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Where I live, it can get very cold. Not always very efficient to open windows for 5 months out of the year. A great option for keeping CO2 levels down in a ho

Where I live, it can get very cold. Not always very efficient to open windows for 5 months out of the year. A great option for keeping CO2 levels down in a house is with an HRV (or ERV) [1] that will heat the fresh air coming in to cycle it throughout the house. [1] https://en.wikipedia.org/wiki/Heat_recovery_ventilation https://en.wikipedia.org/wiki/Heat_recovery_ventilation

thadk 4y ago
There is an open source 3D printable unit design here which I installed in my window and works well for relatively efficiently exhausting the CO2 from one person in cold weather: https://www.openerv.org https://www.openerv.org (license: CC BY-NC-SA 3.0) I did not 3D print mine, but ordered it, though as an early adopter, adjustment was required.
- pbhjpbhj 4y ago
  Do you know, is there a document explaining the design somewhere? I can see from the Google images some of the parts, but not clearly all the parts nor the flowpaths and such.
westurner 4y ago
From the ERV/HRV (Energy Recovery Ventilation / Heat Recovery Ventilation) wikipedia page: https://en.wikipedia.org/wiki/Energy_recovery_ventilation#Types_of_energy_recovery_devices https://en.wikipedia.org/wiki/Energy_recovery_ventilation#Ty... : > During the warmer seasons, an ERV system pre-cools and dehumidifies; During cooler seasons the system humidifies and pre-heats.[1] An ERV system helps HVAC design meet ventilation and energy standards (e.g., ASHRAE), improves indoor air quality and reduces total HVAC equipment capacity, thereby reducing energy consumption. > ERV systems enable an HVAC system to maintain a 40-50% indoor relative humidity, essentially in all conditions. ERV's must use power for a blower to overcome the pressure drop in the system, hence incurring a slight energy demand. In Jan 2023, the ERV wikipedia article has a 'Table of Energy recovery devices by Types of transfer supported': Total and Sensible : > [ Total & Sensible transfer: Rotary enthalpy wheel, Fixed Plate ] > [ Sensible transfer only: Heat pipe, Run around coil, Thermosiphon, Twin Towers ] Latent heat: https://en.wikipedia.org/wiki/Latent_heat https://en.wikipedia.org/wiki/Latent_heat : > In contrast to latent heat, sensible heat is energy transferred as heat, with a resultant temperature change in a body. Sensible heat: https://en.wikipedia.org/wiki/Sensible_heat https://en.wikipedia.org/wiki/Sensible_heat There's a broader Category:Energy_recovery page which includes heat pumps. https://en.wikipedia.org/wiki/Category:Energy_recovery https://en.wikipedia.org/wiki/Category:Energy_recovery Are heat pumps more efficient than ERVs? Do heat pumps handle relative humidify in the same way as ERVs?:
- lsaferite 4y ago
  IME you don't use an ERV alone. You'd use it _with_ a Heat Pump. The ERV is all about transferring heat from one airstream to another. It's _not_ a device that manages indoor temperatures though, just recovers some of the latent energy in the air. In the process it's also managing humidity mainly as a by-product. The humidification properties of the ERV allow you to run the Heat Pump in a more efficient manner. I have an HVAC geek friend who explained the whole process, but essentially (in non physics/fluid dynamics[?] terminology), if the Heat Pump doesn't need to dehumidify air it can operate more efficiently.

thadk 4y ago

There is an open source 3D printable unit design here which I installed in my window and works well for relatively efficiently exhausting the CO2 from one person in cold weather: https://www.openerv.org https://www.openerv.org (license: CC BY-NC-SA 3.0) I did not 3D print mine, but ordered it, though as an early adopter, adjustment was required.

pbhjpbhj 4y ago
Do you know, is there a document explaining the design somewhere? I can see from the Google images some of the parts, but not clearly all the parts nor the flowpaths and such.

westurner 4y ago

From the ERV/HRV (Energy Recovery Ventilation / Heat Recovery Ventilation) wikipedia page: https://en.wikipedia.org/wiki/Energy_recovery_ventilation#Types_of_energy_recovery_devices https://en.wikipedia.org/wiki/Energy_recovery_ventilation#Ty... : > During the warmer seasons, an ERV system pre-cools and dehumidifies; During cooler seasons the system humidifies and pre-heats.[1] An ERV system helps HVAC design meet ventilation and energy standards (e.g., ASHRAE), improves indoor air quality and reduces total HVAC equipment capacity, thereby reducing energy consumption. > ERV systems enable an HVAC system to maintain a 40-50% indoor relative humidity, essentially in all conditions. ERV's must use power for a blower to overcome the pressure drop in the system, hence incurring a slight energy demand. In Jan 2023, the ERV wikipedia article has a 'Table of Energy recovery devices by Types of transfer supported': Total and Sensible : > [ Total & Sensible transfer: Rotary enthalpy wheel, Fixed Plate ] > [ Sensible transfer only: Heat pipe, Run around coil, Thermosiphon, Twin Towers ] Latent heat: https://en.wikipedia.org/wiki/Latent_heat https://en.wikipedia.org/wiki/Latent_heat : > In contrast to latent heat, sensible heat is energy transferred as heat, with a resultant temperature change in a body. Sensible heat: https://en.wikipedia.org/wiki/Sensible_heat https://en.wikipedia.org/wiki/Sensible_heat There's a broader Category:Energy_recovery page which includes heat pumps. https://en.wikipedia.org/wiki/Category:Energy_recovery https://en.wikipedia.org/wiki/Category:Energy_recovery Are heat pumps more efficient than ERVs? Do heat pumps handle relative humidify in the same way as ERVs?:

lsaferite 4y ago
IME you don't use an ERV alone. You'd use it _with_ a Heat Pump. The ERV is all about transferring heat from one airstream to another. It's _not_ a device that manages indoor temperatures though, just recovers some of the latent energy in the air. In the process it's also managing humidity mainly as a by-product. The humidification properties of the ERV allow you to run the Heat Pump in a more efficient manner. I have an HVAC geek friend who explained the whole process, but essentially (in non physics/fluid dynamics[?] terminology), if the Heat Pump doesn't need to dehumidify air it can operate more efficiently.