IMG_3825 Published 2018-09-02 at 1000 × 750 in Paul Novus MVHR Enthalpy Heat Exchanger The old G4 (extract from the house. top) and F7 (intake from outside, bottom) filters after 4 months of use IMG_3825 by Marsh Flatts Farm Self Build Diary is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.