Home Energy Score Pilot Results: Minnesota

Dave Bohac NorthernSTAR

Center for Energy and Environment dbohac@mncee.org, 612‐802‐1697

Residential Energy Efficiency Technical Update Meeting Denver, CO August 9 ‐ 11

     

                    

     

       

         

Home Energy Score Goals

• Lower the cost hurdle for homeowners to receive a quantitative energy assessment

• Increase motivation for residential retrofits

• Develop consistent data collection process

• Collect comparative data on U.S. homes

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Part I: A Home’s Energy Score

Key Elements: Asset rating

36 to 67 data entry fields

Total Energy

Source Energy

19 Climates

Even Bins

Benchmark for home size

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Part II: Recommended Upgrades

Now

At Replacement

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CEE’s Residential Energy Programs

Community Engagement & Recruitment

Neighborhood Workshop

Home Visit & Materials

Follow up Calls Major Upgrades

Collect data at visit Email or mail report

 

                        

                                     

                                  

Pilot Objectives

• Determine how the Home Energy Score integrates with field operations for residential energy visits – Additional data collection time requirements – Usability of data collection sheet and scoring tool interface

– Ability of different field personnel to make consistent estimations

• Assess the homeowner response to having their home scored – Do homeowners understand the score?

– Does it work as an effective motivational tool?

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Pilot Objectives

• Compare default house air leakage to actual measured.

• Measure the predictive capability of the building performance model against utility bill data, SIMPLE model and REM/Rate results.

• Assess the correlation of recommendations produced by the score with in‐person retrofit recommendations.

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Pilot Overview

• 154 Homes in Minneapolis and Apple Valley, MN

• February 1, 2011 – June 15, 2011

• Workforce: 2 Qualified Assessors • Process for selecting homes:

– Random selection of homes enrolled in our residential energy program

• Delivery mechanism to homeowner – Part of program: Community Energy Services, be.Apple Valley

– Score was mailed or emailed approximately 3 weeks after visit – No Home Energy Score recommendations

• Blower Door test performed

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         Demographics of Pilot Homes: Construction Year

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Demographics of Pilot Homes: Number Stories

Foundation Type Basement ‐ 95% Slab‐on‐grade ‐ 4% Crawlspace ‐ 1%

Water Heater Nat. Gas ‐ 96% Electric ‐ 3% Oil ‐ 1%

Heating System Furnace ‐ 75% Boiler ‐ 25%

AC System Central ‐ 71% None ‐ 29%

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Wall Cavity Insulation by Construction Year

R > 11

4 ≤ R < 11

R = 11

R < 4

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Attic Cavity Insulation by Construction Year

R > 30

R < 15

15 ≤ R ≤ 30

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Home Energy Score Results for MN Pilot Homes

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5

4

3

2

6

7

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All Homes (154 total)

Home Energy Score: Existing

Score With Upgrades

“Zone of Unattainability”

1 to 4 Existing – 27% With Upgrades – 6% (Two houses remained a 1)

7 to 10 Existing – 41% With Upgrades – 83% (no houses achieved a 10)

   

      

        

         

HES Recommended Upgrades

Recommendation % Houses Seal gaps and cracks 63%

Basement walls to R‐11 53%

Attic floor to R‐38 34%

Seal ducts 5%

No recommendations 15%

Average of 1.6 recommendations per house

     Attic Insulation HES Recommendation

 

                                   

           

         

           

Lessons Learned: Process

• Did not add significant time to home visits, once “rhythm” was established: 30 minutes in‐home and 15‐20 minutes data entry

• Mechanical system info was hardest to obtain:

Percent of time the following inputs were available

Heating Cooling Water Heater Attic Insulation

AFUE Year SEER Year Eff Year

64% 36% 12% 78% 14% 77% 65%

     

                    

    

 

 

 

 

 

         

Analysis: Utility Bill Comparison

• 51 homes with HES & utility data*

• Weather‐normalized Utility Bills to HES model Average

Home Energy Score

Average Utility Bill

Difference Between Average

Average Absolute Deviation

Source 253 MMBtu

215 MMBtu

18% 36%

Site Gas 1,558 therms

1,219 therms

28% 38%

Site Electric

7,192 kWh

7,123 kWh

1% 59%

And corrected basement floor area

     Analysis: Gas Use Comparison

       

                

                           

Recommendations for the National Launch

• Improve recommendations & cost estimates – Allow Qualified Assessor to tailor recommendations

• Consider shrinking the “zone of unattainability” – Group similar home types along different scales – Provide options for regional customization

 

         

                

   

                  

           

Further Work

• Compare HES to program upgrade recommendations

• Methods to segment housing stock to provide more motivating existing/upgrade scores

• Compare utility/HES/SIMPLE energy results

• Will have 50 houses with REM/Rate analysis – compare to other data

• Compare actual to default house air leakage

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 Extra Slides

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Homeowner Observations • Overall people were excited to participate and see their score

• Most common question was about survey (knowledge before or after visit?)

• People often asked if information sheet was their home

• Confusing or complex parts of the score and process – Source Energy

– Based on a model & concept of asset – Who they are being compared to

• CEE didn’t use in‐person delivery – 33 percent of email recipients didn’t open email – Provided as free add‐on to home visit

          

       

Demographics of Pilot Homes: Construction Year Wall Insulation

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33% with R‐value < 4

          

Demographics of Pilot Homes: Construction Year Attic Insulation

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             Home Energy Score Results for MN Pilot Homes

   HES Recommended Upgrades

     

                  

                                              

                               

Lessons Learned: Score and Recs

• Numerical scorecard is a helpful motivating tool – 83% with score ≥ 7 after upgrades

• Several homes did not receive motivating scores – 11% score a 5 or less after upgrades – 44% can only increase score by 1 or zero points – 15% had no recommendations

• Recommendations not consistent with program – No wall insulation and some attics with low R‐Values – High frequency of basement wall insulation

     

                    

    

 

 

  

 

       

         

         

             

Analysis: Utility Bill Comparison

• 115 homes with gas + electric data

• Weather‐normalized Utility Bills to HES model Average

Home Energy Score

Average Utility Bill

Average Absolute Deviation

Average Deviation

Source 253 (278) MMBtu

215 (221) MMBtu

36% (45%) 28% (35%)

Site Gas 1,558 (1,779) therms

1,219 (1,200) therms

38% (57%) 33% (52%)

Site Electric

7,192 (7,279) kWh

7,123 (7,820) kWh

59% (53%) 38% (25%)

Subset of 51 with Corrected Basements (All Houses)

     

     

Conditioned vs. Unfinished Basements

61 homes post‐basement correction

   

  

Site Electricity Use

Post‐Basement Correction Pre‐Basement Correction

   

  

Site Gas Use

Post‐Basement Correction Pre‐Basement Correction

     Analysis: Gas Use Comparison

     

                 

                

Conditioned vs. Unfinished Basements

(1) Conditioned basement Unfinished basement that is 5‐10F (2) Unconditioned basement

cooler than above grade area??? (3) Vented crawlspace (4) Unvented crawlspace (5) Slab on grade

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