NW REM/RateTM & SEEM Comparison

Dan Wildenhaus, FluidThomas Anreise, Fluid

Regional Technical ForumJuly 16, 2013

REM/Rate Modification• The Need: As Northwest ENERGY STAR Homes is transferred to the

marketplace, continual support for the prescriptive options (BOPs) will be going away. Essentially the program will be moving away from “prescriptive” and toward “performance” for compliance.

• SEEM is not set up to be a program implementation tool, and REM/Rate already provides a widely used national platform

• Differentiation is that compliance in the NW will be based on projected annual energy use, not HERS score.

The ASK: Approve the use of a modified “NW” version of REM/Rate for use as a compliance tool for above-code homes. The tool will be permitted for use in demonstrating equivalency with BOP specifications. Tool will not be used to determine custom savings or overall consumption.

WHERE ARE WE GOING?

Initial Analysis

• Initial analysis* focused on difference in total consumption between the software to determine areas that would require attention

• Comparison of component loads across the two software guided the continuation of these efforts

* REM/Rate™ vs SEEM, Ben Hannas, Ecotope, 2012

Starting Point

Seattle Homes Boise Homes Kalispell Homes

Analysis Methodology• For the analysis, the BOP home was used as the Reference Home

(Baseline)• For all runs, all inputs were aligned between SEEM and

REM/Rate. Areas where input format varies between the two software:– Duct Leakage

• In SEEM, specified as supply or return duct leakage fraction of total system flow (0-1) at NSOP

• In REM/Rate, specified as CFM @50 pa– T-stat setpoints

• SEEM allows input of set up and set back temps, as well as schedule• REM/Rate allows input of set up temps and calculates set back temp internally

• Detailed tables in the workbook specify the inputs used

Analysis MethodologyTstat setpoints

SEEM REM

Set UpSetback (Furn)

Setback (HP) Set Up Setback

IDBoise3 70.3 65.6 66.1 70.3 Auto

WASeattle3 70.3 65.6 66.1 70.3 Auto

MTKalispell3 67.0 62.7 62.3 67 Auto

Set up and Set back temps consistent with most recent SEEM 94 calibration.

Consumption Analysis

• Component loads were examined and key areas underwent adjustment in REM/Rate software:– Ground Contact

• Foundation options narrowed to align with SEEM model and initial analysis results

• Ground contact model adjusted for closer alignment with SEEM heat loss outputs

– Heat Pump Behavior• Adjusted for closer alignment with SEEM, based on detailed SEEM

outputs (annual back up heat, etc.)– Amplitude of Infiltration and Duct Leakage models and heat

loss through building assemblies adjusted

Model Heat Cons Diff (kWh)

Heat Cons Diff (%)

Cool Cons Diff (kWh)

Cool Cons Diff (%)

Furnace runs

BOISE_1344_VENTCRAWL_DUCTATTIC_40KFURN18KAC base 1220 25% -160 -12%

BOISE_1344_VENTCRAWL_DUCTCOND_40KFURN18KAC base 1512 39% -94 -9%

KALISPELL_1344_VENTCRAWL_DUCTATTIC_40KFURN18KAC base 1095 15% -150 -22%

KALISPELL_1344_VENTCRAWL_DUCTCOND_40KFURN18KAC base 1640 28% -121 -23%

SEATTLE_1344_VENTCRAWL_DUCTATTIC_40KFURN18KAC base 1241 36% 39 6%

SEATTLE_1344_VENTCRAWL_DUCTCOND_40KFURN18KAC base 1224 44% 2 0%

BOISE_2688_CONDBASEMENT_DUCTATTICCOND_40KFURN18KAC Base -192 -2% 136 9%

BOISE_2688_CONDBASEMENT_DUCTCOND_40KFURN18KAC Base 456 6% 62 5%

KALISPELL_2688_CONDBASEMENT_DUCTATTICCOND_40KFURN18KAC Base -906 -6% 38 6%

KALISPELL_2688_CONDBASEMENT_DUCTCOND_40KFURN18KAC Base 266 2% 33 6%

SEATTLE_2688_CONDBASEMENT_DUCTATTICCOND_40KFURN18KAC Base -137 -2% 310 52%

SEATTLE_2688_CONDBASEMENT_DUCTCOND_40KFURN18KAC Base 106 2% 249 51%

Model Heat Cons Diff (kWh)

Heat Cons Diff (%)

Cool Cons Diff (kWh)

Cool Cons Diff (%)

