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REM as a Compliance Tool Infiltration Trade-off

REM as a Compliance Tool Infiltration Trade-off. REMRate vs. SEEM February 19th , 2014. Presentation Objectives. To approve REM Rate for use as a compliance tool with infiltration as a trade-off measure. Infiltration has been tested for trade-off with heating system efficiency.

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REM as a Compliance Tool Infiltration Trade-off

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  1. REM as a Compliance Tool Infiltration Trade-off REMRate vs. SEEM February 19th, 2014

  2. Presentation Objectives • To approve REM Rate for use as a compliance tool with infiltration as a trade-off measure. • Infiltration has been tested for trade-off with heating system efficiency. • Most frequent request for trade off • Presented at July 2013 meeting; RTF concluded infiltration not ready for use in trade-offs and requested further analysis • NW REM Rate has been approved for use as a compliance tool, allowing a rater to trade off or combine any number of measures to create a home that meets or beats the BOP home on annual energy use. The caveats that were applied during the initial approval: • No use of infiltration as a trade-off component. • No use of slab insulation as a trade-off component (so an R-60 passivehaus slab or an R-5 BOP slab both have to be modeled as BOP-level) • No specifying heat pumps above 9.0 hspf

  3. Compliance • Modeled home achieves equivalent or better energy performance than the reference design home • Reference design home is a home that meets the minimum standards for Energy Star. • REM Rate qualifies as a compliance tool if it provides the same results as SEEM for compliance tests. • i.e. both tools agree on which trade-off scenarios provide compliance.

  4. What is REM Rate? • REM Rate – Seasonal proprietary modeling simulation tool designed for users trained in RESNET standards. • “Northwest” REM Rate has been modified for closer alignment with SEEM outputs (see July presentation and decision) and Northwest ENERGY STAR Homes’ specific modeling guidelines. • No significant changes were made to REMRate’s engine since last RTF presentation 7/16/2013 • Analysis was expanded

  5. Initial analysis/presentation Sensitivity Analysis

  6. Initial analysis/presentation Sensitivity Analysis

  7. Initial analysis and presentation • CLEAResult team also analyzed 4 scenarios in which multiple trade-offs were applied, according to frequently requested/currently available options • Envelope upgrade – improved walls and windows • Wall/Ceiling U-value trade-off • Ducts inside vs. wall U-value trade-off • Infiltration vs. Heating efficiency • Discrepancies in the Infiltration vs Heating efficiency trade-off prompted a request for further analysis

  8. Current Analysis – REM Rate and SEEM Simulations Conducted. • Three climate locations: • Boise • Kalispell • Seattle • Two duct locations •  Attic • Conditioned space • RTF prototype homes • 1344 • 2688 (basement runs only) • Two heating fuels/systems • Gas furnace with AC •  Heat Pump • Multiple foundation types • Post + pier • Vented crawlspace • Slab on grade • Conditioned basement

  9. Scenarios Simulated:

  10. REM Rate vs SEEM – Matching Inputs • REM Rate allows user to assign ductwork to multiple locations. (half can be located in the attic and the other half the conditioned basement, for example.) • For Conditioned basement runs, 50% of the supply and 50% of the return were allocated to the attic and conditioned space. So for the basement homes, we have models with the following duct locations: • Conditioned space • Conditioned space/Attic • SEEM only allows one duct location for supply and one for return. • For the SEEM runs, the “Conditioned space/Attic” duct location run results are an average of two identical runs: one with 100% of the ductwork in the Attic and  one with 100% of the ductwork in Conditioned space

  11. REM Rate & SEEM Matching Inputs (Contd.) • REM Rate has an auto setback of 2 degrees. SEEM thermostat set-points and schedule were changed to match REM Rate inputs • Set up temps as defined by calibration from May, 2013. Described here:

  12. REM Rate & SEEM Matching Inputs (Contd.) • REM Rate auto-calculates internal gains. SEEM internal gains inputs were adjusted to match REM Rate via HERS formulae.

  13. Compliance Comparison • Scenario are said to “Agree” when REM Rate and SEEM both indicate compliance or non-compliance for the same scenario. • Agreement for almost all HP scenario • 72 % of the Furnace scenario agree.

  14. Compliance Comparison – Heat Pump • The following scenario’s do not show agreement • In each case, REM Rate estimates compliance; SEEM does not. • Difference in estimated heating energy consumption vary between 55 to 223 kWh. • This is manifestation of the difference in slope presented in slide 6. To get a complete understanding of agreement between HSPF and ACH trade-off, more scenarios need to be modeled. • Staff recommend that REM Rate be used for HP trade-off for only those scenarios that show agreement with SEEM.

  15. Compliance Comparison- Furnace. • 17 of the 24 disagreements between REM Rate and SEEM are 3 ACH – 90 AFUE tradeoff. • Estimates of consumption between SEEM and REM Rate vary from 50 kWh and 160 kWh for this tradeoff. • No consistent pattern in difference in consumption. i.e. SEEM consumption not always higher than REM Rate, or vice-versa. • For 10 of the 24 disagreements, REM Rate shows no change in heating energy consumption (between baseline and scenario run); SEEM shows a potentially large change (~500 kWh).

  16. Presenter Proposal •  We need to be able to allow Raters to use infiltration as a potential trade-off componentas part of their analysis. We suggest a range of 1.5-5.0 ACH50. • Heating system efficiency was used as the other trade off component because this is one of our more frequent requests. • This was what was modeled as one of the “scenarios” for the original analysis

  17. Staff Recommendation • REM Rate be used for compliance only for those scenarios that show agreement with SEEM as per CLEAResult analysis reviewed by staff. • As per slides 5 & 6, there is a difference in the way SEEM and REM Rate model infiltration. • No changes have been made to the infiltration engine since the last presentation. • This trend manifests itself in the comparison analysis conducted.

  18. RTF Proposed Motion “I _________ move that the RTF: (Pick one) • Allow use of infiltration as a knob for all possible trade off for testing compliance. • Allow use of infiltration trade offs with heating efficiency for Heat Pumps and Furnaces for testing compliance. • Allow use of infiltration tradeoffs for Heat Pumps and Furnaces for only those cases that showed a compliance match with SEEM for testing compliance.”

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