That Zehnder unit is fantastic. The filter, not so much. (“ISO Fine” is IMO particularly embarrassing. It should say something more like “ISO ePM 1 40%”, and th

That Zehnder unit is fantastic. The filter, not so much. (“ISO Fine” is IMO particularly embarrassing. It should say something more like “ISO ePM 1 40%”, and then buyers would think “40%? that’s lousy!”). Even the fancier ComfoWell filter is crap. And they’re overpriced, have lots of resistance, and don’t last long. You can confirm how poorly it works with a portable particle counter. Get something like this if you have space: https://www.hvacquick.com/products/residential/Air-Filters/Powered-HEPA-Filters/HVACQuick-IFHB-Series-Inline-HEPA-Filter-Boxes https://www.hvacquick.com/products/residential/Air-Filters/P... And consider putting it upstream of the Zehnder unit in the outdoor intake duct. Then it will extend your ISO Fine filter’s lifetime to effectively infinity. Or you could replace it with ISO Coarse. Or with nothing :)