Hi, We have been in our home for a little over a year. The previous owners turned the garage into an extra room. The room is not heated and does not have ac. Does anyone know the process of putting a vent into that room so that whenever we turn on the heat or ac it can flow through that room too? The boiler room is also in the garage. Any and all help will be appreciate.

Do you have a boiler or forced air? Is the ducts in the rest of the home just for AC and radiators for heat?

I'm sorry Northernheat. I do not understand your question. I can tell you that my house was built in 98. I'm not sure if that will help you. My vents are in the ceiling. I have central heat and air. No radiators.

You said you had a boiler room, so I thought you might have a boiler in it. If the furnace is in the Garage, you can simply cut a 4" x 10" hole in the plenum. Then install a register in the hole that you can open and close as needed. Most codes will not allow a return air opening in a garage though. It can send gas, odors and CO from your can throughout the house.