A Return on Investment Model for Passivhaus Posted May 30, 2013 by ITGirl & filed under Speaking Engagements. Leave a comment... Name: You can only use alphabetic characters, hyphens and apostrophes Email: You must enter a valid email address 5 + 10 = Anti-spam: please prove you are human. You must enter a valid numerical answer. You must correctly answer the equation. Comments must be more than 20 characters, and may only contain standard punctuation.Example: . ? ! , " '