New Construction CalibrationPreliminary Research and a Request for Guidance on Issues Raised in December

Regional Technical ForumJanuary 22, 2013

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Overview.• SEEM estimates of total heating energy

(Calibration Phase I)– Does sample include U-values as low as NC levels?– Is the captured effect right for NC?

• Supplemental heat in new construction homes (Calibration Phase II)– How common is supplemental heat in NC homes? – When present, does supplemental heat affect NC

homes as described in the Phase II results?

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Background: Phase I

975

429

SEEM Calibration

SF RBSA Pie: 1404 Homes

Approved (Modified) by RTF on Dec. 17, 2013

U-Value Questions Raised at December Meeting:1. Does the calibration sample include U-values as

low as current NC levels?2. Will low NC U-values effect SEEM-VBDD

differences as suggested by the calibration?

• Compared SEEM (69/64°F) heating energy estimates to billing data.

• Restricted to 429 RBSA homes with well-known characteristics, no non-utility fuels, and clear heating signatures in billing data.

• Regression used to determine adjustment factors that align SEEM (69/64°F) with billing data.

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U-Value Question 1Does the calibration sample include U-values as low as current NC levels?

1992Vintage recorded for 401 calibration sample units. Of these, 137 (34%) were 1993 or later.

Only 9 were post-2008.

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U-values didn’t change much between 1992 and 2008...

…but they may have really decreased after 2008.

U-Value Question 1

20081992

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Summary: U-Value Question 1Does the calibration sample include U-values as low as current NC levels?

• Lots of post-92 sites but few post-08 sites • Post-92 sites are fairly well-insulated

o Average post-92 ceiling R-value is 30o About half have ceiling R-value over 38

So well-insulated post-92 sites are well-represented. (But still, there are few actual post-08 sites.)

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U-Value Question 2Calibration Phase I found that the difference

SEEM 69/64 kWh - VBDD kWhis correlated with U-value.

Adjustments developed to better align SEEM 69/64 with VBDD. Are the adjustments right for NC?

Will the U-value correlation hold for NC homes the same as in older homes?• What’s driving the correlation? • Would the driver(s) change with NC?

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U-Value Question 2y-value is percent difference between SEEM 69/64 and VBDD.

Pattern is consistent across the two vintage groups.

Pre-1992 Post-1992

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U-Value Question 2What does the pattern mean?y > 0 if SEEM > VBDD, so plot says…• SEEM 69/64 > VBDD for

high-Uo homes;• Difference roughly

constant for Uo over 0.15 • Difference decreases as

Uo decreases; • Changes sign for Uo below

0.075 or so.

Pre-1992 Post-1992

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U-Value Question 2What does the pattern mean?y > 0 if SEEM > VBDD, so plot says…• SEEM 69/64 > VBDD for

high-Uo homes;• Difference roughly

constant for Uo over 0.15 • Difference decreases as

Uo decreases; • Changes sign for Uo below

0.075 or so.

As a reminder, the calibration adjusts SEEM 69/64 kWh to wipe away the pattern…

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 0.1 0.2 0.3Uo

SEEM adjustment factor

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U-Value Question 2Pattern wiped away when we apply Phase I adjustments.

y-value is residual percent difference

(What’s left after accounting for variables in regression model.)

Pre-1992 Post-1992

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U-Value Question 2Are the adjustments right for NC? Will the U-value correlation hold for NC homes the same as in older homes?

– Will the correlation hold for NC homes the same as in older homes?

– Does the model correct for the effect properly in NC homes?

Pattern does hold for post-92 homes.

Does the post-92 data really tell us how we should adjust SEEM (69/64) for new construction homes?

Model does adjust correctly for post-92 homes.

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U-Value Question 2Does the post-92 data really tell us how we should adjust SEEM (69/64) for new construction homes?

• What’s driving the patterns? • Would the driver(s) change with NC?

What’s at stake?

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U-Value Question 2What’s at stake? NC homes have Uo values corresponding to the sloped portion of the line. Example: Measure to reduce Uo from 0.75 to 0.50. – Would decrease heat load by at least 33%

• Suppose SEEM (69/64) at Uo = 0.75 is 5000 kWh;• And SEEM (69/64) at Uo = 0.50 is 0.67 x 5000 kWh.

– Adjustment factors: 0.90 at Uo = 0.75 and 0.98 at Uo = 0.50.– Savings = 5000x0.9 – 5000x(0.98x0.67) = 5000x0.24 kWh– Un-calibrated, it’s: 5000 – 5000x0.67 = 5000x0.33 kWh.

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U-Value Question 2Does the post-92 data really tell us how we should adjust SEEM (69/64) for new construction homes?

• What’s driving the patterns? • Would the driver(s) change with NC?

What’s at stake?• Calibration does tend to decrease WX savings;• Not using RBSA for NC calibration may trigger expensive

study requirement.

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Fundamental Question

Should we use RBSA to calibrate for new construction?• If so, do we need to alter how we do the

calibration?• If not, what should we do?

Discussion, recommendation?

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Fundamental Question

Basic choice for the RTF:1. “The RBSA data speaks to NC.” So use

adjustment from existing calibration and category is “proven”.

2. “The RBSA data does not speak to NC.” So the category is “provisional”.

a) Make no calibration adjustment or… b) Constant adjustment factor that doesn’t change

with U.

