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?

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