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I've got a question about a new house - a friend of my mother's is buying a new place and when she did a walkthrough (before the drywall was up), she noticed that all the heating registers and returns are near the tops of the walls (on both floors of a 2 story). When quizzed about this the builder (foreman?) claimed it 'worked better this way'.

The registers don't have any directional control (so you can't really aim the heat downwards or anything).

This seems more than a little odd to me - I'd have assumed that you'd want heat registers near the floor with cold air returns at floor level, but some distance away (to give hot air ability to rise, cool to fall). Is this some kind of compromise position for central air? Does it actually work well?

Added: The house is in Maryland, not too far from Baltimore, so both heating and cooling are important. I'm informed also that the house is built over a crawlspace, if that matters.

  • Where (roughly) is this at? Or asked another way, will she predominantly use the heating or the cooling? – Russell Steen Jan 27 '11 at 21:26
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Physics dictates that for heating, on the walls near the ceiling is not going to be good for overall room heating. However, depending on the structure of the house and location of the hvac system, they may be placed there to avoid long and convoluted runs of ducting which can decrease the efficiency.

Taking just the room into consideration you're going to tend to concentrate heat near the top and not heat the floor, much like in a lake you will have a distinct transition between the warm surface and colder bottom. Ceiling fans are going to be a must to evenly distribute the heat.

So it may be the most efficient setup for that house, but it's definitely not the best setup as a general rule.

You're far enough north that heating costs are generally going to be worse than cooling costs.

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I was to say that the tend started a few years ago, at least in the U.S. -- the issue isn't so much that it's a great place from a warm-air-rises view, it's an issue that floor registers just suck so much.

  • With high registers, you can basically put whatever you want, where ever you want. (well, maybe not tall bookshelves or shoji screens right in front of the vent). With floor registers, you can't put anything too close, or you might not get good airflow in the room.

  • Things fall in floor registers (and even worse ... liquids that your kids don't tell you about, that then have a chance to get interesting before the air next kicks on.

I'm having a hard time finding good information on when the trend started, hoping I could find a larger list of advantages. I want to say the reason for moving them up higher was based on data from an airport where they were using an HVAC distribution system that was a series of pipes that went straight up and hooked at the last second, with a high enough flow rate to throw the warm air out over larger areas, so they could eliminate registers, run fewer ducts, etc.

I don't know if they use the 'throwing air' trick with booster fans for larger rooms when they're using this in residential construction, or if that'd be too noisy.

update : I should've also added -- you of course want this on your internal walls; you don't want wall registers like this on an external wall where you're taking space that might've had insulation. Ducting through crawl spaces are another place where the ducting might be getting in the way of adding insulation.

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The reality is that contractors look to install the cheapest possible. From a design aspect the introduction of heat is within the 300mm from the ground up. Walls or floor. Walls is better because it is less problematic as regards to items or dust dropping into the floor units The greater the flow the more efficient it is in mixing the warmer with the cooler

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