The pros of decentralised ventilation
Published: 08 July, 2016
Decentralised ventilation can be answer for larger spaces, explains Robert Griffin of Hoval
Factories, warehouses, supermarkets and other large areas provide special challenges for HVAC systems. There are two reasons why large buildings and halls sometimes provide problems for building services equipment.
The first is obvious — because they are large, and conventional systems are designed for smaller spaces.
The second depends on the type of space. For example, a supermarket has different needs to a pharmaceutical warehouse, and an exhibition hall has different demands for ventilation systems from a paper-production hall.
In addition, buildings frequently change their use over time. Where today’s screws will be produced, tomorrow’s cultural events could take place. The manufacturers of indoor climate systems try to satisfy these demands.
One reason for increased use of decentralised systems is the adaptability of the units. For example, in industrial buildings problems often arise due to high oil-contamination of extract air. The separation performance of a normal extract air filter is insufficient, and, consequently, 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 so unit quickly becomes very dirty.
Ventilation manufacturers can provide a solution that uses special 2-stage filters, whilst exposed unit parts are protected with coatings and vulnerable materials such as seals are replaced by oil-resistant materials.
What happens to the oil? The oil-laden condensate is 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. Customers in garden centres and hypermarkets are not likely to be happy with draughts or with noise from ventilation units when shopping.
With special sound insulation, the low noise levels required for the these areas can be guaranteed.
Similarly, by using air injectors that distribute supply air at different temperatures, draughts are eliminated. The air-distribution pattern can be changed automatically and is infinitely variably between vertical to horizontal. As a result, customers are more comfortable, stay longer and are inclined to buy more.
Indoor climate units equipped with adjustable air injectors guarantee air distribution without draughts
At the design stage think about installation and 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 acceptable.
This is one of the reasons for the increase popularity of roof-mounted decentralised units, as they offer several advantages. Because the systems are installed at high level or on the roof, no precious floor space is wasted and they are easily accessible from the roof for servicing and filter replacement.
Switching off of the whole system is not necessary. Flexibility is guaranteed during the building life cycle; each unit is serving 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 can be met.
With the principle of island solutions contamination of one hall zone by another — as can occur with central plant – is avoided. For large installations this also makes phased investment possible.
Unlike central air handling units, decentralised systems normally work without supply and extract ductwork. Not only does this make the design easier, it also facilitates the operation of cranes or — as is often necessary — installation of new production machinery. The installation costs also decrease as a consequence. Nowadays, installation is simple with pre-wired 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, resulting in a further reduction in investment.
Most savings, though, can be realised by means of lower running costs. Facilities-management data shows that the construction cost of a building in relation to the whole life cycle is only 30%. The remaining 70% is the running costs, so reducing running costs can deliver a fast return on investment.
For instance, the manager of a hypermarket found that a slightly higher investment has already been amortised after two years. Since then the lower running costs have contributed to increased profits.
One major contributor to lower running costs is heat recovery, where much of the heat energy in the extract air is recovered and transferred to the incoming supply air via a plate or rotary heat exchanger. In such cases, it is important that the system works automatically and is ‘user-friendly’. Ventilation units with built-in heat recovery are cutting running costs
Whether for exhibition halls, sport centres, shopping centres, industrial buildings or warehouses; the different uses and requirements can be met with a decentralised ventilation system. The adaptability of the units, as well as their quality, guarantees a long-term cost-effective and efficient solution for the building owner and manager — while also helping consultants and architects meet their clients’ needs.
Robert Griffin is Technical Sales Manager with Hoval.