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Background: Phase II• Independent of Phase I.• Based on VBDD kWh estimates—does not use SEEM estimates. • Identifies variables that drive patterns in electric heating energy

among “program-like” RBSA homes. Variables relate to: - Non-utility heat sources, - Gas heat sources, and - Phase I filters.

552

Gas Heated, 249

Electric Heated, 180

In Utility Programs, but not in SEEM

calibration, 423

SEEM Calibration

SF RBSA Pie: 1404 Homes

Approved by the RTF on September 17, 2013.

Supplementary heat questions from Dec. Meeting:1. How common is supplementary heat NC homes?2. How do supplementary heat sources affect

electric heating energy in NC homes?

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Supplementary Heat Question 1How common are non-electric heat sources in new construction homes?

Calibration captured effect of supplemental heat using three indicator variables:– Off-grid high …over 40 MBtu reported – Off-grid med (Z1) …between 5 and 40 MBtu and in Zone 1– Gas Heat High …over 5000 kWh gas heat from VBDD

analysis

Has the population changed with respect to these variables?

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Supplementary Heat Question 1How common are non-electric heat sources? Are they becoming more (or less) common?

…no clear visual evidence of a `92 change in Zone 1.

1993-2011

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Supplementary Heat Question 1How common are non-electric heat sources? Are they becoming more (or less) common?

…also no clear visual evidence of a `92 change in Zones 2/3.

1993-2011

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Supplementary Heat Question 1

Visual evidence Previous two graphs based on full RBSA (1400+ sites). They reveal no evidence of any change concurrent to the 1992 code change.

Analytical evidence Next several slides look at cross-tabs (based on 585 “program-like” homes). These find no statistically evidence of any change.

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Supplementary Heat Question 1Analytical evidence for…Change in Off-grid high frequency pre-/post-1992? No statistically significant evidence:

*All zones combined—results are similar when Zone 1 and Zones 2/3 are tested separately.

…doesn’t rule out a change, but we have no evidence of one.

All Sites Under 40 MBtu Over 40 MBtu Row Total

Vintage ≤ 1992 411(85.8%)

68(14.2%)

479(100%)

Vintage > 1992 97(91.5%)

9(8.5%)

106(100%)

Total 508(86.8%)

77(13.2%)

585(100%)

Pearson p-value* for evidence of a change: 11.6%

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Supplementary Heat Question 1Analytical evidence for… Change in Off-grid med (Z1) frequency pre-/post-1992?No statistically significant evidence:

…doesn’t rule out a change, but we have no evidence of one.

Zone 1 Sites Not 5 - 40 MBtu 5 - 40 MBtu Total

Vintage ≤ 1992 291(74.2%)

101(25.8%)

392(100%)

Vintage > 1992 56(68.3%)

26(31.7%)

82(100%)

Total 347(73.2%)

127(26.8%)

474(100%)

Pearson p-value for evidence of a change: 26.9%

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Supplementary Heat Question 1Analytical evidence for… Change in Gas-high frequency pre-/post-1992?No statistically significant evidence:

…doesn’t rule out a change, but we have no evidence of one.

All Sites Gas kWh < 5000 Gas kWh > 5000 Total

Vintage ≤ 1992 450(93.9%)

29(6.1%)

479(100%)

Vintage > 1992 102(96.2%)

4(3.8%)

106(100%)

Total 552(94.4%)

33(5.6%)

585(100%)

Pearson p-value for evidence of a change: 35.7%

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Summary: Sup.Heat Question 1Has the population changed with respect to the frequency of high non-electric heat?

– If a change has occurred it has left no evidence in the RBSA.

– Have looked into a few sources and found nothing promising.

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Supplementary Heat Question 2When present, how do supplementary heat sources affect electric heating energy?

Is the effect on new construction similar to that described in the Phase II calibration model?

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Supplementary Heat Question 2Gas effect on new construction seems the same as in the Phase II calibration model.

Not enough data to sayanything about differentialgas heat effects.

(Most homes with natural gas do not use electricity as primary heat source.)

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Supplementary Heat Question 2But NC effect of non-utility heat apparently not the same as in the Phase II calibration model!

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Supplementary Heat Question 2But the net effect is the same… Ideal post-92 model would:– Increase electric heat estimate for post-92 sites with Non-

utility MBtu = 0, and– Decrease electric heat estimate for post-92 sites with Non-

utility MBtu > 40.

Net effect would be to decrease post-92 average estimate by (roughly) the post-92 residual average (increase if negative). This mean (-0.03) does not differ from zero by a statistically significant amount.

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Other data Sources?• Super Good Cents

– No wood heat data, and probably not representative anyway• NEEA Res. NC (SF and MF) Billing Analysis; SF Res. NC Characteristics and

Practices (RLW, 2007)– Raw data indicated that secondary heat sources exist in large numbers, but doesn’t say

what the heat sources (or fuel types) are.– Looking ahead to part of Wood Heat Question 2, no electric billing data collected for

homes with gas heat. • NEEA NW EStar Homes Energy Analysis, 2006-7 (KEMA, 2010)

– Unclear whether off-grid heat data was collected for this study. It’s not mentioned anywhere in the report.

• NEEA Baseline Characteristics of Res. Sector (Ecotope, 2000) – Data collection form does ask about wood heat, but hard to imagine this giving better

answers than the most recent RBSA.• NEEA Residential Energy Compliance Study (Cadmus, 2013)

– Lots of building characteristic data for a sample representative of current NC. No wood heat or billing data.