A transition module for an energy recovery ventilator unit. The module comprises a frame having two opposing major surfaces with two separate through-hole openings therein. The module also comprises a self-sealing surface on one of the major surfaces and surrounding the two through-hole openings. One of the through-hole openings is configured to separately overlap with return air openings or supply air openings located in a first target side of one an energy recovery ventilator unit or an air handling unit and in a second target side of the other one of the energy recovery ventilator unit or the air handling unit. The other of the through-hole openings is configured to separately overlap with the other of the return air openings or the supply air openings located in the first and second sides.