natural ventilation for infection control in health …€¦ · natural ventilation for infection...

BUILDING DESIGN AND ENGINEERING APPROACHESTO AIRBORNE INFECTION CONTROL

AUGUST 3 – 14, 2009 – Harvard School of Public Health

Natural Ventilation for Infection Control in Health Care

Settings:

Mixed Mode

Hal LevinBuilding Ecology Research Group

Santa Cruz, California 1

22

IEA Annex 35 -- HybVent Buildings

3

Shares of Non-ResidentialBuilding Energy Use

0% 5% 10% 15% 20% 25%

Percent of non-residential total

Office

Warehouse/Storage

Mercantile

Education

Public Assembly

Lodging

Service

Health Care

Food Service

Public Order/Safety

Food Sales

Vacant

Other

Primary Energy Use

Total Floorspace

Healthcare

44

Natural and Mixed Mode Ventilation Mechanisms

Courtesy of Martin Liddament via Yuguo Li

Mixed Mode Ventilation

Sketch of school systemSketch of B&O Building

Natural Ventilation

Cross Flow Wind

Mixed Mode Ventilation

Wind Tower Stack (Flue) Stack (Atrium)

Fan Assisted Stack

heated/cooledpipes

heated/cooledceiling void

Top Down Ventilation

chilled pipes

Buried Pipes

5

Main Hybrid Ventilation Principles

• Natural and mechanicalventilation

• Fan-assisted natural ventilation

• Stack and wind-assisted mechanical ventilation

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.

7

Pollutant concentration as a function of outdoor air exchange rate

0

1

2

3

4

5

6

7

8

0 1 2 3 4 5Ventilation air changes per hour (ach)

Con

cent

ratio

n (µ

g/m

3 )

EF = 1 µg/m2•hr

EF = 5 µg/m2•hr

EF = 10 µg/m2•hr

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: 559–565

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9

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

1010

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

0 100.00% 100.00% 100.00% 100.00% 100.00% 100.00% 100.00%

5 60.65% 47.24% 36.79% 28.65% 22.31% 17.38% 13.53%

10 36.79% 22.31% 13.53% 8.21% 4.98% 3.02% 1.83%

15 22.31% 10.54% 4.98% 2.35% 1.11% 0.52% 0.25%

20 13.53% 4.98% 1.83% 0.67% 0.25% 0.09% 0.03%

25 8.21% 2.35% 0.67% 0.19% 0.06% 0.02% 0.00%

30 4.98% 1.11% 0.25% 0.06% 0.01% 0.00% 0.00%

35 3.02% 0.52% 0.09% 0.02% 0.00% 0.00% 0.00%

40 1.83% 0.25% 0.03% 0.00% 0.00% 0.00% 0.00%

45 1.11% 0.12% 0.01% 0.00% 0.00% 0.00% 0.00%

50 0.67% 0.06% 0.00% 0.00% 0.00% 0.00% 0.00%

60 0.25% 0.01% 0.00% 0.00% 0.00% 0.00% 0.00%

Conclusions(Qian et al, Building and Environment, 2010)

11

“… 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.

12

IAQ-Energy Trade-off

1313

Local ventilation - exhaust

Design Drawing Prototype in the test room

14

ACH can be misleading?

V=10 m3 V=10 m3

V=30 m3

V=10 m3

q=30m3/h

q=1 ach

q=30m3/h

q=1 ach

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.

16

ASHRAE Std. 55-2004Adaptive vs. Static Comfort Model: Offices

Comparison of adaptive models’ predicted indoor comfort temperatures with predictions by the “static” PMV model.

buildings with natural ventilation

20

21

22

23

24

25

26

27

-5 0 5 10 15 20 25 30 35

mean outdoor effective temperature (oC)

com

fort

tem

pera

ture

(o C)

RP-884 adaptive model"static" model (PMV)

buildings with centralized HVAC

20

21

22

23

24

25

26

27

-5 0 5 10 15 20 25 30 35

mean outdoor effective temperature (oC)

com

fort

tem

pera

ture

(o C)

RP-884 adaptive model with semantics

"static" model (PMV)

CENTRALLY-CONTROLLED HVAC SYSTEMS

NATURALLY VENTILATED BUILDINGS

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Adaptive Model Research (offices):Brager and de Dear

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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

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.

