CTT1 CIBSE Top Tips 1: Ventilation in Buildings
CTT1 CIBSE Top Tips 1: Ventilation in Buildings
Further CIBSE Top Tips
CIBSE Top Tips Information Sheet 1: Ventilation in Buildings
Buildings need to be both properly ventilated and energy efficient. This information sheet is intended to help property operators, facilities managers and designers to understand how buildings are ventilated and what they can do to ensure buildings provide a healthy, comfortable and productive working environment in an energy efficient manner. By following the information provided, building operators, facilities managers, designers and employers will be able to demonstrate compliance with Regulation 6 Ventilation in The Workplace (Health, Safety and Welfare) Regulations 1992. Where there may be concern or areas of high risk then it is recommended that professional advice is sought.
Top Tips for Ventilation in Buildings
- Buildings need to be both properly ventilated and energy efficient
- Unnecessary ventilation can waste energy and cost a lot of money
- General ventilation provides clean, fresh, uncontaminated air, in sufficient quantities to dilute odours, fumes and contaminants in the air
- Where there are contaminants based on vapours, fumes and gases, re-circulation is not recommended
- In industrial premises, it is important to ensure that enough fresh air is supplied to dilute and remove the dust, fumes or vapour produced
- Where dust, fumes and vapours are produced, it is essential to carry out a COSHH Risk Assessment
- It is important to ensure that supplied or make-up air comes from an uncontaminated area
- The position of the room air inlet will have an effect on comfort factors such as draughts and should be considered at the design stage
- Filter removal and replacement must be considered by ensuring sufficient space and means of access is provided
- Mechanical ventilation systems need to be kept in effective working order.
Buildings account for over 45% of UK energy use and carbon emissions. Various energy management policies aim to reduce this figure. As the performance of building insulation and construction techniques steadily improve, energy lost through ventilation accounts for a growing proportion of total building energy consumption. Unnecessary ventilation can waste energy and cost you a lot of money. For example, ventilation accounts for around 30% of heat loss in most commercial buildings (an estimated 25% in industrial buildings).
Building Regulations require that buildings be adequately ventilated to ensure the health and safety of building occupants. There is plenty of evidence that well ventilated workplaces are more comfortable, healthier and more productive places to work.
Building owners and operators have to balance the need to reduce energy use with the need to provide workplaces and public spaces that are appropriately ventilated for the activities that take place in them.
In industrial buildings, general ventilation can also be provided to supply clean, fresh, uncontaminated air in sufficient quantities to dilute odours, fumes and contaminants in the air. This type of system provides airflow to the entire volume of a space, either by natural or mechanical (controlled) means of ventilation. It can be applied to a range of tasks involving small, medium or large-scale use of solids, liquids, vapours and gases. Where dust, fumes and vapours are produced, it is essential to carry out a COSHH Risk Assessment to satisfy the requirements of Regulation 6 of The Control of Substances Hazardous to Health Regulations 2002 (as amended). General Ventilation may be insufficient to prevent workers exposure to harmful airborne contaminants. Local Exhaust Ventilation or other control strategies may be required.
How buildings are ventilated
Buildings can be ventilated in three different ways:
- they can be naturally ventilated with outside air
- they can be fully closed, with no user controlled openings, and ventilated mechanically, or
- they can use a combination of the two approaches.
Natural ventilation uses the natural driving forces of wind (wind effect) and temperature differences within the building (the stack effect or hot air rising) to drive airflow through the building on a daily or even hourly basis. The outside environment influences natural ventilation performance. Natural ventilation will normally be enough to control dusts and vapours in offices or shops (e.g. from cleaning materials) and other applications including schools.
Mechanical ventilation uses fans, ducts and control systems to drive the ventilation process, and is generally independent of the outside environment in typical weather conditions .
Most large buildings such as city centre offices, public buildings, shopping malls and hospitals are mechanically ventilated. In addition to providing air from outside the building, mechanical systems are also often used to distribute heated or cooled air. To improve the efficiency of the system a proportion of the air may be re-circulated, and air being exhausted from the building is often passed through heat exchangers to recover heat. In an industrial premise with dusts, clean, filtered air can be re-circulated into the workroom. Where there are contaminants based on vapours, fumes and gases, re-circulation should be approached with caution. See Institute of Local Exhaust Ventilation Engineers (ILEVE) guidance.
In a factory or other building where an industrial process takes place, there will normally need to be controlled general ventilation to remove contaminated air and make it up with clean replacement air. This can be a wall-mounted fan to extract or supply air, with venting through airbricks, grills or louvres, or a more complex ducted air supply and removal system.
Mixed Mode or Hybrid ventilation uses a combination of both natural and mechanical ventilation.
