NISTIR 88-3801-1

ZIP-The Zip-Code

Insulation Program,

Version 2.0

Economic Insulation Levels for

New and Existing Houses by

Three-Digit Zip Code

Users’ Guide and Reference Manual Stephen R. Petersen

(Revised edition)

U.S. DEPARTMENT OF COMMERCE

National Institute of Standards

and Technology

Gaithersburg, MD 20899

Sponsored by

U.S. Department of Energy

Conservation and Renewable Resources

Office of Buildings Energy Research

Building Systems and Materials Division

1000 Independence Avenue, SW

Washington, DC 20585

ILS. DEPARTMENT OF COMMERCE

Robert A. Moffiteacher, Secrete^

NATIONAL WSTTTUTE OFSTANDARDS

AND TECHNOLOGY

John W Lyons, Director

NIST

NISTIR 88-3801-1

ZIP-The Zip-Code

Insulation Program,

Version 2.0

Economic Insulation Levels for

New and Existing Houses by

Three-Digit Zip Code

Users’ Guide and Reference Manual Stephen R. Petersen

(Revised edition)

U.S. DEPARTMENT OF COMMERCE

National Institute of Standards

and Technology

Gaithersburg, MD 20899

Sponsored by

U.S. Department of Energy

Conservation and Renewable Resources

Office of Buildings Energy Research

Building Systems and Materials Division

1000 Independence Avenue, SW

Washington, DC 20585

January 1991

ILS. DEPARTMENT OF COMMERCE

Robert A. Mosbacher, Secretary

NATIONAL INSTITUTE OF STANDARDS

AND TECHNOLOGY

John WL Lyons, Director

ABSTRACT

ZIP 2.0 (the ZIP Code Insulation Program) is a computer program developed to

support the DOE Insulation Fact Sheet by providing users with estimates of

economic R-values for thermal insulation in new or existing single-family

houses. The ZIP program currently calculates economic levels of insulation

for attics, cathedral ceilings, exterior wood-frame and masonry walls, floors

over unheated areas, slab floors, basement and crawlspace walls, ductwork in

unconditioned spaces, and water heaters. Site-specific estimates can be made

for any location in the United States by entering the first three digits of

its ZIP Code. Climate parameters are contained in a file on the ZIP diskette

and automatically retrieved when the program is run. The user must designate

the type of heating and cooling equipment present in the house. Default

energy and insulation price data are also retrieved from the ZIP diskette, but

these can be overridden to correspond to local prices. A comprehensive report

is displayed with the economic R-values, advisory material, and a list of the

user’s input assumptions. The program and supporting files are contained on a single 5-1/4 inch diskette for use with microcomputers having an MS-DOS

operating system capability. ZIP is intended for use by homeowners,

homebuilders, architects, utilities, insulation manufacturers and installers,

university extension services, conservation advocacy groups, and government

agencies at any level.

iii
PREFACE

The ZIP computer program was developed to support the calculations and data

base used to estimate the economic levels of insulation published in the U.S.

Department of Energy’s Insulation Fact Sheet (DOE/CE-0180 , Technical

Information Center, P.0. Box 62, Oak Ridge, TN 37830, 1987). Programmatic

direction of this project and the DOE Insulation Fact Sheet has been provided

by David McElroy of the Oak Ridge National Laboratory.

Sections 1 through 6 of this user’s guide are included in a flat (ASCII) file

on the ZIP disk under the name ZIP. DOC.

iv
CONTENTS

Page

ABSTRACT iii

PREFACE iv

1. INTRODUCTION 1

2. CALCULATION OF ECONOMIC LEVELS OF INSULATION 2

3. PROGRAM INSTALLATION 3

4. RUNNING ZIP 3

4.1 House and Heating/Cooling System Data 4

4.2 Energy Prices 5

4.3 Selecting Insulation Systems for Analysis 5

4.4 Water Heater Data 6

4.5 Existing Houses Only--Existing Levels of Insulation 7 4.6 Insulation Costs 7 4.7 Duct Insulation 9

5. ZIP REPORT FORMAT 9

6. FINISHING UP 10

APPENDIX A. COMPUTATIONAL ALGORITHMS 13

APPENDIX B. ENERGY PRICE AND INSULATION COST FILES 25

List of Screen Illustrations

1. Start-up display 4

2. Menu for selecting insulation systems of interest 6

3. Selecting existing level of insulation in attic 7

4. Designating attic insulation costs for selected R-values 8

5. Selecting duct size to be insulated 9

6. Screen display of results of ZIP analysis (example) 11

7. Additional information displayed at the end of a ZIP analysis ... 12

List of Tables

Al. HSLOPE and CSLOPE coefficients for attics, roofs, and exterior

walls 14

A2. HSLOPE and CSLOPE coefficients for floors and basement and

crawlspace walls 15

A3. Duct coefficients for attics, vented crawlspaces (vcs) and

controlled-ventilation crawlspaces (eves) 16

A4 . Regression equations for estimating annual heating and cooling

requirements by ZIP region 19

A5. Reduction in water heater standby losses (SBL) due to the

installation of an insulating jacket 21

A6 . Standby losses (as a percent of annual energy requirements) used

in ZIP analysis of water heater jackets 23

Bl. Regional cost adjustment factors 27

v

1. INTRODUCTION

ZIP, the Zip Code Insulation Program, determines economic levels of insulation

for new and existing houses in any location in the United States, given the

first three digits of its Zip code. Economic insulation levels are determined

for attics, cathedral ceilings, exterior walls, floors over unheated areas,

slab floors, basement and crawlspace walls, and ducts in unconditioned spaces.

In addition, ZIP will determine if a water heater insulation jacket is a cost

effective investment, based on information supplied by the user.

The economic levels computed by ZIP reflect the type and approximate energy

efficiency of the heating and cooling systems specified by the user, as well

as local energy prices and current installed insulation costs. Local climate

data for the three-digit Zip code are retrieved from the ZIP disk. Default

energy and insulation price data are also retrieved from the ZIP disk, but it

is recommended that users override these latter values with estimates of local

energy and insulation prices if available.

ZIP is a public domain computer program developed by the National Institute of

Standards and Technology (NIST, formerly the National Bureau of Standards)

under the sponsorship of the United States Department of Energy (DOE) 1

. As

ZIP is in the public domain, it may be freely copied and distributed. However

it is requested that attribution be given to the National Institute of

Standards and Technology.

ZIP and its supporting data files are provided on a single 5-1/4 inch floppy

disk (360K DSDD format) for use with microcomputers having an MS-DOS operating

system (typical IBM-PC /XT/AT and compatible systems). This condensed guide to

the ZIP program is contained in file ZIP. DOC on the ZIP disk and can be

printed directly from the disk.

The original ZIP program was written to calculate economic levels of

insulation reported by three-digit ZIP Code in the Department of Energy’s

"Insulation Fact Sheet" (DOE/CE-0180 , January 1987). The "Insulation Fact

Sheet" provides useful information related to the choice of insulation

materials for particular applications and suggestions related to its proper

installation. This 12 page publication can be obtained from the U.S.

Department of Energy, Technical Information Center, P.0. Box 62, Oak Ridge, TN

37830.

The ZIP program has now been expanded and enhanced for more general use,

allowing users to obtain more detailed recommendations based on local climate

and cost conditions. ZIP is intended for use by any government or private

agency (such as a utility company) being asked to provide advice to consumers

on economic levels of insulation for new or existing houses. ZIP can also be

used by insulation manufacturers, insulation installers, and by homeowners

(either on their own personal computer or at some central location such as a home show, utility office, or energy conference). Where local building codes

1 Neither NIST nor DOE assumes any liability resulting from the use of

the information provided by the ZIP program or from any errors or omissions in

the program.

1
require more insulation than suggested by ZIP, the building codes should take

precedence

.

2. CALCULATION OF ECONOMIC LEVELS OF INSULATION

The economic levels of insulation calculated by ZIP for each component are

based on an incremental analysis. Successive levels of insulation in each

component of the house are evaluated to determine how far it pays to keep

adding insulation and where to stop. For example, the economic analysis for

attic insulation is performed at R-0 (no insulation), R-ll, R-19, R-22, R-30,

R-38, and R-49. Only if an increase in R-value is found to generate

additional savings greater than additional cost will that increase be included

in the recommended insulation level for the component.

Economic calculations in ZIP are based on long-term reductions in heating and

cooling costs. For new houses, a 30-year life is used in calculating presentvalue energy savings. The economic level of insulation calculated for a new

house will be the level which has the lowest present-value insulation cost

plus energy cost over a 30-year period. For existing houses, a 20-year life

is used in the calculations.

