Comfort
SagiCofim is the gold standard, guaranteeing comfort across a broad spectrum of indoor environments, such as auditoriums, museums, offices, shops, public buildings and hospitals.
Using integrated components and solutions, it guarantees maximum comfort levels by optimising key parameters during the design phase: slower airflow speeds in occupied areas, high induction ratios, low temperature gradients, energy savings and contained sound levels based on their specific applications.
APPLICATIONS
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.
Critical issues and benefits
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.
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.
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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.
DOVE POSIZIONARE I DIFFUSORI?
Il sistema di diffusione dell’aria, oltre a garantire una velocità residua non superiore a 0,2 m/s e non inferiori a 0,12 m/s, deve consentire di ottenere una temperatura ambiente uniforme, senza ristagni o correnti d’aria. La scelta degli apparecchi da utilizzare per la diffusione dell’aria dipende dal tipo di impianto e dalle caratteristiche architettoniche dell’ambiente..
Il sistema di diffusione dell’aria, oltre a garantire una velocità residua non superiore a 0,2 m/s e non inferiori a 0,12 m/s, deve consentire di ottenere una temperatura ambiente uniforme, senza ristagni o correnti d’aria. La scelta degli apparecchi da utilizzare per la diffusione dell’aria dipende dal tipo di impianto e dalle caratteristiche architettoniche dell’ambiente.
- In ambienti privi di controsoffitto (ristrutturazioni) la soluzione consiste in genere nell’usare bocchette rettangolari nella parte alta delle pareti che dividono i locali dal corridoio, con distribuzione d’aria di tipo tangenziale al soffitto, alimentati da canali nel controsoffitto del corridoio. Questa soluzione sfrutta la massima altezza dei locali, ma risulta adatta soltanto per impianti a portata costante con aria immessa a una temperatura non inferiore a 20 °C per evitare cadute d’aria fredda. Migliori prestazioni si ottengono utilizzando diffusori lineari a parete ad alta induzione, adatti a essere installati direttamente nelle pareti divisorie e dotati di attenuatore acustico. Questi diffusori sono adatti alla diffusione di aria a portata variabile, a temperatura che può essere inferiore di 8 K rispetto all’ambiente.
- In ambienti di altezza fino a 4 metri e dotati di controsoffitto vengono utilizzati diffusori a soffitto di varia forma, nella versione tradizionale a lancio tangenziale (con effetto Coanda) oppure a flusso elicoidale. È sempre consigliabile adottare diffusori ad alta induzione, in particolare per impianti VAV, che consentono una rapida miscelazione dell’aria immessa con quella ambiente: ciò permette, in regime di raffreddamento, di adottare differenziali elevati di temperatura (fino a 14 K). La ripresa dell’aria viziata dall’ambiente viene solitamente effettuata mediante griglie di estrazione a parete, o con griglie di transito sulle porte verso il corridoio.
- La distribuzione dell’aria a pavimento si basa su un principio semplice: mettere in pressione il plenum del pavimento sopraelevato con aria proveniente dall’impianto di trattamento, per poi immetterla in ambiente mediante diffusori installati a filo dei pannelli. Le riprese verranno effettuate nella parte superiore dell’ambiente, a parete oppure a soffitto attraverso i corpi illuminanti. Il principale vantaggio di questa soluzione è costituito dalla flessibilità, grazie alla possibilità di modificare il punto di uscita mediante lo spostamento dei pannelli dotati di diffusori, in base alla configurazione delle postazioni di lavoro. Un altro aspetto positivo riguarda l’eliminazione dei canali di distribuzione dell’aria e quindi la riduzione dell’ingombro del controsoffitto. Dal punto di vista del comfort la diffusione consente elevati livelli di benessere e di qualità dell’aria, in quanto il naturale movimento dell’aria dal basso in alto trasporta il calore, i contaminanti e la polvere lontano dalla zona occupata, verso la parte superiore dell’ambiente.
- In casi particolari, come auditorium, teatri, cinema, sale conferenze, può essere conveniente per il benessere degli spettatori considerare l’idea di un “microclima personale” ottenuto tramite diffusori a piede di poltrona, efficaci allo scopo e opportuni anche per il risparmio energetico che comportano, risparmiando la necessità di raggiungere l’intero ambiente, di solito molto vasto e con zone (in alto e ai lati) meno significative per la climatizzazione.
