Iqaluit RCMP say the arsonist was one of two people who died.
More than 80 people were forced into a frigid -50 C night when flames tore through the 22-unit Creekside Village complex in February 2012.
The units were being used as a residence for Nunavut Arctic College and all the tenants but one were students or their families.
Everyone was left homeless and without any possessions.
There were concerns voiced at the time that the apartment block didn't meet modern building codes, but a landlord spokeswoman said the building was regularly inspected.