Fresh outdoor air all year round.
Fresh outdoor air all year round.
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The TW4 decentralized Energy Recovery Ventilator is a machine that transfers clean outdoor air inside and moves polluted air outdoors, while harvesting ~85-90% of the heat energy - so you get fresh air without the downsides of heating or cooling it.
The WM12 is basically two TW4 modules side by side in a piece of tough polypropylene foam, so you can put it in a window.
As of June 2025, this project is now on hold while I focus on the mass manufacture of the Big Quiet Fan.
Also note this has been a long journey and some things are kind of history now. I am generally planning on focussing on the heavy duty attenuator approach, not the lightweight 3d printed noise splitter. The heavy duty attenuator is more expensive but it also blocks traffic/exterior noise, and the higher cost is very small as building systems go, and it will last an extremely long time.
Secondly, the storm valve has proven to be basically unnecessary but it will be an optional add on, after adapting it to the new heavy duty attenuator. The HEPA filter will be an optional add on that you put in place primarily for use during summer to pressurize the house with filtered air, probably. The prototypes work great in terms of noise, flow and energy capture, however there are a number of details I need to finalize before it's really "done".
Core performance figures:
85% sensible, ~80% latent heat recovery at maximal speed, higher at lower speeds. This varies very little with temperature, humidity or season.
High air flow - 60 CFM actual average net fresh air in heat recovery mode on maximum speed.
Extremely quiet - essentially inaudible on low, 37 dBa on medium, ~42.5 dBa per module (half of a pair) on max. The noise has no buzzing or other particularly annoying character, noise variation over time due to the periodic fan reversal is also very minor on high and undetectable at medium and low power.
~20x greater rate of return on investment, compared with typical, conventional ductless ERV units, due to long term design, maintenance costs, higher energy recovery and other factors combined. ~3x the return on investment of typical ducted HRV/ERV units. >10x ROI of photovoltaic panels in many areas like Ottawa, Canada. See spreadsheet on learn more page for details.
Other details include:
Optional HEPA (H13) filter, using widely available filters (requires exterior plate and hood). (it's a cabin air filter for a car, widely available so no problem finding replacements)
Designed and built to last for >50 years, for greatly superior return on investment, with no long term component availability concerns.
Can be configured to work with common home automation systems, including Google Home, Alexa and Home Assistant for scheduling, many kinds of sensor-based operation, interfacing with knobs and switches without wiring, etc using MQTT.
Can be controlled over WiFi using MQTT, including from a phone.
Very low electrical energy consumption - 2 watts on low, 7 watts at maximum power, per module.
Effectively reduces CO2 levels, reduces transmission of airborne pathogens and improves Indoor Air Quality in all metrics.
Storm valve add-on to prevent intrusion of air or water during a storm (requires exterior plate and hood).
Automatic wind compensation to ensure precisely balanced air flow in both directions. This gives both optimal efficiency and also prevents unwanted pressurization of the dwelling.
Powerful, Economical, Quiet, Flexible, hackable, maintainable, modifiable.
Optional heavy duty attenuator attenuates traffic and other exterior noise effectively.
Will be able to work in unidirectional mode, but this functionality has not been added to the firmware yet. The heat exchangers can be removed in summer for higher airflow with even less noise. This can be used to provide abundant fresh air, and with the HEPA filter, HEPA filtered air to pressurize the house with. Other people call this "free cooling mode" because it can be used to bring in night air to cool a house down, however in reality you generally want more air than any such machine can provide, for that purpose, to get good cooling.
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