Mexico, while Phoenix is in the deSert, isolated from maritime air.

Although the greater humidity in Brownsville causes an extra 10% in its

annual cooling requirements over Phoenix, it can be seen that the loads

for Phoenix are actually greater than Brownsville's in proportion to

their degree days. Other factors, probably the daily range and sunlight

which are greater in Phoenix than Brownsville, are offsetting the humidity effect. Their combined influence causes a difference of over 10%

between Phoenix and Brownsville.

35
5.3 CONCLUSIONS

It has been shown that, although degree days represent heating and

cooling requirements fairly well in the aggregate (Figures 3.1 and 3.2),

there is still considerable variation between individual stations with

similar numbers of degree days to the base 65°F. Part of this variation

has been explained as due to the discrepancy between 65°F and the proper

degree-day base temperature for a given building, but other causes of

variation which the degree-day parameter cannot measure are solar radiation, the daily temperature range, and humidity.

36
6. CONCLUSION

The TRY climate data tapes for computer energy calculation have been

climatologically analysed. The deviation of each TRY from the true

average year (as represented by the long-term record) is quantified

using annual degree days and annual average temperatures (Tables 1.1 and

4.1). The deviation between TRY and long-term degree days is found to

exceed 10% at numerous locations. The more extreme percentage deviations

occur at locations with insignificant numbers of degree days. The deviation in annual average temperature ranges from 0 to 2.6°F.

Annual heating and cooling requirements of a test ranch house were calculated using each of the 60 available TRY tapes to define the geographic

and climatic diversity of heating and cooling requirements in the U.S.

The ranch house was designed with care to assure its representativeness.

The heating and cooling requirements calculated in this way were adjusted

by the above-mentioned degree-day comparison to represent the long-term

record rather than the TRY year itself (Table 4.2). The relationships

37
between these values may be of general use if the heating and cooling

requirements from other residential and small commercial building types

prove to be proportional. It should be noted that the values of heating

and cooling requirements presented in Tables 2.1 and 4.2 are annual accu- mulated energy loads on the house's HVAC system, and may be substantially

lower than the fuel energy required to satisfy those loads through whatever system the house may have.

Combination of the TRY tape analysis and the energy calculations gives a new test of the effectiveness of degree days to different bases in predicting annual heating and cooling requirements. (Figures 3.1 and 3.2),

In this house the optimal heating degree-day base is 53°F and the cooling

degree-day base is 68°F. The effectiveness of climate classification

based on traditional degree day zones to the base 65° could also be

assessed (Figures 5.1 and 5.2). The variation of heating and cooling

requirements within 1000 degree-day bands is large, exceeding 300% in

several bands; but it is perhaps more signf leant that the bands contain

outliers that overlap adjacent bands. Zones based on the heating and

cooling balance points of the house are free of the variation due to

coastal versus inland location, but solar radiation and other climatic

influences continue to cause variation. One may conclude that degreeday-based climate zones are imperfect for organizing annual building

energy requirements, but when necessary, they should be designed so that

the base temperature for the degree days matches as closely as possible

the overall balance point of the building population for which the zones

are intended.

38
REFERENCES

1. National Climatic Center. 1976. Tape Reference Manual " Test

Reference Year. " National Climatic Center, Asheville, N.C. Also

published in the ASHRAE Journal, February 1977, p. 47.

2. Thom, K.C.S. 1954. The Rational Relationship Between Heating Degree

Days and Temperature . Monthly Weather Review. Vol. 82, No. 1,

3. Thom, H.C.S. 1954. Normal Degree Days Below Any Base . Monthly

Weather Review. Vol. 82, No. 5.

4. Thom, H.C.S. 1954. Normal Degree Days Above Any Base by the Universal Truncation Coefficient . Monthly Weather Review. Vol. 94, No. 7.

5. National Climatic Center. 1973. Monthly Normals of Temperature,

Precipitation, and Heating and Cooling Degree Days 1941-1970 . Climatography of the U.S. No. 81 (By State). National Climatic

Center, Asheville, N.C.

6. National Association of Home Builders Research Foundation. 1974.

National Survey of Characteristics and Construction Practices for all

Types of One-Family Homes . Washington, D.C.

7. Kusuda, Tamami. 1976. NBSLD, The Computer Program for Heating and

Cooling Loads in Buildings . NBS Building Science Series 69.

National Bureau of Standards, Washington, D.C.

8. Phipps, Harry. 1976. The RUF Concept as an Energy Measurement

Tool . ASHRAE Journal, Vol. 18, No. 5, p. 28-30.

9. Filliben, J.J. 1976. DATAPAC: A Data Analysis Package . Proceedings of the Ninth Interface Symposium on Computer Science and Statistics. April 1-2, Boston, MA. p. 212-217.

10. Environmental Data Service, National Oceanic and Atmospheric Administration Climatography of the U.S. No. 60: Climates of the States . (A series of publications).

11. American Society of Heating, Refrigerating and Air-Conditioning Engineers. 1975. ASHRAE Standard 90-75, Energy Conservation in New

Building Design . ASHRAE, N.Y., N.Y.

12. Socolow, R.H., and Sonderegger, R.C. 1976. Twin Rivers Program on Energy Conservation in Housing: 4 Year Summary Report . Report

No. 32, Center for Environmental Studies, Princeton, N.J.

