How does heat circulate in my house? Is it more efficient to have the vents on the outside walls of the house?

Question

We are going to replace our 1922 Octopus Gravity furnace with a new efficient model. Currently all of the vents are in the floor on the inside of the house and the cold air returns are on the floor at the outside walls. I was told by a HVAC contractor that we should move the vents to the outside walls for maximum heat circulation and efficiency. Is this true?

Answer 1

IT doesn't make sense to me.  You don't want anything in the hvac system to have to travel any further than you need to.  I think adding ceiling fans might help move your air around and also leaving the fan at the furnace on all the time.  I do this in our house year round.

Answer 2

In the simple physics sense, it is a little less efficient. You are putting the hot incoming air near the cold wall. It technically increases the heat loss more.

But that is not the point.

Ever seen the trick where you put one hand in cold water, the other in warm water then put them both in room temperature water?  The cold hand feels the room temp water as hot and the hot hand feels it as cold, but of course the water is the same for both.

The same thing is going on here.

The windows and outside walls are losing heat. If you sit in a chair in the middle of the room or worse near the windows and heat is coming from the inside wall, it will FEEL cold no matter what the air temperature. This is because the outside walls and windows are drawing the heat from you.

In that case you are more likely to turn the heat higher to feel comfortable making "inside wall" less efficient.

Vents on the outside walls will feel many times better for you and likely you will not need to turn the heat up as high.

That is the bottom line.

You want the incoming heat to insulate you from the cold spots. That means the vents on the outside walls.

Answer 3

Not sure I'd agree with the words you attribute to the contractor but air outlets are generally located on the perimeter of houses that are built these days.  Think of it this way.  Where does the heat go in the winter time?  Most goes up through the roof and the next greatest loss is through the outside walls, windows, and doors.  Having heat from the furnace piped to the outside walls does two things.  It makes you feel more comfortable if you are near the wall and requires more heat (you are heating a greater amount of space because in  the old system, the heat mostly remained toward the center of the house).   So, are heating systems more efficient with vents on the perimeter?  Yes, they are more efficient in keeping you comfortable.  No, that system will use more energy than when the heat is concentrated in the center of the house.

Answer 4

To maintain the most CONSTANT temperature in your house, you want to have your hot air vents located on the OUTSIDE walls, as close to, if not directly under, any windows or doors.  You want to counter your major heat loss areas before you encounter any fluctuation in temperature.  a heat vent on the opposite side of the room from a window would result in a noticeable temperature difference from one side of the room to the other.

by putting supplies, on the outside, and returns towards the inside, or center of the house, you create currents which balance the temperatures out in each room.

the key to comfort with a heating system is CONSISTANCY, with as little fluctuation as possible.

edit:  the person before me is close, but not quite right...  each house is rated for a certain amount of heat loss.  this is determined by the R-value of your walls, ceilings, and windows.  This is then converted to a "BTU requirement", so the placement of your vents will in NO WAY affect efficiency of anything, as placement of vents will not affect how much heat your house requires.  Your problem is with comfort, nothing more.

Answer 5

That is what I've been told for years........90% of heat loss is up and the rest goes thru your windows.........so we always cut a vent under every window and glass door.........they must be right it seems to work.........so until someone tells me better I will be putting lots of insulation in attics and good curtains on windows with insulated glass and heat ducts in front of them.    Good luck

Answer 6

Heat travels hot to cold so I would think you would loose more heat with the vents on the outside walls when the temp is cold outside.Maybe it'll slow down the cold infiltration.

You know if it's worked the way it is though.

If it has ,I wouldn't modify your airflow.