ESISTE UN SISTEMA “INTELLIGENTE” CHE SENTE L’AFFOLLAMENTO E GLI AMBIENTI NON OCCUPATI?
Gli spazi destinati al lavoro sono dinamici: uno stesso ambiente, nell’arco della giornata, può essere abitato da nessuna, da una o poche o da molte persone. Sia per ragioni di comfort sia per evitare sprechi energetici può convenire un sistema di diffusione dell’aria che percepisca le mutate condizioni e provveda di conseguenza..
Gli spazi destinati al lavoro sono dinamici: uno stesso ambiente, nell’arco della giornata, può essere abitato da nessuna, da una o poche o da molte persone. Sia per ragioni di comfort sia per evitare sprechi energetici può convenire un sistema di diffusione dell’aria che percepisca le mutate condizioni e provveda di conseguenza.
La Demand Controlled Ventilation si realizza con una nuovissima tipologia di trave fredda che introduce il concetto di “soffitto intelligente”, dove l’impianto di climatizzazione segue gli spostamenti del personale nella struttura e si adegua alle loro esigenze momento dopo momento. Grazie a una sonda che controlla il livello di CO2 in ambiente, a un rilevatore di presenza e a una trave motorizzata con ugelli a geometria variabile che può controllare agevolmente le variazioni di flusso, si ottiene un adeguamento costante della temperatura alle necessità locali, e inoltre un risparmio energetico che tocca il 60%.
CRITICITÀ IN INSTALLAZIONI MUSEALI
La criticità delle installazioni museali deriva in genere da due fattori: la preziosità delle opere che vi sono custodite (antiche, fragili delicate, come per esempio quadri, affreschi e stoffe), e la struttura stessa del museo, che non di rado è una struttura antica e in sé pregevole (palazzi, chiese, e così via)..
La criticità delle installazioni museali deriva in genere da due fattori: la preziosità delle opere che vi sono custodite (antiche, fragili delicate, come per esempio quadri, affreschi e stoffe), e la struttura stessa del museo, che non di rado è una struttura antica e in sé pregevole (palazzi, chiese, e così via).
Il criterio fondamentale consiste nel mantenere le condizioni il più possibile costanti 24 ore al giorno. Per garantire la stabilità di tali condizioni è necessario adottare una serie di accorgimenti: evitare pareti calde o fredde nei pressi delle opere, così come vetrate di grandi dimensioni e tubazioni d’acqua. Alcuni locali cuscinetto possono contribuire a preservare le condizioni interne delle singole sale espositive. Alcuni oggetti museali particolarmente sensibili alla temperatura, all’umidità e alla qualità dell’aria richiedono di essere conservati in condizioni non compatibili con la presenza continua di persone. Vengono collocati in spazi confinati di microclima controllato, ovvero in vetrine oppure teche climatizzate.
La norma UNI 18029:1999 prescrive una metodologia per la misurazione in campo elle grandezze ambientali termoidrometriche e di illuminazione ai fini della conservazione di beni di interesse storico e artistico. La norma UNI 10969:2002 fornisce invece i principi generali per la scelta e il controllo del microclima per la conservazione dei beni culturali in ambienti interni.
Quindi, al momento di concepire il più adeguato sistema di distribuzione e diffusione dell’aria, occorre tener presente che l’efficacia del risultato non può essere disgiunta dalla cura progettuale di non realizzare strutture invasive e dannose per l’equilibrio architettonico ed estetico.
- Diffusione a soffitto: nel caso di impiego di diffusori a soffitto questi devono presentare non soltanto elevate prestazioni, ma anche un limitato impatto estetico, in modo da integrarsi col progetto architettonico. La soluzione ideale è l’impiego di elementi lineari, che s’integrano facilmente nei controsoffitti e nelle preti. Nella versione ad altissima induzione sono molto adatti a impianti a portata variabile, e possono essere utilizzati sia per la mandata sia per la ripresa dell’aria.
- Diffusione a pavimento: la diffusione dell’aria a dislocamento a pavimento è adatta alle applicazioni museali in quanto s’integra facilmente col progetto architettonico, fornisce basse velocità d’aria in prossimità delle opere e un ridotto livello sonoro.