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Ventilation SystemsAll houses need ventilation, while traditionally this is done bypassive 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 warmthe incoming fresh air saving energy.

Natural or Passive Ventilation schemesSome 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

http://www.smartkontrols.co.uk/cooling_overview.htm

SmartKontrols technology

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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.

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, CO2 and/or air flow sensors,• A control system with weather station

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Local air movement fans

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BRE – Environmental OfficeWatford, UK

Not in handout materials (copyright limitation)

25

BRE Environmental Office (1997)

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BRE’s Environmental Office Building

• Low energy fans for use on still air days

• Glass for solar heating of thermal chimney

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BRE Environmental Office Building: Ventilation and Cooling

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Wind floor 18F

Memorial Hall

Entrance Hall

Lecture Rooms

Graduate School

Offices

Library Car Parking

Roof Garden

119.5m

Heat Storage TankRain Water Tank

Canteen

Roof Garden

Wind floor on 18FWind floor on 18F

The 1st Hybrid Vent. for High rise Bldgs in JapanThe 1st Hybrid Vent. for High rise Bldgs in Japan

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Wind floor 18F

Memorial Hall

Entrance Hall

Lecture Rooms

Graduate School

Offices

Library Car Parking

Roof Garden

119.5m


Canteen

Roof Garden

Entrance Hall on 1FEntrance Hall on 1F

30

Wind floor 18F

Memorial Hall

Entrance Hall

Lecture Rooms

Graduate School

Offices

Library Car Parking

Roof Garden

119.5m


Canteen

Roof Garden

Memorial Hall on 23FMemorial Hall on 23F

Memorial Hall on 23F

31

Wind floor 18F

Memorial Hall

Entrance Hall

Lecture Rooms

Graduate School

Offices

Library Car Parking

Roof Garden

119.5m


Canteen

Roof Garden

Graduate School on 19-22FGraduate School on 19-22F

Graduate School on 19 - 22F

32

Wind floor 18F

Memorial Hall

Entrance Hall

Lecture Rooms

Graduate School

Offices

Library Car Parking

Roof Garden

119.5m


Canteen

Roof Garden

Natural Ventilation Shafts for 19-22FNatural Ventilation Shafts for 19-22F

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Wind floor 18F

Memorial Hall

Entrance Hall

Lecture Rooms

Graduate School

Offices

Library Car Parking

Roof Garden

119.5m


Canteen

Roof Garden

Canteen on 17FCanteen on 17F

34

Wind floor 18F

Memorial Hall

Entrance Hall

Lecture Rooms

Graduate School

Offices

Library Car Parking

Roof Garden

119.5m


Canteen

Roof Garden

Lecture Rooms on 6-16F & B1-3FLecture Rooms on 6-16F & B1-3F

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Typical lecture room floorTypical lecture room floor

Lecture Rooms

Escalator

Refresh SpaceWC WC

M/RM/R

Wind is exhausted at the top of Wind is exhausted at the top of Escalator (Wind floor on 18th level)Escalator (Wind floor on 18th level)

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Wind floor 18F

Memorial Hall

Entrance Hall

Lecture Rooms

Graduate School

Offices

Library Car Parking

Roof Garden

119.5m


Canteen

Roof Garden

Gymnasium on B3FGymnasium on B3F

37

Wind floor 18F

Memorial Hall

Entrance Hall

Lecture Rooms

Graduate School

Offices

Library Car Parking

Roof Garden

119.5m


Canteen

Roof Garden

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

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

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To improve Indoor Air Quality and Save Energy

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 CO2 sensor - BEMS

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Hybrid Ventilation SystemHybrid Ventilation System

VAV

Air Handling Unit(Middle season:all fresh air conditioner)

Lecture Room

NaturalVentilation Conditioned Air

To each Class RoomReturned Air

EscalatorHall

Fresh Air

Exhausted AirFrom each Class Room

To Wind Floor (18th level)

Motor Damper

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SensorsSensors

Anemometer,State of natural ventilation window (open or close),Integrated time while windows are open