In performing these calculations, a seven percent annual rate of return, over

and above general inflation, is used to discount future savings to present

value. If inflation is currently five percent, this is approximately

equivalent to requiring a minimum 12 percent rate of return on the investment

over its life. That is, the last increment of insulation used in each

application must earn at least this rate of return to be considered cost

effective. Moreover, residential energy savings are not taxed. Thus, for

homeowners this 12 percent rate of return is an after-tax rate, significantly

higher than most tax-free investments available to homeowners.

Note that the first increments of insulation typically return much higher

dividends than the last increment. Thus the average rate of return on the

entire investment tends to be considerably higher than the minimum acceptable

level, especially if there is little insulation to start with.

In general, the more severe the climate, the higher the cost of energy, the

lower the heating and cooling system efficiencies, and the lower the

incremental cost of insulation from one level to the next, the more it pays to

add insulation and the higher will be the economic level. In some cases the

economic level of insulation is quite sensitive to these variables. For

example, a relatively small change in the incremental cost of insulation

(i.e., the cost of moving from one R-value to the next) or the cost of energy

can change the economic level of insulation in a given location. You may want

to determine the sensitivity of the economic levels of insulation to changes

in these input variables before concluding your analysis.

There are other benefits from installing economic levels of insulation in

houses. These might include increased occupant comfort, reduced demand for

scarce energy resources, reduced peak energy demand, reduced pollution, and

even reductions in global warming. However, none of these additional benefits

are explicitly included in the ZIP analysis of insulation savings.

2
The energy savings computed in the ZIP analyses for each level of insulation

are not reported. These calculations are based on an analysis of uniform

surface areas (typically one square foot or one linear foot) for each

component in a typical house under average operating conditions over a typical

weather year. They would not provide any meaningful estimate of savings for

the user’s own house since the area of each component is unknown. Usually an

energy audit of the house to be insulated is needed to make a meaningful

estimate of the total savings that can be expected.

3 . PROGRAM INSTALLATION

ZIP 2.0 can be installed on and run from a hard disk or run directly from a floppy disk. To install ZIP on a hard disk, make a subdirectory called ZIP

and copy all the files on the ZIP disk to that subdirectory. (If the floppy

is in drive A, type COPY A:*.* d:\ZIP , where d: is the drive location of

subdirectory ZIP.) If you are going to run ZIP from a floppy drive, you

should copy all the files on the original disk to a disk formatted on the

drive you intend to run it from. Then run ZIP from the copy, saving the

original as a backup. (Take care not to run the original (360 KB) disk in a high density (1.2 MB) disk drive; it will likely be destroyed during the disk

write process.) In general, hard disk installation is preferred since ZIP

will read and write the supporting data files much faster.

The following files are contained on the original ZIP disk. All of these

files (except the user’s guide file, ZIP. DOC) are needed to run the program.

ZIP2.EXE

CLIMATE2.DAT

INSC0ST2 . NEW

INSC0ST2 .RET

ZIPINFO . FIL

ENPR90.ASC

ELEC90.ASC

DOEENPR . NE

DOEENPR .MW

DOEENPR.SE

DOEENPR.

W

ZIP. DOC

The executable version of ZIP.

A file of climate data, keyed to three-digit ZIP Codes.

A file of default insulation prices for new houses.

A file of default insulation prices for existing houses.

On-line summary of ZIP program.

Gas, oil and LPG (propane) prices by state.

Electricity prices (winter and summer) by ZIP code.

\

\ DOE projections of energy price escalation rates for the

/ four major regions of the U.S.

/This user’s guide.

4 . RUNNING ZIP

To start ZIP, insert the disk into the current disk drive and type ’ ZIP2’. If

ZIP is run from a hard disk, make the ZIP subdirectory the current directory

and type ’ZIP2’. If you have a color monitor, ZIP will automatically detect

this and run in color. If you have a monochrome monitor that runs in the

color mode, adding "/M" to "ZIP2" may make it easier to read the highlighted

characters on the menus.

Screen 1 shows the initial screen display when ZIP is started. The user can

proceed immediately into a ZIP analysis by pressing <Enter>. Further start-up

options are provided in the menu bar at the bottom of the ZIP logo. For

3
example, more information on the ZIP program can be displayed, or default

input data from a previous run can be retrieved by selecting "Get File" and

then selecting a previously saved input data file from the list shown on the

screen. (You will be able to save your input data at the end of the ZIP run

for later retrieval.) When you retrieve a file, the data in this file serve

as the default data for the current run; you can edit this data if desired as

you proceed through the data input process.

The Zip-Code Insulation Program, Version 2.0 (1990)

Proceed More Info Get File Quit

Use cursor to highlight choice and press <Enter>

From the National Institute of Standards and Technology

Sponsored by the U.S. Department of Energy

Screen 1. Start-up display

When you proceed with the ZIP analysis, the first entry is the postal Zip code

for the location of interest. Enter the first three digits of the Zip code

and ZIP will respond with the reference location and the corresponding heating

degree days (base 65F) and cooling degree hours (base 74F) . The reference

location is typically the location designated by the U.S. Postal Service as

the main post office at the three-digit Zip code level. If the location is

acceptable, press <Enter>; otherwise select "Try another Zip Code" and enter

another Zip Code as requested.

4.1 House and Heating/Cooling System Data

ZIP asks the user to designate whether the analysis is for a new or existing

house, the type and approximate efficiency of the heating and cooling systems,

and the presence of ductwork in unconditioned spaces. If there is ductwork in

unconditioned spaces, ZIP will ask if the house has two or more stories. Note

that a default response is always available, and that if the ZIP analysis is

repeated, the user’s last response for each question will become the default

value for the current run.

4
If a new house application is selected, a wider range of insulation options

for exterior walls and exterior foundations is allowed than for existing

houses. If an existing house analysis is selected, you will be asked to

specify the approximate existing level of insulation in the attic, floor,

crawlspace walls, and supply ducts after these systems are selected for

analysis

.

Six different heating systems can be selected in ZIP: four furnace types,

including natural gas, fuel oil, LPG, and electric resistance; electric

baseboard; and electric heat pump. If a heat pump is designated for space

heating, it will automatically be assumed to provide space cooling as well,

and no cooling questions will be asked. Otherwise, two electric cooling

systems can be selected: central and window air conditioners. (An

evaporative cooling system can also be selected. However, no cooling savings

from insulation are calculated for this latter system.) In addition, the user

can specify the approximate operating efficiency of the heating and cooling

systems (low, medium, high, or very high). These system specifications are

needed to calculate the purchased energy savings corresponding to any given

reduction in space heating and cooling loads. If there is ductwork in attics,

crawlspaces, or other unconditioned spaces, an adjustment is also made to the

equipment efficiency to reflect duct losses (10 percent for one-story houses,

15 percent for houses with two or more stories).

4.2 Energy Prices

Current energy prices for heating and cooling, corresponding to the type of

systems selected, are then requested in the units shown (e.g., kWh, therms,

gallons). Default values are retrieved from data files on the disk. These

default values reflect energy prices at the state level (or, in the case of

electricity, at a representative location within the state, based on the ZIP

code entered for the analysis). However, it is recommended that the user

overwrite these default values with energy prices that reflect the utility

rates actually encountered at the building site. These prices should include

all taxes and fuel adjustment costs (but not kW demand charges, if any). If

declining (or increasing) block rates are applicable (for example, kWh prices

are often lower for kWh usage above 500 kWh per month than for the first 500

kWh), the energy cost should reflect the cost of the last units purchased each

month (during the months of major usage), not the average cost for all units.

If there are different prices for summer and winter usage (as is often the

case for electricity), the price used for cooling should be based on the

summer rate and the price for heating on the winter rate. To change the

default prices on the screen, press "Y" (Yes), then type the new prices over

the old prices.

4.3 Selecting Insulation Systems for Analysis

Screen 2 shows the menu for selecting the insulation applications of interest

to the user. Press <F3> to select all systems or use the cursor keys to move

from box to box; press the space bar to toggle the selection marker (X) on or

off in each box. Only data pertinent to the applications marked with an X

will be requested and displayed after this point. Note that for some

applications (e.g., cathedral ceilings and crawlspace walls) the analysis of

rigid foam sheathing can be separately specified from mineral wool batts or

5
blankets (or loose fill insulation materials of any kind). This is primarily

because typical R-values for rigid foam sheathing differ significantly from

those of batts/blankets/loose fill insulation materials.

Since rigid foam sheathing typically costs more than mineral wool/loose fill

for a given application, its economic R-value will be lower. However, for

some applications rigid foam sheathing may be more suitable. Expert

consultation may be needed to determine the appropriate material in specific

circumstances. In the case of new wood- frame wall construction, a combination

of mineral wool insulation and rigid foam sheathing is assumed for R-values

above R-13.

