Residential Duct InsulationNew Deemed Measure Proposal –

A Second Look

Regional Technical ForumMay 4th, 2010

At the April RTF Meeting…• Look into the ETO’s evaluation numbers in more detail and determine

whether/how the RTF should apply them• Recommend changing a few assumptions, requirements

– 75% of ducts in crawlspace, vs 90%; 150 square foot minimum duct area, vs 250.

• Recommendation to run model with 50% duct insulated, 50% un-insulated

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Measure Life

Energy Savings

Levelized Cost

B/C

(years) (kWh/yr) (mils/kWh)1 805 7 1.72 1,542 -29 3.23 2,236 -41 4.71 401 7 1.72 768 -29 3.23 1,115 -41 4.71 397 8 1.72 761 -29 3.23 1,104 -41 4.7

Duct Insulation(Existing <3/4" 100%, install R11)

18 $662

MeasureHeating

ZoneMeasure

Cost

Duct Insulation(Existing <3/4" 50% / R4.2 50%, install R11 on uninsulated)

18 $331

Duct Insulation(Existing <3/4" 50% / R11 50%, install R11)

18 $331

Another Look at ETO’s In-House Evaluation Numbers

• Savings convert to about 400 kWh/year• PTCS Duct Sealing was required, but may not have always

occurred• Median linear feet: 182

3

Number 2006-2007 ETO study Measure counts

1 Duct Sealing 388

2 Duct Insulation 285

Overlap

3 Duct Insulate+duct sealing 191

4 Only Duct Insulation 9

5 Only Duct sealing 31

6 Only Duct Seal + Duct insulate 13

Thoughts?

• Is this Deemable?– Early sunset date with a required evaluation

effort?

• Savings metric? – Per house? Per linear foot? Other?

• Savings Calculation?– Use 50/50 savings?

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Residential Duct InsulationNew Deemed Measure Proposal

Regional Technical ForumApril 6th, 2010

Proposed Deemed Measures

• Savings and costs are “per house”• Insulation of flex duct not allowed• Cooling Zone 1 shown. Zones 2 and 3 are very similar (slightly larger savings)

Measure Life

Energy Savings

Levelized Cost

B/C

(years) (kWh/yr) (mils/kWh)1 155 423 0.32 297 189 0.53 431 109 0.71 212 216 0.42 404 81 0.93 587 34 1.21 805 7 1.72 1,542 -29 3.23 2,236 -41 4.7

18Duct Insulation(Existing <3/4", install R11)

MeasureHeating

ZoneMeasure

Cost

$662

$662

$83918

18

Flex Duct Replacement(Existing R4.2 or less; install R8)

Duct Insulation(Existing <1.5", install R11)

6

Savings Methodology & Inputs

7

“True R-Values of Round Residential Ductwork”Larry Palmiter and Erin Kruse, Ecotope, Inc. ACEEE Summer Study 2006

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More InputsPrototype

Regional Mix

Duct Insulation

Foundation Area (ft2)

Modeled Duct Area (ft2)

Small (1344) 75% 82% 1344 290Medium (2200) 16% 18% 1584 380Large (2688) 9% 0% not used not usedAverage Size (sqft) 1,602 1,495 1386 306

Important Assumption: Savings between Small and Medium prototypes varies by a factor of ~ 2.

Heat Pump 80%FAF 20%

Heating System

AC 80%No AC 20%

Cooling System

lin. Feet sq. feet lin. Feet sq. feet6 49% 35% 0% 0%8 32% 31% 0% 0%

14 16% 28% 100% 100%18 3% 6% 0% 0%

Supply Duct in Unconditioned Space

Return Duct in Unconditioned SpaceNominal

Duct Dia. (in)

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Intermediate Savings Calculation ResultsAn

nual

Sav

ings

(kW

h/ye

ar)

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ETO Impact Evaluation Results

• Equivalent kWh (assuming 80% gas efficiency):– ranges from 400 to 1050 kWh/year.

