BUILDING DESIGN AND ENGINEERING APPROACHES TO AIRBORNE INFECTION CONTROL AUGUST 3 14, 2009 Harvard School of Public Health

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1 BUILDING DESIGN AND ENGINEERING APPROACHES TO AIRBORNE INFECTION CONTROL AUGUST 3 14, 2009 Harvard School of Public Health Natural Ventilation for Infection Control in Health Care Settings: Mixed Mode Hal Levin Building Ecology Research Group Santa Cruz, California 1

2 IEA Annex HybVent Buildings 2 2

3 Shares of Non-Residential Building Energy Use Other Vacant Food Sales Public Order/Safety Food Service Health Care Healthcare Primary Energy Use Total Floorspace Service Lodging Public Assembly Education Mercantile Warehouse/Storage Office 0% 5% 10% 15% 20% 25% Percent of non-residential total 3

4 Natural and Mixed Mode Ventilation Mechanisms Natural Ventilation Mixed Mode Ventilation Cross Flow Wind Wind Tower Stack (Flue) Stack (Atrium) Mixed Mode Ventilation heated/cooled ceiling void chilled pipes heated/cooled pipes Sketch of school system Sketch of B&O Building Fan Assisted Stack Top Down Ventilation Buried Pipes Courtesy of Martin Liddament via Yuguo Li 4 4

5 Main Hybrid Ventilation Principles Natural and mechanical ventilation Fan-assisted natural ventilation Stack and wind-assisted mechanical ventilation 5

6 Ventilation for Indoor Air Quality Control When optimizing ventilation for indoor air quality control, the challenge is to achieve an optimal equilibrium between indoor air quality, thermal comfort, energy use and environmental impact during periods of heating and cooling demands. 6

7 Pollutant concentration as a function of outdoor air exchange rate 8 7 Concentration (µg/m 3 ) EF = 1 µg/m 2 hr EF = 5 µg/m 2 hr EF = 10 µg/m 2 hr Ventilation air changes per hour (ach) 7

8 The relationship between infection risk, and the ventilation rate and the quanta generation. The unit of quanta generation is quanta per hour Qian et al, 2010, Building and Environment 45:

9 Impact of ventilation rate on infection rate (Nardell et al, 1991, Am Rev Resp Dis) 9

10 Decay of droplet nuclei concentration in an isolation room for different ventilation rates and duration of time Ventilation rate Time (minutes) 6 ACH 9 ACH 12 ACH 15 ACH 18 ACH 21 ACH 24 ACH % % % % % % % % 47.24% 36.79% 28.65% 22.31% 17.38% 13.53% % 22.31% 13.53% 8.21% 4.98% 3.02% 1.83% % 10.54% 4.98% 2.35% 1.11% 0.52% 0.25% % 4.98% 1.83% 0.67% 0.25% 0.09% 0.03% % 2.35% 0.67% 0.19% 0.06% 0.02% 0.00% % 1.11% 0.25% 0.06% 0.01% 0.00% 0.00% % 0.52% 0.09% 0.02% 0.00% 0.00% 0.00% % 0.25% 0.03% 0.00% 0.00% 0.00% 0.00% % 0.12% 0.01% 0.00% 0.00% 0.00% 0.00% % 0.06% 0.00% 0.00% 0.00% 0.00% 0.00% % 0.01% 0.00% 0.00% 0.00% 0.00% 0.00% 10 10

11 Conclusions (Qian et al, Building and Environment, 2010) field measurement study performance of natural ventilation in a TB hospital and an outpatient clinic possibility of using natural ventilation for infection control. measured ventilation rate found to be much higher than the CDC recommended 12 ACH for isolation rooms. However, when all openings are open, pressure difference between corridor and ward and between ward and outdoor << 1 Pa, and cannot be measured by conventional equipment. observed airflow direction through an open door or window can be unstable during the measurement when the wind is weak. [M]echanical exhaust fans installed can create negative pressure. When all openings were closed and fans turned on, ventilation rate was as high as 12.6 ACH and pressure difference between ward and corridor was also high. [M]easured results indicate NatVentilated ward may be converted to an isolation room by installing exhaust fans when natural forces are not sufficiently strong. [C]onfirmed: natural ventilation could provide a high ventilation rate, especially when all the openings in the ward were fully open. The high ventilation rate is expected to reduce the risk of cross-infection. 11

12 IAQ-Energy Trade-off 12

13 Local ventilation - exhaust Design Drawing Prototype in the test room 13 13

14 ACH can be misleading? V=10 m 3 V=10 m 3 V=30 m 3 V=10 m 3 q=30m 3 /h q=1 ach q=30m 3 /h q=1 ach 14

15 Ventilation for Temperature Control When optimizing ventilation as a natural cooling strategy, the challenge is to achieve an optimal equilibrium between cooling capacity, cooling load, thermal mass and thermal comfort. 15

