PSE Delta Q Project Results

Bruce Manclark, Delta T

Bob Davis, Ecotope

RTF meeting, 5 January 2009

Puget Sound Energy Delta Q Project Description

• 40 homes divided into two groups– 20 homes received PTCS duct sealing– 20 homes received a two stage duct sealing

procedure• High pressure holes first• Low pressure holes next

• Time accounting of each activity (overhead, testing, sealing)

The Tests

• Duct Blaster: two point (25 and 50 Pa) test of supply + return plus one side (other side leakage determined by subtraction).

• Delta Q (series of automated blower door tests with air handler off and on)

• Sum of the flows: comparing air handler flow (measured with TrueFlow) to calibrated flow hood hood measurements.

• Testing was performed after each round of duct repair.

The Quick Summary

• Delta Q is not a test for (most) field crews to use.• Delta Q can be a valuable part of program

design and QA.• Duct sealing is cheap, it’s the bidding, the testing

and the driving that cost too much.• Duct sealing is a lousy description; duct repair

(reconstruction?) is better.• Some homes need experts to diagnose and fix

them. (But most do not.)

What is Delta Q?

• Duct leakage measurement method– Measures supply & return leakage to outside at

operating conditions– Originally proposed about 10 YO; specifics of testing

developed by Ecotope, LBNL, BNL in late 90s onward– Univ of Illinois Small Bldgs Research Council (SBRC)

completed report last summer on updated method

• Requires blower door with automated control and specialized software

• Best suited to existing construction (typically leakier and not subject to pass/fail testing)

The Big Problems With The Duct Blaster Test

• It measures leakage at one pressure at one point in the system.

• No programs require 2 point tests (25 and 50); this would at least enable error checking

• Most programs do not encourage/require split system testing.

• It’s sort of complicated.• It takes too much time.• It’s easy to do wrong.• It’s tempting to lie, especially on the pre-sealing

number…

+2125+50

Duct Blaster Testing tests with the entire duct system at the same pressure

Leakage at operating conditions varies greatly

Category Number of cases median

Single story house 24

2 story house 14

House size (ft2) 1850

-- size lower quartile1 1600 ft2

--size 75th %ile2 2800 ft2

Houses built pre-1980 17

Houses built 1980-1990 11

System airflow3 (CFM) 34 898

Supply plenum static pressure (Pa) 36 34.5

Return plenum static pressure (Pa) 36 67.5

As found system leakage to out at 50 Pa4

20 521

As found system leakage to out at 25 Pa

20 346

Test Test sequence n Median leakage (CFM)

dQbothsides As Found 25 294

DB to out at 50 Pa

As found 20 521

DB to out at 25 Pa

As found 20 346

dQbothsides Final 25 117

DB to out at 50 Pa

Final 22 175

DB to out at 25 Pa

Final 23 110

The Not So Dry Hole

“an oil well that has been drilled but that produces no oil, or not enough to make it economically profitable”

– Don’t duct seal ducts in conditioned space– Don’t waste time on (most) returns in the NW– Always duct seal the high pressure holes

regardless of Duct Blaster number

Insert Cites data

• Total dropped from 209 CFM@ 50 Pa to 111 CFM@ 50Pa.

• The supply only leakage was reduced from 144 CFM@ 50Pa to 74 CFM@ 50Pa.

• BUT.. delta Q estimated supply leakage at 125cfm

• After cut in: delta Q reported 45 CFM

The Cites Residence(a small epiphany)

Floor Insulation Crews Can Really Destroy Duct Systems

Duct Sealing can’t happen without duct repair

The House of No Return

Some Jobs Need an Expert

Average DQ Test Time

Average Duct Pressurization Test Time

Average Sum of Flows Test

Average High Pressure Duct Sealing Time

Average Second phase High Pressure Duct Seal Time

Average Total High Pressure Approach Duct Seal Time

Average PTCS Duct Seal Time

55 min. 57 min. 31 min 124 min 101 min. 225 min. 174 min

Where the time went

Labor Rates Neighborhood ApproachHourly Rates $75 $75$/mile $1.00 $1.00Miles RT 45 15

Strategy HoursLabor Cost Miles

Bidding Cost

Close rate

Cost per sold job hours

Labor Cost Miles

Sunk Time cost

Bid/seal 2 $150 $45 $195 50% $390 1 $75 $45 $120

Knock once test 1 $75 $45 $120

Knock once w/o testing 1 $75 $45 $120

Knock once Neighborhood with testing 0.2 $15 $15 $30

Knock once Neighborhood w/o testing 0.2 $15 $15 $30

In conjunction with other WX measures with testing 0.1 $8 $5 $12 50% 24 1 $75 $45 $120In conjunction with other WX measures w/o testing 0.1 $8 $5 $12 50% 24 1 $75 $45 $120Stand alone, no bid, with testing 1 $75 $45 $120

