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Residential Weatherization Calculator

Deriving Realistic Savings Estimates for the “Uninsulated” House

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What Is The Issue?

• All prior evaluations have measured “average” savings for the mix of ResWX measures installed in programs

• The “average” house already was partially weatherized

• Savings from the installation of individual measures has been estimated using engineering simulation models “calibrated” to an average package of measures.

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Simulation Model Assumptions

• Historically, all “cost-effectiveness” analysis has held “consumer behavior” (i.e., thermostat set-point) constant across all thermal integrity levels– 65 F weighted average set point

• 70 F – 8 hours/day• 62 F – 16 hours/day

• This assumes that consumers in very poorly insulated homes would prefer to be just as comfortable as those in well insulated homes

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Prior Modeling Assumption Justification

• Experience in the Hood River Conservation Project showed that once houses were “super-weatherized” consumers:

– Stopped burning as much wood

– Set up the thermostat on their electric heat

• BPA ResWX evaluations have shown that “net” savings increased over time as comparison group use “rebounded” after the rate increases of the early 1980’s dissipated

• If they can afford it, people will keep their homes warmer

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Re-Calibration Process

• Compared Simulated Space Heating Use with Sub-metered Space Heating Use

• Sample – 617 SGC Homes w/Zonal Heat (Sample contains only sub-metered homes with space heating use of at least 1.0 kWh/sq/ft/yr.)

• Some homes had wood heat & used it• Average Use = 3.48 kWh/sq.ft./yr• Average Size = 1596 sq.ft.• Weather – Portland & Seattle

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Approach

• Fit Regression Line Through Sub-metered Use vs. Building Heat Loss Rate

• Adjusted SUNDAY Simulation Set-point Temperature, Thermal Mass and Internal Gains to Match “Heating Slope” of SGC Data Set

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SGC Sub-metered Use vs. Building Heat Loss Rate

Zone 1 - SGC Homes with Zonal Heating Systems

R2 = 0.26

0

5,000

10,000

15,000

20,000

175 275 375 475 575 675 775

Building UA (BtuF)

An

nu

al S

pac

e H

eati

ng

Use

(k

Wh

)

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Simulations Results Compared to SGC Submetered Data – Total UA

0

5,000

10,000

15,000

20,000

25,000

150 350 550 750Building UA (BtuF)

Sp

ace

Hea

tin

g U

se (

kW

h/y

r) Portland - Std

Seattle Std

Portland - w/Takeback

Seattle w/Takeback

Portland w/Basement& TakebackSeattle w/Basement &TakebackSGC Submetered

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Simulations Results Compared to SGC Submetered Data – UA/Sq.Ft.

0

5,000

10,000

15,000

20,000

25,000

0.10 0.20 0.30 0.40 0.50 0.60Building UA/Sq.Ft. Floor Area (BtuF)

Sp

ace

Hea

tin

g U

se (

kW

h/y

r) Portland - Std

Seattle Std

Portland - w/Takeback

Seattle w/Takeback

Portland w/Basement& TakebackSeattle w/Basement &TakebackSGC Submetered

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Sample Results Zone 11350 sq.ft. Home w/Zonal Heat

0

500

1,000

1,500

2,000

2,500

3,000

Ann

ual S

avin

gs (

kWh)

FLOORR19

FLOORR30

WALL R11 ATTICR19

ATTICR38

DG Low EWINDOW

CL35

Current Value First Measure Middle Measure Last Measure

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Recommendation

• Use Standard Modeling Input Assumptions for purposes of determining “cost-effectiveness”

• Use “Modified” Modeling Input Assumptions for purposes of estimating “realizable” savings from weatherization– Thermostat set-point decreases by 0.1 F for every 15

Btu-F Increase in Heat Loss Rate for non-basement house and 0.15 F for homes with basements

– 3000 Btu/hr Internal Gains (Inefficient Appliances)