Select Insulation Systems for Analysis

Press <Space Bar> to Toggle System On [X] or Off [ ].

F3 = mark all. Use cursor keys to move around screen.

ATTIC; CRAWLSPACE WALLS:

[ ] 1. batt /blanket /loose fill [ ] 1. batt /blanket /loose fill

CATHEDRAL CEILINGS: [ ] 2. rigid foam sheathing

[ ] 1. batt /blanket /loose fill BASEMENT WALLS (HEATED SPACES):

[ ] 2. rigid foam sheathing [ ] 1. Exterior Insul . (rigid foam)

EXTERIOR WALLS (ABOVE GRADE): 2. Interior Insulation:

[ ] 1. Wood Frame (batt /blanket

)

[ ] a. batt /blanket

2. Concrete-Masonry: [ ] b. rigid foam sheathing

[ ] a. batt /blanket /loose fill BASEMENT WALLS (UNHEATED SPACES):

[ ] b. rigid foam sheathing [ ] 1. Exterior Insul. (batt/blkt)

FLOORS

:

2. Interior Insulation:

[ ] 1. Over unheated spaces (batt) [ ] a. batt /blanket

[ ] 2. Concrete slab (rigid foam) [ ] b. rigid foam sheathing

[ ] DUCT INSULATION [ ] WATER HEATER INSULATION

Press <PgDn> when finished.

Screen 2. Menu for selecting insulation systems of interest

4. A Water Heater Data

If water heater insulation is checked, four questions are asked about the

water heater; its type, its capacity (in gallons), its expected remaining

life, and the price of the heating fuel. Six types of water heaters are

displayed for selection: gas, oil, and electric, with either mineral wool or

foam tank insulation. If the water heating fuel is the same as the space

heating fuel, the default unit price will be the same as entered for space

heating. If electric water heating is used, the user will be asked to enter

both the winter electricity rate and the summer electricity rate. The actual

electricity rate used in the analysis will be based on two-thirds (eight

months) of the winter rate plus one- third (four months) of the summer rate.

The economic analysis of a water heater insulating jacket is limited to the

owner’s expectation of the water heater’s remaining life, with no salvage

value credited. The water heater is assumed to be located inside the house.

However, potential beneficial heat gain from the tank during heating hours and

undesirable heat gain during cooling hours is not considered in the analysis.

6
4.5 Existing Houses Only--Existing Levels of Insulation

If the ZIP analysis is being performed for an existing house, the user is

asked to specify the approximate existing level of insulation in the attic,

floors over unheated spaces, crawlspace walls, and supply heating ducts if

these systems have been selected for analysis. These selections are made from

a menu displaying several R-values and the approximate equivalent thickness of

insulation in inches. An example of this selection menu is shown in Screen 3

for attic insulation. In most other applications in existing houses (e.g.,

exterior walls), ZIP asks if there is any existing insulation in the

component. If the user indicates that some insulation already exists in such

components, ZIP advises that further insulation is generally impractical,

since the cost of removing or penetrating wall coverings is often

prohibitively costly and the potential savings is significantly reduced.

Attic Insulation - Batt /Blanket /Loose Fill

How much insulation is there in your attic now?

Approximate Equivalent in Inches

Existing

Insulation Fiberglass Cellulosic

Level

Batt Blown

Blown

(0) None 0

(1) R-7 2.5 2.0 -3.0 2. 0-3.0

(2) R-ll 3.5 3.75-5.0 3. 0-3.

5

(3) R-19 6.0 6.5 -8.75 5. 0-6.0

(4) R-22 7.0 7.5 -10.0 6. 0-7.0

(5) R- 30 9.0 10.25-13.75 8. 0-9.

5

(6) R-38 12.0 13.75-18.25 10.3-12.

Screen 3. Selecting existing level of insulation in attic

4.6 Insulation Costs

Default insulation costs for each application checked are displayed. For most

applications, three to eight different insulation levels are shown along with

default estimates of their installed cost. An example of this insulation cost

menu is shown in Screen 4 for attic insulation. ZIP will evaluate each of

these levels to determine which is the most cost effective in this analysis,

using the costs shown. The user can accept these default values; however it

is recommended that the user enter values specific to the building site.

The default insulation costs include contractor installation, except for the

water heater jacket, which is assumed to be installed by the homeowner. For

do-it-yourselfers, these costs can be modified to reflect materials only or

include the labor cost, as desired. In general, the higher the insulation

cost, the lower will be the economic level of insulation, and vice versa.

7
Attic Insulation Costs (Batt/Blanket /Loose Fill):

(cost per square foot of gross attic area)

R-ll % $ 0.34 per square foot

R-19 e $ 0.47 per square foot

R-22 e $ 0.54 per square foot

R-30 e $ 0.67 per square foot

R-38 <a $ 0.85 per square foot

R-49 e $ 1.05 per square foot

Screen 4. Designating attic insulation costs for selected R-values

Before the insulation costs are requested, ZIP will display guidelines related

to appropriate selection and entry of cost data. These guidelines are as

follows

:

o All costs are to be entered in terms of thermal resistance (R) value,

not thickness.

o All costs are to be entered per square foot or per linear foot for the

indicated R-value (as specified). If your cost estimates are for the

total job, you must convert them to dollars per square foot or per

linear foot of the insulated area (as indicated).

o Insulation costs should include both material and labor costs if

professionally installed.

o If you are doing the job yourself, you can omit labor costs, or

include the cost of your time, as you prefer. Economic insulation

levels will generally be higher if labor costs are not included.

o All insulation costs should include the cost of structural modifications

or coverings if these additional costs cannot be justified for other

purposes

.

o Each R-value for any given application is expected to cost more than the

previous R-value, never the same or less.

o Technically speaking, the difference in cost for each additional

increment of insulation relative to the previous increment (e.g., R-19

relative to R-ll) is more important than the total cost of that

increment. Therefore, take care to make the cost differentials

reasonable

.

Entering a price of $99.99 for any level of insulation will eliminate that

level from the economic analysis. (This is useful if a particular level is

unavailable or inappropriate for the application of interest.) Note: the

cost of each successive level of insulation must be higher than the previous

level, unless $99.99 has been entered for the previous level.

8
4.7 Duct Insulation

If insulation on supply and return ducts in unconditioned spaces is to be

analyzed, the approximate cross-section dimensions must be identified for the

most representative sizes. The approximate size for each is selected from a menu of choices, as shown in Screen 5. Insulation costs for ducts are stated

in dollars per linear foot of duct. Insulation costs per linear foot are

typically higher for larger perimeter ducts than for ducts with small

perimeters. Moreover, these costs tend to increase faster with increases in

R-value than for other applications. This is because the outside perimeter

(and thus the amount of insulation needed to wrap around it) increases with

each new level. Both of these factors should be considered when specifying

duct insulation costs. If supply ducts are used for air conditioning, the

duct insulation should include a vapor barrier on the outside, sealed to

prevent moisture from condensing on the ducts and wetting the insulation.

Economic insulation levels are computed and reported separately for supply and

return ducts in attics, vented crawlspaces, and controlled-ventilation

crawlspaces

.

SUPPLY DUCTS in unconditioned spaces:

What is most typical duct size (approximate size in inches)?

Round Rectangular

(A) 4 (F) 3 x 12

(B) 6 (G) 6 x 12

(C) 8 (H) 8 x 14

(D) 10 (I) 10 x 16

(E) 12 (J) 12 x 20

Screen 5. Selecting duct size to be insulated

5. ZIP REPORT FORMAT

The results of the economic analysis for the designated location are displayed

directly on the screen as shown in Screen 6. The Zip code and reference

location, number of annual heating degree days (base 65F) and cooling degree

hours over 74F are shown. Also included at the top of the report are the

types of heating and cooling equipment, seasonal energy efficiencies, and the

fuel prices used in the analysis. If the ZIP analysis is for a new house, the

economic level of insulation is shown for each application. For existing

houses, the existing level, amount to be added, and total level for each

application are shown.

Note that the economic levels of insulation for both floors over crawlspaces

and for crawlspace walls are shown if both were selected for analysis.

However, only one of these methods would be used in most houses. For

crawlspaces that can be safely closed off, it is usually more economical to

9
insulate the walls than the floor above if the wall area is less than the

floor area. If the crawlspace cannot be safely closed off (or it is not

allowed by the local building code authority), the floor above should be

insulated instead. In this latter case, care must be taken to insulate water

pipes and any ductwork in the unheated area.

