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Residential Duct Insulation

Residential Duct Insulation. New Deemed Measure Proposal – A Second Look Regional Technical Forum May 4 th , 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

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Residential Duct Insulation

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  1. Residential Duct Insulation New Deemed Measure Proposal – A Second Look Regional Technical Forum May 4th, 2010

  2. 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

  3. 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

  4. 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?

  5. Residential Duct Insulation New Deemed Measure Proposal Regional Technical Forum April 6th, 2010

  6. 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)

  7. Savings Methodology & Inputs • SEEM Modeling • 3 Site Built Prototypes (1344 ft2, 2200 ft2, 2688 ft2) • 1344 and 2200 prototypes: supply ducts in crawl; return in attic • 2688 prototype: basement, so not included in final numbers • Fully Weatherized (Package 8) with Sealed (PTCS) Ducts • Attic: R38, Floor: R30, Windows: u-0.30, Walls: R-13, ACH: 0.35 • Modeled both electric FAF and Heat Pump • Heat Pump = 8.0 HSPF (HPA3) • Used the 5 baseline heat pump control strategies • Duct Insulation Options • Flex Duct • Replace R-4.2 flex duct with R-8 flex duct • (R-11 flex duct was not analyzed because of high cost) • Hard Duct • Uninsulated (3/4” or less) to R-11 • R-4.2 (1.5” or less) to R-11 • Used “True R-Values”, assuming round ducts & R-2.8/inch • Assumed R-2 for “uninsulated” ducts case

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

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

  10. Intermediate Savings Calculation Results • Annual Savings (kWh/year)

  11. ETO Impact Evaluation Results • Equivalent kWh (assuming 80% gas efficiency): • ranges from 400 to 1050 kWh/year.

  12. 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

  13. 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.

  14. 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

  15. 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)

  16. 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?

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