4 ms·

This dude built their own and got bad mold problems https://youtu.be/LiptsaKmq80?feature=shared https://youtu.be/LiptsaKmq80?feature=shared

keep_reading 3y ago
Exactly my concern... Just buy the Aprilaire 8100 and don't risk mold...
- dotancohen 3y ago
  What does that system cost? There is no pricing information on the website.
- persolb 3y ago
  How does that remove the condensation though? That's the cause of the mold problem. Edit: looks like somehow it moves moisture between the exhaust/intake somehow... not just heat.
zug_zug 3y ago
Fascinating video. There was a comment on his video asking "Wouldn't this introduce the same amount of humidity/mold as opening a window?" Curious if anybody has any more insight.
- geon 3y ago
  There could be some issue with condensation. The moisture from the indoor air could get trapped and leak.
- aifooh7Keew6xoo 3y ago
  I think the issue is that when the heat exchange occurs one way, the HRV is effectively a condenser. Moisture builds on the heat exchange surfaces of the heat exchanger, particulates, spores, etc. in the air deposit nutrients and viable life in the crud, it thrives and multiples right into the incoming airstream for your residence. When the window is opened the air mixes without a surface for condensation and there's much less immediate deposition so there's not an enriched medium to sustain accelerated growth entirely in the air stream, but it still probably occurs to some extent in a more diffuse manner that produces a significantly lower ambient spore/toxin/particulate load
thadk 3y ago
Wow, even just that bit about mold being able to colonize a dehumidifier without its own MERV/HEPA filter is an important and hard to realize insight.
schneems 3y ago
Ive been deep down the HVAC rabbit hole. You really need 3 separate systems to do it right: - ERV - Dehumidifier - HVAC And basically no regular installer does it right. Lots of efficiency nerds over at Green Home Builders, subscription required.
- samstave 3y ago
  Should throw in a UV bath as well - to kill any airborne spores/other critters.
  - schneems 3y ago
    It’s been a long time since I looked into it, but IIRC the exposure time doesn’t make sense in a duct. RealSexyCyborg talked a lot about this during the pandemic. Though that analysis was limited to the Covid virus. Also to watch for: Some solutions produce irritants like ozone. Not to say they aren’t appropriate, just that they don’t come risk free. It would be a good question for that forum for sure.
    - hinkley 3y ago
      It’s probably a win if it just keeps anything from growing in the exchanger. Condensation and all that.
leoedin 3y ago
It seems that the problems he had were in summer. There's many climates where HRVs are only really needed in winter - in which case those problems wouldn't happen. Basically, as long as the outside air is drier than the inside air, an HRV will work well. The moment the outside air contains more moisture, ventilating will just drive up the humidity of your space - causing many issues.
- jnsaff2 3y ago
  In my climate the problem is air being too dry inside during winter. Outside air is normal humidity 50-80% RH at -10C. Inside it will be 20% and way too dry. Ventilation, heat recovery and moisture recovery would be ideal. During summer we rarely cook with and AC and windows are open most of the time.
- mnw21cam 3y ago
  Absolutely, there are plenty of climates where HRV (aka MVHR) is quite sufficient. In inland areas (most of the US, and a fair chunk of Europe), the temperature difference between summer and winter is enough that a HRV is unlikely to be sufficient. Somewhere like the UK or somewhere near the equator and high altitude, a HRV system probably will be absolutely fine. In the UK, the outside air dew point in the depths of winter is likely to be between -5 and 15 °C, and in summer likely between 10 and 25 °C. That might be a little dry at the driest, and a little sticky on a couple of days in the summer, but it's perfectly reasonable to just bring that air into the house without messing with the humidity. Most UK houses are too humid and don't have enough ventilation. However, as soon as you start wanting to cool a house because the outside air is too hot, then that outside air will basically have 100% relative humidity when it is cooled to your house temperature, and it will probably have condensed out a load of its moisture onto whatever was cooling it, so you absolutely do need to mess with the humidity.

keep_reading 3y ago

Exactly my concern... Just buy the Aprilaire 8100 and don't risk mold...

dotancohen 3y ago
What does that system cost? There is no pricing information on the website.
persolb 3y ago
How does that remove the condensation though? That's the cause of the mold problem. Edit: looks like somehow it moves moisture between the exhaust/intake somehow... not just heat.

zug_zug 3y ago

Fascinating video. There was a comment on his video asking "Wouldn't this introduce the same amount of humidity/mold as opening a window?" Curious if anybody has any more insight.

geon 3y ago
There could be some issue with condensation. The moisture from the indoor air could get trapped and leak.
aifooh7Keew6xoo 3y ago
I think the issue is that when the heat exchange occurs one way, the HRV is effectively a condenser. Moisture builds on the heat exchange surfaces of the heat exchanger, particulates, spores, etc. in the air deposit nutrients and viable life in the crud, it thrives and multiples right into the incoming airstream for your residence. When the window is opened the air mixes without a surface for condensation and there's much less immediate deposition so there's not an enriched medium to sustain accelerated growth entirely in the air stream, but it still probably occurs to some extent in a more diffuse manner that produces a significantly lower ambient spore/toxin/particulate load

thadk 3y ago

Wow, even just that bit about mold being able to colonize a dehumidifier without its own MERV/HEPA filter is an important and hard to realize insight.

schneems 3y ago

Ive been deep down the HVAC rabbit hole. You really need 3 separate systems to do it right: - ERV - Dehumidifier - HVAC And basically no regular installer does it right. Lots of efficiency nerds over at Green Home Builders, subscription required.

samstave 3y ago
Should throw in a UV bath as well - to kill any airborne spores/other critters.
- schneems 3y ago
  It’s been a long time since I looked into it, but IIRC the exposure time doesn’t make sense in a duct. RealSexyCyborg talked a lot about this during the pandemic. Though that analysis was limited to the Covid virus. Also to watch for: Some solutions produce irritants like ozone. Not to say they aren’t appropriate, just that they don’t come risk free. It would be a good question for that forum for sure.
  - hinkley 3y ago
    It’s probably a win if it just keeps anything from growing in the exchanger. Condensation and all that.

leoedin 3y ago

It seems that the problems he had were in summer. There's many climates where HRVs are only really needed in winter - in which case those problems wouldn't happen. Basically, as long as the outside air is drier than the inside air, an HRV will work well. The moment the outside air contains more moisture, ventilating will just drive up the humidity of your space - causing many issues.

jnsaff2 3y ago
In my climate the problem is air being too dry inside during winter. Outside air is normal humidity 50-80% RH at -10C. Inside it will be 20% and way too dry. Ventilation, heat recovery and moisture recovery would be ideal. During summer we rarely cook with and AC and windows are open most of the time.
mnw21cam 3y ago
Absolutely, there are plenty of climates where HRV (aka MVHR) is quite sufficient. In inland areas (most of the US, and a fair chunk of Europe), the temperature difference between summer and winter is enough that a HRV is unlikely to be sufficient. Somewhere like the UK or somewhere near the equator and high altitude, a HRV system probably will be absolutely fine. In the UK, the outside air dew point in the depths of winter is likely to be between -5 and 15 °C, and in summer likely between 10 and 25 °C. That might be a little dry at the driest, and a little sticky on a couple of days in the summer, but it's perfectly reasonable to just bring that air into the house without messing with the humidity. Most UK houses are too humid and don't have enough ventilation. However, as soon as you start wanting to cool a house because the outside air is too hot, then that outside air will basically have 100% relative humidity when it is cooled to your house temperature, and it will probably have condensed out a load of its moisture onto whatever was cooling it, so you absolutely do need to mess with the humidity.