Active Window System (AWS)

The Active Window System is a new window system that aims at changing the traditional window concept to an active element that promotes energy efficiency, indoor air quality and user comfort. This new window system is based on the following technological pillars: 

1. Modular wood frame system: The wood frame new design was conceived to be easily adaptable to different configurations, such as different climates, different insulating glazing units (IGU) or integration of different shading devices. It was designed to be easy to manufacture and to install both, in-wall and insulated block installation. 
2. Movable adaptive shading system: The AWS can integrate different shading systems, such as external shading, electrochromic glass or integrated venetian blinds. In the latter case, the venetian blinds are allocated in a semi-ventilated external chamber in front of the insulating glass unit and protected by an external openable glass. This configuration allows to easily maintain the system.  
3. Integrated decentralized ventilation device: The AWS, as a multifunctional window system, allows the integration of decentralized ventilation devices, such as passive trickle vents for assuring certain natural ventilation or active compact mechanical ventilation machines with heat recovery. 
4. Interaction between shading semi ventilated cavity and decentralized ventilation device: The most advanced configurations of the AWS include the venetian blinds in the semi ventilated cavity and the ventilation device in a way that they collaborate with each other, with the aim of exploiting the shading cavity ventilation for optimising indoor air quality and energy consumption. This could be done in different ways depending on the type of ventilation device (passive or active) and the season.  

Key innovation figures

• New modular wood frame made by natural and recyclable material. Its modular design allows to adapt it easily to different climate requirements, different IGUs or integration of different shading devices without any extra effort in design and manufacturing. Besides, it has been developed to simplify the installation process and reduce the installation error risks.
• Possibility to integrate the shading device in front of the IGU in a protected but accessible semi-ventilated cavity. This allows to access the shading device for cleaning, maintenance, or replacement in presence of any malfunctioning.
• A catalogue of different AWS configurations to be applicable in different climates and with different shading and ventilation design options. The technical feasibility, thermal performance at system and building level were simulated for each configuration and are currently being validated through tests.
• Interaction between the ventilation of the shading cavity and the ventilation of the indoor space to make them collaborate and further improve the thermal performance of the window system.
• Shading control strategies optimised between visual/thermal comfort and winter/summer energy savings for different climates, facade orientations and shading types.

Testing & prototypes

Two mock-ups of the Active Window System have been manufactured by Eurofinestra: one conceived for cold climates with vacuum-insulated glazing (VIG) and a second one conceived for mild climates with double-glazing. Both mock-ups have, in turn, three different configurations depending on the ventilation mode mounted and tested at each moment, i.e. natural ventilation, passive ventilation through trickle vents, or active ventilation through a mechanical ventilation device, as shown in the following scheme.

Both mock-ups with their three ventilation modes are being tested one after the other in the “Flexi” lab facility of Eurac laboratories. The presence of a small climatic chamber behind the façade of this facility allows testing the AWS prototypes under external real conditions and internal controlled conditions. Results of the testing campaign will allow to verify the assumptions made during the simulation activity, calibrate the built models and get more insight on how this complex window systems behave under real conditions. Namely, the tests aim at assessing for each AWS configuration:

1. the thermal performance
2. the risk of condensation under most critical conditions (cold and clear sky nights)
3. the air movement and flowrates in the shading ventilated cavity

For that, two different instrument setups are being used, as shown in the following table and pictures.

Currently all the data is being measured and analysed in order to understand better the actual performance of the different AWS configurations under real conditions. 

Technology development

If you want to know more about the Active Window System, you can check out the following publications.