- decentralised façade ventilation units for heating and cooling
- fresh air enters via the shortest route through the façade
- modular construction for seamless work on site
- easy integration into building management systems
- separate fans for fresh air and recirculating air mode, thus independent from the heat requirement or supply of fresh air in the space
- low-turbulence and low-noise cooling/ventilation
Decentralised façade ventilation system.
AREAS OF APPLICATION / INSTALLATION
- heating, cooling and ventilation of residential and non-residential buildings
- decentralised ventilation system for use in raised floors or floor cavities
- lengths coordinated to the building grid, any intermediate length is available
... ALSO GOOD TO KNOW
- combination with other Kampmann duct models, such as Katherm HK, is made possible thanks to standardised widths and grid
- no need for centralised ventilation and air conditioning system, nor ductwork
- floor tray underneath the heat exchanger, without fittings, simplifies cleaning and maintenance
- F7 air filter
- modular indoor units: fresh air, secondary air, empty duct
- ball valves and constant flow valves integrated in the trench (optional)
- adaptable in the event of a change of use without the need for manual intervention into the technology
- consumer-related energy cost calculation
|Kavent BA plus decentralised façade ventilation||download as||.pdf, 928,09 KB|
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|Spezial Commercial buildings||download as||.pdf, 2,17 MB|
An inspection hatch should be provided with conventional systems that are used as an underfloor façade ventilation unit to be able maintain and replace the fresh air motor, if necessary.
An inspection hatch is no longer required with a further development of the series, the Kavent BA plus, as all unit components, from the fresh air motor to the element, can be removed in sections through the grille opening. All unit components are designed in functional units that can even be replaced whilst the unit is running, if need be. This design significantly reduces the investment costs during floor laying.
a) How is the extract air conveyed?
In most cases the extract air is conveyed via the door into the corridor. The extract air is then drawn out from there.
The extract air ducting must generally comply with fire regulations. The extract air ducting and inserts required depend on the design of the fire protection concept. In most cases, it is possible to convey the air into the corridors through overflow openings in the air or in the wall. There are also sound absorption overflow openings here that have a fire protection function. When sound absorption demands are extremely high (meetings rooms, directors' rooms etc.), this is achieved through extraction in the ceiling area.
This could take the form of Belimo Fan Optimizer controls. With these controls, the motor on the extract air damper sends out a signal to the extract air fan to increase the speed when it is fully open. This way, the system is automatically controlled and ensures that there is always enough negative pressure in the corridors.
Often corridors must comply with F30. Solutions are also possible where the suspended ceiling is used as an extract air duct. This could solve the problem of fire protection overflow openings.
Overflow openings in the outer façade whereby the air is carried outside by the overpressures have not proved effective. This was tried with a few projects but the process is very rarely used now. The disadvantages are the rise in pressure due to wind suction or pressure. These systems also only work when the internal doors are closed. However, it is important to ensure that the pressure differences do not allow air to get pushed into the building or drawn out of the building unchecked. Heat recovery is certainly almost impossible or very laborious with this system and, as such, the attempt to introduce heat recovery with the completed product was abandoned.
b) Extract air ducting/combined supply and extract air unit
Combined supply and extract air units have the disadvantage that the air intake and outlet are located close to each other on the façade. This infringes on DIN EN and VDI 6022. DIN EN 13779 contains detailed information about the clearance required between the supply and extract air openings.
This can be disregarded if it has been specifically agreed with the builders. The short circuit is also not very pronounced as the air volumes are not very large.
A major disadvantage of the heat recovery in a Kavent unit is that the heat can only then be used again with this unit. The internal loads are particularly high on the south and west façades. These often suffice to cover the heat requirement for an outdoor temperature of 0 °C to +5 °C. Furthermore, heat recovery can only be used when the ventilation is running, in other words, during the day, as heat recovery during the night would not make sense.
Heat recovery in a Kavent unit must definitely have a bypass so that the heat exchanger can be bypassed in summer. Moreover, the heat exchanger is always in the supply air so that the additional pressure loss from the heat exchanger is influenced by the fan. It is almost like running a marathon with a rucksack to avoid the danger of becoming thirsty en route. It makes more sense here to wait for a supply station at a central point despite being thirsty in between.
The amount of maintenance required and the cost of the heat exchanger and the bypass in a decentralised unit should not be ignored.
c) Centralised extract air with heat recovery (heat pump)
The concept with centralised extract air is implemented in most buildings. The advantage is that heat is brought to a higher temperature using a heat pump in the centralised extract air and then it is made available for feed in to the general heating network. For example, in this way the shaded sides of the building can use the warmth for heating. It is also possible to use this heat to preheat supply air to kitchens, for heating in underground car parks (only allowed in conjunction with a separate ventilation system for emergencies that also guarantees safe smoke extraction in the event of a fire) and for preparing domestic hot water etc.
No, the power consumption of the fans is less than 30 Watt. This is 0.275 Watt/m³/hr. Centralised ventilation runs at approx. 1 to 1.6 Watt/m³/hr. EC motors are more economical.
