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Comment by RGamma | Hacker News Reader

I highly recommend installing a decentralized ventilation system with enthalpy exchanger in often used rooms like the sleeping room.

It's super efficient and improves air quality a lot when your building is highly insulated. The enthalpy part is important because winter air is pretty dry after heat exchange. Bonus points when you can fit good air filters (ePM1 50%+). Also, some systems offer a summer bypass for cooling in summer without AC as well as "smart functions" like orchestration of multiple devices or automatic control via CO2/humidity sensor.

Central ventilation is unfortunately very hard to retrofit...

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> ePM1 50%+

If there’s actual poor air quality (smoke, etc), this is inadequate. 50% is fine for a recirculating system — fine particles will be reduced by half on each pass. For for a single pass system, if you have 50 μg/m3 outdoors (quite common in a lot of places, sadly) you get 25 μg/m3 coming in through your fancy ventilation system, which is not great.

What you want is a great honking filter, 95% or better, with a prefilter. You’ll pay several hundred dollars for that big filter, but you’ll be running it at low velocity (maybe 150cfm of flow in a 24”x24” filter housing), so it will have minimal pressure drop and will last a long time. Even an actual HEPA filter wouldn’t be out of place here.

But even the really fancy European ERV/HRV brands use those inadequate ePM1 50% filters. I’ve even measured them with a handheld particle counter — they work every bit as poorly as one would expect from the specs. And those filters are small, and they gunk up quickly.

Yeah, it's far from optimal, sadly. The best I found for my device were (allegedly) ePM1 70%. We get quite a lot of smoke exposure from badly behaved fireplaces/unsuitable (palette) wood right now and it reeks.

Got any suggestions how I could retrofit a better filter solution for my device (Zehnder ComfoSpot50). It has "slotted" filters like these https://cleanfilter.eu/en/product/zehnder-comfospot-50-filte.... Maybe something to chain outside in front of the intake or inside after the outlet (though I'm afraid I could run the Comfospot out of specs..)?

Or I guess I could kind of suboptimally get a standalone one.

These handheld particle counters look intriguing. Unfortunately a bit on the expensive side... Maybe I can borrow one, might give me some hard data for contacting my municipality about this.

I bought one of these to jury-rig into a Zehnder system:

https://www.hvacquick.com/products/residential/Air-Filters/P...

Haven’t actually finished connecting it yet. It’s nicely constructed, though.

Looks good. Though it would be massive PITA to fit that with my device :(

I'll look around a bit but I'll probably get a standalone indoor one.

IKEA has IMO the best standalone air filter right now.

Already ordered a Levoit Vital 200S Pro. Levoit EverestAir unfortunately is unavailable here.

IQAir Atem X and Allermed devices, that I've read good things about, are too expensive right now (and too large as well, considering the ~20m^2 room is relatively crammed).

Hope the device is a sane choice. As usual I needed to prevent myself from overanalyzing while battling spam blogs and broken corporate sites.

The IKEA things apparently are "only" EPA12, but totally ok for my case... Might still evaluate one if the Levoit doesn't perform well for some reason.

I think IKEA is on the right track with their lower efficiency filter. For a standalone air filter, you care about the rate of removal of contaminants, which is roughly (concentration of contaminants) · (flow rate) · (filter efficiency), and you probably end up caring the most about the particle size at which the filter is least efficient. So a real HEPA filter has .9995 for that last factor, and .99 is barely worse. Even MERV 13 at 75% or so isn’t so bad.

For a given amount of power consumption, you end up with (concentration of contaminants) · (flow rate) · (filter efficiency) / (power), which is (at fixed contaminant level and a fixed quality of fan) roughly proportional to (filter efficiency) / (pressure drop at design flow rate) and this is where IKEA is making the right tradeoff: those non-HEPA filters have considerably less pressure drop and only fail to filter a percent or so of the air going through.

Yeah, the Starkvind seems a better long term choice wrt energy consumption (and perhaps filter availability, but definitely filter price (performance?)). Thanks for the input and enjoy the new year.

The thing about HRV/ERV filters is that it is effectively a pre-filter, because the real filtering is supposed to be done by the HVAC system that the HRV/ERV dumps into.

You still get your HEPA filtering, because that's on your HVAC system.

Yeah I'm surprised how ventilation system is hardly seen in German houses. I suffer from terrible headaches in winter in Germany. On the other hand when I spend winter in France with closed windows and heating on, I have no issues. The only difference is in France where I stay, there is a modern ventilation system.

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