Lunos e2 HRV

Credit: Four Seven Five

What makes this product green?

  • Energy-conserving equipment
  • Prevents moisture or air quality problems
  • Improves air quality


Manufactured by Lunos and sold in the United States by Four Seven Five, the Lunos e² through-wall fans provide ductless, continuous heat recovery ventilation using ceramic regenerative heat exchangers. Installed through 12" thick or greater exterior walls using a 6" opening, they are wired in groups of two or four so that while one fan exhausts, the other supplies air. Heat/cold is absorbed in one direction and the airflow is reversed every 70 seconds, balancing the heating/cooling with filtered fresh air, according to the company. Intended for Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. or super-insulated homes, one pair covers 500–600 ft2 (8' ceilings). These units also work well in retrofit applications.

Manufacturer Information

Four Seven Five
131 Union St.
Brooklyn, NY 11231
Phone: 718-622-1600

Listed in: Air-to-Air Energy Recovery Ventilation