CONFORT

Confort

SagiCofim est une référence en matière de garantie de confort et pour tout type d’installation: applications indoor, auditoriums, musées, bureaux, magasins, bâtiments publics et hospitaliers.

Grâce à des composants et des solutions intégrées, nous garantissons un niveau maximal de confort en respectant les critères suivants: réduire la vitesse de l’air dans la zone occupée, maintenir la plus basse consommation d’énergie et les plus faibles variations de températures, respecter le niveau sonore.

Mission

SagiCofim, specialists in the air diffusion and distribution sector, provide innovative, high-tech solutions for all types of shared human spaces: offices, representative buildings, museums, theatres, cinemas, ateliers and showrooms, residential or hospital accommodation and facilities.

We believe that the most important design element in a building, its primary spatial characteristic, is habitability: that is, the features of the environment and the life going on inside it.

Often, in the professional world, people spend many hours of the day inside these types of building, so the spaces there must be designed to promote their health, well-being and the quality of their work.

In other cases – cinemas, theatres, exhibitions – the spaces have to cope with large influxes of visitors, but perhaps over shorter periods of time or at longer or shorter intervals. Here too, people’s comfort is essential to ensure they can focus on and enjoy their time spent here.

Sometimes, the venue has been around for a long time: it may be extremely old, grand and of significant historical and artistic interest. Here too, it is important to make sure that the beauty of the building is preserved at the same time as protecting the well-being of the people visiting it.

We are air experts, and we believe that this variety of different situations presents us with an important and vital challenge: to create an environment, a microclimate, that is human-centric and meets the needs of every person in it. Technology helps us to do this, providing us with a wide variety of solutions that we adapt to suit each specific case.

We are the preferred choice for designers and installers who, in new and old buildings alike, are looking for a partner with the breadth of skills to take care of the entire air diffusion and distribution, ventilation, humidification and acoustics side of a project. We are also the ideal partners for customers looking for high quality individual components.

Our extensive experience has shown us that right from the very beginning of the design process, the client and the designer must work together to define the project objectives and to make the right technical choices to meet them, to guarantee:

  • the quality of indoor air to control contamination of the air, of production processes and of workers themselves, by maintaining optimum quality standards (to combat “sick building syndrome” that affects a large number of workers, caused by ill-designed and poorly maintained ventilation systems);
  • the physical and dynamic isolation of individual environments;
  • the optimum life cycle of the installation. Nowadays, Life Cycle Cost – which concerns both the economic and energy aspects of a project, but also the guaranteed performance of the systems – is a determining factor, both on a design and management level, when assessing the quality and suitability of a system or installation.

Our convictions, reflected in our professional practices, have allowed us to collaborate on many important design studies. We have designed and implemented high level integrated solutions throughout Italy and Europe (Royal Palace of Milan, Carlo Felice Theatre in Turin, Prada Foundation in Milan, etc.).

SagiCofim is capable of ensuring this level of performance because it develops, designs and manufactures at the highest level: it owns its own factories with advanced production processes, equipped with highly automated production lines for building aeraulic components and the whole range of filters and filtering systems. It feeds and updates the production processes through its specialist Research, Development and Testing Centre, that operates in close collaboration with the Polytechnic University of Milan on both the theoretical research phases and on carrying out and validating tests carried out in the field.

At its headquarters in Cernusco sul Naviglio (Milan), it also has its filter and filtration system manufacturing unit; here there is a technologically advanced testing circuit, annexed to the production line, for testing every high and very high efficiency HEPA and ULPA filter in accordance with EN 1822 standards, to further guarantee the quality of every product that leaves the factory.

The aeraulic components are produced at its Bareggio facilities, outside Milan, and in Teglio in Valtellina (Sondrio).

SagiCofim’s international vocation is demonstrated through projects carried out and under way in several European and international locations. Its French headquarters in Lyon focusses primarily on the commercial side of the business and it also has a presence in other European countries through operative agents with proven technical skills, who are able to evaluate and advise on the situation in hand.

Beyond Europe’s borders, SagiCofim has a particularly well-established, recognised presence in certain areas undergoing rapid industrial development, such as Korea, India and the United Arab Emirates.

