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

Mark TernesMike Gettings

Oak Ridge National Laboratory

2009 National Weatherization Training Conference

July 22, 2009

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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

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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)

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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

Comparison of UA CalculationsComponent BESTEST MHEA (final)

Floor – R-11 108.8 100.2Floor – R-0 363.3 284.3Wall – R-19 43.8 43.3Wall – R-11 87.9 97.2Wall – R-0 213.7 357.8Ceiling – R-57 25.9 45.5Ceiling – R-19 75.1 81.2Ceiling – R-11 114.3 116.2Windows – DP, wood, argon 81.0 119.8Windows – SP, metal 280.4 251.1Doors 13.2 11.9Infiltration – 0.67 ACH 118.2 67.9Infiltration – 1.5 ACH 264.5 170.1

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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

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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

Comparison of Space-Heating Loads

Test configuration

Annual space-heating load (MBtu)BESTEST range MHEA

L100A 48.75 to 79.48 64.3L110A 71.88 to 103.99 86.9L120A 37.82 to 64.30 53.6L130A 41.82 to 53.98 43.7L140A 43.24 to 56.48 50.1L150A 40.95 to 71.33 54.2L155A 43.53 to 74.18 57.0L160A 48.78 to 81.00 63.7L170A 61.03 to 92.40 74.3L200A 106.41 to 185.87 136.3

Comparison of Change in Loads

Test configuration

Change in annual space-heating load compared to a base case

(MBtu)BESTEST range MHEA

L100A

L110A 19.36 to 28.12 22.6L120A -18.57 to -7.67 -10.7L130A -27.5 to -5.97 -20.6L140A -24.42 to -4.56 -14.2L150A -12.53 to -3.02 -10.1L155A -1.54 to 6.88 2.8L160A -3.72 to 5.1 -0.6L170A 7.12 to 17.64 10.0L200A 56.39 to 107.66 72.0

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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

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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

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Results and Conclusions Regarding MHEA’s Space-Heating Energy Consumption Calculations

MHEA accurately calculates the space-heating energy consumptions of the tested systems

Heating system comparison

Change in space-heating energy consumption (%)

RESNET range MHEA

78% to 90% AFUE gas furnace -13.3% to -11.6% -13.3%

6.8 to 9.85 HSPF heat pump -29.0% to -16.7% -18.3%

6.8 HSPF HP to electric furnace 41.8% to 80.8% 52.3%

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So.......

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%

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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

Pre-Weatherization(Original MHEA Field Validation Study)

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Actual Energy Use - with Supplemental (MBtu)

MH

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tio

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MB

tu)

> +30%

23 homes

< -30%

2 homes

18 homes

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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%

Pre-Weatherization(After Final Modifications)

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Actual Energy Use - with Supplemental (MBtu)

MH

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> +30%

12 homes

< -30%

5 homes

26 homes

Energy Savings(Original MHEA Field Validation)

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MHEA Estimated Savings (MBtu)

Act

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< -50%

26 homes

> +50%

2 homes15 homes

Energy Savings(With 0.6 Savings Factor)

-20

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MHEA Estimated Savings (MBtu)

Act

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Sav

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s -

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< -50%

10 homes

> +50%

7 homes26 homes

Energy Savings(0.6 Energy Factor and Billing Adjustment)

-20

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MHEA Estimated Savings (MBtu)

Act

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Btu

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< -50%

10 homes

> +50%

3 homes

30 homes

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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

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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

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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

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Conclusions

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