Screen 7 shows the additional information displayed at the end of a full ZIP

analysis. This information is provided to help the user better interpret and

utilize the results of the ZIP analysis. However, it is recommended that the

user read the DOE Insulation Fact Sheet or other insulation guidelines, or

consult an insulation expert, before selecting the type of insulation to be

used and installing it.

6 . FINISHING UP

While the ZIP output report is displayed on the screen, the following options

are available by pressing the designated key, as indicated in the menu bar at

the bottom of the screen:

P The entire report displayed on the screen is sent to the printer.

This report includes the economic levels of insulation for the

applications considered in this analysis and the input data

specified by the user, including the insulation prices used in the

analysis. (Make sure that the printer is turned on and that the

paper is properly positioned before selecting this option.)

S Start over with another ZIP analysis, using the data input for the

previous run as the default choices at every question in the new

run.

R Save this report as a flat file on your disk, for later retrieval

by a word processor.

I Save your input data to the disk for retrieval in a later ZIP

analysis. You will be asked to enter a file name for this

datafile. Use any valid DOS filename (eight character maximum).

Do not enter a filename extension; the extension ".ZIP" is

automatically tagged to the filename you enter.

Q Quit and return to DOS.

You cannot back up after the ZIP report is displayed. You must press S and

move through the data input screens again. However, you do not need to

reenter your data since they are now the default responses to every question.

10
Economic Insulation Levels for Zip 111XX -- New House

Reference Location: Queens, NY

Heating Degree Days ( 65F) =approx . 5000 Cooling Degree Hrs(74F)=approx. 9000

Heating Equipment: Natural Gas Cooling Equipment: Central- Electric

Seasonal Efficiency: 651 SEER (seasonal eff.): 8.0 Btu/Wh

Unit Fuel Cost: $0. 650/therm Unit Fuel Cost: $0. 140/kWh

Attic Insulation R-38

Cathedral Ceiling Insulation

Batt/Blanket R-30

Rigid Foam R-16

Wood-Frame Wall Insulation R-23

Masonry Wall Insulation

Batt/Blanket R-19

Rigid Foam R-12

Floors over Crawlspace (If crawlspace walls uninsulated)

Batt/Blanket R-19

Crawlspace Wall Insulation (If floor above is uninsulated)

Batt/Blanket R-ll

Crawlspace Wall Insulation (If floor above is uninsulated)

Rigid Foam R- 5

Slab-Edge Insulation (Rigid Foam) R- 5

Insulation of Basement Walls:

Exterior Insul . for Heated Basement (RF) R-10

Interior Insul. for Heated Basement

Batt/Blanket R-19

Rigid Foam R-12

Exterior Insul. for Unheated Basement (RF) R- 0

Interior Insul. for Unheated Basement

Batt/Blanket R- 3

Rigid Foam R- 6

Insulation of Supply Ducts in Unconditioned Spaces:

Ducts in Attics: R- 8

Ducts in Vented Crawlspaces: R- 8

Ducts in Unvented Crawlspaces: R- 6

Insulation of Return Ducts in Unconditioned Spaces:

Ducts in Attics: R- 6

Ducts in Vented Crawlspaces: R- 4

Ducts in Unvented Crawlspaces: R- 4

Water Heater Insulation Yes

Screen 6. Screen display of results of ZIP analysis (example)

11
Additional information:

Always specify insulation by R-value, not by thickness. If loose-fill

materials are used, make sure that they are installed according to weight

(e.g., pounds per square foot) or bag count and not simply to a target

depth, as significant settling may occur after installation is completed.

These economic R-values are valid only if they can be installed without

making structural modifications to accomodate them, unless the cost of

such modifications is explicitly included in the insulation costs.

Compression of insulation will generally reduce its effectiveness.

ALL insulation products should be kept away from unprotected heat sources.

Insulate the floor over the crawlspace or the crawlspace walls, not both.

Crawlspace walls should only be insulated if the crawlspace is closed off,

unventilated, and dry all year. The ground should be covered with a vapor

barrier (e.g., 4- or 6-mil polyethylene sheeting) to minimize moisture

migration into the crawlspace. Note: some building codes may not allow

unventilated crawlspaces. If radon gas is a problem at the building site,

closing off the crawlspace may not be advisable.

If insulating floors over crawlspaces or other unheated areas, make sure

that exposed water pipes are freeze-protected and ductwork is properly

insulated in those areas.

Before insulating ducts, loosen any existing insulation at all joints and

tape all joints to minimize air leakage. A non-flammable vapor barrier

should cover the insulation on any supply ducts used for air conditioning.

The water heater jacket should not cover combustion air inlets (if any),

pipes, controls, relief valves, or the flue at the top of the heater.

Screen 7. Additional information displayed at the end of a ZIP analysis

12
APPENDIX A. COMPUTATIONAL ALGORITHMS

This appendix documents the computational algorithms used to determine the

economic R-value for each insulation system evaluated in ZIP. The methodology

is divided into five steps. The first four steps are repeated for each Rvalue evaluated for each insulation system. The fifth step is used to

determine the economic R-value for that system.

For each R-value in each insulation system:

(1) Calculation of reductions in annual energy usage

(2) Calculation of savings in annual energy costs

(3) Calculation of total present-value savings in energy costs

(4) Calculation of net present-value savings

For each insulation system:

(5) Determine R-value with greatest net present-value savings

(1) Calculation of reductions in annual energy usage

Reductions in annual heating requirements (AAHR), annual cooling requirements

(AACR), and corresponding purchased energy requirements, are calculated for

each R-value relative to the base case (no insulation in new houses, existing

insulation in existing houses), on a square foot or linear foot basis as

indicated. The methodology used in ZIP for calculating these reductions is

basically the same for all envelope insulation systems. Different methods are

used for evaluating insulation used to wrap heating and cooling ducts and

water heater tanks.

ENVELOPE COMPONENTS

For all envelope components, reductions in annual heating requirements and

annual cooling requirements for each R-value are estimated on a representative

area basis: Btu per square foot of area for attics, ceilings, floors, and

exterior walls and Btu per linear foot of wall perimeter for basement and

crawlspace walls. Crawlspace walls are assumed to be 2 feet high; basement

walls are assumed to be 8 feet high. The computational methodology used to

calculate these reductions in annual energy consumption is as follows:

AAHR = HSLOPE x HDD65 x AU/1000000

AACR = CSLOPE X CDH74 x AU/1000000

where HSLOPE = Btu/unit area-yr-HDD65

,

CSLOPE = Btu/unit area-yr-CDH74

,

HDD65 = heating degree days base 65F,

CDH74 = cooling degree hours base 74F,

and AU = reduction in the U-value of the attic or wall due to the

increase in insulation level.

(a) HSLOPE AND CSLOPE coefficients for attics, cathedral ceilings, and

exterior walls

.

The reductions in annual heating requirements and annual cooling requirements

for these components are estimated using HSLOPE and CSLOPE coefficients

13
derived from the Lawrence Berkeley Laboratory PEAR2 program in support of the

proposed ASHRAE 90. 2P Standard for the Energy Efficient Design of New Low-Rise

Residential Buildings3

. These parameters are shown in table Al.

Table Al. HSLOPE and CSLOPE coefficients for

and exterior walls

attics, roofs.

Component HSLOPE CSLOPE

Attic 25.91 1.978

Cathedral Ceiling 23.18 1.702

Wood-Frame Exterior Walls 21.19 1.005

Masonry Exterior Walls 20.02 0.739

(b) HSLOPE and CSLOPE coefficients for floors over unheated crawlspaces,

crawlspace walls, and basement walls:

The reductions in annual heating requirements and annual cooling requirements

for these components are estimated using equations derived from "Selection of

Optimal Foundation Insulation," by Jeff Christian4. These equations use

HSLOPE and CSLOPE coefficients similar to those used for attics and exterior

walls. However, in some cases these two variables are not constants, but are

computed as a function of HDD65 (HSLOPE) and CDH74 (CSLOPE), using the

coefficients shown in table A2 and the following equations:

For HDD65 < 2500, HSLOPE = HDD65/2500 x HSLOPE(l)

For HDD65 >= 2500, HSLOPE = HSLOPE(l)

For all CDH74 , CSLOPE = I(z) + Slope(z) x CDH74

Christian reported three intercept (I) and slope (S) terms for each component

in the cooling mode, depending on the magnitude of CDH74: (z=l) climates with

less than 15000 CDH74, (z=2) climates with CDH74 between 15000 and 30000, and

(z=3) climates with CDH74 greater than 30000. Note that this methodology

differs slightly from Christian in that HSLOPE for locations with HDD65 < 2500

are computed as a fraction of the HSLOPE(l) parameter. This is done to force

the HSLOPE functions for locations above and below 2500 HDD65 to intersect at

2 Lawrence Berkeley Laboratory, "PEAR.l: Program for Energy Analysis of

Residences," Berkeley, California, 1987.