- Diffusione a parete: Quando non sono realizzabili i sistemi di diffusione a soffitto o a pavimento – come in edifici storici con soffitti decorati e pavimenti artistici – è necessario realizzare delle false pareti. Saranno poste a circa 300 mm dalle pareti originali, creando un’intercapedine sfruttata per la posa dei canali di mandata e di ripresa e per alloggiare unità di trattamento locali progettate con spessore molto contenuto.
CRITERI DI BASE PER L’ALLESTIMENTO DI UN’ESPOSIZIONE TEMPORANEA
Allestire un’esposizione temporanea come una mostra d’arte comporta problematiche specifiche spesso impegnative per chi deve occuparsi di tutelare le opere che verranno esposte.
Le esigenze riguardanti le condizioni termoigrometriche ideali per i diversi oggetti e manufatti sono spesso contrastanti tra loro e non sempre compatibili con il benessere dei visitatori e degli addetti: sarà necessario adattare opportuni compromessi..
Allestire un’esposizione temporanea come una mostra d’arte comporta problematiche specifiche spesso impegnative per chi deve occuparsi di tutelare le opere che verranno esposte.
Le esigenze riguardanti le condizioni termoigrometriche ideali per i diversi oggetti e manufatti sono spesso contrastanti tra loro e non sempre compatibili con il benessere dei visitatori e degli addetti: sarà necessario adattare opportuni compromessi.
In questo contesto il trattamento dell’aria occupa un ruolo di rilievo: le opere d’arte richiedono attenzioni che di norma superano le condizioni di base dei locali che le ospitano, e inoltre possono differire in un caso o nell’altro, rendendo indispensabile un impianto capace di creare microclimi diversi in zone contigue disposte lungo il percorso di visita.
Il criterio fondamentale consiste nel mantenere le condizioni il più possibile costanti 24 ore al giorno. Per garantire la stabilità di tali condizioni è necessario adottare una serie di accorgimenti: evitare pareti calde o fredde nei pressi delle opere, così come vetrate di grandi dimensioni e tubazioni d’acqua. Alcuni locali cuscinetto possono contribuire a preservare le condizioni interne delle singole sale espositive. Alcuni oggetti museali particolarmente sensibili alla temperatura, all’umidità e alla qualità dell’aria richiedono di essere conservati in condizioni non compatibili con la presenza continua di persone. Vengono collocati in spazi confinati di microclima controllato, ovvero in vetrine oppure teche climatizzate.
La norma UNI 18029:1999 prescrive una metodologia per la misurazione in campo elle grandezze ambientali termoigrometriche e di illuminazione ai fini della conservazione di beni di interesse storico e artistico. La norma UNI 10969:2002 fornisce invece i principi generali per la scelta e il controllo del microclima per la conservazione dei beni culturali in ambienti interni.
Per le mostre temporanee allestite in spazi espositivi non dotati di impianti in grado di garantire condizioni particolarmente stringenti, la soluzione ideale è rappresentata dagli impianti a espansione diretta VRF a pompa di calore con unità terminali collegate mediante tubazioni frigorifere a una o più unità motocondensanti esterne. Questa soluzione non comporta la presenza di acqua negli ambienti espositivi, garantisce una rapida risposta alle variazioni del carico, richiede spazi ridotti per il passaggio delle tubazioni e delle unità esterne, e permette una facile installazione e rimozione dell’impianto.
CRITICITÀ DEGLI IMPIANTI IN OSPEDALI E CASE DI CURA
Nel caso di nosocomi o case di degenza e di cura la qualità dell’aria non è soltanto un mezzo per ottenere benessere, ma spesso è anche un alleato indispensabile per combattere infezioni e contenere sorgenti inquinanti interne..
Nel caso di nosocomi o case di degenza e di cura la qualità dell’aria non è soltanto un mezzo per ottenere benessere, ma spesso è anche un alleato indispensabile per combattere infezioni e contenere sorgenti inquinanti interne.
LINK
STRATIFICAZIONE DELL’ARIA IN UN EDIFICIO PER LO SPETTACOLO
Gli impianti a portata costante CAV si utilizzano in prevalenza per uffici caratterizzati da una zona singola (per esempio un open space), nella quale si immette aria con temperatura variabile in rispondenza a un termostato ambientale..
Nel caso di nosocomi o case di degenza e di cura la qualità dell’aria non è soltanto un mezzo per ottenere benessere, ma spesso è anche un alleato indispensabile per combattere infezioni e contenere sorgenti inquinanti interne.
LINK
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.
Critical factor 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.
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