Concept and type of ventilation for large areas. Ultimate guide for planners and investors.

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Factories, warehouses, hypermarkets and other large areas provide special challenges for HVAC systems. Which concept and type of ventilation to choose?

There are two different reasons why large interiors and halls sometimes provide problems for the building services equipment (BSE). The first cause is obvious: because they are large and conventional systems are designed for smaller spaces. The second cause depends on the wide variety of space use. A hyper­market has different needs from a pharmaceutical warehouse, an exhibition hall has other demands of the ventilation system than a paper production hall. In addition the use of buildings is changing more and more within their lifetime. Where today screws will be produced, tomorrow culture events take place. The manufacturers of indoor climate systems try to satisfy these demands.

Decentralised solution

Fig. 1: Large areas make high demands on the building services

What is central and decentralized option of ventilation?

During design it is important to pay attention to the principal differences between the various systems. There are central and decentralized options. With central stations the air will be treated centrally with a large unit and will be distributed via ductwork. Decentralized systems, where several autonomous units will be located within the room, prove to be particularly suitable for halls and large areas. They are more flexible than central plants and, as case studies and comparison calcu­lations show, are usually more cost-effective. Earlier decentralized ventilation systems were mainly used in industry, today the designs are so advanced and flexible, that they can also be used in large show-rooms, supermarkets and other "comfort halls".

The reason for this popularity is the suitability of decentralized climate systems for halls, i. e. single storey buildings with at least 4 m headroom and a minimum floor area of 100 m². Depending on the size of the hall and the specific ventilation requirements different decentralized units will be used to provide particular solutions.

Example: oil-contaminated extract air

One reason for greater use of decentralized systems is the excellent adaptability of the units. For example in industry often problems arise due to high oil-contamination of extract air. The separation performance of a normal extract air filter is insufficient and the filter life is much too short. Using inappropriate designs, the oil drops from the unit into the working area or is removed with the exhaust air. The unit quickly becomes very dirty. With a new conceptual approach, the manufacturer can provide a solution. In the ventilation units special 2-stage filters can be used, exposed unit parts are protected with coatings and vulnerable materials, for example seals, are replaced by oil-resistant materials. What happens to the oil? The oil-laden condensate will be filtered and separated inside the unit and removed via an oil and condensate drain.

A comfortable shopping environment increases sales

Particular requirements have to be met in each area. The customer in garden centres and hypermarkets is not likely to be happy with draughts or with noise from ventilation units when shopping. With special sound insulation the low noise levels needed in the shopping hall can be guaranteed. Also draughts are not obligatory. Air injectors can distribute supply air at different temperatures without draught around the shopping area. With high-quality units, as provided by Hoval, the air distribution pattern can be changed automatically and infinitely variably between vertical to horizontal. As a result the customer stays longer in a com­fortable store and buys more – the manager is a happy man!

Indoor climate units TopVent

Fig. 2: Indoor climate units equipped with adjustable air injectors guarantee air distribution without draughts 

At the design stage think about installation & maintenance

The type and duration of installation along with maintenance factors should be considered at the design stage. Interruption of a manufacturing process or disturbance of activities in a department store are not allowed. That's the reason roof mounted decentralized units are an intelligent choice. They offer several advantages. Because the systems are installed at high level or on the roof, no precious floorspace will be wasted. The installation takes place quickly and simply through the roof. Usually several units are installed in one hall. Because of decentralization the filters can be changed in each unit within minutes during normal working hours. Switching off of the whole system is not necessary.

Flexibility is guaranteed during the building life cycle: each unit is provided for only one particular hall area. So inside one large space different requirements, such as the operating mode (fresh air/recirculation), room temperature and working time (1-, 2- and 3-shift work) can be met. With the principle of island solutions contami­nation of one hall zone by another – as possible with central plant – is avoided. For large installations the investment is possible step by step. 

Short amortization time due to low running costs

Unlike central air handling units decentralized systems normally work without supply and extract ductwork. Not only is the design made easier, but also the operation of cranes or – as is often necessary – installation of new production machinery. The installation costs also consequently decrease. Nowadays, installation is simple with prewired units, that can be changed at a later date. Also the air injectors give very effective air distribution, allowing a lower air volume to be used. This means lower investment costs.

But most savings can be realised by means of lower running costs. As shown in facility management data the construction cost of a building in relation to the whole life cycle is only 30 per cent. The remaining 70 per cent concerns the user. Also for indoor climate systems there are similar calculations for running costs. The manager of a hypermarket found that a little higher investment has already been amortized after two years. Since then the lower running costs increases his profits. The reason for it is very simple and is called heat recovery. The warm extract air hands over most of its heat energy through a plate or rotary heat exchanger to cold supply air. 

Also the system should work automatically to ensure minimum energy use, but at the same time be "user-friendly".

Ventilation units RoofVent
Fig. 3: Ventilation units with built-in heat recovery are cutting running costs

A "win-win" situation

Whether exhibition halls, sport centres, shopping centres, industrial buildings or warehouses, the different uses and requirements can be met with a decentralized system. The adaptability of the units as well as their quality guarantees for the building owner and manager a long-term cost-effective and efficient solution. The concepts are well received not only by consultants and architects but also directly by manufacturers. By means of technical expertise and innovation, highly adaptable products come to the market – and that helps all of us.

Have a ventilation topic caught your eye? Please share! 

Author
Dipl.-Ing. (FH) Stephan Eder
 
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