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ASHRAE/IESNA Standard 90.1
Merle F. McBride, Ph.D., P.E., MemberSenior Research Associate
Owens CorningASHRAE Summer Meeting
Nashville, TNJune 28, 2004
Current Standard 90.1 Economic Analysis Methods
Overview
Background
Life Cycle Cost Analysis
Scalar Ratios
National Energy Savings
Examples
Background – Std. 90.1-1989
Professional Judgment
Economics – Pipe Insulation
Imbalance
Envelope
Lighting
HVAC
ASHRAE Standard 90.1-1989 Relative Stringency
0
0.2
0.4
0.6
0.8
1
1.2
Envelope Mechanical Lighting
Building Technology
Re
lati
ve
Str
ing
en
cy
1991 Proposal – LCC Analysis
Energy Savings
Tier I - 25%
Tier II - 50%
Tier III - 75%
LCC Economics
Balanced
Professional Judgement
ASHRAE Standard 90.1-1999 Relative Stringency
0
0.2
0.4
0.6
0.8
1
1.2
Envelope Mechanical Lighting
Building Technology
Re
lati
ve
Str
ing
en
cy
1999
1989
Life-Cycle Cost Economic Analysis (ASTM E 917)
LCC = FC + M + R + E - RV
where
LCC = life-cycle cost ($)
FC = first cost ($)
M = maintenance and repair costs ($)
R = replacement costs ($)
E = energy costs ($)
RV = resale value or salvage ($)
Present Value
PVLCC = FC + PVM + PVR + PVE - PVRV
where
PVM = M x UPWF
PVR = R x UPWF
PVE = E x UPWF
PVRV = RV x SPVF
Uniform Present Worth Factor
UPWF = [(1+i)n -1] / [ i x (1+i)n]
Single Present Value FactorSPVF = 1/(1+D)n
where
i = fuel escalation rate (decimal)
n = measure life (years)
D = discount rate (decimal)
Economic Assumptions
PVLCC = PVFC + PVM + PVR + PVE - PVRV
PVLCC = PVFC + PVE
OBJECTIVE
Determine minimum PVLCC
0 0 0
LCC Theory
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
50000
0 5 10 15 20 25 30 35 40 45 50
Energy Conservation Measure
LC
C (
$)
First Costs
Energy Costs
LCC
1-16
Incremental LCC
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 5 10 15 20 25 30 35 40 45 50
Energy Conservation Measure
Incre
me
nta
l L
CC
($)
Incremental Energy Savings
Incremental First Costs
1-17
Expanding Energy Savings Terms FYSh x Ph x UPWFh + FYSc x Pc x UPWFc = FC x SPVF
where
FYSh = first year savings for heating (therms)
Ph = price of heating fuel ($/therm)
UPWFh = UPWF for heating (dimensionless)
FYSc = first year savings for cooling (kWh)
Pc = price of heating fuel ($/kWh)
UPWFc = UPWF for cooling (dimensionless)
FC = incremental change in first cost ($)
Expanding First Year Saving Terms
FYSh = U x h x HDD65
FYSc = U x c x CDD50
where
U = incremental change in U-factors
h = heating regression coefficient
c = cooling regression coefficient
HDD65 = heating degree days base 65oF
CDD50 = cooling degree days base 50oF
Define Scalars and Scalar Ratios
Sh = scalar ratio for heating = UPWFh/SPVF
Sc = scalar ratio for cooling = UPWFc/SPVF
S2 = SPVF
SR = scalar ratio, Sh/S2 and Sc/S2
Combining Terms
U x h x HDD65 x Ph x Sh + U x c x CDD50 x Pc x Sc = FC x S2
Divide by S2:
U x h x HDD65 x Ph x Sh + U x c x CDD50 x Pc x Sc = FC
S2 S2
Apply the definition of the scalar ratio:
U x h x HDD65 x Ph x SR + U x c x CDD50 x Pc x SR = FC
Scalar Ratio
Energy Savings
Economic Life
Fuel Escalation Rates
Heating
Cooling
Discount Rate
First Costs
Loan Life
Loan Interest Rate
Tax Rates
Federal
State
Economic Applications
1 - Single Measure, Long Life
Opaque Envelope Elements
U-factors, 30 years
2 - Multiple Measures, Long Life
Fenestration
U-factors, SHGC, 30 years
3 - Single Measure, Short Life
HVAC Equipment
COP, 15 years
Fenestration
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
0 10 20 30 40 50 60 70 80 90 100 110
Construction Option
Do
lla
rs First Costs
Energy
LCC
1-18
ASHRAE Std. 90.1R National Energy Model #1
0
200
400
600
800
1000
1200
1400
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Scalar Ratio
Avg
. Nat
iona
l Ene
rgy
(Mill
ion
Btu
)
90.1-1989
25%
50%
75%
ECONOMIC DATA INPUT CALC SCALARS HEATING COOLING
Loan Life (Years, max 100) 30 First Cost Scalar - S2 1.059 1.059
Discount Rate (%, Nominal) 6.1% Scalars - Sh & Sc 14.67 14.67INVESTMENT COST DATA Scalar Ratio - SR 13.9 13.9
Purchase and Installation ($) $1,000Down Payment ($) $0Loan ($) $1,000Loan Interest Rate (%) 8.3%Yearly Loan Payment ($) $91.35
HEATINGHeating Energy Price ($/therm) 5.60Heating Fuel Escalation Rate (%, Nominal) 2.5%
COOLINGCooling Energy Price ($/kWh) 0.08Cooling Fuel Escalation Rate (%, Nominal) 2.5%
TAXESState Tax Rate (%) 6%Federal Tax Rate (%) 15%Combined Tax Rate (%) (A) 20.1%
Notes
'Federal' x (1-'State') + 'State' = 'Combined'.
Table 1 ASHRAE Standard 90.1 - Scalar Ratio Calculations
SCALAR RATIOS
Federal tax liability, the combined tax rate is:
0
ECONOMIC CALCULATIONS
A = To account for the deductibility of State tax from
Scalar RatiosFuel Escalation Rates: 2-10%
Discount Rates: 4-16%Interest Rates: 6-16%
0
5
10
15
20
25
30
35
40
45
50
0 5 10 15 20 25 30 35 40 45 50
Measure Life (years)
Sc
ala
r R
ati
o
Current Standard 90.1 Economic Analysis Methods
ASHRAE Summer MeetingNashville, TNJune 28, 2004
ASHRAE/IESNA Standard 90.1
1-37