Questions critiques et avantages

Critical issues of air diffusion systems

The air in buildings can be distributed by two very different systems: either mixed flow or displacement systems:Regardless of the type of system chosen, it must fulfil certain functions and requirements. The air must be diffused uniformly throughout the entire space, to ensure a full air-wash..

The air in buildings can be distributed by two very different systems: either mixed flow or displacement systems.

  • Mixed flow systems are the original air-conditioning method; still today most vents and diffusers on the market are developed with this system in mind. They work by mixing primary air, emitted by the vent or diffuser, with secondary air (the air already in the room or space), at an equal temperature and speed.
  • The displacement system is a more recent method and was developed in Northern Europe for use in industrial settings. It works by emitting a flow of fresh air,with specific characteristics, from low down in the area. This fresh air does not mix with the air already in the zone, but rather it displaces it and carries it upwards, where it is then returned through air grilles or other extraction units and then fully or partially exhausted. It is on this principle that the so-called “displacement diffusers” operate.

Basic requirements
Regardless of the type of system chosen, it must fulfil certain functions and requirements. The air must be diffused uniformly throughout the entire space, to ensure a full air-wash, and must:

  • Neutralise the thermal loads, positive or negative, present in the room;
  • Maintain the temperature gradients within determined limits both on the vertical and horizontal plane;
  • Create uniform motions within the determined speeds throughout the entire area;
  • Collect suspended dust in the room and carry it towards the return devices.

On the other hand, they must also be sure not to create any uncomfortable conditions for the people in the environments:

  • Excessive air speed;
  • Formation of stagnant or layered zones;
  • Flows of cold air in the area;
  • Formation of localised currents (usually due to uneven air distribution);
  • Excessive temperature variations in the room on the vertical and/or horizontal plane;
  • Short-circuits of the supply air towards the return grilles.

Features of a mixed flow system

In a mixed flow system, the pattern of air circulation may be a combination of currents, sub-currents and swirls depending on the size of the room, the location of partitions and furniture, the activity of its occupants, temperature gradients, and the position of air diffusers and return equipment.

In a mixed flow system, the pattern of air circulation may be a combination of currents, sub-currents and swirls depending on the size of the room, the location of partitions and furniture, the activity of its occupants, temperature gradients, and the position of air diffusers and return equipment.

The air circulation in the area depends primarily on the outflow speed and on the physical properties of the diffuser. The turbulence of the airflow in the occupied area is linked to the characteristics of the airflows emitted by the diffuser itself. Diffusers should be chosen for their ability to distribute the air in a uniform pattern, without producing any direct blasts of cold air into the occupied zone. They are sized to produce the maximum air velocity without exceeding the sound levels for that environment. The most commonly used terminals and diffusers are: wall vents, ceiling diffusers, linear ceiling diffusers.

High Induction Diffusers

Over the last few years, a new type of diffuser has been developed that differ to previous types in that they operate on the principle of high induction. The most well-known types are: helical flow (swirl) diffusers, wall and ceiling-mounted versions, variable or fixed geometry, linear, square, rectangular or circular diffusers with multiple streams, floor diffusers, nozzles and under-chair diffusers.

All the diffusers mentioned here operate on the principle of a mixed flow system: where the conditioned air supplied into the room mixes with the ambient air through the induction effect provided by the diffuser.

Features of an induction system

These systems combine the primary “fresh” air, emitted by diffusers, and the secondary air already present in the room.  Depending on requirements, the two can be mixed quickly or slowly, with the aim of equalising the ambient temperature and airflow speeds. The greater the induction ratio the quicker the air is mixed.

One of the most significant developments in the air diffusion industry is the introduction of induction systems. Induction works by the primary or supply air emitted from the diffuser drawing in a certain quantity of ambient air. The two flows are mixed together and this equalises the temperature.