13. Peavy, B.A. , Burch, D.M., Powell, F.J., and Hunt, CM. 1975. Com- parison of Measured and Computer-Predicted Thermal Performance of a Four Bedroom Wood-Frame Townhouse . BSS 57. National Bureau of

Standards, Washington, D.C.

39
14. Department of Housing and Urban Development. 1973. Residential

Energy Consumption, Single-Family Housing . Report No. HUD-HAl-2

Prepared by Hittman Associates, Columbia, MD.

15. Coblentz, C.W., and Achenbach, P.R. 1963. Field Measurements of Air

Infiltration in Ten Electrically-Heated Houses . ASHRAE Transactions

69, p. 358.

16. Martin, H.R., Achenbach, P.R., and Dill, R.S. 1953. Effect of Edge

Insulation Upon Temperature and Condensation on Concrete-Slab Floors . BMS 138. National Bureau of Standards, Washington, D.C.

17. Dill, R.S., Robinson, W.C., and Robinson, H.E. 1945. Measurements

of Heat Losses from Slab Floors . BMS 103. National Bureau of

Standards, Washington, D.C.

18. Bareither, H.D. , Fleming, A.N., and Alberty, B.E. 1948. Temperature

and Heat-Loss Characteristic of Concrete Floors Laid on the Ground . Research Report 48-1. University of Illinois. Small Home Council - Building Research Council.

40
APPENDIX A

1. List of the TRY tapes available May 1977.

Latitude Longitude Elevat Station Selected TRY N °

' W °' feet

Albany, NY 1969 4239 07345 19 Albuquerque, MM 1959 3503 10637 5311 Amarillo, TX 1968 3514 10142 3607 Atlanta, GA 1975 3339 08426 1010 Birmingham, AL 1965 3334 08645 620 Bismarck, ND 1970 4646 10045 1647 Boise, ID 1966 4334 11613 2838 Boston, MA 1969 4222 07102 15 Brownsville, TX 1955 2554 09726 19 Buffalo, NY 1974 4256 07844 705 Burlington, VT 1956 4428 07309 332 Charleston, SC 1955 3254 n o n ri o 41 Cheyenne, WY 1974 4109 10449 6126 Chicago, IL 1974 4159 08754 658 Cincinnati, OH 1957 08431 761 Cleveland, OH 1969 4124 08151 777 Columbia, MO 1968* Jo49 09213 887 Detroit, MI 1968* 4214 08320 633 Dodge City, KS 1971 3746 09958 2582 El Paso, TX 1967 Q 1 /. Q J i4o 10624 3918

Fort Worth, TX 1975 3250 09703 537 Fresno, CA 1951 3646 1 1943 328 Great Falls, MT 1956* 4729 11122 3662 Houston, TX 1966 2959 09522 96 Indianapolis, IN 1972* 3944 08617 792 Jackson, MS 1964* 3219 uyuuu 31 Jacksonville, FL 1965 3025 08139 24 Kansas City, MO 1968* 3918 09443 1014 Lake Charles, LA 1966 3007 09313 9 Los Angeles, CA 1973 J J50 11824 105 Louisville, TY 1972* 3811 08544 477 Lubbock, TX 1955 3339 10149 3254

Madison, WI 1974 4308 A o n o n 858 Medford, OR 1966 4222 12252 1312 Memphis, TN 1964* 3503 08959 563 Miami, FL 1964* 2548 08016 7 Minneapolis, MN 1970 4453 09313 834 Nashville, TN 197 2* 3607 08641 590 New Orleans, LA 1958 2959 09015 4 New York, NY 1951 4047 07358 132 Norfolk, VA 1951 3654 07612 22 Oklahoma City, OK 1951 3524 09736 1285 Omaha, NE 1966 4122 09601 1323 Philadelphia, PA 1969 3953 07515 5 Phoenix, AZ 1Lyjl Q m 3326 11201 1117 Pittsburgh, PA 1957 4027 OoOOO 747 Portland, ME 1965 4339 07019 /. o Portland, OR 1960* 45 Jo 12236 21 Raleigh, NC 1965 3552 07847 434 Richmond, VA 1969 3730 07720 Sacramento, CA 1962 3831 12130 17 St. Louis, MO 1972* 3845 09023 535

Salt Lake City, UT 1948* 4046 11158 4222

San Antonio, TX 1960* 2932 09828 788 San Diego, CA 1974 3244 11710 13 San Francisco, CA 1974 3737 12223 8 Seattle-Tacoma, WA 1960* 4727 12218 400

Tampa, FL 1953 2758 08232 19 Tulsa, OK 1973 3611 09554 668 Washington, DC 1957 3851 07702 10

* Leap Year

41
Appendix A (continued)

2. Selection procedure for TRY years.

Source: "Tape Reference Manual, Test Reference Years," National

Climatic Center, Asheville, N.C.*

The principle of selection is to eliminate years in the period of record

containing months with extremely high or low mean temperatures until only

one year remains. The period of record examined for 59 United States

stations is 1948-1975. The 60th station, Portland, Oregon, has a period

of record of 1949-1975.

Extreme months are arranged in order of importance for energy comparisons. Hot Julys and cold Januarys are assumed to be the most important.

All months are ranked by alternating between the warm half (May to October) and the cold half (November to April) of the year, with the months

closest to late July or late January given priority. The resulting order

is given in the center column below. If, in addition, it is assumed that

that hot summer months or cold winter months are more important than cool summer or mild winter months, then the order of extreme months will be

down the first column below from "Hottest July" to Coolest April" and

then down the last column from "Coolest July" to "Warmest April."

