Uneven heating by gas furnace in attic


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Old 03-03-09, 06:30 AM
K
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Uneven heating by gas furnace in attic

We just bought a house in Durham, NC. We have a forced hot air furnace (manufactured in 2000) rated at 69,000 BTUs. It is installed in our attic.

Square footage of house = 1550sq. ft.
Two stories, 3 bedrooms on second floor
Air return on First floor.

We are having a difficult time figuring out how to even out heating our home. When we bought it all the upstairs vents were closed. Even so, the upstairs was warm and the downstairs cool. We set the thermostat at 68 in the day and 64 at night. The neighbor (a contractor) said that the gas log fireplace should be on in the first floor living room to help even the temp out. If that is on, then the downstairs warms up more and the furnace is not on as much. If we open up any of the vents in the upstairs bedrooms it becomes much too warm upstairs. The hot air "whistles" as it tries to come out the registers.

However, our first gas bill shows that we are using much more gas than our neighbors. Our daughter lives across the street, has about the same size house, but their furnace is on the first floor. Their house seems more evenly heated.

So, are we doing the right thing about keeping the gas log fireplace on to supplement heat or is that a money drain? Any suggestions for getting the heat to be more evenly distributed? Should we disconnect the vents to the bedroom from the furnace (or block them better?)

Thanks
 

Last edited by ktraphagen; 03-03-09 at 06:48 AM.
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Old 03-03-09, 08:14 AM
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Do you have any cold air returns on the 2nd floor at all. That may be your problem.
 
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Old 03-03-09, 08:26 AM
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There is a cold air return in the second floor hallway, near the top of the stairs. It is larger than the one for the first floor.
 
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Old 03-03-09, 09:03 AM
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Unfortunately, warm air wants to rise, not go down. And forced air want to come out the nearest registers, not flow to remote parts of a house.

What you probably have is a warm air duct system that may be improperly sized or may have a defect in it somewhere. If you want air to go from the attic to the first floor, it will go that if you have a big enough fan and a big enough duct to carry the air.


Unfortunately, large ducts are relatively expensive to install, while undersized ducts that don't do the job are less expensive. It may be that the ductwork to the first floor is just plain too small.

Alternatively, something could be blocking or plugging it up.

You need to go up in your attic and trace out the warm air ductwork visible there. How many branches off the warm air plenum go to the 2nd floor and how many to the first floor, and what sizes are they?

I might look for ways to disconnect the ductwork going to the first floor to check the airflow and see if it seem reasonable or blocked.

If you can't figure this out, I'd look for a good installer who will come in and check out the airflow system and make recommendation for repair or improvement.

You might, for example, need to run additional ductwork through a 2nd floor closet to get more air to additional 1st floor heating registers.
 
 

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