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Weatherization Assistant: What’s New in Versions 8.4 and 8.5. Mark Ternes Mike Gettings Oak Ridge National Laboratory 2009 National Weatherization Training Conference July 22, 2009. Purpose of This Presentation.

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weatherization assistant what s new in versions 8 4 and 8 5

Weatherization Assistant: What’s New in Versions 8.4 and 8.5

Mark Ternes

Mike Gettings

Oak Ridge National Laboratory

2009 National Weatherization Training Conference

July 22, 2009

purpose of this presentation
Purpose of This Presentation
  • Discuss MHEA field test and analyses results that led to important technical changes in Version 8.4
    • MHEA field validation (overall performance)
    • BESTEST (UA values and space-heating load)
    • RESNET procedures (energy consumption)
    • True-up using the MHEA field validation homes (overall performance)
  • Summarize potential program impacts from use of the revised MHEA
  • Identify and discuss other changes that have been made in Version 8.4 and 8.5
mhea field validation study
MHEA Field Validation Study
  • Validation performed at DOE request before full implementation of MHEA
  • Validation report published November 2007 (ORNL/CON-501)
  • Findings (86 homes)
    • MHEA over predicted space-heating energy savings of weatherization measures by ~200% on average per home
    • MHEA achieved an average realization rate of ~35% (actual savings divided by predicted savings)
home energy rating system hers building energy simulation test bestest
Home Energy Rating System (HERS) Building Energy Simulation Test (BESTEST)
  • Uses a basic single-family, site-built house that is simplistic enough to be modeled in MHEA
  • 10 different test configurations of this basic house
    • Insulation and infiltration levels
    • Glazing properties and orientation
    • Shading
    • Internal loads
conclusions regarding mhea s ua calculations
Conclusions Regarding MHEA’s UA Calculations
  • Some deviations from BESTEST occur:
    • NOT because MHEA calculations are wrong
    • But because MHEA accurately reflects mobile home construction or for other explainable reasons
  • MHEA accurately calculates the UA-values of mobile home envelope components
space heating load analysis
Space-Heating Load Analysis
  • MHEA UA-values made to equal BESTEST values to focus the analysis on the load calculation engine
  • BESTEST criteria are based on the results from three hourly simulation programs
    • DOE-2
    • BLAST
    • SERI-RES
  • Loads calculated for a Denver climate
  • Space-cooling loads not examined
conclusions regarding mhea s space heating load calculations
Conclusions Regarding MHEA’s Space-Heating Load Calculations
  • MHEA passes the BESTEST criteria for each of the 10 test configurations, usually falling near the midpoint of BESTEST’s allowable range
  • MHEA accurately calculates the space-heating load of a mobile home
  • MHEA’s loads essentially track BLAST and are about 3-9 MBtu higher than DOE-2
resnet procedures
RESNET Procedures
  • Tests space-heating energy consumption calculations for various heating systems using the BESTEST base case test configuration
  • Compares energy consumption of one heating system to another
    • 90% AFUE furnace to a 78% AFUE unit
    • 9.85 HSPF heat pump to a 6.8 HSPF unit
    • Electric resistance furnace to a 6.8 HSPF heat pump
  • RESNET results are based on the results of six hourly simulation programs
    • Two DOE-2.1 tools
    • Two DOE-2.2 tools
    • Micropas version 6.5
    • TRNSYS version 15
results and conclusions regarding mhea s space heating energy consumption calculations
Results and Conclusions Regarding MHEA’s Space-Heating Energy Consumption Calculations
  • MHEA accurately calculates the space-heating energy consumptions of the tested systems
  • MHEA found to accurately calculate:
    • UA-values
    • Space-heating loads (essentially equivalent to BLAST or DOE-2)
    • Space-heating energy consumptions
  • But re-analysis using the MHEA field validation mobile homes showed that:
    • MHEA still over predicted savings by 168%
    • MHEA still achieved a realization rate of only 37%
modifications to true up mhea predictions to field validation results
Modifications to True-Up MHEA Predictions to Field Validation Results
  • Modeling of field validation homes in MHEA
    • Turned off programmable thermostat measure (12% of the homes)
    • Floor insulation levels of 0 in. changed to 0.5 in. (14% of the homes)
  • Engineering modifications to MHEA
    • Changed MHEA’s internal load assumptions to be more consistent with HERS and NEAT
    • Reduced MHEA’s infiltration loads by ~25%
    • Added an R-value of 1 to the ceiling, floor, and walls
  • Applied a 0.6 correction factor to MHEA’s energy savings calculations
results from true up modifications
Results from True-Up Modifications
  • MHEA’s over prediction of energy savings reduced to just 28%
  • MHEA’s realization rate increased to 78%
  • Use of MHEA’s optional billing adjustment feature can further improve MHEA’s accuracy on individual homes
    • Over prediction of energy savings reduced to 16%
    • Realization rate increased to 87%
simulation of program impacts from use of the revised mhea
Simulation of Program Impacts from Use of the Revised MHEA
  • Compared recommendations from the revised MHEA (Version 8.4) to the original (Version 8.3)
    • Frequency that measures are recommended
    • Average investment levels per home
  • 18 mobile homes in Ohio
    • 13 heated by natural gas
    • 5 electrically heated
  • Columbus weather (5723 HDD)
  • State-supplied fuel and installation costs
  • Included health & safety and repair items
program impact results and conclusions
Program Impact Results and Conclusions
  • Use of the revised MHEA does NOT eliminate the recommendation of insulation measures
    • Roof: from 72% of the homes to 61%
    • Floor: from 89% of the homes to 61%
    • Wall: 17% for both versions of MHEA
    • Storm windows: 83% of the homes to 39%
  • Average investment levels remained high
    • Average investment per home dropped from $2832 to $2193
    • Recommended investment level changed less than $130 in 39% of the homes
mhea steering committee comments
MHEA Steering Committee Comments
  • MHEA is now more accurate
    • Estimated energy savings and SIRs are more reasonable
  • The changes made in the revised MHEA move the recommendations in the right direction
    • Measures with questionable economics – like storm windows or insulating a roof with a decent amount of insulation in it – are less likely to be recommended
  • Recommend issuing the revised MHEA once remaining programming issues are resolved
  • MHEA’s basic engineering calculations were found to be accurate
  • Several adjustments had to be introduced into MHEA to make its energy estimates agree with measured field data
  • Recommendations appear to be reasonable
  • Program impacts compared to Version 8.3 appear to be reasonable and as expected
  • Final report published December 2008 (ORNL/CON-506)
  • Version 8.4 of the Weatherization Assistant with the revised MHEA was released November 14, 2008