Ventilation

A ventilation strategy must be developed to ensure that sufficient ventilation is provided to all spaces to meet the requirements of the BCA/NCC and associated standards.

Each room and space must be categorised as required by the BCA into the associated groups, including:

• Habitable spaces, where people will occupy for a time longer than 20 minutes, including all teaching spaces, libraries, offices and toilets
• Storage spaces

The need for ventilation equipment must be minimised by employing passive sustainable design principles (eg. good natural ventilation, rotary ventilators etc).

Where active ventilation systems are required, they must be designed from a “Whole of Life” (WOL) perspective to provide:

• Value for Money
• Fitn for purpose
• Long term reliability
• Minimal maintenance requirements
• Low maintenance costs

Specifically ventilation equipment must :

• Enable healthy learning environments with indoor air quality (IAQ) that supports learning and teaching (i.e. IAQ that is fit for purpose for schools)

• Support sustainable design principles including reducing energy consumption
• Be accessible and serviceable - easy to maintain with minimal impact on school use when maintenance is being performed

The ventilation systems may include any or all of the following:

• Natural ventilation
• Mechanical ventilation
• Mechanical exhaust and fume extraction
  • Dust extraction from machines
  • Duplicating printing room ventilation
  •  Fume cupboards and exhaust cabinets
  •  Chemical store ventilation
  • Ceramic kiln ventilation
  • Hot metal exhaust ventilation
  • Darkroom ventilation
  • Welding area ventilation
  • Toilet and change room ventilation
  • Kitchens (materials learning unit)
  • Light commercial kitchens

The installations must comply with the requirements of the BCA/NCC and related standards. 

Ensure effective co-ordination between disciplines. Organise the information from all sources to meet a set programme.

At sketch plan stage:

• Locate and estimate the size of the plant rooms in consultation with the Architect.
• Design appropriate ventilation system.
• Co-ordinate with other disciplines for provision of water supply, tundish for drain, power supply, structural openings etc, associated with the ventilation system.
• Prepare life cycle cost analysis as required. Assets requiring life cycle costing would include exhaust systems, supply air systems,
• Prepare estimates as required.
• Ensure that compliance is met with AS1668 Parts 1&2.  This is particularly the case with ventilation rates, distances between intakes and exhaust points, also distances to boundaries, adjacent buildings and trafficable areas.

Equipment Life-Cycle Cost Calculations

For new schools and when replacing or updating major ventilation system  components, a simple life-cycle cost should be calculated. This should be based on the Life Cycle Cost considerations following over a period of time, e.g 20 years and/ or the life of the asset.

As part of the Whole of Life analysis, the life cycle costs must consider the following:

• Capital cost of the asset
• Capital cost of any supporting/ enclosing structure (plant rooms/ platforms) and/ or servicing equipment (e.g. access ladders etc)
• Multi-service integration and interface - provision (and costs) of any supporting services (e.g. power etc.)
• Reticulation of ductwork, piping and of cables, if applicable
• Provision for expansion of plant and equipment (if a likely possibility)
• Resource (power etc.) consumption costs. Based on; 1 year, 5 years, 10 years and / or 20 years.  Resource consumption costs should be based on likely rates, envisaged usage requirements (seasonal and hours of operation)
• Maintenance required and cost of this maintenance for the realistic life span of the asset
• Frequency, nature and costs of capital upgrades needed over the life of the asset to maintain fit for purpose
• Cost of disposing of the asset or its components

The following should also be considered:

• Future improvements and updates. Flexibility and change.
• Value for Money from any chosen material, equipment or product.
• Life span of the asset.
• Accessibility for servicing

Design Conditions

• Noise criteria         NR 45 

Refer to DG / ACOUSTICS

• Provide by way of building openings allowing cross ventilation, and induced by thermal currents created via high level vents.
• Fully analyse local site conditions to allow for the impact of winds upon openings that may effect the operation of a facility (particularly canteens).
• Consider the impact of opening windows on internal noise levels.
  Refer to DG / ACOUSTICS
• Ensure that all permanent openings (eg louvres) have a vermin mesh.

Modern dry photocopiers are designed for low emissions, provided they are properly maintained (including replacement of the ozone filter). The ventilation system is to be designed to serve the whole room and is not intended to provide localised exhaust at equipment.

Provide ventilation systems to meet the following performance requirements in new photocopier and printing rooms:

• Discharge air from the ventilation unit to the outside of the building via a vermin proofed louvre.
• Draw Make-up air from inside the building through wall or door grilles.
• Inlet and exhaust grilles require security bars to preserve the physical security of the duplicating room.
• Locate the inlet/s and exhaust to achieve good airflow across the room in plan and elevation to pick up all machine emissions.
• Minimise noise emission from the ventilation equipment to the environment. Refer to section 11.04.

DUPLICATING/ PRINTING ROOM VENTILATION (cont.)

• Ensure the airflow doesn’t draw equipment emissions across operator’s face.
• Note that the room door in many schools may be left open in normal daily operation. Allow for this when locating the exhaust fan so that cross ventilation is achieved with make-up air drawn through the door opening.
• Install and treat the exhaust fan to achieve the internal noise level requirements in section 11.06.
• Provide controls for the operation of the exhaust system.  This should be a variable speed controller located adjacent to the room lighting switch with minimum and maximum settings corresponding to the limits below. This switch is to be labelled with function and an instruction when it is to be used. Required speed range: minimum of 6 air changes per hour and maximum of 15 air changes per hour. 
• Controls should also include a  time clock restricting operation to normal school hours.
• When installing a new system in an existing building, remove any existing ventilation system and replace glazing or wall where there is an existing window mounted exhaust fan. Make good any damaged surfaces.
• Ventilation of old photo copiers will require a system to be designed in accordance with the equipment manufacturer’s instructions.