Why buildings are ventilated
There are a number of reasons to ventilate a building, including:
- Providing sufficient fresh air for occupants and removing exhaled air and odours;
- Maintaining indoor air quality and the performance of building occupants;
- Maintaining a comfortable temperature appropriate to the task(s) being undertaken;
- To remove excess heat, pollutants and odours arising from localised sources such as kitchens, toilets, photocopier rooms, server rooms;
- To move heated, cooled or humidity controlled air around a building;
- To prevent condensation and mould growth within the building fabric;
- To support the efficient operation of processes within the building.
- To remove contaminated air (due to dust and fume etc.) from industrial premises
- To provide make-up air to replace air extracted by Local Exhaust Ventilation (LEV).
Most people have experienced a stuffy warm room, and understand the effect of an inadequately ventilated atmosphere. It may happen because there are many people producing heat and breathing out carbon dioxide, with insufficient fresh air being supplied to replace the warm, carbon dioxide laden air.
How much ventilation do I need?
The quantity of ventilation required depends on a number of factors, including the fresh air required for the number of people expected to be in the space, what they will be doing, how they are expected to dress, the types of local heat sources such as lighting, small appliances and computers, any sources of pollutants in the space, such as copiers, and sources of humidity such as catering equipment.
In industrial premises, it is important to ensure that enough fresh air is supplied to dilute and remove the dust, fumes or vapour produced. The rate of ventilation for an area is normally expressed in ‘air changes per hour’ i.e. the number of times per hour that the entire air volume of the area is changed. It is important to note that because of mixing in the room, it does not mean that all the original air is replaced with each air change. The rate selected depends of the type of room and the activity being undertaken. Typical applications range between 5 and 15 air changes per hour.
If a Local Exhaust Ventilation (LEV) system is supplied as part of a strategy to control airborne contaminants hazardous to health, it is important to ensure that supplied or make-up air comes from an uncontaminated area.
Ensure air intakes are not sited in contaminated areas or near where contaminated discharged air is exhausted. Likewise, ensure discharge exhaust air is kept away from doors, windows and other air inlets. Where possible, it is important to ensure that air comes from a fresh source, flows past the worker and then past the work activity to the extraction point.
CIBSE Guide B2 gives detailed guidance on the appropriate ventilation rates for a wide range of specific building types.
How the building itself influences the need for ventilation
The fabric of the building will also have an effect on the ventilation rate. Solar heat gains will increase the need to cool spaces in warm weather. Heavyweight building materials can absorb more heat than lightweight materials, so the construction will have an effect on temperature and on ventilation. Other thermal properties of the building fabric, including insulation, glazing and window choice, blinds and shading and even the shape and orientation of the building can affect temperature gains (and losses) and therefore the required rate of ventilation.
Buildings are never totally sealed, they all leak air, a process known as infiltration. The infiltration rate is the rate at which conditioned air leaks out to be replaced by unconditioned air, and this rate affects the ventilation requirements. Some older buildings have particularly high infiltration rates.
Design and installation considerations
The designer’s objective must be to design an air distribution system where arrangements of ductwork and the selection and disposition of the components, particularly the means of air regulation, will promote a balanced and stable airflow.
The position of the room air inlet will have an effect on comfort factors such as draughts and should be considered at the design stage.
Noise problems can arise due to terminals, plant room equipment or emission to atmosphere.
Adequate space needs to be allowed to accommodate installation, maintenance and replacement of central plant.
Fire dampers are required to prevent the spread of fire in ductwork. Adequate provision is required for access to maintain their integrity.
Avoid the use of abrupt bends, area reductions and sharp objects inside duct joints. Avoid long duct runs since these can create balancing difficulties.
Access doors and covers should be easy to open and be constructed and installed to match the type and location of any thermal, acoustic or fire insulation. The location of, and distance between, openings depends on the quality of supply and extract air and on the defined or available cleaning method. The designer should take specialist advice and stipulate the requirements for periodic internal cleaning and maintenance of the ductwork.
Ductwork should be insulated where appropriate to reduce energy use and avoid condensation.
When specifying new fan motors, always specify higher efficiency motors as they will save you up to 5% on energy costs, for little or no extra capital cost.
Variable speed fans can slow down when ventilation demands decrease. This will save money on electricity as well as reducing heating/cooling costs.
Make sure fans aren't running when they're not required. This not only wastes energy, but also removes heat from the building.
Instruments should be provided and located as required. These components (e.g. dampers, sensors, airflow-measuring devices) should be installed so that they can be cleaned in-situ or removed for cleaning and be easily accessed safely.
Filter removal and replacement must be considered by ensuring sufficient space and means of access is provided.
The air quality within a building is influenced by the contaminants in the form of particles and gases that are generated within the building envelope and those brought in from outdoors. The designer should specify the requirements for the Cleanliness Quality Class to be achieved. BS EN 15780: 2011 provides further guidance. The Cleanliness Quality allows the specifier to set measurable maximum acceptable dust accumulation levels, as a benchmark for acceptance.
