Designing for Window Systems

As a highly experienced company in the field of automated windows and natural ventilation systems, part of our job is to help you develop accurate specifications for your project. Below are some of the most important considerations for you to take into account in the design phase of your project.

Window Actuators

Arens offer both chain and linear actuators that can be used for three main purposes:

  • Allow manual operation of high level windows and louvres for natural ventilation
  • Provide a fully automated natural ventilation system
  • Facilitate natural and smoke ventilation systems

Window Sizes

Ideally, awning sashes should be at least 500mm high in order to avoid the need for chains to be shortened. Windows should also be 450mm wide or greater to ensure there is adequate space for the actuator to be mounted. Arens do offer some custom solutions for smaller windows, but early consultation will be required.

If your design is going to incorporate wide sashes, it is important to consider that any window that is greater than 1200mm will require two points of attachment. This is recommended by many window manufacturers to avoid bending or twisting of the frame.


In high wind loads some fastenings will not hold to timber and aluminium sections. In coastal and exposed locations as well as multi-level buildings this is particularly important to consider. Likewise, if your project is going to incorporate any form of displacement air conditioning this can lead to increased pressure on the windows and attachments.

Calculations may be required to ensure that the most appropriate fastenings are selected.

Window Openings and Locations

High level operable windows reduce a number of risks that may exist with lower level windows.

  • As they are out of reach, the likelihood of entrapment is lowered.
  • During night purging security issues are reduced. Not only are the windows located at a high level but their opening is restricted to ensure the risk of intrusion is minimised.
  • Draughts, particularly in the cooler months, can be avoided with high level windows. Mixing of cooler air that is entering, with the warmer air that exists at a high level ensures that the air reaching occupants is at a more suitable temperature.

Stays and Hinges

It is important that the capabilities of the hinges match the degree of opening that is desired. For example if top hung hook hinges are being used, it is likely that the chain in the actuator will need to be restricted.

When stays are selected for awning sashes their travel must match or exceed the chain stroke of the actuator chosen.

Non-friction stays or hinges must be used. It is also important to note that stays with rubbing blocks are not acceptable. Even when the friction screw is adjusted to non-friction, the design of these particular imposes unacceptable opening loads as the sash opens through the second half of the opening movement.

Co-ordination with mechanical and electrical specifications

When choosing electric actuators for your windows it is essential to coordinate with mechanical and electrical specifications. Details such as; how they are to be switched and powered, where the windows to be controlled are to be located, the number and location of GPOs and how the cabling is to be brought through the window sill are essential to consider.


The cable dimensions required will be determined by both the number of actuators and the length of the run.


If you require any further information or advice when developing your window automation specifications, or would like some further information on Arens products, please feel free to contact us.