The “induction ratio” of a diffuser is the ratio of secondary air induced to the primary air within a specific distance from the diffuser. The greater the induction ratio, the faster the two airflows mix together and the temperature equalised. High induction diffusers are, therefore, particularly suited to environments that require high air exchange levels, as they effectively diffuse large volumes of air and prevent any cold air drops. High induction diffusers are capable of distributing air with very high induction ratios and can therefore work with large temperature ranges, up to 14K. This enables a reduction in the airflow required compared to traditional diffusers.

Where ceiling-mounted diffusers are used, not only should they be high-performance models, but they should also be of minimal aesthetic impact to ensure they blend into the architectural features of the environment.

The Indul range of diffusers, for example, work by emitting several individual jets of air directly into the occupied area, so in a non-tangential pattern, as shown in the image at the side.

features of a displacement system

Air diffusion by displacement works differently to traditional systems. The incoming air is not mixed with the ambient air. The air is actually almost always emitted from the bottom and rises upwards, removing heat from warm surfaces (lights, furniture, computers, people) as it does so, and taking with it any pollutants dispersed in the room. The warm, polluted air is removed by air return intakes on the ceiling and exhausted or partially recycled. As such, the environment will produce a separational “boundary layer” at a certain height: beneath this layer the air is clean and the temperature is controlled, whilst above it, the air contains an accumulation of pollutants and is warmer.

Air diffusion by displacement works differently to traditional systems. The incoming air is not mixed with the ambient air. The air is actually almost always emitted from the bottom and rises upwards, removing heat from warm surfaces (lights, furniture, computers, people) as it does so, and taking with it any pollutants dispersed in the room. The warm, polluted air is removed by air return intakes on the ceiling and exhausted or partially recycled. As such, the environment will produce a separational “boundary layer” at a certain height: beneath this layer the air is clean and the temperature is controlled, whilst above it, the air contains an accumulation of pollutants and is warmer.

In standard office environments, where most people work from sitting, the boundary layer is around 1.5m from the ground. In commercial, craftwork or industrial settings, however, where people are mainly standing, the boundary layer is usually set at around 1.8m. As such, displacement systems are very effective for use in high-ceilinged buildings, since the controlled area will remain below a defined height (1.5 or 1.8m), which obviously has its own advantages.

Operation

The temperature of the air emitted by displacement diffusers is very close to comfortable room temperatures. In civil settings, the supply air temperature is around 20/23°C, so a temperature differential of around 2 – 5 K. In settings used for more intensive activities, however, such as large distribution warehouses, recreational facilities, foyers, etc., the supply air may be as low as 18°C. In mid-season periods, like spring and autumn, when conditions allow, displacement systems can operate in free-cooling mode using just outdoor air. The displacement effect will only occur if the supply air is at a lower temperature than the ambient air. Whereas if the diffuser is supplied with warm air the displacement effect is lost and a standard mixing effect will occur. As such, heating the rooms must be done via a traditional separate system (e.g. radiators, heated floor, etc.).

It is worth noting that the displacement method can be used all year round, including in winter, to control the air quality. Rooms are heated by a separate system using underfloor heating or radiators under the windows. In general, the sound power level of displacement diffusers stays under or equal to 35 dB(A) under nominal conditions for civil sector applications. In most cases, therefore, the perceived sound pressure level in the occupied areas is acceptable and will not disturb any occupants.

Construction

Displacement diffusers are usually vertical, cylindrical, semi-cylindrical, rectangular or for corner fitting.
Depending on the model, they can be installed in the floor, in the middle of the room, on the wall or in corners. The diffuser is fed by a vertical circular duct connected from the bottom or the top.

The outer surface of the diffuser is made from a perforated plate. The air flows evenly, at low speeds, through the whole surface of the plate and is distributed into the room.
The rectangular models are made from a shallower unit and can therefore be recessed flush with the wall or, more commonly, wall-mounted to protrude out into the room.

Displacement diffusers can be installed in small areas, such as offices, restaurants and shops, as well as in very large areas like shopping centres.

Selection

There is a specific way of choosing displacement diffusers that differs from the method for choosing mixer diffusers.

One of our advisers will be happy to assist you. You can contact us by clicking here

Critical issues when designing a new office building

Proper definition of glazed surfaces and the use of glass that can help to provide a heat shield, are essential requirements for buildings wishing to maintain an optimum temperature without excessive energy consumption.