The maintenance procedure is quite easy. Lift up the grille and open a lid. The filter and fresh air damper with the actuator are accessible. The fan can also be pulled out as far as the grille with an overall frame width of more than 365 mm. If the convector is connected with flexible hoses on the waterside it can also be pulled out to clean it (including the duct tray underneath it and a condensation tray if available). If the modular dimensions of the façade are not small, the valves can be placed with the actuators in the duct tray that is accessible from above through the grille so that the maintenance of all relevant parts can be done easily and directly. The major advantage of maintaining decentralised ventilation systems is also that the design barely disturbs normal office operations as only the room controller for the units located in this room needs to be switched off for a short time and the other units in the remaining rooms can continue to be operated. The units in each room are also switched off for such a short time that no real change can be felt to the indoor climate, meaning that the room can continue to be used after any maintenance and even during maintenance in most cases. The tools and accessories needed for the maintenance can be quickly and easily carried from room to room as bulky equipment, such as ladders etc., are not required. Maintenance can be done especially quickly if an additional set of filters for the rooms to be maintained is taken along and the filters are then replaced quickly, with the contaminated filters being cleaned in the workshop later (if possible).
Investigations are being made in another building with regards maintenance. The investigations established that the maintenance of a decentralised system can be even more cost-effective than the maintenance of a centralised system, especially when the maintenance work required in the air ducts is taken into consideration.
In one specific case, the maintenance costs were calculated at 1.5% (only the decentralised ventilation units without additional units [such as Kavent BA, chilled ceiling etc.] in a possible combination that must be calculated separately with approx. 1% of the respective investment costs) as opposed to the centralised ventilation system at 3-4% of the investment costs.
Negative pressure of maximum 150 to 200 Pascal occurs after only a few days or hours even with the most extreme conditions on certain corners of the building. The fan does not get as much air if this negative pressure prevails. Based on the fan characteristic line, the fan rotates a little quicker, which is equivalent to a form of self-regulation of the fan that only however operates in a limited range. The volume of supply air drops in the most extreme conditions, potentially even to zero, whereby a switch-off command is then generated again via a transmitter on the building management system. Negative pressure occurs with wind suction, whereby air is drawn out of the room through additional leaks in the façades and joints and this is then counterbalanced to some extent with the increased infiltration through the opposite façade (overpressure due to wind pressure) and the room doors and corridors so that a natural exchange of air is nevertheless achieved.
These extreme situations represent perhaps 5 hours per year. However, to limit the danger of under or minimum supply, EC motors with constant volume flow controls are used. The speed of the fan is increased in relation to the rising external resistance using these controls, whereby the conveyed air flow volume remains constant. However, noises also increase due to the higher speed. These controls have a relatively large sphere of activity with a range of 220 Pa to 320 Pa depending on the volume of air (the higher the volume of air, the lower the external resistance to be bridged). However, pushing them to the maximum due to the increasing speeds and the associated escalating noises is not advisable. If the external resistance becomes too great, such that the self-regulation controls or constant volume controls on the fan are unable to bridge them, then the fresh air damper is automatically closed as it is designed as a return damper. The damper has a lightweight design and is only released by the actuator as it is opened by the suction power of the fan. However, it is advisable to enter a switch-off command via a transmitter on the building management system on site here too before the external resistance becomes too great, in order to maintain an acceptable level of noises.
Façade designers and manufacturers have shown with many projects that they have completed that there are different options to incorporate the fresh air intake. There are solutions for double and single façades that can be integrated so that they are barely visible. Please contact us and we will put you in touch with the appropriate contact.
This can be achieved in conjunction with other systems. There is the possibility of positioning the Kavent BA unit together with the Katherm HK. The standard widths of both grilles are the same but, for example, the units could be alternated. The cooling outputs in recirculating mode should be more energy-saving as the high outdoor air temperature does not need to be reduced first. Furthermore, the air volume of the Katherm HK is often higher than with the Kavent BA, as higher noises are accepted for a short period of time when cooling the temperature, so that higher and more optimum air circulation is achieved in conjunction with the improved depth of penetration into the room. However, it is also possible of course to combine the units with other systems, such as chilled ceilings, chilled beams etc.
A combination of three systems is designed and used in most buildings; the Kavent BA system for fresh air supply, a chilled ceiling or concrete core cooling to meet the cooling load and the Katherm HK system to cover the peak loads that cannot be met by the other two systems. This is done above all to keep the noises to the absolute minimum required. This is achieved by "silently" cooling by the chilled ceiling or concrete core cooling. Other noise sources are only tolerated when the cooling loads become too high.
As discussed in a previous question ("How is extract air conveyed?"), heat recovery is certainly possible. This results in an energy saving being made because the unit only operates in line with demand. For example, demand-oriented controls are possible using the building management system in conjunction with a movement sensor in the room.
When an employee leaves the room, the ventilation goes off and only turns back on again when the employee re-enters the room. For example, the set-back temperature times can be controlled individually in line with demand using this combination of systems. Large centralised systems are even operated around the clock in some cases as it is not possible to know when the offices are occupied. An operating time of 06.00 hrs to 20.00 hrs (14 hours) is normal in administration buildings. However, the offices are generally only occupied for a maximum of 8 hours. A significant energy saving of up to 50% can be made here.