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Measure Cost

• ETO Data– Based on 522 duct insulation jobs– All started at R-2 or lower

• While it’s possible to calculate a cost for the R-4.2 to R-11 case ($372), it’s probably way too low. So, it was assumed to have the same cost as the uninsulated case (same installation cost, same R-11 batt)

– Median Cost• $535 per job• $0.29/linear foot/∆ R-value

– Median Job Size: 182 linear feet• Note on Savings – this compares well with what was

modeled in SEEM (assuming 30% duct area in contact with floor or attic insulation)

• Bruce Manclark Data– Based on calls to installers– R8 flex duct = $4 - $5 per linear foot

• includes removal/disposal of old, installation of new– R-11 on hard ducts: $1.50 to $1.65 per square foot of

material• Material needed is 1.5 times uninsulated duct area

$-

$500

$1,000

$1,500

$2,000

1 51 101 151 201 251 301 351 401 451 501

Proj

ect C

ost

Job Number

ETO Data

$-

$0.25

$0.50

$0.75

$1.00

1 51 101 151 201 251 301 351 401 451 501

$ /

lin. ft

/ R

Job Number

ETO Data

Flex Duct ReplacementR4.2 to R8 R4.2 to R11 R0 to R11

ETO n/a $372 $601Bruce M. $839 n/a $723Average $839 $662 $662

Duct InsulationCost ($/house)

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Proposed Measure Requirements• Measure Definitions

– Flex Duct Replacement• Existing supply flex duct shall be rated R-4.2 or lower. Replacement flex duct shall be rated R-8 or higher.

– Hard Duct: Existing <1.5” thick, install R-11• Existing supply duct insulation shall be 1.5” thick or less. Supply and return ducts in unconditioned

spaces shall be insulated to a nominal value of R-11 or higher.– Hard Duct: Uninsulated (existing <3/4” thick), install R-11

• Existing supply ducts shall have less than 3/4” of insulation. Supply and return ducts in unconditioned spaces shall be insulated to a nominal value of R-11 or higher.

• Measure Requirements– Only applies to houses where a significant portion of the supply ducts are located in a vented,

unconditioned crawlspace or attic, or in an unconditioned garage. – Significant means: no less than 90% (by area) or 250 square feet, which ever is less.

– Ducts shall be sealed for air-leaks to PTCS standards prior to insulating.– Insulation installations shall follow the RTF’s Weatherization Specifications.– Flex duct installations shall follow manufacturer’s instructions.

• Reporting Requirements– Crawlspace Foundation Area– House Square Footage– Amount of Insulation Installed

• Length of flex duct• Total area of duct insulation

– Project Cost• Sunset Date

– In 2 years, the measure savings will be re-visited by the RTF.13

How Should Savings be Reported?• By House

+ Simple, can’t get it wrong- The assumed averages may not match what gets reported- What about houses with some insulation already existing?

• By House Square Footage+ An attempt at normalizing- House square footage doesn’t necessarily correspond to duct insulation area (two stories,

basements, etc.)- (Partial insulation?)

• By Foundation Area+ Better normalization- More complex; not intuitive; (partial insulation?)

• By Linear Feet of Duct+ Even better normalization- More complex; less intuitive; reporting errors are common- Doesn’t take into account different duct sizes

• By Duct Area+ Good normalization- Difficult to determine and verify; complex

The proposal is by House. Whole house, or nothing.Discussion Encouraged, Implementers Should Also Discuss

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Some More Things to Think About…

• Do we have adequate confidence to deem these measures?– Modeling assumptions

• Existing & replacement R-values don’t account for “real world” installations• House size and duct location both have a significant impact on the savings results

– How should existing insulation levels be verified?

• Should the measures be designed in a different way?– Higher insulation levels for colder climates?– More/less options for existing insulation levels/types?

• Should the RTF attempt to deem additional duct-related measures?– Duct Repairs (replacing damaged flex duct)– Duct Re-Design (to increase airflow for heat pumps)

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Proposed Deemed Measures (again)

• Savings and costs are “per house”• Insulation of flex duct not allowed• Cooling Zone 1 shown. Zones 2 and 3 are very similar (slightly larger savings)

Next Steps: Thoughts?

Measure Life

Energy Savings

Levelized Cost

B/C

(years) (kWh/yr) (mils/kWh)1 155 423 0.32 297 189 0.53 431 109 0.71 212 216 0.42 404 81 0.93 587 34 1.21 805 7 1.72 1,542 -29 3.23 2,236 -41 4.7

18Duct Insulation(Existing <3/4", install R11)

MeasureHeating

ZoneMeasure

Cost

$662

$662

$83918

18

Flex Duct Replacement(Existing R4.2 or less; install R8)

Duct Insulation(Existing <1.5", install R11)

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