If you’re working on a Passive House (or Passivhaus) project, there will come a time when you will have to decide whether to certify your project through PHI (the Passivhaus Institut) or PHIUS (the Passive House Institute U.S.). Before their split in 2011, they were essentially one and the same, where PHIUS was the American “branch” of the European PHI. But due to irreconcilable differences, sadly, our “parents of passive house” got a divorce and now you have to choose which one you will stay with for the holidays.