Hottest July Coolest

Coldest January Mildest

Hottest August Coolest

Coldest February Mildest

Hottest June Coolest

Coldest December Mildest

Hottest September Coolest

Coldest March Mildest

Warmest May Coolest

Coolest November Warmest

Warmest October Coolest

Coolest April Warmest

The first step in the selection process is to mark all 24 extreme months.

Continue marking months starting with next-to-the-hottest July, then nextto-the-coldest January and so on down the first column and then down the

second column above until only one year remains without any marked months.

If two or more years remain without any marked months, the process is

repeated with the third, fourth, etc., hottest or coldest extremes until

only one year remains without any marked month. The remaining year is

the Test Reference Year.

The weather in the test year is a standard for comparison of heating and

cooling systems. It is not considered sufficiently typical to yield

reliable estimates of average energy requirements over several years.

42
APPENDIX B

By S.R. Hastings

Architectural Research Program, NBS

Design of the Representative Ranch-Style House

The design of this house evolved from statistics compiled by the National

Association of Homebuilders (NAHB) and from the designer's experience in

residential construction practices. The source of the statistics is the

"National Survey of Characteristics and Construction Practices for All

Types of One-Family Homes" completed by NAHB in February of 1974. The

survey covered a total of 84,000 homes built by 1,600 builders selected

randomly from the 27,000 builder members of NAHB.

From this survey, three house designs have been developed to represent

the total new housing stock:

1. A 1200-square-foot ranch.

2. A 1300-square-foot town house.

3. A 2000-square-foot two-story traditional house.

The 1200 square foot ranch house was selected for the computer analysis

because it was felt to be the most prevalent house design. The 1974 NAHB

survey reports that single-family detached houses represent 73 percent of

the housing stock (excluding mobile homes). The most common height is one story, representing 52 percent of the single-family detached houses.

The predominant number of bedrooms Is three, representing 67.7 percent of

the single-family houses. The average floor area for the single-familydetached house was 1568 square feet. The three-bedroom ranch design used

to represent one-story houses is reduced in floor area to 1200 square

feet for two reasons: 1) it was felt that one-story houses would tend to

have smaller floor areas than the overall average floor area of all

single-family detached houses which include two-story houses, split-level

houses, and houses with basements. 2) it was felt that since the publication of the survey in 1974 there has been a trend (which will continue

into the future) toward more compact houses as the cost of land, materials, and labor continue to increase.

The house design includes interior partitioning for the sake of completeness although the computer analysis focuses on the exterior envelope.

Windows have been excluded from the side walls, as is common practice due

to probable closeness of houses to either side. Window proportions have

been arbitrarily specified for the front and rear elevations. The window

areas were selected as the minimum desirable for the room areas, independent of orientation since it is an unknown. Once the house is sited, it

is desirable for the sake of energy conservation to increase the window

area on the south exposure. It should be noted that this design is meant

meant to be representative of construction practices and is not a house

specifically designed for energy conservation. The house is represented

in Figure B.l. More detailed documentation on the design of the ranch

43
Appendix B (continued)

as well as the townhouse and two-story houses is available in NBSIR 77-

1309: Three Proposed Typical House Designs for Energy Conservation

Research . It should be noted that the ranch illustrated therein has a slightly smaller aspect ratio of 28 x 42 feet.

Following are the material specifications for the ranch house design

combined with percentages of all single-family houses reported to have

such materials.

Material Specification NAHB Reported

Foundation/ Floor Percent of Total

Slab on grade 34.1

Basement (8" cone, walls) 62.7

1" perimeter insulation (R 5)

(NAHB reported percentage of houses without) 23.9

Carpet 85.1

Exterior Walls

Wood siding (no percentage)

Composition sheathing (R 0.63) (no percentage)

2" X 4" studs @ 16 inches on center 78.1

3 1/2" kraft paper batt insulation (R 11) 71.1

1/2" drywall (no percentage)

Windows

Doublehung 32.7

Single-glazed 69.8

Without storm sash 75.1

Doors

Solid wood (front entry) 66.5

No storm door 75.1

Sliding glass door (dining area) (no percentage)

Roof/ Ceiling

Single-gable form 74.7

Asphalt shingle 85.1

1/2" plywood sheathing 54.7

2" X 4" trusses 24" on center 62.6

Insulation, 6"± loose fill (R 19) 41.2

1/2" drywall ceiling 80.1

Plumbing/Mechanical

Warm-air ducted 79.1

Natural gas furnace 48.9

Central A.C. (electric) 66.7

Domestic hot water (electric) 50.9

44
I

45
APPENDIX C

Description of the Heating and Cooling Load Modeling Procedures

Used for the Representative Ranch House

1. Approach

The ranch house design described In Appendix B was used as a basis for

calculating annual heating and cooling requirements at each of the 60 TRY

locations using the NBSLD loads calculation prograin[7]. This appendix

describes in detail how that modeling effort was accomplished, including

assumptions of how the building was used,

2. Insulation Levels

Since the purpose of the research described here is to define heating and

cooling requirements as a function of the geographic variation in climate, a single insulation level is used in all computations. The level

selected is that required to meet ASHRAE Standard 90-75 [11] in a site

with 5,000 heating degree days"*", the median for the continental U.S.

