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
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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
17
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
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.
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
24
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
Heat Storage TankRain Water Tank
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
Heat Storage TankRain Water Tank
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
Heat Storage TankRain Water Tank
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
Heat Storage TankRain Water Tank
Canteen
Roof Garden
Natural Ventilation Shafts for 19-22FNatural Ventilation Shafts for 19-22F
33
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
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
Heat Storage TankRain Water Tank
Canteen
Roof Garden
Lecture Rooms on 6-16F & B1-3FLecture Rooms on 6-16F & B1-3F
35
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)
36
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
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
Heat Storage TankRain Water Tank
Canteen
Roof Garden
Library B3-1FLibrary B3-1F Day-lighting even on B3F
38
Library B3-1FLibrary B3-1F Day-lighting even on B3F
39
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
40
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
42
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
43
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
Design Intial ConstructionRe-construction RepairRenovation MaintenanceOperating Energy DemolitionRelease of HCFCs
-26%g-SO2/a/m2
276.5
372.3
0 100 200 300 400 500 600
Case Study
Reference
Design Intial ConstructionRe-construction RepairRenovation MaintenanceOperating Energy DemolitionRelease of HCFCs
-26%g-SO2/a/m2
414.8
558.1
0 1000 2000 3000 4000
Case Study
Reference
Design Intial ConstructionRe-construction RepairRenovation MaintenanceOperating Energy DemolitionRelease of HCFCs
-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
Not in handout materials (copyright limitation)
52
Armoury Tower, Shanghai
Not in handout materials (copyright limitation)
53Not in handout materials (copyright limitation)
54Not in handout materials (copyright limitation)
55
Queen’s College, de Montefort University, Leicester, UK
Not in handout materials (copyright limitation)
56Not in handout materials (copyright limitation)
57
Umno Tower - Penang, Malaysia
Not in handout materials (copyright limitation)
58
Wind flow around building – air pressure contoursUmno Tower - Penang, Malaysia
Vertical section Level 12
Not in handout materials (copyright limitation)
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Wind pressure diagramsUmno Tower - Penang, Malaysia
Not in handout materials (copyright limitation)
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