Proper definition of glazed surfaces and the use of glass that can help to provide a heat shield, are essential requirements for buildings wishing to maintain an optimum temperature without excessive energy consumption.

Inside, the layout must be flexible and divided into communal spaces and individual offices where it must be possible to adjust the air conditions to suit.

A critical factor to consider is the space allocated for the installations: keeping this to a minimum is considered extremely important considering the user demands for the entire building (surface area for installations is usually between 6 and 10% of the total). Most newly constructed offices use false ceilings or raised floors to store the service equipment in: these spaces can also be used to the advantage of the air diffusion systems (e.g. concealed “chilled beams” in the ceiling).

Temperature, relative humidity and air speed

The intended temperature should be between a maximum of 26°C in the summer and a minimum of 20°C in winter. During the summer period, the temperature difference between the outdoor and indoor air should not exceed 7°C. In winter, when the building is empty, this can be between 10 and 16°C.

Acceptable humidity levels are between 50 and 60% in summer and between 35 and 45% in winter. These levels keep dehumidification processes to a minimum and, therefore, save energy and operating costs.

Air quality

Quality standard UNI 10339 prescribes a minimum per capita flow of outdoor air of 11 l/s for individual offices and open spaces and 10 l/s for meeting rooms. UNI EN 13779 however, distinguishes between environments based on the indoor air quality: 20 l/s per person for class IDA 1 (high quality), 12.5 l/s for class IDA 2 (medium), 8 l/s for class IDA 3 (moderate). Air handling units used for filtering the outdoor air are fitted with F7/F8 efficiency bag filters, downstream of G3/G4 efficiency pre-filters.

The outdoor air intakes should be located on the roof; if they are on the building frontage, they should be at least 4 metres above ground level and far from any traffic or contaminated air exhaust points.

Sound levels

Maximum permitted sound levels inside are 35 dB(A) for individual offices and meeting rooms and 40 dB(A) for open plan offices.

Is a constant flow or variable flow system best?

CAV (constant air volume) systems are mainly used in offices made up of a single area (e.g. open plan), where the temperature of the supply air is varied in response to a thermostat.

CAV (constant air volume) systems are mainly used in offices made up of a single area (e.g. open plan), where the temperature of the supply air is varied in response to a thermostat.

This type of system can also be used in offices with different areas and different loads: in this case the temperature of the supply air emitted into the different zones can be varied through use of a hot-water supplied re-heat coil located in the air duct leading to the related zone; alternatively, double duct systems can be used where two separate ducts for hot and cold air lead into a mixing box where the two flows are mixed together.

This type of system enables precise temperature control, but is more suitable for small offices. The necessary air ducts takes up a lot of space and are expensive to install, and they can also waste energy during the mid-seasons, where there might be simultaneous requests for heating or cooling in different parts of the office.

VAV (variable air flow) systems meet the needs of large modern commercial-use buildings, with internal spaces divided into open-plan areas. They are particularly effective for reacting to changes in cooling requests in the indoor areas.  Air in the perimeter areas, which can be very different depending on the season and the location, is treated by way of VAV boxes fitted with re-heating coils, to modulate flow rates when in cooling mode and to operate in constant mode instead, using re-heat coils, during winter.

The total airflow treated and distributed by a VAV system is less than a CAV system, when it is calculated based on the maximum simultaneous load. As such, the size of the processing units are smaller, as are the ducts and therefore energy consumption related to the air distribution process.

WHERE SHOULD DIFFUSERS BE POSITIONED?

An air diffusion system, as well as guaranteeing residual velocity no greater than 0.2 m/s and no lower than 0.12 m/s, must ensure a uniform air temperature, without any stagnant areas or drafts. The choice of air diffusion equipment will depend on the type of system and on the architectural features of the building.

An air diffusion system, as well as guaranteeing residual velocity no greater than 0.2 m/s and no lower than 0.12 m/s, must ensure a uniform air temperature, without any stagnant areas or drafts. The choice of air diffusion equipment will depend on the type of system and on the architectural features of the building.