16 ASHRAE Std Adaptive vs. Static Comfort Model: Offices Comparison of adaptive models predicted indoor comfort temperatures with predictions by the static PMV model. 27 buildings with centralized HVAC 27 buildings with natural ventilation comfort temperature ( o C) RP-884 adaptive model with semantics "static" model (PMV) comfort temperature ( o C) RP-884 adaptive model "static" model (PMV) mean outdoor effective temperature ( o C) mean outdoor effective temperature ( o C) CENTRALLY-CONTROLLED HVAC SYSTEMS NATURALLY VENTILATED BUILDINGS 16

17 Adaptive Model Research (offices): Brager and de Dear 17

18 Low Energy Cooling Technologies Night cooling (natural ventilation) Night cooling (mechanical ventilation) Slab cooling (air) Slab cooling (water) Evaporative cooling (direct and indirect) Desiccant and evaporative cooling Chilled ceilings/beams Displacement ventilation Ground cooling (air) Aquifer Sea/river/lake water cooling 18

19 Types of HybVent Components There are no real hybrid ventilation components as such. In nearly all cases hybrid ventilation systems consist of a combination of components, which can be used in purely natural systems or in purely mechanical systems. However, the availability of appropriate components is essential for the successful design and operation of a hybrid ventilation system. 19

20 SmartKontrols technology Ventilation Systems All houses need ventilation, while traditionally this is done by passive trickle vents above windows, often some form of mechanical ventilation may be needed. Simple bathroom extracts can be driven from the lighting circuit, but these simply throw away the warm air. Heat Recovery Ventilation Units extract the heat from the extract air and use this to warm the incoming fresh air saving energy. Natural or Passive Ventilation schemes Some houses employ Natural Ventilation techniques, using the buoyancy of warm air to create the stack effect, enhancing ventilation through a wind tower. Such schemes employ automatic opening windows or vents at low and high level, which must be inhibited during high winds, etc. Typically, our solution will feature: a small smart Box panel with the smart Module near to the motorised windows a weather station with wind speed and direction can inhibit the opening of windows under certain conditions a rain sensor may also be fitted 20

21 To combine natural and mechanical forces in the air distribution system, components can include: Low-pressure ductwork (size, surface, angles) Low-pressure fans with advanced control mechanisms such as frequency control, air flow control, etc Low-pressure static heat exchangers and air filters (filter s.p. relates to filter efficiency, e.s.) Wind towers, solar chimneys or atria for exhaust. Underground ducts, culverts or plenums to pre-condition supply air. 21

22 For control of thermal comfort, indoor air quality and air flow, components can include: Manually operated and/or motorized windows, vents or special ventilation openings in the facade- and in internal walls, Room temperature, CO 2 and/or air flow sensors, A control system with weather station 22

23 Local air movement fans 23

24 BRE Environmental Office Watford, UK Not in handout materials (copyright limitation) 24

25 BRE Environmental Office (1997) 25

26 BRE s Environmental Office Building Low energy fans for use on still air days Glass for solar heating of thermal chimney 26

27 BRE Environmental Office Building: Ventilation and Cooling 27

28 The 1 st Hybrid Vent. for High rise Bldgs in Japan 119.5m Memorial Hall Graduate School Wind floor 18F Canteen Lecture Rooms Offices Roof Garden Roof Garden Entrance Hall Library Car Parking Rain Water Tank Heat Storage Tank Wind floor on 18F 28

29 Entrance Hall on 1F 119.5m Memorial Hall Graduate School Wind floor 18F Canteen Lecture Rooms Offices Roof Garden Roof Garden Library Entrance Hall Car Parking Rain Water Tank Heat Storage Tank 29

30 Memorial Hall on 23F 119.5m Memorial Hall Graduate School Wind floor 18F Canteen Lecture Rooms Offices Roof Garden Roof Garden Entrance Hall Library Car Parking Rain Water Tank Heat Storage Tank Memorial Hall on 23F 30

31 Graduate School on 19-22F 119.5m Memorial Hall Graduate School Wind floor 18F Canteen Lecture Rooms Roof Garden Offices Entrance Hall Roof Garden Graduate School on 19-22F Library Car Parking Rain Water Tank Heat Storage Tank 31

32 Natural Ventilation Shafts for 19-22F 119.5m Memorial Hall Graduate School Wind floor 18F Canteen Lecture Rooms Offices Roof Garden Roof Garden Library Entrance Hall Car Parking Rain Water Tank Heat Storage Tank 32

33 Canteen on 17F 119.5m Memorial Hall Graduate School Wind floor 18F Canteen Lecture Rooms Offices Roof Garden Roof Garden Library Entrance Hall Car Parking Rain Water Tank Heat Storage Tank 33

34 Lecture Rooms on 6-16F & B1-3F 119.5m Memorial Hall Graduate School Wind floor 18F Canteen Lecture Rooms Offices Roof Garden Roof Garden Library Entrance Hall Car Parking Rain Water Tank Heat Storage Tank 34

35 Typical lecture room floor WC Refresh Space WC M/R Escalator M/R Lecture Rooms Wind is exhausted at the top of Escalator (Wind floor on 18th level) 35