3 American Society of Heating, Refrigerating, and Air-Conditioning

Engineers, Inc., "Standard 90. 2P: Energy Efficient Design of New Low-Rise

Residential Buildings", Atlanta, Georgia, 1987.

4 Christian, J. E. , "Worksheet for Selection of Optimal Foundation

Insulation, Thermal Performance of the Exterior Envelopes of Buildings IV,

proceedings of the ASHRAE/DOE/BTECC/CIBSE Conference December 4-7, Orlando,

Florida, American Society of Heating, Refrigerating, and Air-Conditioning

Engineers, 1989, pp 800-814.

14
Table A2. HSLOPE and CSLOPE coefficients for floors

and basement and crawlspace walls

Component: HSLOPE(l) CSLOPE parameters

1(1) S ( 1 ) 1(2) S(2) 1(3) S ( 3

)

Floors over 21.435 -1.78 0.000095 -1.07 0.00003 -1.16 0.00003

unheated spaces3

Slab floors on grade:

2 ft vertical 19.38

exterior

2 ft horizontal 19.42

with R-5 gap

Crawlspace walls:

Wood -frame walls 17.4

Masonry walls 19.34

-1.90 0.00015 1.03

-3.02 0.00019 -0.33

-2.16 0.00016 1.43

-2.38 0.00017 -1.23

-0.00005 -1.94 0.00005

-0.00001 -1.89 0.000045

-0.00007 -2.50 0.00006

0.00003 -1.23 0.00003

Basement Walls (Conditioned space)

Full-wall 155.1 -0.1 0.00010

insulation

Half-wall (4 ft) 80.4 0.21 0.00006

4.74 -0.00018 -6.98 0.00020

2.52 -0.00008 -3.05 0.00010

Basement Walls (Unconditioned space)

Full-wall 59.1 -10.68 0.00058 -1.34 -0.00006 -8.92 0.00021

insulation

Half-wall (4 ft) 5.07 -3.45 0.00022 0.71 -0.00005 -3.11 0.00008

2500 HDD65. (Christian’s coefficients tend to be somewhat higher for values

slightly below 2500 HDD65 than for the 2500 HDD65 value.)

Calculation of reductions in annual purchased energy requirements for all

envelope components:

Reductions in annual energy purchases for heating and cooling (AEPh and AEPC ) are calculated for each envelope component by dividing reductions in AHR and

ACR by the corresponding seasonal energy efficiency of the heating and cooling

systems

:

AAEPh = AAHR / EFFh

AAEPC = AACR / EFFC where EFFh = seasonal efficiency of the space heating system,

and EFFC = seasonal efficiency of the space cooling system.

15
For air conditioners, EFFC is derived by dividing SEER by 3.412 Btu/Wh. For

heat pumps, EFFh is derived from the HSPF to reflect the severity of the

winter climate (heating degree days 65F, HDD65F)

:

EFFh = HSPF / 6 . 5 x 1.06 x [2.3 - 0.1(HDD65F/1000)

]

DUCT INSULATION

The analysis of duct insulation savings is based primarily on the methodology

developed for the California Energy Commission (CEC) by Charles Eley

Associates 5. These reports provide coefficients, summarized in table A3, for

computing HVAC supply duct efficiency factors for heating and cooling in

ventilated attics, ventilated crawlspaces, and controlled-ventilation

crawlspaces. Efficiency factors are based on the effective R-value of the

duct insulation, and are computed separately for one-story and two-or-more

story houses, as follows:

where

EFFduct

Rinst

Ci and C2 0.7

EFFduct “ Ci - C2 / (Rinst + °*7)

= efficiency of HVAC ducts,

= installed R-value of ducts,

= coefficients as shown in table A3, and

= surface conductance on the outside surface of the ducts.

Table A3. Duct coefficients for attics, vented crawlspaces (vcs),

and controlled ventilation crawlspaces (eves) 6

Heating

(attic & vcs)

Cooling

(attic

)

Cooling

(vcs

)

Heating

(eves

)

Cooling

(eves

)

One-story houses:

Cj 0.891

C2 0.323

0.892

0.425

0.892

0.147

0.923

0.201

0.910

0.126

Two or more stories:

C x 0.927

C2 0.215

0.928

0.283

0.928

0.098

0.949

0.126

0.941

0.084

5 Charles Eley and subcontractors, Volume 1, Assumptions and Algorithms . California Energy Commission, Sacramento, CA, June 1988. A preliminary report

with the same title dated May 19, 1987 provides a more comprehensive

methodology for this analysis.

6 Coefficients for controlled ventilation crawlspaces were derived from

table 2-1 in the CEC June 1988 methodology.

16
While duct efficiencies can be expected to change somewhat as a function of

climate, the change in duct efficiency as a function of insulation R-value was

found to vary little with climate within the extremes of the state of

California, where this methodology was developed.

The energy losses per square foot of duct surface area can be calculated on an

annual basis by using a ratio of duct surface area to floor area of 15 percent

for one-story houses and 10 percent for two-or-more-story houses, as prescribed in the CEC methodology. The savings per square foot of duct

surface for each increase in duct efficiency can then be calculated, based on

the AHR and ACR per square foot of floor area.

Annual energy savings (AES) for insulation level i, relative to insulation

level i-1, on supply ducts in any location are estimated separately for

heating (s=l) and cooling (s=2) as follows:

AES ( k , s , i ) = AHR/EFFh x [ l/EFFduct (k, s , i-1 ) - l/EFFduct (k,s,i) ] AES (k, s , i ) = ACR/EFFc x [ l/EFFduct (k, s , i-1 ) - l/EFFduct (k, s , i) ]

where

AES = AHR =

ACR =

EFFh = EFFduct — EFFC =

k =

s =

i =

annual energy savings per square foot of duct surface area,

annual space heating requirements per square foot of floor

area

,

annual space cooling requirements per square foot of floor

area

,

heating system efficiency or HSPF,

duct efficiency corresponding to k, h, and i),

cooling system efficiency or SEER,

with indexes:

location (1 = attic, 2 = vented crawlspace, 3 = controlled

ventilation crawlspace),

season (1 = heating, 2 = cooling),

insulation level (0, 1 , 2 ,..., n; 0 = base case before adding

insulation)

.

Note: EFFh and EFFC do not include additional adjustments for duct losses as

described above for the calculation of insulation savings in the building

envelope

.

Savings for insulation on the return ducts are estimated using adjustment

factors derived from a more comprehensive analysis based on the 1987 version

of the CEC methodology. The analysis of return ducts was based on a 70F

return air temperature. The adjustment factors are 0.35 for heating in attics

and crawlspaces, 0.6 for cooling in attics, and 0.8 for cooling in

crawlspaces. The adjustment factors are applied directly to the savings

computed for the supply ducts.

To compute the actual savings from improvements in duct efficiency, estimates

of the annual space heating (AHR) and annual cooling requirements (ACR) per

square foot of floor area are needed. However, AHR and ACR per square foot

vary significantly from house to house, even in the same climate, due to

differences in design, air leakage, and operational profile. Furthermore,

these requirements will vary significantly with the degree to which the

various insulation recommendations for the structural components of the house

17
are implemented. Thus it is difficult to estimate the actual savings from

improvements in duct efficiency without detailed thermal modeling of the

house. For this reason, conservative estimates of AHR and ACR per square foot

in each three-digit Zip code area were sought so as not to overestimate the

savings from duct insulation in ZIP.

Two sets of estimates of the annual heating and cooling requirements of a 1500

square-foot house in 323 locations, calculated in support of ASHRAE 90. 2P

standards development by Merle McBride 7

, were used for this purpose. The

first set was calculated using the design requirements specified in ASHRAE

Standard 90-80A (1980) for energy conservation in the design of new singlefamily housing. The second set was based on design criteria similar to the

proposed ASHRAE Standard 90. 2P expected to supersede Standard 90-80A in 1990.

It is assumed that most existing houses, even with upgraded insulation, will

have AHR and ACR per square foot at least as great as those for houses built

to the 1980 standard, while new houses will have lower AHR and ACR, consistent

with the more stringent requirements of ASHRAE 90. 2P. Thus ZIP uses the first

set of AHR and ACR estimates for computing savings from improvements in duct

efficiency in existing houses and the second set for computing savings in new

houses

.