  • In environments without false ceilings (refurbishments) the usual solution is to use rectangular vents at the top of the dividing walls between the rooms and the hallway, distributing the air tangentially to the ceiling, fed by ducts in the hallway’s ceiling. This solution makes maximum use of a building’s height, but is only suitable for constant flow systems that supply air no cooler than 20°C to avoid any cold air drops. Better results can be achieved by using high induction linear wall diffusers, that can be installed directly into the dividing walls and are also equipped with noise attenuators. These diffusers are ideal for diffusing air at variable flows and at temperatures that can be less than 8K compared to the ambient temperature.

  • In environments up to 4 metres high and fitted with false ceilings, various-shaped ceiling-mounted diffusers can be used, either in their traditional versions that provide tangential flow (with Coanda effect) or helical flow versions. We always recommend using high induction diffusers, especially for VAV systems, which enables the supply air to mix quickly with the ambient air: when in cooling mode, this enables high temperature differentials (up to 14K). The polluted ambient air is usually extracted through wall-mounted extraction grilles, or through transit grilles in the doors leading into the hallway.

  • Underfloor air distribution is based on a simple concept: pressurise the air in the supply plenum located in the space between the raised floor and the concrete using air from the air handling unit, and then diffuse it directly into the environment through diffusers installed in the floor panels. The outlets will be located in the upper part of the room, on the wall or ceiling through the light fittings. The main benefit of this solution is its flexibility, thanks to the option to modify the ventilation points by moving the panels with the diffusers in, based on the layout of the workstations. Another positive is the lack of requirement for air ducts, so this reduces the space taken up in the false ceiling. From a comfort point of view, this type of air diffusion permits high air quality and well-being levels, since the natural movement of the air from low to high moves the heat, pollutants and dust away from the occupied areas, towards the upper parts of the room.

  • In specific cases, such as auditoriums, theatres, cinemas, conference halls, the idea of a “personal microclimate” could be an option, which ensures the comfort of individual spectators through the use of under-chair diffusers. As well as being highly effective, this solution also saves energy as it avoids the need to adjust the entire environment, which is usually extremely large and has areas (at the top and sides) that do not really require air-conditioning.

IS THERE SUCH THING AS A “SMART” SYSTEM THAT CAN DETECT WHETHER AREAS ARE CROWDED OR EMPTY?

Work spaces are very dynamic: the same environment at various stages throughout the day might be empty, have one or only a few people in it or be very crowded. To ensure optimum comfort, as well as to avoid any wasted energy, an air diffusion system that can detect a change in conditions and respond accordingly may be the right choice.

Work spaces are very dynamic: the same environment at various stages throughout the day might be empty, have one or only a few people in it or be very crowded. To ensure optimum comfort, as well as to avoid any wasted energy, an air diffusion system that can detect a change in conditions and respond accordingly may be the right choice.

A brand-new type of chilled beam technology has been developed, which introduces the concept of “smart ceilings”, called Demand Controlled Ventilation. This type of air-conditioning system follows the movements of people within the building and adapts to their requirements from one minute to the next. Using a sensor to test the CO2 levels in the air, a presence detector and a motorised beam with variable vents to easily adjust airflow rates, the temperature can be constantly adjusted based on actual occupancy, and can also save up to 60% on energy consumption.

CRITICAL FACTORS OF MUSEUM INSTALLATIONS

The critical nature of museum installations is usually down to two factors: the preciousness of the works kept there (antique, fragile or delicate, such as paintings, frescoes and fabrics), and the museum building itself, which is often very valuable in its own right (palaces, churches, etc.).

The critical nature of museum installations is usually down to two factors: the preciousness of the works kept there (antique, fragile or delicate, such as paintings, frescoes and fabrics), and the museum building itself, which is often very valuable in its own right (palaces, churches, etc.).