The maximum permissible ceiling and slab transmittance (U-value) are specified for this degree-day number in the ASHRAE Standard. The wall,

window, and door U-value s are combined and must not exceed an average

U-value that is specified in the Standard. The average value for 5,000

degree days is U = 0.235 Btu/hr ft^ °F, and may be met by various combinations of wall, window, and door U-values. The representative ranch

house, equipped with storm windows, no storm door, and wall cavity insulation with a resistance of R = 0.8 hr ft^ °F/Btu (equivalent to 1/4 inch

of fiberglass batt insulation), will meet this value. The same house

with no storm windows, no storm door, and cavity insulation with resistance R = 3.6 (equivalent to one inch of fiberglass batt Insulation) will

also meet the required value. Neither of these insulation thicknesses

is available on the market, the usual minimum being 3-1/2" batts, with

resistance R = 11,

Since conventional building materials and practices are to be simulated

in the ranch house, the design with single glazing (no storm windows) and

3-1/2" of wall insulation was chosen. This design has sufficient insulation to meet the ASHRAE 90-75 Standard for locations with up to 7,800

degree days, or the equivalent of Madison, Wisconsin. Only three locations among the 60 climate stations tested here have degree-day numbers

in excess of this.

The NAHBRF statistics suggest that the Standard is conservative and does

not specify insulation levels as high as those being installed in current

typical residential wood-frame construction. The insulation levels given

Heating and cooling degree days are assumed to be calculated from the

traditional base temperature of 65°F unless otherwise stated.

46
Appendix C (continued)

in Appendix B are representative of a large proportion of housing being

built in southern as well as northern regions of the U.S.

3. Operating Conditions

In the simulation of the space heating and cooling of the ranch house,

the operating conditions of the house have to be assumed and inserted in

the NBSLD program.

The primary operating condition is the control of interior temperature.

In this simulation, the interior temperature is allowed to float between

68° and 78°F. Within this 'dead band', no loads are imposed on either

the heating or cooling system. Below 68° the heater comes on to maintain

68°, and above 78° the air conditioner comes on to maintain 78°. These

temperature settings are felt to be representative of prudent and quite

conventional residential temperature control.

The operating conditions of a building also include the heat loads

imposed by appliances, lights, and the occupants themselves throughout

the day. These loads act to decrease the heating and increase the

cooling requirements of the house. The loads are large enough to have a significant influence on the energy requirements of the building.

NBSLD calculates heating and cooling loads on an hourly basis throughout

the day. Experiments on occupied buildings which yielded hourly profiles

were found to be very sparse. After reviewing the experimental data

obtained at Twin Rivers [12]^ the modeling assumptions used in two previous computer studies [13,14]jand unpublished assumptions used by other

researchers, it was decided to employ the profiles prepared by Hittman

Associates in a study for HUD[14]. Assuming an occupancy for two adults

and two children, the hourly loads caused by appliances, lights, and

occupants are presented in Figure C.l.

4. Infiltration and Ventilation Rates

The displacement of internal air by external air also influences the

heating and cooling requirements of the building. The extent of such air

displacement in the computer simulation is largely determined by the

assumptions made in setting up the program. This simulation incorporated

some changes in the basic NBSLD calculation procedures.

The air displacement takes place as infiltration or ventilation. Infiltration may be defined as uncontrolled air leakage through the building

envelope imposing heating or cooling loads on the building, while ventilation is controlled air displacement for removal of unwanted internal

heat or odors. Natural ventilation occurs through windows and vents and

is controlled by the occupants. Mechanical ventilation by window fans or whole-house fans is not included in this simulation.

47
48
Appendix C (continued)

The version of NBSLD used here calculates infiltration as a function of

the wind speed and temperature difference between inside and outside of

the house, using an empirical relationship developed by Coblentz and

Achenbach[ 15 ] . The relationship is scaled in this study so that the air

change rate under winter design conditions (15 mph wind, 70°F temperature

difference between inside and outside) is 0.5, and the minimum air change

rate is set at 0.1,

The maximum ventilation rate in a given hour is assumed to be 12 times

the infiltration rate calculated as described above (Dr. Charles M. Hunt,

NBS, private communication). However, the ventilation is assumed to be

limited, so that internal heat gains are removed at a rate which maintains an interior temperature of 78°F.

If larger ventilation rates are climatically possible, they are assumed

to go unused (as when the occupants control ventilation by lowering windows). This assumption is employed in this version of NBSLD to avoid the

necessity of iteratively recomputing the heat gains or losses through the

envelope at the reduced room temperatures.

If, at 7 8°F, the internal heat gains are greater than the maximum possible ventilative heat removal for that hour, natural ventilation becomes

unable to maintain interior comfort conditions. At this point, all windows are assumed closed and air conditioning is employed to remove the

heat and maintain the interior air temperature at 78°F.

Another modeling assumption is the rate of ventilation in the attic above

the heated or cooled space in the house. The ventilation rate in the

attic is fixed at two air changes per hour.

5. Floor Slab Model

The way in which the floor slab is modeled has a major influence on the

heating and cooling performance of the house. The state of the art in

building energy analysis programs cannot at present analytically describe

the three-dimensional heat flow in the slab (through it and laterally

along it). In addition, current algorithms do not adequately predict the

hourly and seasonal thermal performance of a solid of great depth such as

the earth below the slab.