Maintenance, examination and testing of ventilation systems
Mechanical ventilation systems need to be kept in effective working order. Maintain the systems as advised by the supplier or installer. In the absence of such information, guidance is available in B&ES SFG 20. CIBSE Guide M Maintenance engineering and management provides good practice information. Follow any special procedures before any systems are opened or entered, e.g. purging or cleaning. Do not forget you may need PPE for some maintenance tasks.
Inspection of the ventilation system will usually start with a visual check of all the equipment (e.g. dampers, protective devices against weather, insects and rodents, the hygiene of the coils, fans and insulation, the presence of water and condition of condensate drain pans and humidifier reservoirs). Such inspection should be at least once a week for signs of damage or faults. A smoke test can quickly determine if the outside air is entering the system.
If a Local Exhaust Ventilation (LEV) system is supplied as part of a strategy to control airborne contaminants which may be hazardous to health, it is necessary for their commissioning, maintenance and testing to be carried as defined by the COSHH Regulations. Additionally, operators must be trained in the use of the equipment. Operator health surveillance and monitoring may also be necessary. Records must also be kept for periods up to 40 years. A user manual or logbook is helpful in setting out the frequency of checking, maintenance and parts replacement. For LEV systems with no user manual or logbook, you may need the help of a competent person who can determine the performance needed for adequate control. Records of all examinations need to be kept to enable you to demonstrate that the system has been maintained and examined regularly in accordance with Regulation 9 of COSHH. ILEVE provides a Competency card to its members who have had their competencies assessed and are able to advise on matters of Local Exhaust Ventilation.
The maintenance of the filters can be based on the time intervals or on the condition. The life of the filter will depend upon the concentration and nature of the contaminants (e.g. pollution, dust, fume), the efficiency of the filter, the dust holding capacity corresponding to rise in pressure loss between clean and dirty conditions and the face velocity at the filter.
Three aspects of safety need to be addressed concerning ductwork:
- During design: there are safe and secure means of access to the ductwork and associated plant and equipment (e.g. filter housing) for inspecting, maintenance and cleaning
- During installation: that the ductwork can be installed safely and securely
- During building operation: maintenance and fire protection are maintained. Avoid using fibrous materials which may be detrimental to health to act as sound absorption.
Cleaning and housekeeping
To enable cleaning to be carried out safely and efficiently, it is important that the air distribution system is designed and installed so that all internal surfaces and components can be accessed. A comprehensive standard for access installation is provided by BS EN 12097: 2006 Ventilation for Buildings – Ductwork – Requirements for Ductwork Components to Facilitate Maintenance of Ductwork Systems.
Components (e.g. dampers, sensors, airflow-measuring devices) should be installed so that they can be cleaned in-situ or removed for cleaning.
There are several methods available for cleaning systems of dust, debris, and other surface contamination; vacuum, steam. Caution: Never allow the use of brushes or compressed air for removing dust from clothing, surfaces or from inside machinery. Cleaning methods are fully described in B&SE Guide to Good Practice - Internal Cleanliness of Ventilation Systems TR19 (2013) and BSRIA FMS 1/97 Guidance and Standard Specification for Ventilation Hygiene. Methods will vary according to the air distribution system.
The cost of not ventilating appropriately
Inadequate building ventilation can have a significant negative impact on operating costs by impairing employee performance, since the cost of running and staffing the business is usually the most significant to users. Over a ventilation system life of ten to fifteen years, a 1% reduction in productivity will usually significantly exceed any savings made on the design and installation costs of the system. Therefore, it is important for building owners and operators to ensure that buildings are ventilated to provide a healthy and effective environment.
In prestige office buildings, the need to keep the occupants happy and comfortable is often considered more important than energy efficiency measures. This is often because the level of occupant complaints logged by the facility manager is a key performance indicator, whilst efficient use of energy is not. Owners and operators need to balance the requirements for good ventilation and energy efficiency and ensure that both the building management team and the occupiers understand this.
Where Local Exhaust Ventilation has been provided to control a hazardous material as required by COSHH, duty holders/facilities managers should proceed with caution when considering reducing air flows to save energy and should seek competent advice. ILEVE members can assist with this.
One approach to indoor temperature control is to allow indoor temperature to drift in response to adaptation to climate conditions. Again, ventilation can play an important role by offering a degree of passive cooling and air movement. Proper design of the ventilation system can significantly reduce whole life costs of the building.
 Under extreme conditions of heat or cold the effectiveness of some of the plant, which provides the sources of heating or cooling for the ventilation system may be adversely affected.
