At first glance, a natural smoke and heat exhaust ventilation system may appear relatively straightforward: provide openings through which smoke and heat can escape in the event of a fire, equip them with suitable electric actuators, and provide the necessary control and power supply.
In practice, however, a number of questions arise already during the design stage.
What aerodynamic free area is actually required? Is the geometric area of a window equal to its aerodynamic free area? How should make-up air be provided? Can any motorised window be used for smoke and heat exhaust ventilation? How should the actuator be selected? How should the smoke control panel be sized? What happens in the event of a mains power failure? And how should the smoke control system interface with the fire detection and alarm system?
These questions should be resolved before the project reaches the construction site.
No.
One of the important parameters in natural smoke and heat exhaust ventilation is the aerodynamic free area – Aa.
EN 12101-2 specifies requirements and test methods for products used for natural smoke and heat exhaust.
The aerodynamic free area is not simply the area obtained by multiplying the width and height of a window. It depends on the characteristics of the specific opening and the way in which it opens.
Therefore, two openings with identical nominal dimensions do not necessarily have the same declared aerodynamic free area.
A common question: “I have a 1 × 1 m window. Does that mean I have an aerodynamic free area of 1 m²?”
No. The declared performance of the specific solution must be checked.
With natural smoke and heat exhaust ventilation, it is not sufficient to consider only the openings through which smoke leaves the building.
Hot smoke and gases rise due to buoyancy and are discharged through openings provided at higher levels. At the same time, an appropriate supply of make-up air must be provided.
The entire airflow path through the space therefore needs to be considered during the design process.
Where are the smoke exhaust openings located? Where will make-up air enter? Are these elements coordinated with the overall smoke control concept?
A common mistake: roof or façade smoke exhaust openings are specified in considerable detail, while the provision of make-up air is left to be resolved later.
Smoke exhaust and make-up air are not two separate issues. They are parts of the same system.
No.
This is one of the important distinctions between ordinary window automation and a life-safety smoke control system.
It is not sufficient to select a window, install an electric actuator with an apparently adequate force and assume that the resulting combination is automatically a suitable solution according to EN 12101-2.
For smoke and heat exhaust applications, the characteristics and appropriate documentation of the specific solution must be verified.
In other words, the actuator should not be considered in isolation.
The window, actuator, installation arrangement and documented solution must be considered as a whole.
This is particularly important when equipment requirements are specified in the design documentation or bill of quantities. An incorrectly specified requirement may later result in a solution that does not meet the intended safety function.
The question “Do I need a 300 N, 500 N or 1,000 N actuator?” is only the beginning.
Actuator force alone is not sufficient for correct selection.
The type and dimensions of the window, opening method, hinge and actuator positions, required stroke, installation arrangement and required open position must all be taken into account.
Actuator stroke is particularly important because it affects the geometry of the open window and consequently the performance of the designed solution.
Large or wide window vents may also require multiple synchronised actuators.
A common mistake: selecting an actuator based primarily on its rated force and only afterwards checking whether it can achieve the required opening with the selected window.
The process should be reversed: first define the required function and opening characteristics, then select the appropriate actuator.
The number of windows alone is not sufficient information.
When selecting a smoke control panel, it is necessary to know the electrical characteristics of the actuators, total current demand, number of motor groups, number of smoke control zones, required inputs and outputs, and the functional logic of the entire system.
For example, ten windows that must always operate simultaneously represent a different control requirement from ten windows distributed across several zones with different activation scenarios.
A control panel should therefore not be selected simply according to “how many actuators can be connected”.
The more important question is:
What exactly must the system do when it receives a fire signal?
Once this is clearly defined, the required zones, groups, inputs, outputs and control panel capacity can be determined correctly.
A smoke control system must be designed with the possible loss of its primary power source in mind.
EN 12101-10 covers power supply equipment for smoke and heat control systems and includes requirements relating to primary and secondary power supplies.
Power supply should therefore not be treated as an auxiliary detail to be resolved after the rest of the equipment has already been selected.
The actuators, control panel, secondary power supply and electrical circuits need to be coordinated with the required system function.
A common mistake: windows and actuators are specified first, and only afterwards is it checked whether the proposed control panel can adequately power and control them.
The electrical design should be developed together with the other parts of the system.
Design specifications sometimes contain only a short statement:
“Connect the smoke control system to the fire detection and alarm system.”
But what exactly should happen when a fire signal is received?
Which smoke control zone should be activated? Which openings should open? Is manual activation required? Which signals need to be exchanged between the systems? How are system conditions and faults indicated?
These are functional requirements that should be defined during the design stage.
It is therefore more useful to define the system operating logic or cause-and-effect matrix than simply to state that the two systems must be interconnected.
This gives the contractor a clear functional requirement and enables the designer to verify whether the proposed equipment can perform all required functions.
Yes, provided that the system is designed accordingly.
Automated windows can be used for natural ventilation during normal building operation while performing a predefined safety function in the event of a fire.
Such a solution requires appropriate actuators and controls, together with clearly defined priorities for the safety functions.
This can be particularly useful in buildings where natural day-to-day ventilation is to be combined with natural smoke and heat exhaust ventilation.
The same principle applies here: these requirements should be established during the design stage rather than after the windows and actuators have already been selected.
An incorrectly selected actuator, an unsuitable combination of window and actuator, inadequate consideration of make-up air, an incorrectly sized control panel or poorly defined control logic are all problems that are considerably easier to resolve on the drawing than on the construction site.
For this reason, ELEKTRO-LOG provides technical support to designers and contractors already during the design stage of natural smoke and heat exhaust ventilation systems.
We can assist with the selection of actuators and smoke control panels, verification of technical characteristics and component compatibility, definition of control functions, and development of the interface between the smoke control system and the fire detection and alarm system.
Our objective is not simply to offer a product.
We want to help answer the more important questions: What must the system do? How will it perform that function? And can the selected equipment perform it reliably?
For natural smoke and heat exhaust ventilation systems, ELEKTRO-LOG provides solutions based on equipment from WindowMaster, a Danish manufacturer specialising in window automation and natural smoke and heat control solutions.
A well-designed smoke control system does not begin with the selection of an actuator or control panel. It begins with correctly defined requirements.
If you have questions during the design stage regarding actuators, smoke control panels, smoke exhaust openings, power supply or control functions, send us your drawings or technical requirements.
It is much easier to verify a solution while it is still on the drawing than to modify it on the construction site.
EN 12101-2 – Smoke and heat control systems – Part 2: Natural smoke and heat exhaust ventilators
Requirements and test methods relating to products for natural smoke and heat exhaust.
EN 12101-10 – Smoke and heat control systems – Part 10: Power supplies
Requirements relating to power supply equipment used in smoke and heat control systems.
WindowMaster – Technical documentation for natural smoke and heat exhaust ventilation systems
Technical documentation relating to certified solutions, aerodynamic free area, actuators, control systems and power supplies.
