Air return placement

They are actually better in the wall, low for heat, high for AC, if not in the ceiling. Floor registers tend to collect dirt.

On AC installs the return usually goes where the installer put his foot through the ceiling. :-)

Agree. And whatever size and number there are already should be fine, unless there is a problem with heating or cooling that room. Unless you're going to run more ducting to another location, you're pretty much limited to what's there anyway.

Ours are in the floor. Fretwell is correct about the dirt. Other than that, it's not a problem. We just change the filter more frequently.

Cindy Hamilton

Returns in floors have been around for as long as there have been forced air systems. Some older homes may have only one large return per floor, especially on the first floor.

Back in the olden days HVAC guys had a round slide rule type duct calculator that would solve for duct sizes based on the machine you had, desired CFM and operating pressure. It would spec round square or rectangular ducts. I am guessing it is on their phone now.

They also may limit decorative or even functional layout of rugs or obstructive furniture e.g., wall units, floor-standing audio speakers, standing lamp bases, etc.

in our 3 level house (2 story with finished basement) - about 600 square foot footprint - there is one6X32' return on each of the 2 main floors and a roughly 8x12 in the basement. The main floor returns ore at the bottom of the interior wall, and the basement one is in the ceiling afjacentto the interior wall. The staircases are all open -no door to the basement. They appear to be adequate for both heating and cooling - although not optimized for either.

As luck would have it, all of ours are under windows, so we're not inclined to put furniture there anyway. Designed for the original gravity furnace, I think.

Cindy Hamilton

Heat OUTLETS are generally placed below windows so the heat helps "hide" the cold draft from the window and helps keep the windows from frosting/condensing/fogging

Cold air leaks through the window and immediately drops down the return. Reduces drafts and pushes air through the gravity furnace. This house (1947) and our previous house (1954) had the returns under the windows. I can't recall how the house before that was laid out.

I suspect the original windows on this house were single-pane, steel-frame. The garage has a couple of them, still.

In fact, the returns were originally let into the wall beneath the window. But the air washed directly down the foundation block and water condensed on the block, promoting mold growth. We re-worked them into the floor with a proper boot and insulation separating the duct from the block.

The building of my house was a helluva stonemason, but some of his other work was downright sketchy.

Cindy Hamilton

I've wondered about the practice of putting the vents on the outside walls. I agree with Clare's reasoning, the windows, outside walls are going to be the coldest, so it makes sense from that standpoint. On the other hand the result is the vent has almost no insulation between it and the cold or hot outside wall. I wonder if any studies have been done to see if there is a noticeable difference in comfort if it was done with vents on interior walls? It would save on energy.

Radiators are usually under windows, but that might be mostly because of it being easier to run pipes.

If some of the perception of being cold comes from radiative heat loss to the cold wall, then putting vents near the walls might let you set the thermostat lower and still feel warm.

The heat registers in my 1956 three bedroom colonial are split almost 50/50 between inside walls and outside walls. Returns are also split in a similar fashion.

There are no returns directly under windows.

There are 3 output registers directly under windows, but most are not. Of the 3, one is in the kitchen. There really was no other place to put it due to lack of open wall space. Another is under a picture window which takes up most of the wall so, again, not much of a choice. The third one is under a window in the addition on the back of the house, but it's also in about the only place it could go based on the layout of the room.

What I'm saying is that it does not appear that the builder followed any "register placement standard". The house stays comfortable, so I'm OK with that.

Picture windows - in my experience - have 2 heat registers. I've owned 2 forced air homes - late '50s and early '90s and every above-ground heat register was under a window - except - bathroom and entrance-way. John T.

The *room* has 2 heat registers. One on the south wall under the window and one on the east (outside) wall.

The north (interior) wall has 2 returns.

Much better comfort with the heaton the outside walls -and also much more efficientway to keep the house comfortable. - particularly with constant low speed air circulation.

Returns under the windows for heating makes acsolutely ZERO sense.

Not with forced-air heating. But many older houses were designed for gravity furnaces.

In my particular case, the uninsulated, masonry exterior walls are so cold that it wouldn't make a blind bit of difference if the heat was on the outside walls.

Most of the returns in my house are just floor-joist bays with some aluminum sheet nailed up to form a primitive duct. We'd intended to run real duct through those bays, but never got around to it.

Cindy Hamilton

You're in Michigan ? with uninsulated walls ? John T.

Concrete block veneered on the outside with split fieldstone (R1 at best). On the inside, 1/4 inch furring strips with vintage 1947 drywall nailed up. Skim coated with plaster. It would be a giant pain to take down the drywall, fur out the walls with

Our heating costs are surprisingly low, probably because the attic has more than 1 foot of blown-in insulation. And the house is only 1200 square feet or so. I'll admit if you're not wearing sleeves in the winter, the arm on the side facing the exterior wall is a little chilly as your body heat radiates outward toward that cold wall.

Cindy Hamilton