NW REM/ Rate TM & SEEM Comparison

1. NW REM/RateTM & SEEM Comparison Dan Wildenhaus, Fluid Thomas Anreise, Fluid Regional Technical Forum July 16, 2013

2. 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.

3. WHERE ARE WE GOING?

4. 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

5. Starting Point Seattle Homes Boise Homes Kalispell Homes

6. 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

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

8. 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 modelsand heat loss through building assemblies adjusted

11. 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

12. 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)

13. 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

19. 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

20. “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

21. “Scenario” Results

24. “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

25. 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

26. 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

27. 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.

28. 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 specificationsand 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).