The NBSLD algorithms approximate slab and earth behavior by modeling the

heat flow through, and the thermal storage of, the slab and earth in one dimension (the vertical direction) only. The slab is underlaid by an arbitrary thickness of earth to a lower boundary with a fixed ground temperature. The insulation value of the slab, the earth thickness to constant ground temperature, and the ground temperature itself, are chosen

to model fluxes realistically.

Three experimental studies of heat flow in slabs on grade were reviewed

[16,17,18]. It was found that the steady-state heat flows determined in

49
Appendix C (continued)

these experiments could be approximated by a hypothetical combination of

slab construction, ground thickness, and ground temperature. Based on

this review, the slab in the ranch house has been modeled as follows:

carpet and padding

4" concrete

1" polystyrene Insulation (R = 5)

6" earth

The dynamic performance of the slab during temperature fluctuations could

not be checked against experimental data, but it is probably realistic

since the two upper layers of the slab are modeled exactly. The insulation below the slab would not be found in a typical slab of today except

around the perimeter. It was found to be necessary, however, in order to

approximate the actual steady-state heat flux of a typical slab built to

ASHRAE 90-75 requirements.

Below the 6" earth layer, a constant ground temperature is assumed.

Review of the ground temperature profiles in the above experiments provided an equation for estimating this temperature. It is based on the

deep ground temperatures given in the NBSLD manual, dry soil tables. [7]

One value is used for the summer months (June through September) and

another for the winter (October through May). The equations for winter

and summer ground temperature at 6" are:

Tq = the ground temperature at 6" below the surface used in modeling the slab

Tq^ = the deep ground temperature derived from nearby locations presented in the dry soil tables[7].

Table C.l presents the 6" ground temperatures used at each location in

this study.

6 . Orientation and Solar Transmission of Windows

The ranch house is oriented with the front door facing south. This

places a larger area of glass on the north side (72 ft ) than the south

(55 ft^), which is less effective solar design than if the house were

rotated 180°. The orientation is felt to be acceptable in that the house

/2

/2

where

50

1
\

Appendix C (continued)

is intended to represent typical, rather than optimal, siting practice.

The small size of south-facing windows is somewhat compensated for by the

lack of any external shading (by terrain, trees or other buildings)

assumed in the model.

All glazed areas in the ranch house are modeled with a shading coefficient of 0.8 to account for the internal drapes and blinds (a shading

coefficient of 1 represents no shading of a single-pane window). The

overhangs in this version of the ranch house are sufficiently small that

they are not modeled.

7 . Listing of the Building Description Coding of the Ranch House

Reference: Kusuda, T. 1976. NBSLD, the Computer Program for Heating

and Cooling Loads in Buildings (NBS Building Science

Series 69) .

The basic program has been modified by James Barnett of the Thermal Engineering Section, NBS, to simulate infiltration and ventilation as described in section 4 above.

Lines 28 and 29 are Barnett' s additions required for an expanded output

version that produces a detailed breakdown of loads through all building

envelope components. The IRF's are demoted to the end of the listing.

The example shown in Figure C.2 is for the Washington, D.C. house.

51
TABLE C.l

Ground Temperatures Used in Heating and Cooling Loads Simulation

Location October-May June-September

Albany, NY 57 66

67 73 Amarillo , TX 67 75 Atlanta, GA 68 75

Bi nningliaiii , AT

63 70 Bismarck, ND 55 64 Boise, ID 56 63

RnQtTin MA 57 64 Brownsville , TX 67 75 Buffalo, NY 57 66

Riir 1 1 n pfnn VT 56 63 Charleston, SC 63 72 Cheyenne , WY 57 63 Chicago , IL 58 67 Cincinnati, OH. 58 66 Cleveland, OH 58 66 Columbia, MO 60 68

Dp f rm' t MT 57 65 Dodpp a tv KS 60 69

67 75 67 75 Fresno, CA 68 75

dre^at Fa 1 1 Q MT 54 61 Houston TX 67 75

-L LLU X dLld ^W J. J. O , X Li 58 67

Jack-Son, MS OJ

*j cH_i\.t>(Jii V ± J.X c , r i_i 69 75

K;5nQ;5Q Ci ^v MO 60 67 65 73

T r»Q Anoolpc PA 68 75

1 mil c?vi lip KY 61 69

TLi iiKhnr-l/- U. U U (J In. , TYX A. 67 75

M^i H "i Qnn WT 56 65 MpHford OR 61 67

Mtrninhn g TN 62 69

Mi;^Tni FT 68 75

Ml nnpanoT i c MW 55 65

MaLNciocTt\ti IIV± J-Xc 1 1 o , TMi IN 67 75

Nplj Ynrk NY 59 67 DU o o

>_/K.xci iiuiud Vj±Ly J wr^. O J

71/ X 58 66

r nixaaexpnia , rii 00

67 73

PiX X ffcKiiraVi L L o UU 1. g 11 PA J Art 58 66 Portland ME 57 64 Portland, OR 59 65 Raleigh, NC 63 72 Richmond, VA 60 68 Sacramento, CA 67 72

St. Louis, MO 60 68 Salt Lake City, UT 57 64 San Antonio, TX 67 75 San Diego, CA 70 78 San Francisco, CA 67 72 Seattle-Tacoma, WA 60 64 Tampa, FL 68 75 Tulsa, OK 63 71 Washington, DC 60 68

52
FIGURE C.2

Q$QSQ$*AFILE( 1 ) .HIWDC(O)

1 2flf0»0r0r0f 3»2»77 (PIER50) ASHRAF 90-7^ H.R.5000 n.D.

