Multifamily Homes: Calibration Update

Regional Technical ForumDecember 8th, 2015

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Objectives

• Update the RTF on the calibration (testing) process

• Change measure status to Planning and Under Review for the following UES measures:– Residential Weatherization – Multi-Family• Currently Out of Compliance

– Residential New Construction – ENERGY STAR Homes Multi-Family • Currently Proven and Under Review, Sunsets this month

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MF Calibration – Current Status• An existing multi-family calibration was approved

in 2012– Based on five small MF billing studies from 1994 to

2010 (pre-dates RBSA)– SEEM heating energy calibrated to billing energy using

thermostat adjustment• In August, RTF directed CAT to test the existing

thermostat based calibration with pre-/post- data to determine if the calibration is good enough for MF weatherization and ENERGY STAR measures

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Existing Calibration (continued)

Reference Prototype Location Heating System

Sample Size (n units) Temp setpoints Actual

Heat EUI (kWh/yr-

ft2)

SEEM Heat EUI (kWh/yr-

ft2)% Diff#

units#

bldgsHeat

Low (F)Heat

High (F)

MF MCS 1994. Multifamily Metering Study

- AAHXWoody Walk-Up Seattle Electric

Zonal 42 5 68 68 3.02 2.45 -18.8%

MF MCS 1994. Multifamily Metering Study Woody Walk-Up Seattle Electric

Zonal 38 4 68 68 3.02 3.41 13.0%

ARRA-FG. ARRA Verification - Forest Glen

(Ecotope)Woody Walk-Up Redmond Electric

Zonal 40 6 68 68 3.68 3.39 -7.8%

New MF-2009 Study (Ecotope)

Double Loaded Corridor Seattle Electric

Zonal 700 10 68 68 3.08 3.12 1.4%

ARRA-AV. ARRA Verification (Ecotope) Townhomes Seattle Electric

Zonal 20 5 66 66 3.16 3.08 -2.7%

Total Units & Buildings: 840 30 Avg. 3.19 3.09 -3.0%

Existing calibration summary:

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Existing Calibration Definition• Thermostat set-point of 68 degrees, no setback.– (Townhouse/Rowhouse set-point at 66F)

• Internal gains calculated with the SEEM MF Calibration Internal Gains Calculator

• Infiltration (mostly) assumed at 0.25 ACH natural unless otherwise known – rare to know for MF building stock

• http://rtf.nwcouncil.org/meetings/2012/09/

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Testing the MF Calibration• CAT hoped to test existing calibration with pre- post- data; recent

pre- post- data for testing were not available• The reports that were available were 20 + years old;

– Good detail but we realized that plug-loads, utility rates, and occupant habits likely too different from current buildings

• New direction: test current calibration on RBSA MF buildings with sufficient billing and audit data:– Low rise (3 stories or less) multifamily buildings with no commercial space

and no common area– Have clearly identified meter data for that building and that building alone– Strong relationship between outdoor temperature and building energy use

• 22 buildings in the dataset currently meet the criteria; 8 RBSA MF buildings compared so far

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Comparison of annual TMY heating estimates from SEEM and a Variable Base Degree Day (VBDD) regression analysis for the eight buildings. The dashed line is 1:1. One building is much larger than the others, which somewhat skews the scale, but the initial trend is encouraging.

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This plot shows the annual TMY heating estimates from SEEM and VBDD normalized by building area. The trend looks encouraging, although here it is more obvious that simulation was a poor match to bills for one building. This was a 10-unit building in Beaverton and the smallest building of the sample of 22. We speculate that larger buildings should be easier to model, as they are less susceptible to the whims of a single housing unit.

Smallest building and also by far worst fit of the 8

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Proposed Direction• Plan: create SEEM runs for the remaining 14

buildings– Once the testing on 22 buildings is complete, make

necessary adjustments to optimize calibration (thermostat setting)

– If necessary to update the calibration, it appears feasible to use monthly TMY output to simultaneously adjust set-point, internal gains, and other poorly known inputs.

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Sunset Date Extension“I _________ move that the RTF set the measure status to Planning and Under Review and set the sunset dates for the following UES measures to March 30th, 2016:– Residential Weatherization – Multi-Family– Residential New Construction – ENERGY STAR Homes

Multi-Family”

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ADDITIONAL SLIDES

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• This graphic compares the so-called UA from both methods. SEEM reports an average heating slope of kWh / degree day, and that quantity is estimated directly in the VBDD regression model. This quantity is more important to match without necessarily having a calibration, because it is largely a function of static observations from the audit: component areas and u-values. The strong trend here is encouraging for the use of these data to assess and possibly update the calibration.

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SOME MONTHLY DATA EXAMPLE SLIDES

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This view shows monthly TMY estimates from both SEEM and VBDD as a function of average outdoor air temperature. The purpose of looking at monthly output is to better understand why certain buildings do or do not match the simulation to the bills. Here we have a bit of offsetting errors, but the overall pattern is not too bad and the total kWh matches well.

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Alternately, here is the site for which the simulation performed the worst. The balance point was over-estimated by SEEM, and the heating slope was severely overestimated by SEEM. One question relevant to the suitability of these data are: what would it take to match the simulation to the billing data? Could reasonable changes to simulation inputs bring the two in line, or do we think something about these data are unusable?

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Changing the setpoint, internal gains, and infiltration to still somewhat reasonable values helped match the two sources. While changing the infiltration brought the heating slope down a little, it still did not bring it in line with the bills. However, overall the changes made were not out of the realm of possibility, so we should accept the characteristics of this site.