Heat

Pump runs

BOISE_1344_VENTCRAWL_DUCTATTIC_30KASHP base 489 27% -49 -4%

BOISE_1344_VENTCRAWL_DUCTCOND_30KASHP base 485 34% -115 -12%

KALISPELL_1344_VENTCRAWL_DUCTATTIC_30KASHP base 605 21% -112 -19%

KALISPELL_1344_VENTCRAWL_DUCTCOND_30KASHP base 432 20% -153 -30%

SEATTLE_1344_VENTCRAWL_DUCTATTIC_30KASHP base 583 55% 59 11%

SEATTLE_1344_VENTCRAWL_DUCTCOND_30KASHP base 536 61% -28 -6%

BOISE_2688_CONDBASEMENT_DUCTATTICCOND_30KASHP Base 159 4% 89 6%

BOISE_2688_CONDBASEMENT_DUCTCOND_30KASHP Base -24 -1% 36 3%

KALISPELL_2688_CONDBASEMENT_DUCTATTICCOND_30KASHP Base 21 0% 45 8%

KALISPELL_2688_CONDBASEMENT_DUCTCOND_30KASHP Base -272 -6% 6 1%

SEATTLE_2688_CONDBASEMENT_DUCTATTICCOND_30KASHP Base 382 16% 277 54%

SEATTLE_2688_CONDBASEMENT_DUCTCOND_30KASHP Base 338 17% 192 42%

Sensitivity Analysis

• As ENERGY STAR qualification would be based on the modeled home’s improvement relative to the BOP home, continued analysis focused on the change in improvement across the two software, rather than total consumption/load

Sensitivity Analysis• Runs were constructed in which individual building

components were adjusted incrementally based on an expected range of values seen throughout the program to compare how the software view these adjustments:– Ceiling U-values (.030 - .017)– Duct Leakage (6%, 4%, 2% @50pa)– Heat Efficiency (85, 90, 94, 96%) (7.2, 8.0, 9.0 HSPF)– Infiltration (6, 5, 4, 3, 2 ACH50)– Ventilation Recovery (70, 85%)– Ventilation Rate (ASHRAE base, -20cfm, -10cfm, +10cfm, +20cfm)

• Examined to inform our work with the infiltration model amplitude– Slab Insulation (R-10, 15, 20 with R-5 perimeter)– Below Grade Wall R-value (R-16 – 28)

Sensitivity Analysis

• Incremental adjustments were modifications to a base BOP home, adjusted with all other measures left as-is

• Workbook tables describe the incremental adjustments for the Sensitivity Analysis and proposed measure packages for the “Scenario” runs

84.00 86.00 88.00 90.00 92.00 94.00 96.00 98.00800

850

900

950

1000

1050

1344 Boise

SEEMREM/Rate

Heating Efficiency

Heati

ng k

Wh/

year

84.00 86.00 88.00 90.00 92.00 94.00 96.00 98.00800

850

900

950

1000

1050

1344 Kalispell

SEEMREM/Rate

Heating Efficiency

Heati

ng k

Wh/

year

84.00 86.00 88.00 90.00 92.00 94.00 96.00 98.00800

850

900

950

1000

1050

1344 Seattle

SEEMREM/Rate

Heating Efficiency

Heati

ng k

Wh/

year

7.00 7.50 8.00 8.50 9.00 9.50700

750

800

850

900

950

1000

1050

1344 Boise

SEEMREM/Rate

Heating Efficiency

Heati

ng k

Wh/

year

7.00 7.50 8.00 8.50 9.00 9.50700

750

800

850

900

950

1000

1050

1344 Kalispell

SEEMREM/Rate

Heating Efficiency

Heati

ng k

Wh/

year

7.00 7.50 8.00 8.50 9.00 9.50700

750

800

850

900

950

1000

1050

1344 Seattle

SEEMREM/Rate

Heating Efficiency

Heati

ng k

Wh/

year

1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5600

650

700

750

800

850

900

950

1000

1050

2688 Boise

SEEMREM/Rate

Infiltration

Heati

ng k

Wh/

year

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5600

650

700

750

800

850

900

950

1000

1050

2688 Kalispell

SEEMREM/Rate

Infiltration

Heati

ng k

Wh/

year

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5600650700750800850900950

10001050

2688 Seattle

SEEMREM/Rate

Infiltration

Heati

ng k

Wh/

year

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5800

850

900

950

1000

1050

1344 Boise

SEEMREM/Rate

Infiltration

Heati

ng k

Wh/

year

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5800

850

900

950

1000

1050

1344 Kalispell

SEEMREM/Rate

Infiltration

Heati

ng k

Wh/

year

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5800

850

900

950

1000

1050

1344 Seattle

SEEMREM/Rate

Infiltration

Heati

ng k

Wh/

year

0.00 5.00 10.00 15.00 20.00 25.000

200

400

600

800

1000

1200

1344 Boise

SEEMREM/Rate

Slab Insulation

Heati

ng k

Wh/

year

0.00 5.00 10.00 15.00 20.00 25.000

200

400

600

800

1000

1200

1344 Kalispell

SEEMREM/Rate

Slab Insulation

Heati

ng k

Wh/

year

0.00 5.00 10.00 15.00 20.00 25.000

200

400

600

800

1000

1200

1344 Seattle

SEEMREM/Rate

Slab Insulation

Heati

ng k

Wh/

year

Sensitivity Analysis• Areas where slopes were not able to be brought in close alignment

are addressed via program requirements and modeling protocol• Program requirements and modeling limitations narrow the

available range of inputs, limiting the potential discrepancies in results

• Key Areas:– Duct Leakage

• Must be PTCS (6%) or tighter– Ventilation Rate

• ASHRAE 62.2 rates or similar– Slab Insulation

• No trade-offs for slab insulation. Must meet BOP requirements, must be modeled at BOP levels

“Scenario” runs

• Once differences were found to be minimal in most cases, both software were used to analyze trade-off compliance scenarios

• Exemplify how REM/Rate will be used to demonstrate compliance and how well the modeling predictions align with SEEM results

• Examples built around common tradeoff requests from Raters/Verifiers

“Scenario” Results

Furnace Savings over BOP (kWh)

Savings Diff.