Regression equations were developed from these two sets of annual heating and

cooling requirements, using heating degree days (65F, HDD65) and cooling

degree hours (74F, CDH74) as independent variables. (These are the same

climate-related parameters used by ZIP for estimating energy savings from

insulation in the structural components.) Separate regression equations were

calculated for ten regions of the United States, with regions based on the

first digit of the Zip code (e.g., 0XXXX serves Maine, Vermont, New Hampshire,

Connecticut, Massachusetts, and Rhode Island, and New Jersey). In cases where

there is significant variation in AHR or ACR within a region, insufficiently

explained by HDD65 or CDH74, separate regression equations were calculated by

state or even within a state. These regression equations, shown in table A4

,

are used to estimate AHR and ACR for both new and existing houses in the ZIP

methodology for duct insulation analysis.

WATER HEATER INSULATION JACKET

The primary reference for calculating energy savings from water heater

insulation jackets is a National Bureau of Standards report entitled

Evaluation of Energy-Conserving Modifications for Water Heaters 8

. Standby

losses before and after wrapping five water heaters with a 1.5 in. fiberglass

insulation kit were measured in an NIST laboratory. The results of this

testing, as generalized for ZIP 2.0, are shown in table A5.

7 Private communication from Dr. Merle McBride, Owens Corning Fiberglas

Corporation, Research Center, Granville, OH, 1989.

8 Pall, R. Jr., Evaluation of Energy-Conserving Modifications for Water

Heaters . NBSIR 79-1783, National Bureau of Standards, July 1979.

18
Table A4 . Regression equations for estimating annual heating

and cooling requirements by ZIP region

AHR1 = Annual heating requirements

ACR1 = Annual cooling requirements

AHR2 = Annual heating requirements

ACR2 = Annual cooling requirements

hdd = hdd65 / 100, and

cdh = cdh74 / 100.

(Btu/yr-1500 sq ft)

(Btu/yr-1500 sq ft)

(Btu/yr-1500 sq ft)

(Btu/yr-1500 sq ft)

for new house

,

for new house,

for existing house,

for existing house,

ZIP OXXXX:

AHR1 = -14.37 + 1.648 x hdd

ACR1 = 2.35 + 0.332 x cdh

AHR2 = -21.4 + 0.814 x AHR1

IF ACR1 < 8 THEN ACR2 = 0 ELSE ACR2 = -5.7 + 0.727 x ACR1

ZIP 1XXXX:

AHR1 = 11.79 + 1.265 x hdd

ACR1 =5.36 + 0.198 x cdh

AHR2 = -30.6 + 0.909 x AHR1

IF ACR1< 8 THEN ACR2 = 0 ELSE ACR2 = -8.4 + 0.968 x ACR1

ZIP 2XXXX:

AHR1 = -17.7 + 1.851 x hdd

ACR1 = 7.73 + 0.172 x cdh

AHR2 = 0.0 + 0.464 x AHR1

IF ACR1< 8 THEN ACR2 = 0 ELSE ACR2 = -6 + 0.98 x ACR1

ZIP 3XXXX

:

IF STATES = FL THEN

AHR1 = -1.78 + 1.296 x hdd

FOR ALL OTHERS:

AHR1 = -6.43

FOR ALL STATES

+ 1.536

• x hdd

ACR1 = 9.08 + 0.148 X cdh

AHR2 = 3.4 + 0.405 X AHR1

ACR2 = -5.3 + 0.967 X ACR1

ZIP 4XXXX:

AHR1 = 21.86 + 1.123 X hdd

ACR1 = 4.17 + 0.176 X cdh

AHR2 = -22.2 + 0.813 X AHR1

IF ACR1< 8 THEN ACR2 = 0 ELSE ACR2 = -7.5 + 0.872 x ACR1

19
Table A4 (continued)

ZIP 5XXXX:

AHR1 = -54.76 + 2.17 x hdd

FOR STATES IA, WI , and MN:

ACR1 = 3.04 + 0.166 x cdh

FOR STATES SD, ND, and MT

ACR1 = 2.27 + 0.104 x cdh

FOR ALL STATES:

AHR2 = 28.9 + 0.417 x AHR1

IF ACR1< 8 THEN ACR2 = 0 ELSE ACR2 - -1.4 + 0.189 x ACR1

ZIP 6XXXX:

AHR1 = 2 + 1.41 x hdd

FOR IL:

ACR1 = 4.66 + 0.153 x cdh

FOR MO:

ACR1 = 9.18 + 0.094 x cdh

FOR KS and NE:

ACR1 - 7.54 + 0.084 x cdh

FOR ALL STATES:

AHR2 = -19.1 + 0.783 x AHR1

ACR2 = -10.3 + 1.028 x ACR1

ZIP 7XXXX:

AHR1 = -6.031 + 1.488 x hdd

FOR LA:

ACR1 =42

FOR AR, TX, and OK : ACR1 = 5.92 + 0.135 x cdh

FOR ALL STATES:

AHR2 = 5.2 + 0.356 x AHR1

ACR2 = -4.3 + 0.901 x ACR1

ZIP 8XXXX:

IF hdd < 20 THEN

AHR1 = 15

IF hdd >= 20 THEN

AHR1 = 8.39 + 1.211 x hdd

FOR WY and ID:

ACR1 = 2.82 + 0.125 x cdh

FOR CO, UT, AZ, NM, and NV:

ACR1 =5.3 + 0.093 x cdh

FOR ALL STATES:

AHR2 = -10.6 + 0.707 x AHR1

IF ACR1< 7 THEN ACR2 = 0 ELSE ACR2 = -6.4 + 0.953 x ACR1

20
Table A4 (continued)

ZIP 9XXXX:

FOR CA:

AHR1 = -1.09 + 0.963 x hdd

AHR2 = 4.6 + 0.564 x AHR1

IF cdh < 3 THEN

ACR1 = 0

ACR2 « 0

IF cdh >= 3 THEN

ACR1 = 14.63 + 0.069 x cdh

ACR2 = -2.14 + 0.54 x ACR1

FOR HI:

AHR1 - 0: ACR1 = 0: AHR2 = 0: ACR2 = 0

FOR OR, WA, and AK:

AHR1 = 4.95 + 1.238 x hdd

AHR2 - -18.75 + 0.734 x AHR1

IF cdh < 3 THEN

ACR1 = 0: ACR2 = 0

IF cdh >= 3 THEN

ACR1 = 4.79 + 0.111 x cdh

ACR2 = 0

FOR ALL REGIONS:

Convert to Btu/sq ft for new or existing house as needed:

AHR = AHR1 x 1000000 / 1500

ACR = ACR1 x 1000000 / 1500

AHR = AHR2 x 1000000 / 1500

ACR = ACR2 x 1000000 / 1500

Table A5 . Reduction in water heater standby losses (SBL)

due to the installation of an insulating jacket

Reduction in SBL (Z)

Electric (standard) 30

Electric (high efficiency tank) 18

Gas (standard) 25

Gas (high efficiency tank) 15

Oil (standard) 25

Oil (high efficiency tank) 15

21
Annual purchased energy savings (AAEP) attributable to the addition of a water

heater jacket are calculated as follows:

AAEP = SBL x reductions

)

x (t tank - tair ) x vtank x 8.25/EFF x 8760

10000

where

SBL = reduction =

t-tank

tair “ vtank “ 8.25 = EFF = 8760 =

standby losses (Z/ hr),

percentage reduction in standby losses due to water heater

jacket

,

tank water temp (avg),

ambient air temp (avg),

tank volume in gallons,

density of water (lb-gal),

water heater recovery efficiency, and

hours /year

.

The GAMA Consumers* Directory of Certified Water Heater Efficiency Ratings9 provides standby losses for all currently marketed water heaters in units

comparable with the approach outlined above. Standby losses vary with the

type of water heater, its volume, and the degree to which the tank is

insulated. The relationships between tank volume and stand-by losses shown in

table A6 were derived from the 1986 GAMA Directory.

In ZIP 2.0, water heater tanks with foam insulation are considered to be high

efficiency tanks, while tanks with fiberglass insulation are considered to be

standard tanks.

Calculation of savings in annual energy costs

Savings in annual heating and annual cooling costs (AESh and AESC ) are

calculated by multiplying reductions in purchased energy requirements by the

unit cost of energy and the units per million Btu.

AESh = AAEPh x ($/unith ) x (unith /million Btu)

AESC = AAEPC x ($/unitc ) x (unitc /million Btu)

where

:

$/unith

$/unitc unith

unitc

the current cost per unit of energy used for heating (e.g.,

$.08 /kWh),

the current cost per unit of energy used for cooling,

the number of units of heating energy per million Btu (e.g.,

293 kWh = one million Btu) , and

the number of units of cooling energy per million Btu.

