Register Module Indoor air quality Air quality is set to become even more significant in the work of the building professional, and this CPD article aims to provide an update on those parameters that are currently thought to contribute to indoor air quality Posted in April Complete the questionnaire The built environment is rightly focusing increasingly on energy efficiency. But it is important to remember that a primary purpose of the occupied building envelope is to provide a safe and comfortable environment for people — and this where internal air quality IAQ becomes a key consideration. Such effects can be highly visible as with condensation or mould , or less so but easily measurable as with radon gas accumulation, for example. By maintaining good levels of IAQ, there are likely to be tangible financial benefits through increased productivity and less workplace sickness [1].

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Mandatory Standard Standard 3. Without ventilation it is possible that carbon dioxide, water vapour, organic impurities, smoking, fumes and gases could reduce the air quality by humidity, dust and odours and also reduce the percentage of oxygen in the air to make the building less comfortable to work or live in.

Well designed natural ventilation has many benefits, not least financial and environmental, although it is also recognised that inside air quality can only be as good as outside air quality and in some cases filtration may be necessary. In other cases mechanical systems or systems that combine natural with mechanical hybrid may provide the ventilation solution for the building.

Ventilation can also have a significant affect on energy consumption and performance and so thorough assessment of natural, as against mechanical ventilation, should be made, as the decision could significantly affect the energy efficiency of the building see Section 6, Energy. Ventilation should not adversely affect comfort and, where necessary, designers might wish to consider security issues and protection against rain penetration prevalent in naturally ventilated buildings when windows are partially open to provide background ventilation.

However leaky buildings are draughty and uncomfortable. Sealing up air leaks improves comfort and saves energy whilst proper ventilation keeps the indoor air pleasant and healthy. If poor attention to detail occurs air leakage can account for a substantial part of the heating costs.

Though air leaks can dilute indoor pollutants, there is no control over how much leakage occurs, when it occurs or where it comes from. Conversions - in the case of conversions , as specified in regulation 4, the building as converted shall meet the requirement of this standard regulation 12, schedule 6. Ventilation is the process of supplying outdoor air to an enclosed space and removing stale air from the space.

It can manage the indoor air quality by both diluting the indoor air with less contaminated outdoor air and removing the indoor contaminants with the exhaust air. Ventilation should have the capacity to: provide outside air to maintain indoor air quality sufficient for human respiration remove excess water vapour from areas where it is produced in sufficient quantities in order to reduce the likelihood of creating conditions that support the germination and growth of mould, harmful bacteria, pathogens and allergies remove pollutants that are a hazard to health from areas where they are produced in significant quantities rapidly dilute pollutant odours, where necessary.

Additional ventilation provision - this guidance relates to the provision of air for human respiration and is in addition to, and should be kept separate from, any air supply needed for the smoke ventilation of escape routes in the case of fire Section 2, Fire and for the safe operation of combustion appliances see Standards 3.

There is no need to ventilate: a store room used only for storage that requires a controlled temperature a room with a floor area of not more than 4m2. This is not intended to include a domestic sized kitchen or utility room where ventilation should be in accordance with the recommendations in the table in clause 3.

Ventilation should be to the outside air. However clause 3. Calculation of volume - for ventilation purposes, a storey should be taken as the total floor area of all floors within that storey , including the floor area of any gallery or openwork floor. Where an air change rate is recommended, the volume of the space to be ventilated may be required. The volume of any space is the internal cubic capacity of the space. Any volume more than 3m above any floor level in that space may be disregarded.

However the movement of uncontrolled infiltrating air through the fabric of a building can cause draughts and can have a significant adverse effect on the energy efficiency of the building as a whole. By improving building techniques it is possible to reduce this infiltrating air to lower levels that can improve energy efficiency see Section 6 Energy. The areas of trickle ventilation shown may not suffice to maintain air quality and therefore an alternative ventilation solution should be adopted.

The options in sub-clause d provide more flexible solutions but may require complex calculations. Wet areas - where a building is naturally ventilated, all moisture producing areas such, as bathrooms and shower rooms, should have the additional facility for removing such moisture before it can damage the building.

Additional mechanical ventilation to such areas should be provided in accordance with the table to clause 3. Opening height - where rapid ventilation is provided, such as an opening window or windows, some part of the opening should be at least 1. This will reduce the problems of stratification of air.

They should be provided in naturally ventilated areas to allow fine control of air movement. A permanent ventilator is not recommended since occupants like control over their environment and uncontrollable ventilators are usually permanently sealed to prevent draughts. The trickle ventilator should be so positioned that a part of it is at least 1.

This will allow at least some movement of air within the building and reduce stratification. Although ventilation should normally be to the external air, a trickle ventilator serving a bathroom or shower room may open into an area that does not generate moisture, such as a bedroom or hallway, provided the room is fitted with a trickle ventilator in accordance with the guidance in clause 3.

A trickle ventilator should be provided in an area containing mechanical extraction to provide replacement air and ensure efficient operation when doors are closed. Pulling moist air from other parts of a building will reduce the further apart the wet rooms are located.

The trickle ventilator should be independent of the mechanical extract so that replacement air can be provided when the extract fan is operating. The location of the trickle ventilator and the extract fan should be located to prevent short-circuiting of the air. Reference should be made to the guidance to Standards 3. There are other recommendations in Section 2: Fire, relating to escape from inner rooms.

A new ventilator and trickle ventilator should be provided to the existing room but, where this is not reasonably practicable , e.

If the extension is constructed over an area that generates moisture, such as a kitchen , bathroom, shower room or utility room, mechanical extract, via a duct if necessary, should be provided direct to the outside air. Any existing system disadvantaged by the work may require to be altered to ensure supply and extracted air are still to the outside air.

Mechanical extract should be provided in rooms where the cubic space per occupant is not more than 3m3, and where the rooms have low ceilings and are occupied by large numbers of people.


CIBSE Software Tools

Register Module The ubiquity of carbon dioxide in building services engineering This module explores how carbon dioxide is ever-present in building services engineering and how this should be considered in a variety of applications Posted in February Complete the questionnaire Carbon dioxide CO2 is omnipresent in the world of the building services engineer. Aside from atmospheric CO2, the gas is used in refrigeration and, commonly, for the assessment and control of indoor air quality IAQ to provide healthy and productive internal environments. A carbon atom forms four bonds with neighbouring oxygen to form CO2 molecules, as shown in Figure 1. Carbon dioxide is often misunderstood as being toxic because it is frequently associated with asphyxiation and even loss of life. CO2 can be toxic at extremely high concentrations and cause asphyxiation; however, such issues are more likely to happen because enclosed environments are vulnerable to CO2 accumulation that displaces the oxygen from the area, so causing hypoxia low oxygen levels in body tissues. When present at relatively high concentrations — typically quoted in references related to building occupants as being above 10,ppm — it is commonly thought to cause drowsiness. The current atmospheric CO2 level1 is reaching beyond ppm Figure 2 on an apparently steadily rising trajectory.


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This article will reflect on the application of natural ventilation as a method of maintaining IAQ, and consider the application and control of natural ventilation for school buildings. As discussed more fully in the December CPD article Hybrid ventilation for schools, ventilation in buildings can be broadly categorised as natural, mechanical or hybrid ventilation. All three ventilation types have appropriate applications; however, determining whether there is an opportunity for natural ventilation would be the normal starting point for a project. Cp is the pressure coefficient, and will depend on the shape of the building and the direction of the wind. Values of Cp are typically determined using wind tunnel tests as well as computational methods.


AM10 Natural Ventilation in Non Domestic Buildings



Module 27: Indoor air quality


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