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Natural Ventilation Strategies Modelled within Schools
Seminar Contents
About Passivent
Natural Ventilation Design- Summer and Winter considerations
School Case Study
Wind Driven Case study
Passivent Commercial• Formed 1997• Schools, Offices, Leisure• Natural Ventilation, Natural
Daylighting, and Mixed Mode cooling systems
• Operate in UK and Ireland
Passivent Domestic • Formed 1984• Dwellings• Natural and Mechanical
ventilation
Sustainability Health and Safety Quality ManagementISO 14001 Management ISO 9001, IIP
OHSAS 18001
Group
About Passivent
Natural Ventilation Design
There are two different aims within the design, and these are often best meet by different product groups;
- Design 1. Ventilation to control the indoor air quality (winter)
- Design 2. Ventilation to control internal temperatures (summer)
Natural Ventilation Design
1. Ventilation to control the indoor air quality (winter design)- Inlet products are typically automatic façade louvre inlets for fine motor control- Outlet products are typically roof mounted outlet terminals / high level Aircools /
Automatic windows- Winter time control via internal CO2 levels
WINTER STRATEGY
Airstract Roof Terminal
Aircool
Natural Ventilation Design
2. Ventilation to control internal temperatures and the avoidance of overheating (summer design)- Inlet products for Rapid Daytime ventilation are typically manual / automatic opening windows- Inlet products for Night time cooling & background ventilation are typically Aircool louvres as weather
resistance, automatic, and secure- Outlet products are typically Roof mounted outlet terminals / high level Aircools- Summer time control via internal & external temperature
SUMMER STRATEGYAircool
Airstract Roof Terminal
School Case Study
21 Zone Primary School employing a Natural ventilation system
Single and two-storey blocks
Modeled using Dynamic Thermal Simulation (DTS) to predict overheating risk and ventilation
Weather file CIBSE Test Reference Year (TRY) hourly weather data for London
Two design strategies modeled for winter and summer time operation
Mixed mode cooling features
School Case Study
Building plans shown with the 6 zones that were selected for thermal modelling
BB101 compliance calculations undertaken for the 6 zones
G030 was selected for a detailed analysis to show hourly temperature and internal CO2 levels for summer and winter design strategiesGround Floor First Floor
Figure 3 Plans showing zones selected for detailed investigation
Table 1 Spaces selected for detailed investigationRoomKey
RoomNumber Function Orientation
G030 Classroom 4B South EastG005 Classroom 2B North WestG019 ICT Room South WestG036 Multi-Purpose South WestF005 Classroom 6B South EastG054 Reception R2 South West
Note: G036 is included because it shares an exhaust outlet with G019.
School Case Study
SUMMER TIME STRATEGY
Windows for Rapid ventilation (8 l/s/p) providing capability for 1000ppm
Background ventilation through Aircool ventilators
Night Cooling strategy reducing peak day temperatures through Aircool ventilators, as secure and provide weather rejection
Manual +Automaticwindows
Aircool Insulatedlouvre
G030Manual +Automaticwindows
2 No. Aircool1100x280mm
F005
2 No. Aircool1100x280mm
Airstract 1250x1250mmRoof Terminal
School Case Study
WINTER TIME STRATEGY
Aircools used for background ventilation requirements (5 l/s/p)
Ventilators provided with a pre-heater to warm the supply air
Ventilators are automatically controlled, based on internal CO2levels
Aircools provide fine control in winter, as opposed to a coarse window opening control.
Automatic control important as people do not react to CO2 levels, they do react to summer temperature levels
Aircool Insulatedlouvre
G030
F005
Aircool c/wpreheater
Aircool c/wpreheater
Airstract Roof Terminal
School Case Study
A simple control strategy was included in the thermal model to mimic the real buildings response using the Passivent controller
Summer- Inlet windows and Aircool louvres operate
based on internal temperature between 20ºC to 24ºC, 0-100% open
- Aircool louvres were opened at night and weekends to simulate night cooling
Winter- Ventilation supplied through opening Aircool
louvres only, during occupied times- All windows remain closed in winter- Aircools controls by CO2 concentration
between 800ppm and 2000ppm, 0-100% open
- Heating set point during occupied times 21ºC
Room G030 Summer Temperature
Typical Summer Week
Internal Temperature, External Temperature, Internal Gains and Solar Gain during a typical week in the summer period
Temperature fluctuates with changes in external conditions and heat gains
Summer averages calculated to show compliance with BB101 (see summary slide later)
Mon Tue Wed Thu Fri Sat Sun Mon
35
30
25
20
15
10
5
0
-5
Tem
pera
ture
(°C
)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Gain (kW
)
Date: Mon 04/Jun to Sun 10/Jun
Air temperature: G030 (grand_avenue_nc_2.aps) Internal gain: G030 (grand_avenue_nc_2.aps) Solar gain: G030 (grand_avenue_nc_2.aps)
Dry-bulb temperature: (grand_avenue_nc_2.aps)
Room G030 Summer Temperature
Summer Months
Internal Temperature and External Temperature during June and July in the summer period
Temperature fluctuates with changes in external conditions and heat gains
Summer averages calculated to show compliance with BB101 (see summary slide later)
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 01
35
30
25
20
15
10
5
0
-5
Tem
pera
ture
(°C
)
Date: Fri 01/Jun to Sat 30/Jun
Air temperature: G030 (grand_avenue_nc_2.aps) Dry-bulb temperature: (grand_avenue_nc_2.aps)
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 01
35
30
25
20
15
10
5
0
-5
Tem
pera