9 Gas Appliance Manufacturers Association, Consumers* Directory of

Certified Water Heater Efficiency Ratines . Arlington, VA, 1986.

22
Table A6. Standby losses (as percent of annual energy requirements)

used in ZIP analysis of water heater jackets

Capacity

(gallons

)

Standby

Hi Eff

losses

Standard

gas : 30 4.0 5.8

40 4.0 5.5

50 3.5 5.3

70 3.3 5.0

oil

:

30 3.0 4.0

50 2.0 3.0

Hi Eff Standard

electric

:

30 1.0 2.0

40 0.9 1.7

50 0.7 1.7

70 0.6 1.5

Calculation of total present-value savings in energy costs

Calculate the total present-value savings (PVS) in energy costs over the

designated insulation life (30 years for new houses, 20 years for existing

houses). Annual savings for heating and cooling are multiplied by the

modified uniform present worth factor (UPW*) corresponding to the life,

discount rate (7 percent real, i.e., net of general inflation), and

corresponding DOE energy price escalation rates (see appendix B), and summed.

(DOE projections of price escalation rates (in real terms) for the specified

energy type and region of the country are retrieved from a ZIP data file.)

PVS - AESh x UPW*h + AESC x UPW*C where

UPW*h = the modified uniform present worth factor for heating

energy, given a study period, the discount rate, and the

annual rate of heating energy price escalation over the

study period, and

UPW*C = the modified uniform present worth factor for cooling

energy, given a study period, the discount rate, and the

annual rate of cooling energy price escalation over the

study period.

23
The UPW* factor is calculated as follows:

UPW* = 2

t (l+d) c

where

life or study period in years,

Ii = IL _i x (1+ei) (energy price index in year i),

1

rate of energy price increase in year i, and

discount rate

Calculation of net present-value savings

Calculate the net present-value savings for each increment of insulation by

subtracting the cost of the insulation from its present-value savings.

Determine R-value with greatest net present-value savings

Determine the insulation R-value for each application of interest that has the

greatest net present-value savings. This is designated as the economic

R-value for that application. The rate of return for any higher level of

insulation evaluate in this analysis will fall below the seven percent

discount rate.

NS = PVS - C

where

C - initial cost (installed) for the insulation level of interest.

24
APPENDIX B. ENERGY PRICE AND INSULATION COST FILES

I. Energy Price Files

There are six supporting data files in ZIP 2.0 related to energy prices. Two

of these files provide default energy prices by state or, in the case of

electricity, by three-digit ZIP code; the last four provide the Department of

Energy’s forecast of residential energy price increases year by year for the

years 1990-2020, one file for each major region (North East, East Central,

South, and West )

.

(1) Gas, oil and LPG (propane) prices by state (file ENPR90.ASC)

Gas prices by state were derived from the U.S. Department of Energy’s (DOE)

Natural Gas Monthly10

, table 28. Prices in dollars per 1000 cubic foot (cf)

were divided by the corresponding heat value (Btu/cf) for each state from

DOE’s Natural Gas Annual 11

, and again by 10 to convert to dollars per therm

(1 therm = 100,000 Btu) . These prices are in 1990 dollars.

Residential fuel oil prices for each state were derived from DOE’s Winter

Fuels Report 12 and State Energy Price and Expenditure Report 13

. Residential

fuel oil prices in the first reference are published for 21 selected states

(table 6). For the remaining states, the ratios of state prices to the

national average, calculated from the second reference, were used to adjust

the average U.S. price in 1990 to reflect state differences. This adjusted

price was not allowed to fall below $1. 20/gallon. (Note: these prices were

based on current oil prices at as of October 15, 1990, in a market reflecting

considerable uncertainty about developments the Middle East.)

Propane prices per state were also derived from DOE’s Winter Fuels Report

(table 7) and State Energy Price and Expenditure Report . The same methodology

used to estimate state-specific fuel oil prices was used for propane prices,

with a lower bound of $0.80 /gallon.

10Energy Information Agency, Natural Gas Monthly . July 1990, DOE/EIA0130(90/07), U.S. Department of Energy, Washington, D.C., 1990.

11 Energy Information Agency, Natural Gas Annual . 1989, DOE/EIA-O131(89)

,

U.S. Department of Energy, Washington, D.C., 1990.

12 Energy Information Administration, Winter Fuels Report . (Week Ending

October 26, 1990), DOE/EIA-0538(90/91-05) , U.S. Department of Energy,

Washington, D.C., 1990.

13 Energy Information Administration, State Energy Price and Expenditure

Report ( 1988

)

. DOE/EIA-0376 ( 88 ) , U.S. Department of Energy, Washington, D.C.,

1990.

25
(2) Electricity prices by ZIP code (file ELEC90.ASC)

The default summer and winter kWh prices in ELEC90.ASC were derived from an

annual DOE report on electrici :y bills for all electric utilities 1 * . The

default kWh prices are representative of the price of last kWhs used monthly

in the peak cooling and heating months in each three-digit ZIP Code region.

Up to eight major electric utilities (based on number of customers) were

identified for each state, and one of these utilities was designated for each

three-digit ZIP Code region in the state. The residential kWh rate schedule

for the designated utility was used as the basis for calculating these default

prices. (Many towns and cities are served by a local municipal utility. Rate

schedules for these local utilities were not incorporated into this analysis.)

Typical monthly electricity bills for usage rates of 250, 500, 1000, and 2500

kWh are reported annually by the DOE for all U.S. utilities. Summer kWh

prices were calculated as the average price of a kWh for monthly kWh usage

rates between 500 and 1000 kWh. Winter kWh prices were calculated as the

average price of a kWh for monthly usage rates between 1000 and 2500 kWh.

1988 kWh prices were updated to 1990 prices using a price index factor of 1.1.

All kWh prices were rounded to the nearest cent.

( 3

)

- ( 6 ) Energy Price Escalation Rates (files DOEENPR.*)

Energy price escalation rates (rates of energy price increase) for the years

1990 to 2020 are derived from the DOE Energy Information Administration’s

forecast of residential energy prices, as published by NIST in Energy Prices

and Discount Factors for Life-Cycle Cost Analysis (1990) 15. Four files are

available (with corresponding filename extensions), one for each major Census

region: (1) Northeast (NE), (2) Midwest (MW), (3) Southeast (SE), and (4)

West (W) . These files contain DOE projections of residential energy prices

for electricity, fuel oil, LPG, and natural gas, in constant 1990 dollars.

ZIP reads these data and converts them to energy price escalation rates as

follows

:

ei - EPi/EPi.i -1

where e i = escalation rate in year i, and

EPi = energy price in year i.

Because the energy price projections are in constant dollars, the resulting

price escalation rates are in real terms (i.e., exclusive of general

inflation), consistent with the use of a real discount rate. The methodology

for calculating modified uniform present worth factors, based on these

escalation rates, is outlined in Appendix A. These energy price projections

are used only to calculate price escalation rates; they are not used as

default energy prices.

1A Energy Information Administration, Electric Sales. Revenue, and Bills

( 1988

)

. DOE/EIA-0540(1988) , U.S. Department of Energy, Washington, D.C., 1990.

15 Lippiatt, B. C., and Ruegg, R. T., Energy Prices and Discount Factors

for Life-Cycle Cost Analysis (1990) . NISTIR 85-3273-5 (Revised 10/90),

National Institute of Standards and Technology, Gaithersburg, MD, 1990.

26
II. Insulation Cost Files

There are two insulation cost files, one for new houses ( INSC0ST2 .NEW) and one

for existing houses (INSC0ST2.RET) . These files provide a general inflation

factor to convert 1985 costs to 1990 costs, a regional cost adjustment factors

for all insulation costs, and specific data for the technical and economic

analysis of insulation in each component of the house. The structure of these

two files is identical. The file for existing houses specifies R-value

increments to be evaluated for exterior walls and basement walls differently

than those in the file for new houses.

The first two lines in the insulation cost file are remark lines that are

ignored

.

The third line contains the general inflation index to be used to update all

insulation prices in this file to the desired year. The prices in this file

are currently in 1985 dollars. The general inflation index of 1.2 is used to

update these prices to 1990 dollars.

The fourth line contains 12 regional cost adjustment factors. These factors

were taken from an NAHB Research Foundation report 16 for ASHRAE SPC 90.2

(energy standard for new low-rise residential buildings). These states in

each region and the adjustment factor currently used in both insulation cost

files are shown in table Bl.

