Random puzzlement #17,462

[light_in_motion]

Why are floor-mounted heating vents for hot air systems customarily placed nearest to the walls, where they're most likely to be blocked by furniture? Doesn't it make more sense to center them so the nice, expensive BTUs can spread out into the room before shooting straight up to the ceiling?

Comments

[hascouf]

They are placed near walls, and preferably under windows to aid in air circulation, or at least that is what the contractor that is retrofitting my in-laws house told them.

[light_in_motion]

Yup. I've certainly heard that before; it just seems counter-intuitive to me. Putting heating elements right under the least-insulated space on an outside wall seems silly. Presumably, there's something about the way it works that I don't understand.

I would think that the next most efficient design to a hypocaust or Siberian chimney would be centered hot air vents directly under ceiling fans.

[corwyn_ap]

For central heating, the design criteria is 'even heating'. Thus, heating units are placed next to the source of the most cold (windows etc.) so that the heat will appear even. In addition, the windows get washed with warm dry air keeping them from condensing water.

At least some of this is flawed in my opinion, and some more of it is out-of-date with modern building standards.

Ceiling fans, contrary to most use, should be blowing up in the winter, this mixes the air without providing a cooling breeze on the occupants.

Heat sources should be in the middle of the structure, preferably with high thermal mass, you are correct. What really gets me is chimney which passes through a wall. Wow, lose heat much?

[light_in_motion]

There isn't much to burn in Siberia. I've been told they traditionally built their houses around the chimneys, which wrapped around and around the structures. Apparently, the smoke would be stone cold when exiting, and one fireplace was sufficient to comfortably heat the whole shebang. In Siberia.

[eclecticmagpie]

The problem with centrally placed heating vents is that the warm air rises, goes across the ceiling, hits the cold window, cools, plunges down the window getting colder and colder, and then races across the floor, making the occupants of the house cold. So they raise the thermostat. So, even though it may *seem* inefficient, it really has hidden advantages other than the "appearance" of even heat. Radiant floor heat capitalizes on this still more, allowing people to be more comfortable with the thermostat lower. Go radiant floor heat

[light_in_motion]

Radiant floor heat - YES. There are few things more pleasant in winter than a floor that's warm under(bare)foot.

I've used the lit newspaper trick in a regular chimney that draws poorly; not such a big deal, unless the door is a long distance from the fireplace. The article sounds like it was well-written. Including a discussion of how to convince the mason is a very good idea.