The fundamental criteria is to keep conditions as constant as possible 24 hours a day. To ensure these conditions are maintained, there are a series of measures that must be taken: avoid positioning works near to warm or cold partitions or walls, as well as to large windows and water pipes. Buffer rooms can be used to help maintain conditions inside the individual exhibition rooms. Some museum exhibits that are particularly sensitive to temperature, humidity and air quality need to be kept under conditions that aren’t necessarily compatible with a constant flow of people. These can be kept in enclosed spaces with a controlled microclimate, or behind conditioned glass or window displays.

Standard UNI 18029:1999 stipulates the method for measuring the ambient thermohygrometric and lighting variables for the purposes of preserving items of historical or artistic interest. Whereas standard UNI 10969:2002 offers some general guidelines on choosing and selecting the microclimate for preserving cultural assets in indoor environments.

As such, when considering the most appropriate air distribution and diffusion system to install, it is not enough to only consider the performance efficiency in isolation, but instead its design should also be sure to be non-invasive and to not compromise the architectural and aesthetic equilibrium of the setting.

  • Ceiling diffusion: Where ceiling-mounted diffusers are used, not only should they be high-performance models, but they should also be of minimal aesthetic impact to ensure they blend in with the architectural features of the environment. The ideal solution is to use linear components, which blend easily into the ceilings and walls. Very high induction versions are highly suited to variable flow systems, and can be used both for air supply and air return.

  • Floor diffusion: air diffusion from ground level by displacement is suitable for museums as this type of system blends in well with the architecture, and delivers low airspeeds near to the works and reduced noise levels.

  • Wall diffusion: When ceiling or floor diffusion systems are not an option – such as in historic buildings with decorative ceilings or artistic floors – then false walls must be built. These will be built approximately 300mm away from the original walls, creating a cavity for the installation of supply and return ducts and for housing local handling units designed to be very slim.

BASIC CRITERIA FOR SETTING-UP A TEMPORARY EXHIBITION

Setting-up a temporary exhibition such as an art display can present specific problems, particularly for those assigned the task of protecting the works going on display.
The ideal thermohygrometric conditions for the different objects and artefacts are often in contrast with one another and not always compatible with the comfort of visitors and workers: in these cases, there is a certain degree of compromise that must be reached.

 

CRITICAL FACTORS OF HOSPITAL BUILDINGS AND HEALTHCARE FACILITIES

In the case of hospitals or healthcare and rehabilitation facilities the air quality is not only a route to good health and well-being, but often it is also a vital ally in combating infections and containing internal sources of pollution.

AIR STRATIFICATION IN ENTERTAINMENT VENUES

CAV (constant air volume) systems are mainly used in offices made up of a single area (e.g. open plan), where the temperature of the supply air is varied in response to a thermostat.

Critical issues of air diffusion system

The air in buildings can be distributed by two very different systems: either mixed flow or displacement systems. Regardless of the type of system chosen, they must fulfil certain functions and requirements. The air must be diffused uniformly throughout the entire space, to ensure a full air-wash..

The air in buildings can be distributed by two very different systems: either mixed flow or displacement systems.

  • Mixed flow systems are the original air-conditioning method; still today most vents and diffusers on the market are developed with this system in mind. They work by mixing primary air, emitted by the vent or diffuser, with secondary air (the air already in the room or space), at an equal temperature and speed.
  • The displacement system is a more recent method and was developed in Northern Europe for use in industrial settings. It works by emitting a flow of fresh air,with specific characteristics, from low down in the area. This fresh air does not mix with the air already in the zone, but rather it displaces it and carries it upwards, where it is then returned through air grilles or other extraction units and then fully or partially exhausted. It is on this principle that the so-called “displacement diffusers” operate.

Basic requirements
Regardless of the type of system chosen, it must fulfil certain functions and requirements. The air must be diffused uniformly throughout the entire space, to ensure a full air-wash, and must:

  • Neutralise the thermal loads, positive or negative, present in the room;
  • Maintain the temperature gradients within determined limits both on the vertical and horizontal plane;
  • Create uniform motions within the determined speeds throughout the entire area;
  • Collect suspended dust in the room and carry it towards the return devices.