Table Bl. Regional cost adjustment factors

Region States Factor

1 MA, RI, NH, ME

2 NJ, NY, PA, DE

3 VA, WV, NC, SC

4 FL

5 AL, TN, MS, LA

6 KY, IA, MO, KS

7 OH, IN, MI, WI

8 MT, CO, WY, ID

9 AZ, NM

10 CA, HI

11 OR, WA

12 AK

VT, CT 1.03

DC, MD 1.04

GA 0.81

0.97

AR, OK, TX, 0.95

NE, 0.98

MN, SD, ND, IL 1.03

UT, NV 0.97

0.97

1.22

1.04

1.30

16 NAHB Research Foundation, Inc., An Economic Data Base in Support of SPC

90.2: Costs of Residential Energy. Thermal Envelope and HVAC Equipment . NAHB

National Research Center, Upper Marlboro, MD, December 1986.

27
The remaining data in the insulation cost files provide not only the U.S.

average cost for each insulation R-value in each component, but provide the

uninsulated U-value, R-value increments, and corresponding U-values for each

increment that drive the ZIP analysis. The fifth line specifies the number of

insulation systems contained in this file (currently 18).

The structure of the remaining lines is the same for each insulation system.

Lines for each system are numbered from 1 for clarity here:

line 1:

Code number for this insulation system (1-18; these are mandatory

identity codes and cannot be changed without making corresponding

changes to the ZIP source code).

Insulation system designator (B/B = batt /blanket , RF = rigid foam)

Number of increments (1-9)

Component type (1 = upper envelope (attic, cathedral ceiling, exterior

walls), 2 = lower envelope (floors, crawlspace and basement walls),

3 = ducts, 4 = water heater insulation).

Area/perimeter designator (1 = analysis on square foot basis, 2 = analysis on linear foot basis)

line 2: Comment that shows on screen with insulation costs

line 3: The uninsulated component U-value (Btu/ sqf t-hr-F)

Remaining lines (one for each R-value):

R-value of insulation increment to be evaluated ( sqf t-hr-F/Btu)

Corresponding U-value (Btu/sqf t-hr-F)

Price per square foot or linear foot, consistent with area/perimeter

designator

Insulation prices in the INSC0ST2.NEW and INSC0ST2.RET files were taken from

the NAHB Research Foundation report and from Christian17

. The prices in

these files are currently in 1985 dollars. They are updated to 1990 dollars

in ZIP using the general inflation index for that period (1.20).

17 Christian, J. E. , "Worksheet for Selection of Optimal Foundation

Insulation, Thermal Performance of the Exterior Envelopes of Buildings IV . proceedings of the ASHRAE/DOE/BTECC/CIBSE Conference December 4-7, Orlando,

Florida, American Society of Heating, Refrigerating, and Air-Conditioning

Engineers, 1989, pp 800-814.

28
01. Summary date 02. Summary prepared by (Name and Phone)

Yr. Mo. Day Stephen R. Petersen (301) 975-6136

9 0 0 1 0 3 05. Software title 04. Software date ZIP-Code Insulation Program (ZIP)

Yr. 9 0

Mo. SL 1

Day

JLJ.

Version 2.0

FEDERAL INFORMATION PROCESSING STANDARD SOFTWARE SUMMARY

06. Short title

03. Summary action New Replacement Deletion e

Previous Internal Software ID

07. Internal Software ID

08. Software type

Automated Data System

[X] Computer Program

| | Subroutine/Module

09. Processing mode

fni Interactive Q Batch

| [ Combination

10. General

Application area

Computer Systems -

| | Support/Utility P

[~^j Scientific/Engineering p

| | Bibliographic/Textual

Management/

Business

Process Control Other

Specific

Economic Analysis of

Thermal Insulation

11. Submitting organization and address National Institute of Standards and Technology

Gaithersburg, MD 20899

12. Technical contact(s) and phone

Stephen R. Petersen

(301) 975-6136

13. Narrative 2.0 is a revised and updated version of ZIP, the ZIP-Code Insulation Program.

ZIP is a computer program developed to support the DoE Insulation Fact Sheet by providing

users with customized estimates of economic levels of residential insulation. These

estimates can be made for any location in the United States by entering the first three

digits of its ZIP code. The revised ZIP program calculates economic levels of insulation

for attics, cathedral ceilings, exterior wood-frame and masonry walls, floors over

unheated areas, slab floors, basement and crawl space walls, ducts in unconditioned spaces,

and water heaters. Climate parameters, energy prices and insulation costs are contained

in a file on the ZIP diskette and are automatically retrieved by ZIP code.

14.

Keywords

building design; building economics; energy conservation; engineering economics;

insulation; life-cycle cost; residential construction; space cooling; space heating;

thermal insulation

15.

Computer manufr and model

IBM PC /XT/AT and

compatible

16.

Computer operating system

MS-DOS

17. Programing language(s)

BASIC

18. Number of source program state- ments 3000

19. Computer memory requirements

256K

20. Tepe drives 021. Disk/Drum units 122. Terminals

1

23. Other operational requirements

Printer

24. Software availability

Available Limited 0In-house only

25. Documentation availability

Available Inadequate In-house only

26. FOR SUBMITTING ORGANIZATION USE

Standard Form 1S5

1974 July

U.S. Dept, of Commerce—NBS

(FIPS. Pub. 30)

185-101

NiST-i 14A U.S. DEPARTMENT OF COMMERCE

(REV. 3-69) NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY

1 . PUBLICATION OR REPORT NUMBER

NT STIR 88-3801-1

BIBLIOGRAPHIC DATA SHEET

2. PERFORMING ORGANIZATION REPORT NUMBER

3. PUBLICATION DATE

JANUARY 1991

4. TITLE AND SUBTITLE

ZIP —The Zip-Code Insulation Program, Version 2.0

(Addendum to User's Guide and Revised Short Guide)

5. AUTHOR(S) Stephen R. Petersen

6. PERFORMING ORGANIZATION (IF JOINT OR OTHER THAN NIST, SEE INSTRUCTIONS)

U.S. DEPARTMENT OF COMMERCE

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY

GAITHERSBURG, MD 20099

7. CONTRACT/GRANT NUMBER

0. TYPE OF REPORT AND PERIOD COVERED

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (STREET, CITY, STATE, ZIP) U . S . Department of Energy

Building Systems Division

1000 Independence Avenue, S.W.

Washington, D.C. 20585

10.

SUPPLEMENTARY NOTES

DOCUMENT DESCRIBES A COMPUTER PROGRAM; SF-105, FIPS SOFTWARE SUMMARY, IS ATTACHED.

11.

ABSTRACT (A 200-WORD OR LESS FACTUAL SUMMARY OF MOST SIGNIFICANT INFORMATION. IF DOCUMENT INCLUDES A SIGNIFICANT BIBLIOGRAPHY OR

LITERATURE SURVEY, MENTION IT HERE.)

ZIP 2.0 is a revised and updated version of ZIP, the Zip-Code Insulation Program. ZIP is a computer program developed to support the DoE Insulation Fact Sheet by providing users with

customized estimates of economic levels of residential insulation. These estimates can be

made for any location in the United States by entering the first three digits of its ZIP

code. The program and supporting files are contained on a single 5-1/4 in. diskette for

use with microcomputers having an MS-DOS operating system. The revised ZIP program

calculates economic levels of insulation for attics, cathedral ceilings, exterior woodframe and masonry walls, floors over unheated areas, slab floors, basement and crawlspace

walls, ducts in unconditioned spaces, and water heaters. Climate parameters are contained

in a file on the ZIP diskette and are automatically retrieved by ZIP code. Regional energy

prices and insulation costs are also retrieved from the diskette, but these can be overridden to better reflect local conditions. A short guide to ZIP is included on the ZIP

diskette. An addendum to the ZIP User's Guide and Reference Manual (NISTIR 88-3801) is

also included under separate cover as NISTIR 88-3801-1.

12.

KEY WORDS (S TO 12 ENTRIES; ALPHABETICAL ORDER; CAPITALIZE ONLY PROPER NAMES; AND SEPARATE KEY WORDS BY SEMICOLONS)

building design; building economics; energy conservation; engineering economics; insulation;

life-cycle cost; residential construction; space cooling; space heating; thermal

insu lat ion

13.

AVAILABILITY UNLIMITED FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE TO NATIONAL TECHNICAL INFORMATION SERVICE (NTIS). ORDER FROM SUPERINTENDENT OF DOCUMENTS, U.S. GOVERNMENT PRINTING OFFICE,

WASHINGTON, DC 20402. ORDER FROM NATIONAL TECHNICAL INFORMATION SERVICE (NTIS), SPRINOFIEU), VA 22181.

14. NUMBER OF PRINTED PAGES

35

IS. PRICE

A03

ELECTRONIC FORM