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Feasibility of Retrofitting Centralized HVAC Systems for Room-Level Zoning Tamim Sookoor Brian Holben Kamin Whitehouse June 7, 2012 International Green Computing Conference (IGCC 12)

U.S. energy usage* 1 *U.S. Department of Energy, 2006

U.S. residential energy use* Homes are ~30% vacant * National Academy of Science,

U.S. residential energy use 2 Homes are ~30% vacant Smart Thermostat: 28% savings --Sensys 2010

U.S. residential energy use 2 Homes are ~50% used when occupied Our goal: Occupancy-driven zoning

U.S. residential energy use Homes are ~50% used when occupied Our goal: Occupancy-driven Zoning 2

Overview Zoning Overview Preliminary Studies Results 3

Overview Zoning Overview Preliminary Studies Results 3

Snap-in zoning retrofit 4

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Low cost DIY: no configuration Focus on forced air Other systems are similar 6

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8 Central HVAC One sensor One air conditioner Snap-in Zoning Zoned HVAC K sensors K air conditioners K+1 Control Signals One air conditioner K sensors Q1: Does room usage vary? Q2: Can a house be partially conditioned? Q3: Does partial conditioning save energy? Q4: Does leakage reduce efficiency?

Overview Zoning Overview Preliminary Studies Results 9

Does room usage vary? Smart home data set over 28 days* 10 Bedroom Kitchen Toilet 12AM3AM6AM9AM12PM3PM6PM9PM12AM * Kasteren et al.

Can a house be partially conditioned? Empirical Study 11 Living Room Kitchen Dining Room Office Bedroo m

Can a house be partially conditioned? Office 12

Does partial conditioning save energy? System turns off faster 13 EnergyPlus Simulation

Does leakage reduce efficiency? Number of external walls Energy (kWh) Insulation Effect

Overview Zoning Overview Preliminary Studies Results 15

Experimental approach Deployed zoning in a 7-room house 7 sets of dampers 21 thermostats Controlled based on temperature 20 days of data Compared to whole-house conditioning 16

Static Dual-Zone 17

Evaluation method SunMonTueWedThuFriSat … Dual-Zone Whole house 18

Energy savings 21% savings Statistically significant at alpha =

Zone airflow 20

Zone airflow 20

Zone airflow 20

Zone airflow 20

Total airflow 21

Conclusions Snap-in Zoning Cheap, easy, & energy saving Many challenges have to be overcome Equipment safety, occupancy prediction Results indicate potential for energy savings 22

Credits & Questions Tamim Sookoor, Brian Holben, Kamin Whitehouse