(kWh)Path Model City SEEM says REM says

NWESH Envelope Path

1344Boise 718 782 65 Kalispell 957 958 1 Seattle 566 567 1

2688Boise 1199 1159 -40 Kalispell 1598 1467 -131 Seattle 997 821 -176

UA Wall Trade-off

1344Boise -81 -122 -41 Kalispell -120 -132 -12 Seattle -64 -93 -29

2688Boise -153 -147 6 Kalispell -215 -191 25 Seattle -120 -88 32

Infiltration/Equipment Trade-off

1344Boise 27 244 217 Kalispell 33 411 377 Seattle 32 147 115

2688Boise 484 704 220 Kalispell 671 1159 487 Seattle 412 499 87

Ducts Inside/Wall UA Trade-off1344Boise -159 -166 -7

Kalispell 1167 577 -590 Seattle 1485 811 -673

Heat Pump Savings over BOP (kWh)

Savings Diff.

(kWh)Path Model City SEEM says REM says

NWESH Envelope Path

1344Boise 244 308 64 Kalispell 340 396 56 Seattle 145 200 55

2688Boise 436 513 78 Kalispell 647 704 57 Seattle 273 337 64

UA Wall Trade-off

1344Boise -23 -49 -26 Kalispell -41 -59 -17 Seattle -13 -24 -12

2688Boise -49 -59 -9 Kalispell -80 -73 6 Seattle -30 -29 0

Infiltration/Equipment Trade-off

1344Boise -307 -655 -348 Kalispell -316 -777 -461 Seattle -185 -450 -265

2688Boise -265 -220 45 Kalispell -94 -103 -9 Seattle -196 -191 5

Ducts Inside/Wall UA Trade-off1344Boise 503 557 54

Kalispell 731 919 188 Seattle 202 303 101

“Scenario” results

• In these scenarios, the modified version of REM/Rate achieves compliance results which align closely with SEEM results.– Over 90% of runs had estimated savings difference

within 10% (of annual consumption)

– Compliance result is consistent across both software for all scenarios

Summary of Modifications to REM/Rate

• Reference Design homes built based on the NWESH BOP for each state• Northwest ENERGY STAR Homes Compliance report to be designed. Compliance is based

on projected annual energy use improvement as compared to the BOP reference design– Compliance is NOT based on HERS score

• Foundation types are locked to 4 foundation types available in SEEM• Window areas overridden to preset levels, prevents additional credit due to reduced

glazing areas• Shading factor inputs for windows locked to SEEM values• Ground contact model adjusted for closer alignment with SEEM outputs• Duct leakage model adjusted for closer alignment with SEEM outputs• Heat pump behavior adjusted to more closely match SEEM heat pump characteristics• Infiltration and ventilation heat loss model adjusted to more closely match SEEM

outputs• Tankless water heaters derated for consistency with DOE/RTF recommendations• DHW gal./day consumption overridden to RTF values• HRV/ERV efficiency input set to align with SEEM input

Summary of Limitations to Modeling Inputs

• Locked NW REM Libraries for building surfaces will be based on Ecotope heat loss tables or other accepted methods

• Foundations must be modeled as foundation types found in SEEM• Slab insulation must meet BOP prescriptive requirements and must be

modeled at BOP level. No trade-offs are available for this measure.• Window areas are overridden to preset levels, prevents consumption

reduction due to reduced glazing areas• Shading factor inputs for windows have been locked• Duct leakage must meet or exceed PTCS standards No tradeoffs for duct

leakage over 6%• Infiltration inputs limited to the range of 2.0 - 6.0 ACH50

• Program default of exhaust ventilation strategy. Integrated supply air ventilation systems must be modeled with air handler fan wattage as the ventilation fan wattage and with rates as specified by NWESH

Future Updates

• Northwest ENERGY STAR Homes has entered an agreement with the EPA that states the EPA will provide updated Reference Design Homes (BOP/minimum requirements) to AEC on an annual basis.

• This will require some interaction with program implementers in terms of working with the RTF Residential Subcommittee on an annual basis.

The Ask

Approve the use of a modified “NW” version of REM/Rate for use as a compliance tool for above-code homes. The tool will be permitted for use in demonstrating equivalency with BOP specifications and will be updated on the same schedule as the NW ENERGY STAR homes BOP paths (if not more frequently as AEC provides updates to all versions of REM/Rate).