Project Details Designed by Ben Valentin of Birdsmouth Construction, this Earth Advantage certified Zero Energy ADU meets the Passive House requirement for airtightness. Triple pane European Glo windows, continuous super-insulation, a mini split heat pump, heat recovery ventilation and a 5.6 kw solar PV array make this ADU extremely comfortable. On top of it, this ADU produces more energy than it consumes over the course of a year. On top of it we think it looks pretty cute.