B&ES (2012) SFG20 Standard Maintenance Specification for Building Services (B&ES: Penrith)
B&SE (2013) Guide to Good Practice - Internal Cleanliness of Ventilation Systems TR19 (B&ES: Penrith)
BSI (2006) BS EN 12097: 2006 Ventilation for Buildings. Ductwork. Requirements for Ductwork Components to Facilitate Maintenance of Ductwork Systems (London: British Standards Institution)
BSI (2011) BS EN 15780: 2011 Ventilation for Buildings. Ductwork. Cleanliness of Ventilation Systems (London: British Standards Institution)
BSRIA (1997) FMS 1/97 Guidance and Standard Specification for Ventilation Hygiene (Bracknell: BSRIA)
CIBSE (2014) Guide M Maintenance Engineering and Management (London: Chartered Institution of Building Services Engineers)
CIBSE (to be published 2015) Guide B2 Ventilation and Air Conditioning (London: Chartered Institution of Building Services Engineers)
TSO (1992) Workplace (Health, Safety and Welfare) Regulations 1992 No. 3004 (London: TSO)
TSO (2002) Control of Substances Hazardous to Health Regulations 2002 No. 2677 (London: TSO)
Within Europe the Energy Performance of Buildings Directive (EU, 2010) covers energy conservation requirements for buildings [link to CIBSE website]. This requires member states to apply minimum requirements covering the energy performance of both new and existing buildings. All new buildings and those undergoing major refurbishment must be “nearly zero energy”.
There is currently (2015) a UK government commitment to achieving zero carbon commercial buildings from 2019. For large businesses there is also the Climate Change Levy and Carbon Reduction Commitment, which are, effectively, taxes on energy use.
The Energy Savings Opportunity Scheme (ESOS) is a mandatory energy assessment and energy saving identification scheme for large undertakings (and their corporate groups). The scheme applies throughout the UK, and will require “large enterprises” to undertake four yearly energy audits covering all buildings. For more information on ESOS and becoming a CIBSE ESOS Lead Assessor visit here.
Part L of the Building Regulations, covering energy efficiency, has recently been revised to set more challenging carbon emissions targets for new non-domestic buildings. Similar changes are anticipated by the devolved administrations.
ASHRAE (2013) Standard 62.1: 2013 Ventilation for Acceptable Indoor Air Quality (Atlanta, USA: ASHRAE)
British Land (2014) Exchange House story: http://views.britishland.com/2014/01/an-energy-efficiency-success-story-at-exchange-house/
BSI (2009) BS 5422: 2009 Method for Specifying Thermal Insulating Materials for Pipes, Tanks, Vessels, Ductwork and Equipment (London: British Standards Institution)
BSI (2010) BS EN 15650: 2010 Ventilation for Buildings. Fire Dampers (London: British Standards Institution)
BSI (2012) BS 5970: 2012 Thermal Insulation of Pipework, Ductwork, Associated Equipment and Other Industrial Installations (London: British Standards Institution)
BSRIA (2000) AG17/00 Achieving minimum outdoor air – commissioning and test procedures (Bracknell: BSRIA)
BSRIA (1998) S10/98 Air Tightness Specification (Bracknell: BSRIA)
CIBSE (2005) AM10 Natural Ventilation in Non-domestic Buildings (London: Chartered Institution of Building Services Engineers)
CIBSE (1996/2006) Commissioning Code A: Air distribution systems (London: Chartered Institution of Building Services Engineers)
CIBSE (2011) KS17 Indoor Air Quality and Ventilation (London: Chartered Institution of Building Services Engineers)
CIBSE (1991) TM21 Minimising Pollution of Air Intakes (London: Chartered Institution of Building Services Engineers)
CIBSE (2000) TM23 Testing Buildings for Air Tightness (London: Chartered Institution of Building Services Engineers)
CIBSE (2012) TM44 Inspection of Air Conditioning Systems (London: Chartered Institution of Building Services Engineers)
DECC (2014) Energy Savings Opportunity Scheme (London: DECC) See https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/351158/ESOS_Guide_FINAL.pdf
Energy Institute (2001) Air Quality and its Association with Human Health Effects - an Update (London: Energy Institute)
HM Government (2010) Building Regulations 2000 Approved Document
F: Ventilation (London: HM Government) See http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partf/approved
HM Government (2013-14) Building Regulations 2000 Approved Document
L: Conservation of Fuel and Power – L1A, L1B, L2A, L2B (London: HM Government) See http://www.planningportal.gov.uk
HSE (2013) L24 Workplace (Health, Safety and Welfare) Regulations 1992. Approved Code of Practice and guidance (London: HSE) See http://www.hse.gov.uk/pubns/priced/l24.pdf
TSO (1992) Workplace (Health, Safety and Welfare) Regulations 1992 No. 3004 (London: TSO)
© CIBSE 2015
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