Agree. HRV / ERV is a powerful concept because it allows you to design better insulated buildings, both with fewer air gaps and thicker wall insulation, while s

Agree. HRV / ERV is a powerful concept because it allows you to design better insulated buildings, both with fewer air gaps and thicker wall insulation, while still reducing indoor CO2 and humidity levels by bringing in fresh air. On the downside, like much in the HVAC world, it requires new construction or a fairly major retrofit to take advantage of it. My guess is that it's only going to make sense for new higher-end construction where other attention is being paid to energy efficiency. (Though I'd love to see a window box HRV for renters, just like window box air conditioners.) If you haven't heard of HRV / ERV yet, this video shows how they work in an impressive but simple demo with the 4 temperature sensors in the last few minutes: https://www.youtube.com/watch?v=QOSelUK6dpQ https://www.youtube.com/watch?v=QOSelUK6dpQ (Also compares aluminum core heat exchanger vs. desiccant enthalpy wheel) For the DIYers, here's a forum full of people building their own HRVs: https://ecorenovator.org/forum/showthread.php?t=891 https://ecorenovator.org/forum/showthread.php?t=891