AutoDuct Lowers Heating Costs with an Automatic Shutter

In many parts of the world, apartment buildings commonly utilize decentralized ventilation systems. Instead of a single large central air handling unit (AHU) serving multiple apartments, each apartment has its own small AHU. Those pull in outside air through short ducts in an exterior wall or ceiling. But in the winter, those ducts allow a draft and potentially increase heating costs. Daniel Porzig's AutoDuct solves this problem by integrating an automatic shutter into the duct.

We aren't HVAC (heating, ventilation, and air conditioning) experts, so we can't say if AutoDuct has any potential unintended consequences. But the concept seems sound: AutoDuct simply closes the duct when cooling is unnecessary, so cold air doesn't flow into the apartment from outside. By eliminating that draft, AutoDuct lowers heating system usage and ultimately lowers energy costs spent on heating.

AutoDuct blocks airflow with a simple, but reliable, screw mechanism that pulls a shutter closed. This is slow, but that isn't a problem for an application like this. Reliability and torque are what matter, and a screw is perfect for that. A geared DC motor drives that screw and a Hall effect sensor detects when the shutter is fully closed. AutoDuct fits onto the interior side of the duct, where the user can mount and access it. It sits in front of the axial fan assembly and/or heat exchanger in the duct.

A custom controller PCB opens and closes the shutter as necessary. It has a Microchip PIC32MX microcontroller, a HM-17 Bluetooth Low Energy module, a real-time clock, and a temperature/humidity sensor. It has different operating modes, so it can open/close based on a schedule, temperature or humidity thresholds, or according to remote signals. It can connect to Apple Homekit via the BLE module, and users can make AutoDuct work with the rest of their systems to, for instance, close the duct any time the heater runs or open it any time the thermostat shows a temperature over a certain level.

All of the custom mechanical parts are 3D-printable and Porzig uploaded them, the PCB files, and all of the code. So if you have a decentralized ventilation system, you can build your own AutoDuct.