T H

T

T

HOutdoor

Solar radiationRainfall

Wind speed at exhaust openingThermometer

T

H Hygrometer

VAnemometer

Wind speed & direction

V

V

VV

VCOdensity

2

T

These data (total 2000 points) are recorded automatically every 10 minutes

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0

200

400

600

800

1,000

1,200

1,400

1,600

1,800B3F

B1F

2F

4F

6F

8F

10F

12F

14F

16F

18F

20F

22F

23F

時間

/年

2000/3

2000/2

2000/1

1999/12

1999/11

1999/10

1999/9

1999/8

1999/7

1999/6

1999/5

1999/4

Ventilation windows were opened for 1100 hours per year

Ventilation windows were opened for 1100 hours per year

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Apr.1999-Mar.2000

Hybrid Ventilation System reduced Space Cooling Energy by 17%

Hybrid Ventilation System reduced Space Cooling Energy by 17%

0102030405060708090

Apr May Jun Jul Aug Sep Oct Nov

Prim

ary

Ener

gy C

onsu

mpt

ion

for

Spac

e C

oolin

g(M

J/m

2)

Reduced by Natural VentilationAir-handlingChilling

44

Operation Energy was reduced by 40%Operation Energy was reduced by 40%

0

500

1000

1500

2000

2500

3000

Reference Case Study Actual

Pri

mary

Energ

y C

om

sum

pti

on［M

Ｊ/a/m

2]

Cooking

Escalator

Elevator

Electr ic Applances

Lighting

Air Handling

HeatSource(Others)

Heat Source(Storage)

1,5831,647

2,696 Apr. 1999 – Mar. 2000

45

LCCO2 will be reduced by 40%LCCO2 will be reduced by 40%

0 50 100 150 200 250

Case Study

Reference

Design Intial ConstructionRe-construction RepairRenovation MaintenanceOperating Energy DemolitionRelease of HCFCs

-37%kg-CO2/a/m2

127.9

202.1

46

Other Loads will be reducedOther Loads will be reduced

0 0.2 0.4 0.6 0.8

Case Study

Reference

Formed Insulation RefrigerantFire extingusher Electric Isolator

-95%

g-CFC11/a/m2

0.036

0.669

0 100 200 300 400

Case Study

Reference


-26%g-SO2/a/m2

276.5

372.3

0 100 200 300 400 500 600

Case Study

Reference


-26%g-SO2/a/m2

414.8

558.1

0 1000 2000 3000 4000

Case Study

Reference


-34%MJ/a/m2

2422.5

3679.9

Depletion of Ozone LayerDepletion of Ozone Layer AcidificationAcidification

Health Damage (Air)Health Damage (Air) Depletion of Fossil FuelDepletion of Fossil Fuel

47

Eco-Economic AnalysisEco-Economic AnalysisInitial cost(Million

Yen)

Energycostreduction(MillionYen/year)

CostPaybacktime(Year)

CO2Reduction

(t-CO2

/Year)

Intial costper unit CO2Reduction(1000 yen/(t-CO2/year))

CO2 cont. for Fresh air Intake 13.5 10.4 1.3 1038 13Day Lithting Hf lamp 31.4 19.6 1.6 981 32CO cont. for Parking Vent. 54.1 18.0 3.0 966 56Variable Air Volume 66.9 17.2 3.9 956 70Thermal Heat Strage 0 5.4 0.0 595 0Escalator control 2.9 5.9 0.5 290 10Variable Water Volume 9.4 9.4 1.0 154 61Natural Ventilation 56.5 2.9 19.2 57 1000Total 234.7 88.8 2.6 5037 47

1999, 2000

234.7 / 20000 Million Yen= + 1.2%

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Additional Initial Cost ｛Yen/(t-CO2/a)｝

47,000JPY/(t-CO2/a)

Photo Voltaics

Eco-Economic AnalysisEco-Economic Analysis

4,000,000JPY/(t-CO2/a)

234.7 / 20000 Million JPY = + 1.2%

Meiji University

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 http://hybvent.civil.auc.dk/puplications/sotar.pdf

(135 pages)

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Annex 35 HybVent Publications are available for download at http://hybvent.civil.auc.dk/

51

Weather conditions and ventilation modeArmoury Tower – Shanghai, China


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Armoury Tower, Shanghai


53Not in handout materials (copyright limitation)

55

Queen’s College, de Montefort University, Leicester, UK


57

Umno Tower - Penang, Malaysia


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Wind flow around building – air pressure contoursUmno Tower - Penang, Malaysia

Vertical section Level 12


59

Wind pressure diagramsUmno Tower - Penang, Malaysia


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