Residential Duct Insulation
New Deemed Measure Proposal –
A Second Look
Regional Technical Forum
May 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
Measure
Duct Insulation
(Existing <3/4" 100%, install
R11)
Duct Insulation
(Existing <3/4" 50% / R11
50%, install R11)
Duct Insulation
(Existing <3/4" 50% / R4.2
50%, install R11 on
uninsulated)
Heating
Zone
1
2
3
1
2
3
1
2
3
Measure
Energy Levelized
Measure
Life
Savings
Cost
Cost
(years)
(kWh/yr) (mils/kWh)
805
7
18
$662
1,542
-29
2,236
-41
401
7
18
$331
768
-29
1,115
-41
397
8
18
$331
761
-29
1,104
-41
B/C
1.7
3.2
4.7
1.7
3.2
4.7
1.7
3.2
4.7
2
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
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
3
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?
4
Residential Duct Insulation
New Deemed Measure Proposal
Regional Technical Forum
April 6th, 2010
Proposed Deemed Measures
Measure
Flex Duct Replacement
(Existing R4.2 or less; install R8)
Duct Insulation
(Existing <1.5", install R11)
Duct Insulation
(Existing <3/4", install R11)
•
•
•
Heating
Zone
1
2
3
1
2
3
1
2
3
Measure
Energy Levelized
Measure
Life
Savings
Cost
Cost
(years)
(kWh/yr) (mils/kWh)
155
423
18
$839
297
189
431
109
212
216
18
$662
404
81
587
34
805
7
18
$662
1,542
-29
2,236
-41
B/C
0.3
0.5
0.7
0.4
0.9
1.2
1.7
3.2
4.7
Savings and costs are “per house”
Insulation of flex duct not allowed
Cooling Zone 1 shown. Zones 2 and 3 are very similar (slightly larger savings)
6
Savings Methodology & Inputs
• SEEM Modeling
• 3 Site Built Prototypes (1344 ft2, 2200 ft2, 2688 ft2)
– 1344 and 2200 prototypes: supply ducts in crawl; return in attic
– 2688 prototype: basement, so not included in final numbers
• Fully Weatherized (Package 8) with Sealed (PTCS) Ducts
– Attic: R38, Floor: R30, Windows: u-0.30, Walls: R-13, ACH: 0.35
• Modeled both electric FAF and Heat Pump
– Heat Pump = 8.0 HSPF (HPA3)
• Used the 5 baseline heat pump control strategies
• Duct Insulation Options
– Flex Duct
• Replace R-4.2 flex duct with R-8 flex duct
– (R-11 flex duct was not analyzed because of high cost)
– Hard Duct
• Uninsulated (3/4” or less) to R-11
• R-4.2 (1.5” or less) to R-11
• Used “True R-Values”, assuming round ducts & R-2.8/inch
– Assumed R-2 for “uninsulated” ducts case
7
“True R-Values of Round Residential Ductwork”
Larry Palmiter and Erin Kruse, Ecotope, Inc. ACEEE Summer Study 2006
8
More Inputs
Prototype
Small (1344)
Medium (2200)
Large (2688)
Average Size (sqft)
Regional
Mix
75%
16%
9%
1,602
Heating System
Heat Pump
80%
FAF
20%
Duct
Foundation
Insulation
Area (ft2)
82%
1344
18%
1584
0%
not used
1,495
1386
Modeled Duct
Area (ft2)
290
380
not used
306
Important Assumption:
Savings between Small
and Medium prototypes
varies by a factor of ~ 2.
Cooling System
AC
No AC
80%
20%
Supply Duct in
Return Duct in
Nominal
Unconditioned Space Unconditioned Space
Duct Dia. (in) lin. Feet sq. feet lin. Feet sq. feet
6
49%
35%
0%
0%
8
32%
31%
0%
0%
14
16%
28%
100%
100%
18
3%
6%
0%
0%
9
Annual Savings (kWh/year)
Intermediate Savings Calculation Results
10
ETO Impact Evaluation Results
• Equivalent kWh (assuming 80% gas efficiency):
– ranges from 400 to 1050 kWh/year.
11
Measure Cost
Cost
Flex Duct Replacement
Duct Insulation
($/house)
R4.2 to R8
R4.2 to R11 R0 to R11
ETO
n/a
$372
$601
Bruce M.
$839
n/a
$723
Average
$839
$662
$662
•
ETO Data
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 R11 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
•
•
Project Cost
•
$2,000
$1,500
$1,000
$500
$-
$535 per job
$0.29/linear foot/∆ R-value
1
51
Job Number
– 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
ETO Data
$1.00
$ / lin. ft / R
•
101 151 201 251 301 351 401 451 501
$0.75
$0.50
$0.25
$1
51
101 151 201 251 301 351 401 451 501
Job Number
12
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
+
-
•
By House Square Footage
+
-
•
Better normalization
More complex; not intuitive; (partial insulation?)
By Linear Feet of Duct
+
-
•
An attempt at normalizing
House square footage doesn’t necessarily correspond to duct insulation area (two stories,
basements, etc.)
(Partial insulation?)
By Foundation Area
+
-
•
Simple, can’t get it wrong
The assumed averages may not match what gets reported
What about houses with some insulation already existing?
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
14
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)
15
Proposed Deemed Measures (again)
Measure
Flex Duct Replacement
(Existing R4.2 or less; install R8)
Duct Insulation
(Existing <1.5", install R11)
Duct Insulation
(Existing <3/4", install R11)
•
•
•
Heating
Zone
1
2
3
1
2
3
1
2
3
Measure
Energy Levelized
Measure
Life
Savings
Cost
Cost
(years)
(kWh/yr) (mils/kWh)
155
423
18
$839
297
189
431
109
212
216
18
$662
404
81
587
34
805
7
18
$662
1,542
-29
2,236
-41
B/C
0.3
0.5
0.7
0.4
0.9
1.2
1.7
3.2
4.7
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?
16