We have a forced air heating system and are doing full renos in entertainment room at one end of the house including flooring. This room is often colder than other rooms. In it there are both a cold air return and a warm air register. Do we need the cold air return in the room? There are two cold air returns in central hallway of house. Also, what space is required around cold air return? Can it be as little as an inch or two under a cabinet?

Think about it for a few minutes. The same amount of air has to leave the duct that has a blower and go back to the furnace on the suction side of that same blower. Can the return be smaller than the supply? Or should it be the same? If it could be smaller , then why didn't the installer make the supply smaller?

As it is, the room is always colder than other rooms because it doesn't get enough heated air to make it warm.

Can you close the door to that room and get the air in the room to go back through the closed door to the hall return? Or will the air go out the cracks around windows and fresh air from outdoors have to come back to the furnace elsewhere in the house through cracks around windows and doors?

Some do believe that furnaces manufacture their own air.

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Yes, you really have to find out the MAKE and MODEL to get good answers. There IS more than one machine made.

Appreciate what you are saying re the same amount of air having to leave the duct and go back to the furnace. This ductwork was apparently put in after rest of hosue after additional room was put in. Think that has to factor into situation too. My questions haven't really been answered. Do we need the cold air return in the room? What space is required around cold air return? Can it be as little as an inch or two under a cabinet?

If the duct feeding the room is 8-inch round, then the duct returning would be the cross-section of an 8-inch round. 8x8 times .8 = 51 square inches, so a 1-inch high return would need to be 51 inches wide.

As long as you don't close the door to the room if the return is in the hall, then that return would do, otherwise when you close the door, there isn't much air returning. If you cut the bottom of the door so there is a 1-inch high opening (and little privacy) then the door would need to be 51 inches wide - not too usual - or you'd on;ly have half the air return when the door was closed.

You can't fool mother nature - she's married to applied physics.

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Yes, you really have to find out the MAKE and MODEL to get good answers. There IS more than one machine made.

Thanks. Much appreciated. The door to the room is a sliding door that links to kitchen and will be open most of the time so I think we are ok that the returns in the hall should be able to handle it.