how to fix cold on 1st floor, warm on 4th

I have been getting different suggestions, and would like to hear from someone who is not trying to sell me. I have a narrow, 4-story townhouse with an open staircase—yes, it acts like a chimney. All the 1st floor hot air goes straight up (forced air gas furnace). My basement is open so I can re-do the ducts to the 1st floor – but I want to close it up so now is the time to fix this. Changes to the ducts upstairs would be VERY hard.

I plan to add another duct to the 1st floor to boost the heat flow, but will that be enough? Should I add a duct fan to this new duct to really boost the flow? Would adding a duct fan to increase the return from the 4th floor help? But this would bring more hot air back to the furnace—how would that heat up the 1st floor? Or should I put a fan in the return on the 1st floor so that more cold air goes back to be heated? My furnace return is only so large, so if I increase the return from the 1st floor, there is less returning from the elsewhere.

Help! The options seem to be:
1. add new duct to 1st floor
2. add duct fan to 1st floor heating duct
3. add fan to return on 1st floor
4. add fan to return on 4th floor

Which ones would be most effective? Any suggestions?

 

belmontram:

Make sure all the grills and dampers are open in the areas that are cold and then completly close the grills in the warmer areas.
if everything goes as it should, the temp in the upper areas will come down.

Give this a try and let us know.

 

Forget about the duct fan. The 2 possible causes for the uneven heat between levels are proper distribution and air leakage. This is based on a simple fact that you cannot take air out of a house, room or level, without replacing it with the same volume of air. This is because the volume of air in the home remains constant.

For example, if a certain volume of heated air rose to the 4th level, the same volume of air on the 4th level must leave the 4th floor. It could either be air into your return vents on the 4th floor, cooler air dropping to the lower levels from the 4th floor or air leaking out of the house from the 4th floor.

First determine the strength of the air coming out and going into your vents on each level. It is only logical that the force of air coming out and going into your vents should be strongest on the first floor because of their proximity to the furnace. If the 4th floor is the strongest, then it would suggest that this was done because of cooling the 4th floor and is resulting in overheating the 4th floor during the winter. This would mean the dampers on your ducts need to be adjusted to send less heated air to the 4th floor and more to the 1st floor. A simple way of determining the strength of the air coming out is using a piece of tissue paper and putting up against the supply vents. You can tell by the movement of the tissue paper how strong the air is coming out.

The stack effect is caused by air leaving the home. Common causes for this are recess lighting, attic entrances and bathroom exhausts. Remember, if a certain volume of air leaves the house, that same volume of air must enter it. The bouyancy of heated air causes it to rise to the 4th floor and it leaves the house through the aforementioned. This creates a vacuum in the home which pulls air into the home. Usually on the lowest level, regardless on how expensive or tight you think your windows and doors are. The result is in order to meet the demand for the 1st floor, the 4th floor overheats.

 

Is there a way are do you have the room now to set up the duct work so you can have a full cold air return on the top floor and a full cold air return on the first floor. This way on heat ,damper the duct so that most of the cold air return is from the first floor. then on AC with the dampers have most of the cold air return from the top floor.This with the furnace blower on run all the time.This has worked very good for us in some geodesic domes ED

 

Thanks for your responses -- the problem is distribution,. I have already adjusted the dampers, and the flow from the 1st floor registers is good. But the problem is this *** but nice looking staircase. There is a 2 ft by 12 by opening along the side, and you can see up to the skylight in the roof. It works like an interior chimney, and the original HVAC guy did not size things right to deal with it.

So my questions are how to get rid of the cold air (or flipside—how to increase the warm air) on the 1st floor? And can I solve that, and deal with the temp difference between floors at the same time?

I am planning to add another duct and register to 1st floor, but not sure if that would be enough? And I was concerned that it would increase the air flow up the chimney?

One guy said using a duct fan to increase the return from the 4th might help, but again wouldn’t that just increase the rate of air flow up the chimney? – like those outside chimney fans to help get smoke out.

Another said to put in a new 1st floor duct, and increase the 1st floor return by enlarging it or adding a fan. This sounds like what Ed in the dome suggested might work (increase return flow in winter from 1st floor). But since the furnace can only handle so much air flow, it means less return air from the 4th – would this matter? Ed, what was the experience in the dome -- or did it not matter if it kept getting warmer.

Any suggestions? Comments? And why no duct fan?

 

If the blower is rated at 2,000 cubic feet per minute, adding a duct fan to a return does not change the amount of air flow. And it will have no affect on the amount of heat to the 1st floor. Take a piece of paper and put it up to all your return vents and take notice of the force that draws the paper to each vent on each level. Then take a piece of plastic and cover the 4th floor return and test the other returns again with the piece of paper. What you'll notice is the force of the draw on the other returns would have increased. Let's assume 5 return vents draw air equally at 400 cubic ft/min. If you cover one of the returns, then the remaining will draw 500 cubic ft./min. This will affect the amount of heat to the remaining levels with open returns. All the duct fan will do on a return is move the air around in the duct and will have no affect on the amount of air leaving the room.

Static pressure is negative on returns and positive on supply ducts. Closing a return in a home where several other returns exists only increases the velocity of the air in the return duct and does not restrict it. If there was only 2 return vents in the home, then closing one might cause a problem with air flow. But that would depend upon the size of the vents.

 

My house has 7 returns. So the flow blocked off at the 4th floor would be made up by the other 6, only one of which is on the 1st floor -- although it is the largest one.

I suppose I could block off more, so the 1st floor cold air is really sucked in -- and/orr I could add another 1st floor return or increase its size. What do you think about doing that?

Would that be better than adding a new duct to the 1st floor? Or would it be best to do both? -- thanks for your help

 

Play around and see what you get with the cold airs. If you can get a biger intake on the first floor do it thats for sure this way it will try to pull the heat down. Dont close to many off at the same time.Just put tape over the 4th floor one or just cover part of it. then work on down covering them floor by floor. Could you hang a ceiling fan center over this stair well to blow down???? ED

 

Ed's idea is probably best. This is more or less trial and error. Closing some but not too many returns won't cost you anything, but installing a duct will. And the ceiling fan will be less than the duct.

 

The skylight is a large one and more than covers the 4th floor ceiling above the staircase,so the ceiling fan won't work. I have blocked off the 4th floor and two others, and the flow into 1st floor return increased quite a bit. (I tried more, but it really iincreased the noise in the return) Thanks for the ideas.

The temp did go up 2 deg. but I can't say you really felt it -- I think the added air flow to the register makes it feel the same on the skin.

Any other suggestions would really be helpful -- thanks

 

Sounds like you need that other cold air there on the first floor. You can take the grill of and see. That cold air grill blocks off about 15% of the squar " in the duct opening. On the fan, could you put like wood beams in an X by or in that skylight for a fan to hang from?. Have you tried to let the fan run all of the time?Dont know if you would want to try this. Some time ago they had a fan set up for the A frame homes to get the hot air down to the floor. This was a small 10" or 12" fan that you would hang up at the ceiling and it just had a cloth like pipe that went down to just off the floorand blow down. Dont know where you would find one now ED