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One of the big trends in green/sustainable building is creating relatively air tight buildings in order to cut down on heating and cooling costs (see: Passiv Ha

One of the big trends in green/sustainable building is creating relatively air tight buildings in order to cut down on heating and cooling costs (see: Passiv Haus, Passive House, Pretty Good House). In order to do that, though, mechanical ventilation is needed. As a result, Heat-Recovery Ventilation & Enthalpy-Recovery Ventilation residential units can be installed for only $2k-$4K. Seems like a worthwhile investment (for when it’s not convenient or possible to open a window).

ip26 7y ago
The other upside to sealing plus mechanical ventilation (instead of leaky-building ventilation) is that your building is always fresh. Leak-driven ventilation leads to a building that is drafty on windy days and stuffy on calm days.
- fyfy18 7y ago
  Plus if the leaks involve air circulating though insulation in the cavity or attic, whatever is in there will end up in your house air. That could be dust from construction, parts of the insulation material, or decomposing rodents.
  - lstodd 7y ago
    Unless the system is of exceptionally poor design, air is never moved at enough speed to pick up dust. If it is, the whatever dust that gets picked up ends up in filters in the first week of operation.
- tekstar 7y ago
  Except these heat exchangers have two filters that need cleaning very 3 months and most people never do it, so they don't really function properly.
  - rypskar 7y ago
    Is the 3 months interval a regional thing, or based on the heat exchanger? Mine have 1 year intervals, and with a subscription for filters it is easy to remember to change the filters
    - mr__y 7y ago
      >Is the 3 months interval a regional thing, or based on the heat exchanger? both. That is it varies between different units but also varies with local conditions, if your local conditions are "heavy-duty" (very high humidity, smog, area with lots of dust or lots of pollens etc.) you should consider replacing more frequently than rated intervals.
Gibbon1 7y ago
Trouble with passive houses is a) people open windows. b) hate fan noise. c) the designs are brittle and prone to catastrophic failure. d) energy consumption isn't going to an issue over the life of the building. e) In Europe and North America the replacement rate for housing is in the low single digits.
- simonebrunozzi 7y ago
  And f) most passive house designs have humidity/mold issues down the road, unless proper and frequent maintenance is done. (I've read about passiv haus and similar a while back).
  - Gibbon1 7y ago
    There is a slow moving disaster in the Midwest where houses constructed in the last 25 years are rotting from the inside due to leaks and internal condensation. Problems are. Sealed construction means moisture can't escape. Think insulation hides problems until major damage occurs. I'm also skeptical because houses we build today should be in use a 100 years from now. And it's really obvious that renewables aren't supply limited like oil and gas. But in the passive house world it's always 1980.
    - tapland 7y ago
      We built a ton of them here in Sweden, but the name escapes me. They were marketed with being able to last for 'at least 20 years' when being built, which should have been a warning sign not to spend $1m on for it on a <$100k family income.
  - lstodd 7y ago
    Mold is only an issue in hot climate. When it's never above 25C / 75F _and_ humidity is controlled, there is never any mold.
    - saiya-jin 7y ago
      Never above 25C... so Iceland, Greenland and Svalbard? Actually not even those, they are pretty humid above 0 celzius
eugenijusr 7y ago
I live in a relatively new apartment building that has heat recovery system installed in all apartments by default. My apartment is 73sqm, the ventilation unit is rated at 300m3/h. The building is located in a busy part of town with lots of traffic around. The city has a humid continental climate (Dfb) so it does get pretty cold during winter. It does help a lot and I couldn't imagine living without it. - Filters out particle pollution - https://twitter.com/eugenijusr/status/1105740301493260289 https://twitter.com/eugenijusr/status/1105740301493260289 - Removes CO2 - averages ~650ppm in all rooms, almost never goes higher than 1000ppm (3 person household). - Retains up to 85% of heat (based on the specs) using the exchanger, but also has an active electric heater inside that can be turned on in winter for ultimate comfort. - Removes moisture from the bathroom and kitchen and dumps it into the drain via a separate drain pipe. - Isolates from the outside noise as you can keep your windows closed shut all the time. It does have some drawbacks however: - Up to +6dB noise in rooms when running at full power (I run it at 20% at night which only adds ~+1dB). - F7 class filters need to be changed every 3-6 months (~50€). - Air intake grill with a pre-filter mesh needs thorough cleaning every 6-12 months as it usually gets clogged with debris in spring and autumn. Not sure if it's due to these drawbacks or lack of knowledge lots of residents don't actually use their unit. You can tell by the open windows all year round. Most say it's too noisy for them - most probably due to lack of maintenance. Others are just plain ignorant saying opening windows is the only way to get "fresh air".

