What is Window Automation?

An actuator is a device which enables a window to be opened and closed automatically or by a rotary handle.

It is the hardware that fits onto the window which pushes and pulls the window open and closed instead of operating the window manually.

Window automation is used predominately for the purpose of natural ventilation and smoke ventilation.

Natural Ventilation

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It may be advantageous to use the windows (which are already installed in the fabric of the building) to provide additional fresh air to supplement an existing heating and cooling strategy. Control of the windows can deliver a low cost solution.

It is very advantageous to design window automation in at concept stage either as a fully blown natural ventilation system or as a hybrid mixed mode solution. Either way using automated windows brings huge cost savings for the running costs and therefore a lower carbon footprint.

Smoke Ventilation

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Natural smoke ventilation uses the inherent buoyancy of hot smoke to rise above escape routes thus leaving the occupants with a greater chance of making a safe escape. By introducing automatic vents at high level that open upon detection of smoke, the smoke is allowed to escape to the atmosphere.

Automatic opening inlet vents / windows at low level maintain the smoke reservoir at a safe level above head height to increase occupant’s visibility during escape.

Manual Opening Vents

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Manual opening vents are used in applications where a number of high level out of reach windows or roof light systems require remote operation safely and securely.

Manual opening systems can be used for most window systems and can be applied to all forms of windows, bottom hung, top hung, side hung and central pivotal orientations.

Remote operation of manual opening vents can be designed to suit all types of buildings.

SE Controls has the ability to design and install tailored solutions to meet the remote manual control requirements for natural ventilation in, offices, schools, colleges, hospitals, public buildings and shopping centers.

The operation of remotely opening either a single or number of high level windows can be achieved by our range of rotary handles available in a range of colours to meet the window profile and actuator to provide an inconspicuous solution.

How would you automate a window?

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In order to automate a window you will need some kind of actuator, a mechanical device which will move the opening part of the window. There a two commonly used types, the chain actuator and the linear actuator.

The reason the chain actuator is unique is that it contains a chain which is a bit like a bike chain but with the subtle difference that it only bends in one way. Because of this unique feature, when the actuator is fixed onto the frame and the chain is connected to the opening window, it won’t bend or collapse when it opens (thereby pushing the window open).
The biggest advantage of this is that the window can open a long way but the mechanism can remain relatively compact and unobtrusive.

The linear actuator has a simple push and pull action. If the window needs to be opened by for example 500mm, then the linear actuator is going to project at least 500mm into the internal space. For this reason, linear actuators are more commonly used at high level, such as in atria where aesthetic impact is not as great. Furthermore the size and weight of these types of vents lend themselves to linear actuators which can achieve higher push forces than chain actuators.

Fortunately mechanical solutions such as those commercial greenhouses and “winding gear” are becoming less common. This is because of aesthetics, reliability and greater performance demanded from the façade by regulations such as Part L of the building regulations.

What do you need to consider when you need to automate a window?

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• Vent height
• Vent width (locking points & weather performance)
• Material (Plastic, aluminium, wood)
• Hinge arrangements
• Weight [Force=Stroke/Height x Weight/2]
• Distance vents need to open
• What free area is required?

How do you control it?

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In order to ensure the effectiveness of the automated windows, it is essential to consider what the design team is trying to achieve. The simplest form of window automation is by using a simple open close switch to control the actuator.

The automated window system may be required to open in case of a fire. In this instance dedicated smoke detector or interface with a fire alarm system. Either way, it is important that the control panel contains a secondary power source such as back up batteries. By definition, this will help to determine the voltage of the actuator; if the control panel is delivering 24V dc then the actuator needs to be 24V dc.

It is possible to use rain sensors to ensure that the window closes if it rains. But more importantly are starting to add a logic sequence into the control strategy.

It may be beneficial for example within a school to limit the opening of the windows within specific time constraints that could simply be achieved by using a 7 day timer.

Because the need for some form of controller is now present to address the logic requirements, consideration is needed whether to increase the effectiveness of the window automation system by adding additional sensors at little extra cost. For instance, if the windows are to open (proportionally) as the room temperature rises. As indoor air quality is becoming increasing important for the well being and performance of the building users, then it is quite straightforward to add CO2 sensing to introduce fresh air and/or purge stale air by opening and closing the windows automatically.

An automated window system can be affected by external environmental conditions, such as wind speed and wind direction. By introducing simple algorithms, the efficiency of the system can be improved.

All aspects of the building’s overall heating and ventilation strategy should be integrated to maximise energy savings. How often is it seen that radiators are on but windows open, or windows open with internal blinds closed to prevent solar gain. It is important to recognise that these elements are complementary and shouldn’t be designed in isolation. If the building has a building management system, then it is often advantageous for the window automation to be linked to it, even if it is just reporting information – simple energy wastage can be avoided.

The window automation system is often linked to the overall fire strategy, hard wired interlinks are common, low cost effective ways of achieving this.

The design process - trying to get it right!

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The issues raised above throw up some very interesting debates over the degree of user interface. SE Controls experience has shown that occupants WANT control of their local environment, they do not want some fancy automatic system deciding when their space is heated and ventilated! Much of this is down to user perception.

We have all heard how people are generally unhappy with condition air systems, too dry, too cold, unhealthy etc. Furthermore too hot for one person is too cold for another.

It is therefore important to give the occupants control and this must be explained to them. They need to buy into it to benefit from it.

In order to evaluate potential schemes then a degree of simulation and modeling is advisable. This will help to identify the best locations and sizes of ventilation openings. It can take solar gain and prevailing wind directions into account when predicting internal temperature conditions.

What regulations govern window automation?

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The need to use automatic opening windows for smoke ventilation are driven by Building Regulations, specifically Approved Document B. In addition, the BS 9999 Codes of Practice, which are interested in designing fire precautions into buildings dependent on their use, require a varying degree of automatic smoke ventilation, which can be achieved through the use of actuated windows.

European product standards are being introduced which covers, amongst other things, the use of windows as natural smoke ventilators. The family of standards are the EN12101. Importantly, where CE marked smoke vents are required, the actuators need to have been tested as a component part of the overall smoke vent. As a result of this, actuators cannot be interchanged. It is important therefore that evidence is collected at design stage that the proposed system is fit for purpose and has the necessary certification in place.

EN60335-2-103 is concerned with protecting the public from an injury which could occur as a result of a mechanical product such as a window actuator. The main danger is finger trapping. A lot of applications for chain actuators are at high level where they are out of reach of anyone (hence the 2.5m rule). However SOME ARE NOT. If vents are underneath 2.5m from the nearest access point (internal or external) than additional protection measures are necessary.

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