ture
(°C
)
Date: Sun 01/Jul to Tue 31/Jul
Air temperature: G030 (grand_avenue_nc_2.aps) Dry-bulb temperature: (grand_avenue_nc_2.aps)
Room G030 Summer CO2 Levels
Typical Summer Week
Internal Gains and CO2 Concentration during a typical week in the summer period
CO2 Concentration (ppm) remained below the 1500ppm average daily target
Mon Tue Wed Thu Fri Sat Sun Mon
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Gai
n (k
W)
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
CO
2 concentration (ppm
)
Date: Mon 04/Jun to Sun 10/Jun
Internal gain: G030 (grand_avenue_nc_2.aps) Room CO2 concentration: G030 (grand_avenue_nc_2.aps)
Room G030 Summer CO2 Levels
Summer Months
CO2 Concentration during June and July in the summer period
CO2 Concentration (ppm) remained below the 1500ppm average daily target
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 01
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
CO
2 co
ncen
tratio
n (p
pm)
Date: Fri 01/Jun to Sat 30/Jun
Room CO2 concentration: G030 (grand_avenue_nc_2.aps)
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 01
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
CO
2 co
ncen
tratio
n (p
pm)
Date: Sun 01/Jul to Tue 31/Jul
Room CO2 concentration: G030 (grand_avenue_nc_2.aps)
Room G030 Winter CO2 Levels
Typical Winter Week
CO2 Concentration during a typical week in the winter period (Aircool units operating only)
CO2 Concentration (ppm) remained below the 1500ppm average daily target
Mon Tue Wed Thu Fri Sat Sun Mon
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Gai
n (k
W)
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
CO
2 concentration (ppm)
Date: Mon 10/Dec to Sun 16/Dec
Internal gain: G030 (grand_avenue_nc_2.aps) Room CO2 concentration: G030 (grand_avenue_nc_2.aps)
Room G030 Winter CO2 Levels
Winter Months
CO2 Concentration during December and January in the winter period (Aircool units operating only)
CO2 Concentration (ppm) remained below the 1500ppm average daily target
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 01
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
CO
2 co
ncen
tratio
n (p
pm)
Date: Sat 01/Dec to Mon 31/Dec
Room CO2 concentration: G030 (grand_avenue_nc_2.aps)
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 01
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
CO
2 co
ncen
tratio
n (p
pm)
Date: Mon 01/Jan to Wed 31/Jan
Room CO2 concentration: G030 (grand_avenue_nc_2.aps)
Modelling Results (Summer)
SUMMER RESULTS
The combination of Day and night cooling natural ventilation is sufficient to meet the overheating criterion specified in BB101, except for the ICT room (G019)
A mixed mode cooling system was employed for the ICT room, only
The combination of Aircool units and opening windows provide sufficient ventilation to meet the CO2 criteria set out in BB101
Table 2 Thermal Performance predictions (two criteria to be met)
RoomNumber of hours
over 28°C.Target is 120
Average Int / ExtTemp Diff (°C)Target is 5°C
Maximum InternalTemperature (°C)Target is 32°C
G030 3 3.8 29.1G005 7 4.1 30.5G019 (ICT) 105 6.3 32.4
G036 3 3.5 29.6F005 4 3.1 30.1G054 7 3.2 30.7
Table 3 Air quality predictions during summer period (Windows and Aircoolventilation May to Sept) (all criteria to be met)
RoomMaximum CO2
Concentration (ppm)Target <= 5000ppm
Maximum Average CO2Concentration (ppm)Target <= 1500ppm
G030 1371.0 1177.3G005 1270.0 1141.1G019 (ICT) 947.0 836.4
G036 985.0 882.3F005 1226.0 1050.4G054 1177.0 1087.3
Modelling Results (Winter)
WINTER RESULTS
The Aircool units alone provide sufficient inlet ventilation to meet the CO2 criteria set out in BB101
The CO2 control strategy proved successful
Table 4 Air quality predictions during winter period (Aircool ventilation Oct to April)
RoomMaximum CO2
Concentration (ppm)Target <= 5000ppm
Maximum Average CO2Concentration (ppm)Target <= 1500ppm
G030 1248.0 1114.9G005 1224.0 1168.6G019 (ICT) 1085.0 1017.1
F005 1173.0 1082.3G054 1132.0 1023.1Note: 1500ppm target equates to satisfying the controllable ventilation at aminimum rate of 3 l/s/person (BB101) [1].
Wind Driven Ventilation Case Study
Wind driven roof mounted device
Air is supplied and exhausted at roof level through the same device, as split into 4 chambers
Best operation in exposed location, with no surrounding obstructions
Ideal for larger spaces, such as Main or Sports Halls, Dance studios, dining rooms, and corridor or foyer spaces.
Not suitable for landlocked classrooms with high occupancy density, as can not revert to Passive stack mode, during periods of low wind speeds and CO2 targets exceeded
Wind Driven Ventilation
Basic System (Louvre)- Typical Application: Areas with higher ceiling
heights, such as foyers, corridors, halls
- Draught risk in low ceiling spaces
Direct Air Dispersal System- Typical Application: Halls and dance studios
- Good air distribution
Remote Air Dispersal System- Typical Application: Offices and classrooms
- Good air distribution & mixing
- Can easily reposition grilles to avoid draughts
Wind Driven Ventilation
Landlocked spaces detail modelling- From modelling it is not appropriate to design landlocked classrooms with their high occupancy
densities, with Wind driven devices with no façade openings in Winter or Summer.
- The CO2 target is exceeded, even with the largest unit, due to times of low wind speeds
- The table below shows an analysis of a school using wind driven devices. 4 systems fail the CO2 criteria, and these are the only 4 rooms with no façade openings
- It is important that the correct product is specified for the correct application, with the high density of spaces within schools
Any Questions?
Thank you
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