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Community and Q&A

Through-wall HRVs/ERVs

Irishjake | Posted in General Questions on

Looking for thoughts or feedback on the thru-wall HRV’s/ERV’s – specifically the Lunos e2 system vs. the TwinFresh Comfo RA1-50-2. (I’m reposting this because it got lost in the last barrage of Chinese spam in the Q &A.)

I’m looking for help to determine which one I should use. They need to be installed next week. I have a 850 sq ft apartment that needs to be ventilated.

What I know about the two systems-
They can both work in unison (every 70 seconds or so, they reverse supply and exhaust), during this time the core is regenerating.
The Luno e2 has a remote wall mount datalogger and control head. (an add-on expense $500+). The units (sold in pairs) and are a couple hundred dollars more than two TwinFresh units too.

The TwinFresh has a higher air flow capability, and higher electrical requirement.


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  1. GBA Editor
    Martin Holladay | | #1

    I don't know a lot. Here's what I know.

    The Lunos has a reputation for being well engineered and for performing well. It's usually used in a retrofit job, not new construction, because that where its high cost can be easily justified (because it is easy to install, not needing ducts). The biggest downside to the Lunos is the relatively low airflow rates.

    I know less about the TwinFresh Comfo, but I always assumed, rightly or wrongly, that it is a knock-off copycat product -- using the Lunos idea and achieving it at a lower price point. I have no idea whether the TwinFresh Comfo made engineering or performance compromises to achieve its lower price. I haven't heard any reviews of the TwinFresh Comfo on GBA yet.

    Good luck. If you install the TwinFresh Comfo, give us a review after it has been up and running for a while.

  2. josh_in_mn | | #2
  3. Irishjake | | #3


    Thanks. I have had the same assumption. Both are from Germany, so I wasn't as suspect as I would have been had the "knock-off" been found to come from Asia. Regardless, the Lunos seems to be a better product and the price point is not that far off.

    The reason behind the choice of a thru-the-wall HRV, is that my rafters are exposed, with all my insulation outboard of the sheathing and vapor barrier. I do not have ceiling space to run a ducted HRV.

    In your blog post you mention the ASHRAE standard. I barely meet the ASHRAE minimum (33 CFM) requirement with the TwinFresh at max speed for the one bedroom apartment with one person occupancy. It is an 770 sq ft apartment + open stairwell and entry vestibule downstairs (850 sq ft total), but is cathedral ceiling, so I'm concerned with cubic volume, and the fact that there will most likely be two adults there.

    Joseph Lstiburek mentions in this document where he challenges the ASHRAE standard that ventilation rates could/should be lower. According to his formula I still need a minimum of 23.5 CFM of ventilation. (Which the TwinFresh meets at high speed). I would need two pairs of the Lunos to exceed even that requirement.

    I'm having a hard time understanding the TwinFresh specs though, as far as watts and amps are concerned. There are two sets of numbers listed for each on the spec sheet (see attached pdf).

  4. josh_in_mn | | #4

    Aside from the fact that they use European style delimiters (comma instead of period to denote decimal) what's confusing?

  5. STEPHEN SHEEHY | | #5

    Zehnder just announced it will be selling a simple through wall unit in the US. I don't know the price.

  6. GBA Editor
    Martin Holladay | | #7

    Response to Joshua (Comment #2),
    Thanks for the link! I had forgotten about that thread.

  7. Irishjake | | #8


    I didn't realize the comma was used instead in Europe - it is perfectly clear now. Thanks for that thread link too!

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