About two years ago we moved into a 35 year old house. The furnace
was replace by the previous owners and is about 10 years old (92+
Rheem). The ductwork appears to be original (except for a few pieces
around the furnace)
A problem we've had last year (and this year too), is that when the
weather cools down, the upstairs is about 5-7 degrees cooler than the
downstairs. Partially closing the downstairs registers helps some,
but I don't want to close too much and reduce the airflow through the
furnace to a level that will cause problems. I'm looking for a
solution to help the heat make it to the upstairs, without causing
problems with the furnace.
In the basement, above the furnace is the sheet metal plenum. There's
a couple of short 6" ducts that run out of this to the rooms directly
above. Off one side of the plenum, extending most of the basement, is
a long (15 feet), rectangular duct, about 20" wide by 14" high;
basically an extension of the plenum. The round ducts for the rest of
the house feed out of this at various points along it's length.
When the furnace is running, you can feel the heat radiating off of
the sheet metal of the plenum "extension". To me this is heat that is
being lost from going to the rest of the house. I was wondering if it
would help to cover this with insulation, and if so, what type? Rigid
foam sheets seem like they would be the easiest, but is that the best
solution? Also, should I just insulate the long extension, or the
plenum on top of the furnace itself?
Any suggestions would be appreciated.
My father had exposed duct work in his garage. I used R-19 kraft faced
batts. I use furring strips along the edges to hold the insulation in place.
First month the electric bill dropped the cost of the parts. We were running
the a/c at the time. Later when the heat turned on we noticed that the
garage was colder but the furnace ran less. Insulate everything that you
can that is exposed. Use at least R-8 for max effect.
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I insulated mine, it made a 2 degree increase upstairs. To get a 7
degree increase you need ductwork or possibly reduce downstairs airflow.
But air temperature in the plenum has to be checked. To little air flow
and the high temps will shorten furnace life . Get a pro out to look at
your set up.
I don't think insulating ducts is going to be the answer.
You have a distribution or second floor insulation problem.
In that house I would say you almost certainly have a distribution
problem and the only way you are going to get that fixed is to have someone
with professional knowledge see your home, measure as needed, and run the
You may be able to gain some by checking insulation. There may be non
in the attic and you may be able to fix that. It should be fixed before
doing the changes to the distribution system.
It is rather unusual that the upstairs would be too cool. I might also
suggest that the distribution problem may be more of a return problem than
We had the same problem in our home, I partially closed most of the
registers over the course of a week to see if things changed. They did
somewhat (though I do like the sleeping areas cooler). After I made sure
that nothing was in the way of my return area (it's in a closet, the mrs
put a laundry basket in front of it), the temps came close to balancing
Thanks for the reply. There is insulation in the attic and walls, but I
know I need more. It's on the list (which keeps growing..) to get done,
but is not really an option at the moment. I'm just trying to maximize what
I have now until I can get to some of the other things.
As far as the returns, I'm also wondering if that's an issue. There's two
16x8 grills upstairs, but probably twice or maybe three times that much
intake area in the downstairs area. I've considered blocking some of the
downstairs returns to force the system to pull more from the upstairs, but I
want to be careful to not cut the airflow too much.
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