On the other hand, they must also be sure not to create any uncomfortable conditions for the people in the environments:

  • Excessive air speed;
  • Formation of stagnant or layered zones;
  • Flows of cold air in the area;
  • Formation of localised currents (usually due to uneven air distribution);
  • Excessive temperature variations in the room on the vertical and/or horizontal plane;
  • Short-circuits of the supply air towards the return grilles.

Features of a mixed flow system

In a mixed flow system, the pattern of air circulation may be a combination of currents, sub-currents and swirls depending on the size of the room, the location of partitions and furniture, the activity of its occupants, temperature gradients, and the position of air diffusers and return equipment.

In a mixed flow system, the pattern of air circulation may be a combination of currents, sub-currents and swirls depending on the size of the room, the location of partitions and furniture, the activity of its occupants, temperature gradients, and the position of air diffusers and return equipment.

The air circulation in the area depends primarily on the outflow speed and on the physical properties of the diffuser. The turbulence of the airflow in the occupied area is linked to the characteristics of the airflows emitted by the diffuser itself. Diffusers should be chosen for their ability to distribute the air in a uniform pattern, without producing any direct blasts of cold air into the occupied zone. They are sized to produce the maximum air velocity without exceeding the sound levels for that environment. The most commonly used terminals and diffusers are: wall vents, ceiling diffusers, linear ceiling diffusers.

High Induction Diffusers

Over the last few years, a new type of diffuser has been developed that differ to previous types in that they operate on the principle of high induction. The most well-known types are: helical flow (swirl) diffusers, wall and ceiling-mounted versions, variable or fixed geometry, linear, square, rectangular or circular diffusers with multiple streams, floor diffusers, nozzles and under-chair diffusers.

All the diffusers mentioned here operate on the principle of a mixed flow system: where the conditioned air supplied into the room mixes with the ambient air through the induction effect provided by the diffuser.

Facteur critique lors de la conception d'un nouvel immeuble de bureaux

Une bonne définition des surfaces vitrées et l’utilisation de verre pouvant servir de bouclier thermique sont des exigences essentielles pour les bâtiments qui souhaitent maintenir une température optimale sans consommation d’énergie excessive.

Proper definition of glazed surfaces and the use of glass that can help to provide a heat shield, are essential requirements for buildings wishing to maintain an optimum temperature without excessive energy consumption.

Inside, the layout must be flexible and divided into communal spaces and individual offices where it must be possible to adjust the air conditions to suit.

A critical factor to consider is the space allocated for the installations: keeping this to a minimum is considered extremely important considering the user demands for the entire building (surface area for installations is usually between 6 and 10% of the total). Most newly constructed offices use false ceilings or raised floors to store the service equipment in: these spaces can also be used to the advantage of the air diffusion systems (e.g. concealed “chilled beams” in the ceiling).

Temperature, relative humidity and air speed

The intended temperature should be between a maximum of 26°C in the summer and a minimum of 20°C in winter. During the summer period, the temperature difference between the outdoor and indoor air should not exceed 7°C. In winter, when the building is empty, this can be between 10 and 16°C.

Acceptable humidity levels are between 50 and 60% in summer and between 35 and 45% in winter. These levels keep dehumidification processes to a minimum and, therefore, save energy and operating costs.

Air quality

Quality standard UNI 10339 prescribes a minimum per capita flow of outdoor air of 11 l/s for individual offices and open spaces and 10 l/s for meeting rooms. UNI EN 13779 however, distinguishes between environments based on the indoor air quality: 20 l/s per person for class IDA 1 (high quality), 12.5 l/s for class IDA 2 (medium), 8 l/s for class IDA 3 (moderate). Air handling units used for filtering the outdoor air are fitted with F7/F8 efficiency bag filters, downstream of G3/G4 efficiency pre-filters.

The outdoor air intakes should be located on the roof; if they are on the building frontage, they should be at least 4 metres above ground level and far from any traffic or contaminated air exhaust points.

Sound levels

Maximum permitted sound levels inside are 35 dB(A) for individual offices and meeting rooms and 40 dB(A) for open plan offices.

Is a constant flow or variable flow system best?

CAV (constant air volume) systems are mainly used in offices made up of a single area (e.g. open plan), where the temperature of the supply air is varied in response to a thermostat.

