Can I rent out my ADU on a short-term basis, like Airbnb?

The City of Ottawa regulates short-term rentals separately from Additional Dwelling Unit zoning, including a permit and principal-residence requirement in most cases. Whether your specific ADU can legally be used as a short-term rental depends on that separate short-term rental permitting process, not just your building permit – worth confirming with the City directly if that's your plan.