Q: I live in a Brooklyn co-op and am renovating a bathroom that has the original tile and fixtures from the building’s conversion in the 1980s. The original bathroom included a light/heat lamp/exhaust fan fixture that we would like to replace with a new, quieter exhaust fan. When we removed the old fixture, it became apparent that the fan was not properly vented to the outdoors; it was merely blowing into the ceiling and insulation. I would like my renovated bathroom to have proper venting to control moisture.

Am I or the co-op responsible for paying to vent the new exhaust fan properly?

A: “Generally speaking, co-op proprietary leases provide that equipment, fixtures and appliances installed by the shareholders are the shareholders’ obligation,” said Lior Aldad, a Manhattan co-op and condominium lawyer. “And that includes things such as utility lines and ducts that service newly installed equipment.”

But, he said, the co-op may not allow changes to the ventilation system if they involve piercing the face of the building.

“Most older buildings do not have a ventilation system in the bathroom but have a window instead,” he said. So, Mr. Aldad said, if there is a window in the bathroom, it might be possible to run a mechanical vent through the window at the shareholder’s expense, with the approval of the co-op.

But if there is no window in the bathroom and the fan vents into the ceiling space, the bathroom may not be in compliance with the venting requirements of the building code. If that is the case, the co-op would probably be responsible for properly venting the bathroom in accordance with the appropriate codes.