2 HASTINGS RAMCH HOUSE 1 3 0.»0.»0.rO.»0.»0.»l.»l.».023'.0?3».023».0?3».0?3».0?3».023

H .023» .023» .023».C23»0.5»0.5»1,»1.»1,

5 ,17» .17f .17» .17» .17r .i+8» .71» .95. .57f .61» .57f .88» .62» .48f .4fl 6 .51 » .48. .65» .70» .81 » 1 .00. .62. .70f .48

7 1..1..1..1..1..1..1..1.. 0,4.0. '+.0.4.0.4.0. 4. 0.4.0, '4 8 0.69. 0. 69.1. .l..l,.l..l..l..l.

9 0,»0.»0..0.»0.»0.»1.»1.. .023. .023. .023. .023. .023. .023. .023

10 ,023. .023. .023. . D23 . 0 . 5 . 0 . 5 » 1 . » 1 . . 1

.

11 .17. .17, .17 » .17. .17. .48. .71. .95. .57. .61. .57. .88. .62. .48. ,48

12 ,51. ,48. ,65. ,70. .81. 1.00. .62. .70. .48

13 l.»1..1..1..1..1..1..1..0.4.0.4,0.4.0.4.0.4.0.4,0,4

14 0,69.0,69.1,.l,.l,.l,.l..l..l.

15 0.»0.»0.»0.»0.»0..1,»1,»,023».023.,023.,023.,023»,0?3.,023

16 ,023. ,023. ,023. , 023 . 0 , 5 . 0 , 5 » 1 . . 1 . . 1

.

17 ,17. .17. ,17. ,17. .17. .48. .71. .95. .57. .61. .57. .88. .62. ,48, ,48

18 ,51. .48. ,65. ,70 r .81 . 1,00. ,62. ,70. ,48

19 l.,l..l.,1..1..1..1..1..0.'+.0.4,0.4,0.4.0.4.0.'+,0.4

20 0.69.0.69. 1 , . 1 , . 1 . . 1 , f 1 . . 1 . . 1 . 21 78. » 78. .78. » 78, .78. '78, .78. » 78. .78. » 78. .78. ,78.

22 7B. » 78. .78. » 78. » 78. » 78. .78. '78. .78. » 78. .78. .78.

23 7B. » 78. .78. » 78. » 78. '78. » 78. » 78. .78. .78. .78. .78.

24 7R. .78. .78. » 78. .78. » 78, » 78, » 73. .78. .78. .78, '78.

25 68. »78. .20. .60.

26 365.0.9

27 8. » 21. » 232. .95. » 20 . » 65 . . 18. ' 68 , . 60 , . 0 , 1 . 76 , 5 . 38 , . 5, » 256 . .20.

28 ******* + *****|-|. R . 90-75*********************

29 ****************************CHANGES 3*30 TO wiATCH TOM « ED'S VFRSIOMS

30 HASTINGS RANCH HOUSE 1 31 0.0.0

32 l.»0.52.1.03.3.0.0..0.5.75.»0.»0.5.0.6.0.1»l.

33 3.4.8.23

34 78. »68, .50000, '50000, .73, .60,

35 1,1

36 4,2»3»2

37 40, '30. .7,96

38 1, 1 . 1200. ' 0. ' 0. . 0. . 0.9. 0. » ROOF

39 0 . » 0 . . 0 . ' 0 . ' 0 . » 0 . . 0 . 40 0 . ' 0 . . 0 . . 0 . . 0 . ' 0 . . n . . 0

.

41 4.10.20. .0. '0.5.0. .0.9.0. ' noOR

42 0. »0. rO. '0. '0. '0. .0.

43 0.'0.»0.'0.'C.'0..0..0.

44 2.2.181.3.0. .0. '0. .0.9'0. . R13.3WALL

45 0. » 0. ,0. .0. . 0. . 0. . 0. 46 0. ' 0 . . 0 . » 0 . ' 0 . » 0 . . 0 . ' 0 . 47 2.3.63.6.0. .0. .0. .0.9.0. . R6.7 STUOS

48 0. .0. .0. .0. .0. .0. .0.

49 0. »0. f 0. .0. .0. »0, '0. '0.

50 3»10'55,1'0, '1,13.0. 8'0. .0. ' SINGLE GLAZED

51 CO. .0. .0. .0. '0. .0.

52 O.'O.'O.'O.'O.'O.'O.'O.

53 2.2.209.06.90. ' 0. ' 0. » 0.9.0.

54 0..0..0.»0..0..0,.0.

55 0, »0, .0. '0. .0. '0. .0. '0.

56 2.3'30.94'90. '0. '0. 'O.'^'O.

57 0.'0..0.'0..0..0..0.

53
FIGURE C.2 (CONTINUED)

58 O.»0.r0.f0.f0.f0.»n.r0.

59 2»2»189.ttrl80. »0, »n. ,0.9»0.

60 0 . » 0 . » 0 . f 0 . » 0 . » 0 . » C

61 0. »0, »0, »0. »0. '0, »0. »0.

62 2»3»58.6»180. »0. »0. f 0.9»0.

63 0 . » 0 , » 0 , » 0 , » 0 . » 0 . » 0

ef* o.»o.»o.fO,»o.»o.fO.»o.

