How to design a radiator cover for good heat distribution?

Question

I want to replace some battered, ugly radiator covers in my 1910 home. I have read that to function effectively, a radiator cover needs openings at the front top and bottom, so that natural convection will pull cool air in from the floor, then at the top of the cover, hot air will flow outward toward the center of the room, rather than straight up as in the case of an uncovered radiator.

Here are my questions:

• Is this true?

• If so, how large should the openings be at the top and bottom of the radiator cover?

• How much clearance should I allow above the top of the radiator? (This clearance may be limited because I don't want to block windows.)

• Should the inside top of the radiator cover have a square corner at the back, or is there some other configuration that will promote better airflow?

• Are there any relevant reference works worth consulting?

Answer 1

A radiator works by heating a room with radiation and convection. Radiation is smaller in percentage as opposed to convection. The heat of the radiator is radiated into the room.

Convection works by sending the warm air above the radiator and drawing in cold below. This circulation is the main method of warming a room. Vertical airflow is required to maximize heating.

To that end to putting a cover on a radiator will effect both radition and convection.

To maximize radiation:

• Add a metal plate behind the radiator on the wall to direct heat away from the wall.
• For the front and side covers, they should have enough openings on the sides and front to radiate heat to the center of the room. You want to hide your ugly radiator, but continue to promote good radiation. Decorative screens/grills work best.

To maximize convection:

• Do not place any large objects, curtains, or any other type of obstructions that could effect airflow in front of or next to the radiator.
• Allow for proper airflow at the bottom of the radiator. The cover should have opening(s) at the bottom to draw colder air through the radiator.
• Allow for proper airflow at the top fo the radiator. The cover should have opening(s) at the top to promote warm air rising.

Some suggestions for the top:

• Make the top a removeable cover
• Make the top a cover that can open and close (much like a cabinet door)
• Add vents/grill/screens to the top

If you add a top that doesn't have any openings, then some effiency is lost for the style and look of your cover. Basically we don't want to block the airflow but we don't want to look at an ugly radiator either.