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Introduction

Provide mechanical exhaust system with high and low level exhaust points to all chemical stores, with a minimum of 15 air changes per hour flow rate.

Air Discharge

Discharge air according to the requirements of BCA. The discharge outlet is to be fitted with bird wire mesh.

Fresh Air Intake

Provide make up air to all chemical stores, (to replace exhausted air) through openings in an external wall, fitted with weatherproof louvres.  All grilles and louvres are to be fitted with vandal proof bars and be fitted with vermin mesh.

For security and fire rating reasons do not use windows/doors or door grilles for air intake.

Control

The Chemical stores ventilation systems are to run continuously.

Ductwork

Use equal friction method for duct sizing with 1 Pa/m maximum pressure drop or 5 m/s maximum air velocity.

Ductwork design to comply with AS 4254.

Ductwork to be bracketed against or close to wall and allowance to be made for a 150 x 150 mm dropper.  Provision to be made for dropper to penetrate shelving to 100 mm from floor for low level exhaust intake.

The following diagram shows a typical Chemical System installation

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Diagram of Chemical Store Ventilation

1.    Low Level Exhaust.

2.    High Level Exhaust.

3.    In-Line Centrifugal Fan.

4.    Alternative Roof Mounted Vertical Discharge Exhaust Fan.

5.    2 Hour Fire Rated Enclosure for Duct to Roof Mounted Fan.

6.    Alternative Vertical Discharge Cowl.

7.    Control Switch.

8.    Air Inlet Louvre in External Wall. 

Provide galvanised steel exhaust hood over all hot metal workstations to remove the fumes and hot air.

Where hot metal and welding share the same area provide separate ventilation for each service.

The exhaust system is to be designed to ensure the Noise Rating level NR45 is not exceeded for the area where the exhaust hood is located.

Exhaust Fan

Use in-line duct-mounted exhaust fan, or a roof-mounted exhaust fan providing that all necessary safety precautions are implemented and safe access is provided for maintenance.

The fan is to be sized to ensure a uniform air velocity of 0.6m/s across the face of the hood.

Air Discharge

Discharge is to be vertical above roof and well clear of any building openings in accordance with the BCA/NCC.

Exhaust ducts that pass through floors and rooms above are to comply with the fire-rating protection requirements in the BCA/NCC.

Fresh Air Intake

Provide for make up  air to enter the workshop, to replace the exhaust air. A weatherproof and vermin-proof grille suitably sized and fitted to an external wall/window is required.

Controls

Provide a  fan on-off control with a 0-4 hour run-on timer, located near the workstation.

Provide mechanical exhaust points adjacent to each welding workstation.

Where welding and hot metal share the same area provide separate ventilation for each service.

Exhaust Point

• Provide extraction at the source of the fumes generated in the welding process by the use of an exhaust plenum.
• The plenums shall be of the side draft type with high and low exhaust points designed to remove the welding fumes away from the operator's breathing zone.
• Minimum exhaust capacity of 250 L/s per plenum.

Air Discharge

• Discharge fumes vertically to the outside of the building in accordance with the BCA/NCC.
• An in-line duct-mounted exhaust fan is to be provided, or a roof mounted exhaust fan would be satisfactory provided the necessary safety precautions are implemented and safe access is provided for maintenance.
• Ducts that pass through floors and rooms above require fire-rating protection in accordance with the BCA/NCC.

Fresh Air Intake

• Include Provision for make up air to enter the workshop to replace the exhaust air in accordance with the BCA/NCC.
• Use weatherproof and vermin-proof grille suitably sized and fitted to openings in external wall for make-up air intake.
• The use of windows/doors for air intake is not recommended.
• For large systems consisting of a number of exhaust points, a ducted filtered supply air system with heating is required.

Ductwork

• Use equal friction method for duct sizing with 1 Pa/m maximum pressure drop or 7 m/s maximum air velocity.
• Ductwork design to comply with AS 4254.
• The exhaust system including ductwork is to be designed to provide a satisfactory operating system with maximum noise levels in accordance with noise levels noted in DG / ACOUSTICS.

Control

The fan on-off control is to be located near the workstation, subject to the approval of the Design Architect.

• Provide an exhaust ventilation system complete with exhaust fan, ductwork and fittings. Provide clean make-up air from outside the building. 
• The exact heat output of the equipment along with the maximum working temperature should be confirmed by manufacturer as a guide of how to size the ventilation. Should the calculation indicate ventilation alone will not sufficiently control the air temperature to allow effective operation of the equipment due to make up air being at an unnaceptable temperature, then air conditioning should be provided to this room.
• The system is to be thermostatically controlled to activate once the room temperature reaches the maximum working temperature of the equipment and is to run continuously until the room temperature falls to an acceptable level. Provide a manual override switch to the system..
• Avoid a rate of temperature change that exceeds the permissible limit of 1^oC per 10-minute period.
• The room should preferably be windowless to avoid entry of sunlight and the associated solar heat gain. 

• Provide ducted exhaust ventilation in accordance with the BCA. 
• The designer is to ensure minimum 15 air changes per hour.
• Equipment within the laundry may require additional mechanical services including the installation of flues, exhaust ducts etc. These are to be provided to the manufacturer's recommendations.

Make-up air for the mechanical exhaust system is to be provided by under cutting doors or by providing a door grille except where room acoustic level requirements prevent this occurring.

Where there is a risk of gas build up in a cupboard enclosing a gas service, (e.g. under a gas cook top and especially with LP gas), ensure the cupboard is adequately vented by way of solid metal grilles/vents in at least one side at the top and bottom.

Ensure ventilation rate and design is in compliance with the gas code AS5601 and ventilation AS1668.2.

Where bottled gases are used, their enclosure is to comply with relevant codes and standards.