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2. 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)

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

4. U.S. residential energy use* Homes are ~30% vacant * National Academy of Science, 2006 2

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

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

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

8. Overview Zoning Overview Preliminary Studies Results 3

9. Overview Zoning Overview Preliminary Studies Results 3

10. Snap-in zoning retrofit 4

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

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23. 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?

24. Overview Zoning Overview Preliminary Studies Results 9

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

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

27. Can a house be partially conditioned? Office 12

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

29. Does leakage reduce efficiency? 14 43210 Number of external walls 0 5 10 15 20 25 30 35 Energy (kWh) Insulation Effect

30. Overview Zoning Overview Preliminary Studies Results 15

31. 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

32. Static Dual-Zone 17

33. Evaluation method SunMonTueWedThuFriSat … Dual-Zone Whole house 18

34. Energy savings 21% savings Statistically significant at alpha = 0.15 19

35. Zone airflow 20

36. Zone airflow 20

37. Zone airflow 20

38. Zone airflow 20

39. Total airflow 21

40. 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

41. Credits & Questions Tamim Sookoor, Brian Holben, Kamin Whitehouse