CAV (constant air volume) systems are mainly used in offices made up of a single area (e.g. open plan), where the temperature of the supply air is varied in response to a thermostat.

This type of system can also be used in offices with different areas and different loads: in this case the temperature of the supply air emitted into the different zones can be varied through use of a hot-water supplied re-heat coil located in the air duct leading to the related zone; alternatively, double duct systems can be used where two separate ducts for hot and cold air lead into a mixing box where the two flows are mixed together.

This type of system enables precise temperature control, but is more suitable for small offices. The necessary air ducts takes up a lot of space and are expensive to install, and they can also waste energy during the mid-seasons, where there might be simultaneous requests for heating or cooling in different parts of the office.

VAV (variable air flow) systems meet the needs of large modern commercial-use buildings, with internal spaces divided into open-plan areas. They are particularly effective for reacting to changes in cooling requests in the indoor areas.  Air in the perimeter areas, which can be very different depending on the season and the location, is treated by way of VAV boxes fitted with re-heating coils, to modulate flow rates when in cooling mode and to operate in constant mode instead, using re-heat coils, during winter.

The total airflow treated and distributed by a VAV system is less than a CAV system, when it is calculated based on the maximum simultaneous load. As such, the size of the processing units are smaller, as are the ducts and therefore energy consumption related to the air distribution process.

Where should diffusers be positioned

An air diffusion system, as well as guaranteeing residual velocity no greater than 0.2 m/s and no lower than 0.12 m/s, must ensure a uniform air temperature, without any stagnant areas or drafts. The choice of air diffusion equipment will depend on the type of system and on the architectural features of the building.

An air diffusion system, as well as guaranteeing residual velocity no greater than 0.2 m/s and no lower than 0.12 m/s, must ensure a uniform air temperature, without any stagnant areas or drafts. The choice of air diffusion equipment will depend on the type of system and on the architectural features of the building.

  • In environments without false ceilings (refurbishments) the usual solution is to use rectangular vents at the top of the dividing walls between the rooms and the hallway, distributing the air tangentially to the ceiling, fed by ducts in the hallway’s ceiling. This solution makes maximum use of a building’s height, but is only suitable for constant flow systems that supply air no cooler than 20°C to avoid any cold air drops. Better results can be achieved by using high induction linear wall diffusers, that can be installed directly into the dividing walls and are also equipped with noise attenuators. These diffusers are ideal for diffusing air at variable flows and at temperatures that can be less than 8K compared to the ambient temperature.
  • In environments up to 4 metres high and fitted with false ceilings, various-shaped ceiling-mounted diffusers can be used, either in their traditional versions that provide tangential flow (with Coanda effect) or helical flow versions. We always recommend using high induction diffusers, especially for VAV systems, which enables the supply air to mix quickly with the ambient air: when in cooling mode, this enables high temperature differentials (up to 14K). The polluted ambient air is usually extracted through wall-mounted extraction grilles, or through transit grilles in the doors leading into the hallway.
  • Underfloor air distribution is based on a simple concept: pressurise the air in the supply plenum located in the space between the raised floor and the concrete using air from the air handling unit, and then diffuse it directly into the environment through diffusers installed in the floor panels. The outlets will be located in the upper part of the room, on the wall or ceiling through the light fittings. The main benefit of this solution is its flexibility, thanks to the option to modify the ventilation points by moving the panels with the diffusers in, based on the layout of the workstations. Another positive is the lack of requirement for air ducts, so this reduces the space taken up in the false ceiling. From a comfort point of view, this type of air diffusion permits high air quality and well-being levels, since the natural movement of the air from low to high moves the heat, pollutants and dust away from the occupied areas, towards the upper parts of the room.
  • In specific cases, such as auditoriums, theatres, cinemas, conference halls, the idea of a “personal microclimate” could be an option, which ensures the comfort of individual spectators through the use of under-chair diffusers. As well as being highly effective, this solution also saves energy as it avoids the need to adjust the entire environment, which is usually extremely large and has areas (at the top and sides) that do not really require air-conditioning.

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