Strategy Hours Hours Hours

1.25 $94 3 $225 4.45 $334 $15 $349 $50 $399 $133

3 $225 3.2 $240 $15 $255 $50 $305 $102

1.25 $94 2.5 $188 4.75 $356 $45 $425 $50 $475 $190

2.5 $188 3.5 $263 $45 $332 $50 $382 $153

1.25 $94 3 $225 5.25 $394 $45 $439 $50 $489 $163

Bidding Crew Sunk Time

Labor Rates Neighborhood ApproachHourly Rates $75 $75$/mile $1.00 $1.00Miles RT 45 15

Strategy

0.2 $15 $15 $30

0.2 $15 $15 $30

0.1 $8 $5 $12 50% 24 1 $75 $45 $120

0.1 $8 $5 $12 50% 24 1 $75 $45 $120

1 $75 $45 $120

Strategy HoursLabor Costs Hours

Labor Costs Hours

Labor Costs

Mileage Costs Total Materials

Total All

Cost/Hr duct seal

Bid/seal 1.25 $94 3 $225 9.25 $694 $135 $829 $50 $879 $293Knock once test 1.25 $94 3 $225 5.25 $394 $45 $439 $50 $489 $163Knock once w/o testing 3 $225 4 $300 $45 $345 $50 $395 $132Knock once Neighborhood with testing 1.25 $94 3 $225 4.45 $334 $15 $349 $50 $399 $133

Knock once Neighborhood w/o testing 3 $225 3.2 $240 $15 $255 $50 $305 $102In conjunction with other WX measures with testing 1.25 $94 2.5 $188 4.75 $356 $45 $425 $50 $475 $190In conjunction with other WX measures w/o testing 2.5 $188 3.5 $263 $45 $332 $50 $382 $153Stand alone, No bid with testing 1.25 $94 3 $225 5.25 $394 $45 $439 $50 $489 $163

TotalsTesting Time Sealing Time

Directions

• Drive the cost of duct repairs down, not up– No bidding– No random drives in Puget Land– No one at a time buying (buy in bulk)– Increased QA– Give it away (because its cheaper that way, at

least when bundled with other services)

More Directions

• Improve duct training – More specifics (how to fix typical problems

with very clear, visual instructions. Use 21st century graphics programs.)

– Include program managers

• Fix the holes that matter

• Negotiate pricing with delivery contractors

• Develop expert contractors

Testing directives?

• Supply side testing

• TrueFlow on returns vs TF at return slot

Cost Effectiveness

• Use 1850 ft2 prototype (3 vintages) • Seattle TMY3 weather (so far)• Feed supply and return leakage fractions (from delta Q,

TrueFlow, and measured plenum static pressures) into SEEM

• Compare median as-found leak fractions for both “high pressure” and “50% reduction (PTCS) cases to midpoint (“high pressure” cases only) and final values to find savings

• Use 20 year measure life and 2 discount rates to find levelized cost of savings

• Heat pump control mix same as RTF mix for base case

Gas lev. Cost

Gas lev. Cost

Elec. Lev cost

Elec. Lev cost

Job type Duct seal type Savings Savings Measure ($/Th) ($/Th) ($/kWh) ($/kWh)

    (Therms) (kWh) cost7% disc. rate

4% disc. rate

7% disc. rate

4% disc. rate

Bid/seal 50% reduce 93 1256 $ 879 ($0.89) ($0.69) ($0.066) ($0.051)

Knock once w/o testing 50% reduce 93 1256 $ 395 ($0.40) ($0.31) ($0.030) ($0.023)

In conjunction with other WX measures with testing 50% reduce 93 1256 $ 475 ($0.48) ($0.37) ($0.036) ($0.028)

In conjunction with other WX measures with testing

1 step high press leak 78 1082 $ 475 ($0.57) ($0.45) ($0.041) ($0.032)

Bid/seal

2 step high press leak 151 2058 $ 879 ($0.55) ($0.43) ($0.040) ($0.031)

Knock once Neighborhood w/o testing

2 step high press leak 151 2058 $ 305 ($0.19) ($0.15) ($0.014) ($0.011)