Comment by amluto
You can multiply 20W by whatever you want, and if you multiply 1kW by the same number, you will get a number that is 50x as large.
Put another way, of course you can naturally ventilate a house to get the same air change rate that an HRV/ERV will get you. But (a) if you live somewhere with poor outdoor air quality, you have no opportunity to mitigate it with natural ventilation and (b) natural ventilation at high rates requires far more active heating and cooling in climates that need heating and cooling.
Even just the power needed to operate a large enough standalone air purifier in a naturally ventilated house will be far larger than the power needed to run a filtered ventilation system that will outperform that standalone filter (in a well sealed house or a positive pressure system).
As I write this, I’m running an ERV that is consuming 25W to supply HEPA filtered air at very slight positive pressure. The same ventilation rate, from unfiltered natural ventilation, would remove 500W of heat, and I’d probably need at least 100W of air purifiers running to get anywhere near the level of filtration that those 25W include at no additional cost.
You seem to be trying to tell me that the 25W would scale to a lot of power if everyone did this but that the 500W I would use otherwise would have no impact because the Romans didn’t worry about it. I’m unconvinced.
(This is a system where I replaced the mediocre and undersized filter from the manufacturer with a monstrous 24"x24"x12" nominal HEPA filter, a 24"x24" MERV 8 prefilter, and a carbon filter mat from McMaster-Carr. I expect the HEPA filter to last for several years, the extremely inexpensive prefilter to last for a year or so, and the carbon filter to need replacement more frequently if outdoor odors from wildfires become an issue. Why HEPA instead of a 99.9% filter with somewhat lower resistance? Because it’s much easier to buy a real HEPA filter and the added resistance is negligible. No additional power is consumed by any of this: it all has less resistance to airflow than even a brand new factory filter. The only real downside is that it’s physically large.)
You seem very proud of your home ventilation system, and very keen to tell us all about it. Im not surprised you dont really care about the power usage to achieve that. Its quite telling that your alternative that you suggest is more power hungry air purifiers.
I however will stick with my house which uses zero external grid power to heat or ventilate it, and I can be happy in the knowledge I am not putting any drain on the national power grid for my comfort.
Also when we have power outages, which is quite often, it makes no difference to my home whatsoever.
Its OK, we can agree to disagree. You are not alone in thinking electricity is an infinite resource. Lets just keep on building houses that require more and more power to run and see where that gets us!