ip26 7y ago

The other upside to sealing plus mechanical ventilation (instead of leaky-building ventilation) is that your building is always fresh. Leak-driven ventilation leads to a building that is drafty on windy days and stuffy on calm days.

fyfy18 7y ago
Plus if the leaks involve air circulating though insulation in the cavity or attic, whatever is in there will end up in your house air. That could be dust from construction, parts of the insulation material, or decomposing rodents.
- lstodd 7y ago
  Unless the system is of exceptionally poor design, air is never moved at enough speed to pick up dust. If it is, the whatever dust that gets picked up ends up in filters in the first week of operation.
tekstar 7y ago
Except these heat exchangers have two filters that need cleaning very 3 months and most people never do it, so they don't really function properly.
- rypskar 7y ago
  Is the 3 months interval a regional thing, or based on the heat exchanger? Mine have 1 year intervals, and with a subscription for filters it is easy to remember to change the filters
  - mr__y 7y ago
    >Is the 3 months interval a regional thing, or based on the heat exchanger? both. That is it varies between different units but also varies with local conditions, if your local conditions are "heavy-duty" (very high humidity, smog, area with lots of dust or lots of pollens etc.) you should consider replacing more frequently than rated intervals.

Gibbon1 7y ago

Trouble with passive houses is a) people open windows. b) hate fan noise. c) the designs are brittle and prone to catastrophic failure. d) energy consumption isn't going to an issue over the life of the building. e) In Europe and North America the replacement rate for housing is in the low single digits.

simonebrunozzi 7y ago
And f) most passive house designs have humidity/mold issues down the road, unless proper and frequent maintenance is done. (I've read about passiv haus and similar a while back).
- Gibbon1 7y ago
  There is a slow moving disaster in the Midwest where houses constructed in the last 25 years are rotting from the inside due to leaks and internal condensation. Problems are. Sealed construction means moisture can't escape. Think insulation hides problems until major damage occurs. I'm also skeptical because houses we build today should be in use a 100 years from now. And it's really obvious that renewables aren't supply limited like oil and gas. But in the passive house world it's always 1980.
  - tapland 7y ago
    We built a ton of them here in Sweden, but the name escapes me. They were marketed with being able to last for 'at least 20 years' when being built, which should have been a warning sign not to spend $1m on for it on a <$100k family income.
- lstodd 7y ago
  Mold is only an issue in hot climate. When it's never above 25C / 75F _and_ humidity is controlled, there is never any mold.
  - saiya-jin 7y ago
    Never above 25C... so Iceland, Greenland and Svalbard? Actually not even those, they are pretty humid above 0 celzius

eugenijusr 7y ago

I live in a relatively new apartment building that has heat recovery system installed in all apartments by default. My apartment is 73sqm, the ventilation unit is rated at 300m3/h. The building is located in a busy part of town with lots of traffic around. The city has a humid continental climate (Dfb) so it does get pretty cold during winter. It does help a lot and I couldn't imagine living without it. - Filters out particle pollution - https://twitter.com/eugenijusr/status/1105740301493260289 https://twitter.com/eugenijusr/status/1105740301493260289 - Removes CO2 - averages ~650ppm in all rooms, almost never goes higher than 1000ppm (3 person household). - Retains up to 85% of heat (based on the specs) using the exchanger, but also has an active electric heater inside that can be turned on in winter for ultimate comfort. - Removes moisture from the bathroom and kitchen and dumps it into the drain via a separate drain pipe. - Isolates from the outside noise as you can keep your windows closed shut all the time. It does have some drawbacks however: - Up to +6dB noise in rooms when running at full power (I run it at 20% at night which only adds ~+1dB). - F7 class filters need to be changed every 3-6 months (~50€). - Air intake grill with a pre-filter mesh needs thorough cleaning every 6-12 months as it usually gets clogged with debris in spring and autumn. Not sure if it's due to these drawbacks or lack of knowledge lots of residents don't actually use their unit. You can tell by the open windows all year round. Most say it's too noisy for them - most probably due to lack of maintenance. Others are just plain ignorant saying opening windows is the only way to get "fresh air".