Air transfer solution: ventilated doors An elegant, but expensive, alternative to door undercuts

22 November 2023 by Rachel Rose

Australian Passive House designer Matt Purves posted online some intriguing photos of bespoke doors he built himself from leftover spruce wall panelling. These were for his home in Tasmania, which is targeting Passive House Plus certification. Ventilation systems need air to be able to move freely between rooms even when doors are closed. This is most often achieved by the use of door undercuts, but they bring their own problems with noise travelling between rooms. 

Matt’s doors have been constructed to allow air to pass through them, but not noise. This is not a readily replicated solution because it was enormously time-consuming but it vividly demonstrates a high-end alternative to door undercuts. His description of the solution was posted to a Facebook group only accessible to members, so he’s kindly agreed we can republish his comments and photos here, as follows:

We didn’t want architraves and planned to utilise the scrap timber we had that matched the spruce wall panels, to create a more seamless interface at door thresholds. This gave us 90mm of depth to play with in the doors to easily create a ventilation channel. However, with veneers and a more typical hollow core door, this could be executed in a 40mm door as well.

We calculated 150cm² was the minimum aperture sizing to move 40m³/hr of air. The aperture we implemented is closer to 320cm². In operation it is easily sufficient and provides silent transfer of air between rooms/zones.

Obviously not an option for all circumstances, as it would be cost prohibitive for a lot of projects if these were outsourced to build or charged out by the builder. These were incredibly time consuming to build—although for us, it was a cost saving measure as the 2400×860-960mm doors became essentially free, bar some glue, sandpaper and a lot of time. Hinges were the only hardware required, given we built in handles. But if the circumstances permit, this is an alternative option to add to the existing remedies.

See more about Matt’s project, Scamander Passivhaus, here on Instagram. You can find him on Linked In.

For a commercial solution that is manufactured overseas and has been tested for airflow and sound adsorption linked here. I’ve heard numbers like $450CAD for the door panel (leaf without frame) but that doesn’t include import etc. The website states “Up to 25 STC with perimeter seal” and 45mm thick. The airflow area is more than a 10mm undercut on the door and I can already think of a few projects I might look at using the Lynden ventilating door on. Does anyone know of any other suppliers?

Comments 3

  1. Well done Mat
    Great to see such innovation and foresight in the industry .
    Congratulations and good luck with all you are doing .

  2. I wanted to use these in the wall to provide the return air path, but they seem to have gone out of business.
    I figured an off the shelf product would be an easier solution than a custom-made door (unless you happen to have a woodworking facility, of course!).

    It always puzzled me that passive houses would default to door undercuts for return air, which kinda defeats the purpose of having a door: separation between spaces (visual and acoustic separation).
    Especially in contrast to how picky IPHA is about other acoustic aspects eg inaudible HRV air flow rates. And now with PHPP v10C criteria 3.27: “For units which use air recirculation for cooling or heating, the efficiency values to be set in the PHPP must be those of the operation mode that fulfils the noise protection requirements in 2.4.4 (typically silent mode).”

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