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Assessing my heating system

user-5449330's picture

I recently bought a 1997 2-story house in Charlotte.  Heating is very uneven; cold and warm areas.   I noticed that the kitchen floor is very warm above the crawlspace furnance.   

Found lots of suggestions on the web.  Vent duct pressure checks,  thermal imaging, energy audits, etc  

I'm looking for some suggestions on the best cost-effective approach to determine if I have any issues.   Not looking for a "Cadillac" solution.

Any suggestions greatly appreciated.

Very warm floor above the (post #214115, reply #1 of 4)

Very warm floor above the furnace? First steps, make sure all the ducts are still properly connected and then find and stop the leaks from the seams.  Use mastic or aluminum foil tape to seal.  Once the air is getting to where is is suppposed to, you can then start balancing the system to distribute the heat evenly.

 

Thanks for the tip! (post #214115, reply #2 of 4)

Thanks for the tip!

Probably the floor is warm (post #214115, reply #3 of 4)

Probably the floor is warm where it is because the space between joists below is being used as a hot air plenum/duct.  This is not "legal" in most of the US, the main reason being that too much air escapes through cracks.  (There's also a fire issue, but it's not a big concern with gas furnaces.)

The first thing you need to do is actually examine the heating system, and map it out to a degree.  Note the condition of the ducts (including especially any leaks), and note whether some duct branches seem unusally and unnecessarily long.  If there are any "flex" ducts in the system, examine them closely for leaks, as they will often develop tears in the fabric or cracks in the metal "bellows".

Obviously, any serious air leaks need to be plugged.  There are several ways to do this, starting with (gag!) "duct tape" but including several far better sealants, and including the actual replacement of some ducts.  And if indeed you do have joist spaces being used for hot air (using them for return air is not usually a problem) then you need to consider how to seal them better.

Sometimes you have a situation where a short duct pours hot air into one part of the house while other longer ducts are "starved" because they receive lower pressure (due to the longer duct runs).  This is especially bad if a shorter run is closer to the thermostat.  This can be rectified to a degree by partially closing the registers on the short runs (if the registers have some sort of control lever) or by inserting "dampers" into the short ducts and adjusting them to reduce airflow.

And note that flex ducts tend to restrict airflow worse than smooth metal ducts.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Thanks (post #214115, reply #4 of 4)

Thanks for your insights.  Lots of things I hadn't considered.   This forum alone makes my subscription worth it.