65 3»10r72.0»180.»1.13»0.a»0.f0,

66 O.»0.»0.»0.»0.»0.»0.

67 O.»0.»0.»0,»0.»0.»0.»0.

66 2»2f209.06»-90. »0. »0. »0.9r0.

69 0.rO.»0.»0.»0.»0,»C.

70 0.f0.rO.»Ot»0.»0,rO.»0.

71 2»3»30.9it»-9C. »0. »0. »0.9»0.

72 0 . » 0 . » 0 . » 0 , » 0 . » 0 . » 0

73 0.»0.»0.»0.»0.»0,fO.»0.

7f 5»<+rl200, »0. »0. »0. »0. »0. » R3.6 SLAB (=Rfl,6 WITH THF POLY^TYR LAYrR)

75 0,r0.»0.»0.»0.»0,»0.

76 0. f 0 . » 0 . f 0. » 0 . » 0. » C . » 0

77 0.4»0.05»112.»1.875f2.0»l.f R19 ATTIC

78 0»0»0»0»0

79

80

81

82 3» IRFl

83 0.»0,»0.»0.f0.6

0.0417»0.07»3'+. »0.29»0. »C.63

85 0.rO,»0.»0,»0.5

86 INSIDE SURF. RES. (ROOF)

87 1/2 IN. PLYWOOD

88 BUILD. PAP.+ASPH. SHIG.

89 1» IRF2

90 0.0'+17r0.0938»50. »n.2»n. »0.45

91 0.292»0.0265»2.0»0.2»0. » 11.

92 0.0'+17»0.0317»20.f .31»0.»1.32

93 0.03125»0.0'+97>37. » ,29»0. 'O.Bg

9't 1/2 IN. GYPBOARD (R13.3)

95 3 1/2 IN. INSULATION Rll

96 1/2 IN. SHEATHING

97 3/8 IN. WOOD SIDING

98 <+» IRF3

99 0.0'+17»0.0938»50.»n,2»0.»0.'+5

100 0.292»0.07»32. » .33»P.

101 0.0tH7r0.0317»20. » .31»0. »1.32

102 0.03125rO.O'+97»37. f .29»0. »0.59

103 1/2 IN. GYPBOARD (P6.7)

lOtf 2X1+ STUD

105 1/2 IN. SHEATHING

106 3/8 IN. WOOD SIDING

107 IPF90-75

108 0.r0.rO.»0.»1.5

109 0.333»1.0»lUO.»0.2»n.

110 0.0833f 0,01667f2.2»0.29rn, »5.

111 0.5»0.75rl00. »0.2»0.

112 CARPET&PADDING (R3.6)

113 1 IN, CONCRETE SLAB

IIH 1 IN. POLYSTYRENE R5

115 6 IN, EARTH TO GRND TEMP

54
NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM. 1. PUHLK ATION OR RliPORT NO. 2. Gov't Acccs.sion BIBLIOGRAPHIC DATA tjqq -i i ^ No. SHEET

3. Recipient's Accession N<j.

4. TITLE AND SUBTITLE

Geographical Variation in the Heating and Cooling

Requirements of a Typical Single-Family House, and

Correlation of These Requirements to Degree Days

5. Publication Date November 1978

6. Performing Organization Code

7. AUTHOR(S)

Edward A. Arens and William L. Carroll

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Projcct/Task/Work Unit No. 7436536

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Energy Research and Development Administration

Office of Conservation

Division of Buildings and Community Systems

Washington, D.C. 20545 and

Department of Housing and Urban Development

Office of Policy Development and Research, Washington, D.C.

13. Type of Report & Period Covered

14. Sponsoring Agency Code

20410

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

bibliography or literature survey, mention it here.) The report has three main purposes

:

First, it assesses 'Test Reference Year' (TRY) hourly climate data tapes to

determine how well they represent long-term average climate when used for estimating

average annual heating and cooling requirements. The report presents a method to

adjust heating and cooling requirements that are computed using TRY data, in order

to make them represent long-term average heating and cooling requirements.

Second, the report quantifies the geographic variation of annual heating and

cooling requirements across the U.S. by computing the heating and cooling requirements of a typical ranch-style residence for the 8760 hours of each of the 60 TRY

tapes, and adjusting the results by the method described above.

Third, the effectiveness of 'degree-day' data for predicting these computed

annual heating and cooling requirements is examined, and the variability of heating

and cooling requirements within degree-day 'zones' of 1000 degree day width is

presented.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons) Building energy conseTvation ; climatic effects on building

energy consumption; computer modeling of building energy consumption; energy

conservation; geographical variation of building consumption; residential energy

consumntion.

