Cold air return near the ground or ceiling?

[affiliateian]

The developer is coming back to put in a cold air return grill of which they had dry walled over. The contractor will check to see if the grill can be installed near the ceiling or the ground (depending if the studs have been sealed off half way up the wall - usually, cold air returns are near the ground).

This is for the top floor of a 3 floor home. Here is my thinking. Experts in this area, please chime in. To help remove more heat in the top floor, I am tempted to ask teh contractor to install the grill close to the ceiling. Aesthetically, it may not be as pleasing but wouldn't this help in drawing away some of the heat in the summer time?

My furnace has a 2 stage motor but the original developer only hooked it up to run on 1 stage. I am getting central A/C put in and their installer thinks he can re-setup the wires so that it can utilize the 2 stage blower. SO... on the hot days, the cold air return will, in theory, pull out more heat from teh top floor (as it is closer to the ceiling). In the cold days, it will still pull away more heat but I am thinking this is ok since the heat will be on anyways. By the way, thermostat is on middle floor. On the not so hot days, I am thinking I can run the blower to circulate air without using the A/C or furnace heat. Our furnace actually pulls air from cold air returns inside the home as well as a duct that draws air from the outside of the house.

Any thoughts, advanatges or disadvantages on whether we should install the cold air return near the ceiling or ground (on the 3rd floor)?

[CJT]

I think it depends on the climate you're in, since "cold air return" is a misnomer in the south during much of the year. In the north, I'd place it low, but high in the south (assuming Northern Hemisphere).

[affiliateian]

CJT, can you explain your reasoning. I need more info, newbie here.

[Jimi]

Y'know, I don't think it really matters where you put the fresh air intake as far as efficiency goies. I think the difference would be very minumal.

I would however, want the cold air intake near the basement where there is a cooler temperature and will cool your house in summertime when you have the furnace shut off and the fan on manual.

[affiliateian]

Also forgot to add, we have a cold air return in the basement. I am thinking I want to disbale this so teh basement does not freeze when the A/C is on in the summer months. Any feedback for this on top of my original question in the first post?

[CJT]

In the south where it's hot much of the year, you want to pull away the hottest air (near the top) to run through your A/C; winter isn't the issue. In the north, where winter IS the issue, you want to draw off the coldest air to feed to your furnace.

At least, that's my thinking on the subject. But I agree with the other poster that it's probably not a huge issue. In either case, the outlet of the AC/furnace will be significantly cooler/warmer than the air in the room, so the location of the return should only make a marginal difference.

[affiliateian]

Thanks for the reply. I read somewhere that the more humid air is alos the part that rises and was hoping the higher cold air return would pull out more moisture and heat from the top floor. So it sounds like there isn't much of a difference whether it's close to the ground or ceiling.

And based on your reply, it also sounds like that I should leave my basement cold air intake as is for cases where I will run the blower for air when the A/C or heat is not on. What about for times when the A/C is on. Would the aold air return in the basement create a negative pressure and draw cold air form the upper 2 floors to cool the basement even more? Any thoughts on whether I should keep the cold air return in the basement woudl ab greatly appreciated. One more thing, the basement is an open design and there is a big gap under the door to teh furnace room. Wouldn't this act like a codl air return?

[udarrell]

Your furnace will be more efficient heating with the return air intakes at the floor level. Depending on where the supply air discharge diffusers are at, & airflow rate and throw, near the ceiling can make a considerable difference in the performance of the A/C mode. If you could have it setup so you could switch from floor to ceiling on the RA intakes it would be ideal. Some are doing that with new construction.

- udarrell - Darrell

[Jimi]

Would the aold air return in the basement create a negative

There could be a negative flow, but no great pressure...again, it would be so small they you wouldn't notice. If your furnace is in a small room where your fresh air intake is, yes the air would go under the door. One thing that you don't adress is the registers. The cold air intake isn't the only variable that can be changed or relied upon for cold and/or heat comfort. You can open and close your registers or floor vents or walls to regulate what air goes where. Depending on where you live they may be needed to be adjusted every season or only once in the houses lifetime. You can do a lot by adjusting your registers so I wouldn't get too worried about the placement of the air intake. Hope that was of some help...Jimi

[affiliateian]

So it sounds like I can keep the basement air return and do some blocking between seasons to see how this affects temperature among the

3 levels.

One last question. What is this backdraft danger for some instnaces where air returns in teh basement can cause? Still can't wrap my head around this yet. Any help would be greatly appreciated!

[dkarnes]

i would not block any air return. unless you enlarge another return in some other location. you have to do calculations on returns so you don't put strain on the blower.

[Stormin Mormon]

Heat rises. Cold sinks.

Where do you think you will find cold air?

[affiliateian]

Was that supposed to be a smart remark?

Just to clarify, the situation changes with the seasons. In the summer months, the main goal would be to have the upper most air return draw the most humid and heated air while in the winter months to maximize the comfort of the entire home. From my research, many home owners have indiacted that having a air returnin teh basement in teh summer with central A/C actually makes the basement much cooler than it needs to be. As another useful poster suggested, maybe keeping all 3 returns and making adjustments to registers and returns to try and "balance" the comfrot levels as much as possible with the changing seasons is the best method. Again, I am a newbie at this and was looking for advice and help. Not smart a$$ remarks with no further explanation... Mr T., have you been fed enough?

[hallerb]

a long time ago a realtive had AC, back in the late 60s. He was wealthy. first air condioning I had ever seen

Anyhow he had 2 sets of air returns with levers to close them off, one high for AC season, one low for heating season. He would turn off the unneeded one depending on the time of year.

Never saw another set up like that, I suspect furnaces today do a better job of circulating air thus the multi speed blowers.

[hallerb]

a long time ago a realtive had AC, back in the late 60s. He was wealthy. first air condioning I had ever seen

Anyhow he had 2 sets of air returns with levers to close them off, one high for AC season, one low for heating season. He would turn off the unneeded one depending on the time of year.

Never saw another set up like that, I suspect furnaces today do a better job of circulating air thus the multi speed blowers.

[Goedjn]

If your ceilings are high enough so that you can have a pool of warmer air at the ceiling and not have your head in it, then having the cold air returns low means that you can cool the air that you're actually living in faster. You'll eventually end up dealing with the extra heat up high, by disfusion, mixing, and radiation, but it buys you a bit of extra responsiveness.

[Doug Boulter]

[e-mail] wrote on 27 May 2006:

Actually, what you want to do in the summer is close (or partially close) some of the basement supply vents so little cold air goes into the basement. You want to leave the return open so the cool, but humid basement air is drawn into the A/C system and dehumidified.

[JefCullen]

[affiliateian]

hmmm, that sounds like a good idea. Just curious. Do you have any other returns besides the ones on your top floor?