Shadowline Diffuser

  • 2021

  • Product
    Hardware and Building

Designed By:

Commissioned By:

Expella Pty Ltd

Designed In:


The Shadowline Diffuser is a modern exhaust diffuser developed by Australian ventilation specialists Expella. This product offers a discreet ventilation grille solution for bathroom and laundry spaces, and has also been recently adapted for use in air-conditioning systems.

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Image: Project: Alexander House by Alexander & Co. Photo: Simon Whitbread
Image: Photo: Simon Whitbread
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  • The design challenge is to improve the aesthetics and function of essential ventilation services (such as exhaust and air conditioning systems), without compromising on performance. Ventilation grilles notoriously detract from the design of an interior. Most grilles on the market are either large and unsightly or small and noisy due to their increased air velocity. Many take a one size fits all approach and do not necessarily distribute air uniformly. Contemporary tastes demand more from ventilation products and bulky, noisy and unsightly grilles no longer cut it for the discerning residential and commercial architecture and interior design market.

  • Expella's Shadowline Diffuser is a hidden ventilation grille that sits discreetly at the junction of a wall and ceiling. The Expella team drew on their expertise in ventilation to fit features traditionally found in large unsightly air grilles, into a concealed, low-profile and effective product. Having recently switched to extruded aluminium to manufacture the product, the team experimented with unique design features to optimise air paths, reduce air turbulence, noise and system pressure. Versatility was an important feature of the Shadowline Diffuser, and the modular, customisable design makes it easy to install and adapt to a range of construction environments.

  • From a SOCIAL perspective, the health of a dwelling is drastically improved. Shadowline Diffuser, an integral component of a ventilation system, allows for a healthier home environment by controlling condensation, mould, indoor humidity and other pollutants (VOCs), resulting in improved air quality. Given the current boom in home renovation, there is significant COMMERCIAL potential for the Shadowline Diffuser, filling a gap in the market for discreet ventilation and air conditioning solutions that appeal to a wide market. The increased aperture of the Shadowline Diffuser reduces system pressure, with the ENVIRONMENTAL benefit of improving energy efficiency of the air movement system.

  • Expella's Shadowline Diffuser is an innovative ventilation grille, manufactured in Australia, that caters to a contemporary aesthetic. The discreet design does not interfere with the aesthetics of the space that it services. Developed by a small team of ventilation experts, the Expella team is excited at how well-received the Shadowline Diffuser has been, and the potential for use in other air movement technologies. Apart from the obvious visual appeal of a hidden grille, product benefits include: -Shadowline concept effective not only for exhaust fans, but air diffusers for air conditioning systems too -Improved air flow characteristics reduce the energy required by the fan to perform its duty -Easy to install, with customisable length -Modular nature of the product makes it highly adaptable, and enables hassle free storage, shipping and handling -Made from strong and durable extruded aluminium -Option to integrate LED lighting -Easy to use clip-in, adjustable brackets -Compatible with Rondo suspended ceiling mounting system -Configurable duct spigot position, orientation and quantity -Cleverly uses the Coanda effect when installed in a vertical wall to efficiently distribute the air in the room without the need for additional ductwork