18. AVAILABILITY Unlimited

1 ! For Official Distribution. Do Not Release to NTIS

1 yl Order From Sup. of Doc, U.S. Government Printing Office ^

Washington, D.C. 20402, SD Stock No. SNO03-0O3-O1992-5

1

1 Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

21. NO. OF PAGES

58

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price

$2. 50

USCOMM-DC 66035-P7E

ir U. S. GOVER^^MENT PRINTING OFFICE : 1978 O - 276-580
\


NBS TECHNICAL PUBLICATIONS

PERIODICALS

JOURNAL OF RESEARCH—The Journal of Research

of the National Bureau of Standards reports NBS research and development in those disciplines of the physical and

engineering sciences in which the Bureau is active. These

include physics, chemistry, engineering, mathematics, and

computer sciences. Papers cover a broad range of subjects, with major emphasis on measurement methodology, and

the basic technology underlying standardization. Also in- cluded from time to time are survey articles on topics closely

related to the Bureau's technical and scientific programs. As

a special service to subscribers each issue contains complete

citations to all recent NBS publications in NBS and non- NBS media. Issued six times a year. Annual subscription: domestic $17.00; foreign $21.25. Single copy, $3.00 domestic;

$3.75 foreign. Note: The Journal was formerly published in two sections: Section A "Physics and Chemistry" and Section B "Mathematical Sciences." DIMENSIONS/NBS

This monthly magazine is published to inform scientists, engineers, businessmen, industry, teachers, students, and

consumers of the latest advances in science and technology,

with primary emphasis on the work at NBS. The magazine

highlights and reviews such issues as energy research, fire protection, building technology, metric conversion, pollution

abatement, health and safety, and consumer product per- formance. In addition, it reports the results of Bureau pro- grams in measurement standards and techniques, properties of matter and materials, engineering standards and services, instrumentation, and automatic data processing.

Annual subscription: Domestic, $11.00; Foreign $13.75

NONPERIODICALS

Monographs—Major contributions to the technical liter- ature on various subjects related to the Bureau's scientific and technical activities. Handbooks—Recommended codes of engineering and industrial practice (including safety codes) developed in cooperation with interested industries, professional organizations, and regulatory bodies.

Special Publications—Include proceedings of conferences sponsored by NBS, NBS annual reports, and other special

publications appropriate to this grouping such as wall charts, pocket cards, and bibliographies.

Applied Mathematics Series—Mathematical tables, manuals, and studies of special interest to physicists, engineers,

chemists, biologists, mathematicians, computer programmers,

and others engaged in scientific and technical work.

National Standard Reference Data Series—Provides quantitative data on the physical and chemical properties of

materials, compiled from the world's literature and critically evaluated. Developed under a world-wide program co- ordinated by NBS. Program imder authority of National

Standard Data Act (Public Law 90-396).

NOTE: At present the principal publication outlet for these data is the Journal of Physical and Chemical Reference Data (JPCRD) published quarterly for NBS by the American Chemical Society (ACS) and the American Institute of Physics (AIP). Subscriptions, reprints, and supplements

available from ACS, 1155 Sixteenth St. N.W., Wash., D.C.

20056.

Building Science Series—Disseminates technical information developed at the Bureau on building materials, components,

systems, and whole structures. The series presents research

results, test methods, and performance criteria related to the

structural and environmental functions and the durability and safety characteristics of building elements and systems. Technical Notes—Studies or reports which are complete in themselves but restrictive in their treatment of a subject.

Analogous to monographs but not so comprehensive in scope or definitive in treatment of the subject area. Often

serve as a vehicle for final reports of work performed at NBS under the sponsorship of other government agencies.

Voluntary Product Standards—Developed under procedures

published by the Department of Commerce in Part 10, Title 15, of the Code of Federal Regulations. The purpose

of the standards is to establish nationally recognized require- ments for products, and to provide all concerned interests with a basis for common understanding of the characteristics of the products. NBS administers this program as a supple- ment to the activities of the private sector standardizing

organizations.

Consumer Information Series—Practical information, based on NBS research and experience, covering areas of interest to the consumer. Easily understandable language and

illustrations provide useful background knowledge for shopping in today's technological marketplace.

Order above NBS publications from: Superintendent of Documents, Government Printing Office, Washington, D.C.

20402. Order following NBS publications—NBSlR's and FIPS from

the National Technical Information Services, Springfield, Va. 22161.

Federal Information Processing Standards Publications (FIPS PUB)—Publications in this series collectively constitute the Federal Information Processing Standards Register.

Register serves as the official source of information in the Federal Government regarding standards issued by NBS

pursuant to the Federal Property and Administrative Services Act of 1949 as amended, Public Law 89-306 (79 Stat. 1127), and as implemented by Executive Order 11717

(38 FR 12315, dated May 11, 1973) and Part 6 of Title 15 CFR (Code of Federal Regulations).

NBS Interagency Reports (NBSIR)—A special series of interim or final reports on work performed by NBS for outside sponsors (both government and non-govenmient).

In general, initial distribution is handled by the sponsor;

public distribution is by the National Technical Information

Services (Springfield, Va. 22161) in paper copy or microfiche form.

BIBLIOGRAPHIC SUBSCRIPTION SERVICES

The following current-awareness and literature-survey bibli- ographies are issued periodically by the Bureau:

Cryogenic Data Center Current Awareness Service. A litera- ture survey issued biweekly. Annual subscription: Domestic, $25.00; Foreign, $30.00.

Liquified Natural Gas. A literature survey issued quarterly.

Annual subscription: $20.00.

Superconducting Devices and Materials. A literature survey

issued quarterly. Annual subscription: $30.00. Send subscription orders and remittances for the preceding bibliographic

services to National Bureau of Standards, Cryogenic Data

Center (275.02) Boulder, Colorado 80302.
U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington, D.C. 20234

OFFICIAL BUSINESS

Penalty for Private Use, S3QD

POSTAGE AND FEES PAID

U.S. DEPARTMENT OF COMMERCE COM-215

SPECIAL FOURTH-CLASS RATE

BOOK