36 Gymnasium on B3F 119.5m Memorial Hall Graduate School Wind floor 18F Canteen Lecture Rooms Offices Roof Garden Roof Garden Library Entrance Hall Car Parking Rain Water Tank Heat Storage Tank 36

37 Library B3-1F 119.5m Day-lighting even on B3F Memorial Hall Graduate School Wind floor 18F Canteen Lecture Rooms Offices Roof Garden Roof Garden Library Entrance Hall Car Parking Rain Water Tank Heat Storage Tank 37

38 Library B3-1F Day-lighting even on B3F 38

39 To improve Indoor Air Quality and Save Energy - Automatically controlled natural ventilation windows and wind floor (18F) design. - Night-purge of VOCs and Internal heat - Variable fresh air intake using CO 2 sensor -BEMS 39

40 Hybrid Ventilation System Natural Ventilation Lecture Room To Wind Floor (18th level) From each Class Room To each Class Room Conditioned Air Escalator Hall VAV Motor Damper Exhausted Air Returned Air Fresh Air Air Handling Unit (Middle season: all fresh air conditioner) 40

41 Sensors TThermometer H Hygrometer V Anemometer Outdoor T H V Wind speed & direction Solar radiation Rainfall T H V Anemometer, State of natural ventilation window (open or close), Integrated time while windows are open T V V Wind speed at exhaust opening CO2 density These data (total 2000 points) are recorded automatically every 10 minutes T V 41

42 1,800 1,600 1,400 1,200 1, B3F B1F 2F 4F 6F 8F 10F 12F 14F 16F 18F 20F 22F 23F 時間 / 年 Ventilation windows were opened for 1100 hours per year 2000/3 2000/2 2000/1 1999/ / / /9 1999/8 1999/7 1999/6 1999/5 1999/4 42

43 Hybrid Ventilation System reduced Space Cooling Energy by 17% Primary Energy Consumption for Space Cooling(MJ/m2) Reduced by Natural Ventilation Air-handling Chilling Apr May Jun Jul Aug Sep Oct Nov Apr.1999-Mar

44 Operation Energy was reduced by 40% Primary Energy Comsumption[MJ/a/m2] ,696 Apr Mar ,647 1,583 Reference Case Study Actual Cooking Escalator Elevator Electric Applances Lighting Air Handling Heat Source(Others) Heat Source(Storage) 44

45 LCCO 2 will be reduced by 40% Design Re-construction Renovation Operating Energy Release of HCFCs Intial Construction Repair Maintenance Demolition Reference Case Study -37% kg-co2/a/m2 45

46 Formed Insulation Fire extingusher Reference Other Loads will be reduced Refrigerant Electric Isolator Reference Design Re-construction Renovation Operating Energy Release of HCFCs Intial Construction Repair Maintenance Demolition Case Study -95% g-cfc11/a/m2 Depletion of Ozone Layer Design Intial Construction Re-construction Repair Renovation Maintenance Operating Energy Demolition Release of HCFCs Reference Case Study % g-so2/a/m2 Acidification Design Intial Construction Re-construction Repair Renovation Maintenance Operating Energy Demolition Release of HCFCs Reference Case Study -26% Case Study % g-so2/a/m2 Health Damage (Air) MJ/a/m2 Depletion of Fossil Fuel 46

47 Eco-Economic Analysis 1999, 2000 Initial cost (Million Yen) Energy cost reduction (Million Yen/year) Cost Payback time (Year) CO2 Reduction (t-co2 /Year) Intial cost per unit CO2 Reduction (1000 yen/ (t-co2/year)) CO 2 cont. for Fresh air Intake Day Lithting Hf lamp CO cont. for Parking Vent Variable Air Volume Thermal Heat Strage Escalator control Variable Water Volume Natural Ventilation Total / Million Yen= + 1.2% 47

48 Eco-Economic Analysis Additional Initial Cost {Yen/(t-CO 2 /a)} Photo Voltaics Meiji University 4,000,000JPY/(t-CO 2 /a) 47,000JPY/(t-CO 2 /a) / Million JPY = + 1.2% 48

49 Official Annex 35 report summarizes initial working phase of the project. Ventilation technologies Control strategies and algorithms Analysis methods Examples of existing systems Solutions to problems in different climates. Available at tions/sotar.pdf (135 pages) 49

50 Annex 35 HybVent Publications are available for download at 50

51 Weather conditions and ventilation mode Armoury Tower Shanghai, China Not in handout materials (copyright limitation) 51

52 Armoury Tower, Shanghai Not in handout materials (copyright limitation) 52

53 Not in handout materials (copyright limitation) 53

54 Not in handout materials (copyright limitation) 54

55 Queen s College, de Montefort University, Leicester, UK Not in handout materials (copyright limitation) 55

56 Not in handout materials (copyright limitation) 56

57 Umno Tower - Penang, Malaysia Not in handout materials (copyright limitation) 57

58 Wind flow around building air pressure contours Umno Tower - Penang, Malaysia Vertical section Level 12 Not in handout materials (copyright limitation) 58

59 Wind pressure diagrams Umno Tower - Penang, Malaysia Not in handout materials (copyright limitation) 59