The sticky says to give a lot of info, so here we go...

Furnace and House Info:
I have a two-year-old Goodman furnace, model GMV95. It is a 95%, high-efficiency furnace. The finished areas of my home equal 1100 sqft. A 70,000 BTU model was chosen to heat the current finished areas plus the 400 sqft basement when the time comes that I finish the basement.

My house is a Cape Cod, in fact, my neighbors all have Capes too. They tell me that their houses are very hard to evenly heat. In the last 2 years I have gutted my whole house down to the studs. I replaced all the windows with Anderson 400 Series. First floor insulation is R13 batt. Second floor insulation is icynene spray foam. The foam was sprayed directly to the roof decking and to the side walls of the house. I decided on the spray foam because all my neighbors tell me that their upstairs is hot in the winter and they absolutely bake in the summer, even with central air. I don't have central air yet, but after the icynene, I can keep the upstairs and downstairs within 1 degree of each other in the winter, even with the whole system being on only one zone!

Question:
The picture below shows how the ductwork for the first floor return vents are run. Sheets of tin are nailed to the floor joists and the cavity serves as the duct. Just looking at the edges, there has to be some nice air leakage. Before I finish the basement I am going to pull down the sheet metal and clean out the return ducts. At that time, should I just put up new sheet metal with a proper seal or should I replace the sheet metal with rectangular duct?

The sheetmetal is called panning and it is used for return air space. A small amount of leakage is to be expected but minimumize if possible. If you are careful you might be able to just use the panning over if not there is panning now that is made of cardboard with a aluminum cover embossed over it and it is approved for use and works well at a much more reasonable price.

Hvac1000,

Since my system is working well now, you are saying to just replace the current panning with the aluminum/cardboard panning?

The other thing I forgot to mention is that my basement's current height is 6'11". This is without sheetrock or finished flooring. When I sheetrock the ceiling, I will not be able to drop the ceiling at all. So is it okay that the new panning is in direct contact with sheetrock?

Thanks again,
Logan

Hvac1000,

Since my system is working well now, you are saying to just replace the current panning with the aluminum/cardboard panning?

The other thing I forgot to mention is that my basement's current height is 6'11". This is without sheetrock or finished flooring. When I sheetrock the ceiling, I will not be able to drop the ceiling at all. So is it okay that the new panning is in direct contact with sheetrock?

Thanks again,
Logan


You do not have to replace the panning at all if it is salvageable.

You could actually use the drywall as the panning if you know what I mean. In the code drywall is considered OK for that usage. This will save you a few $$$.

All panning does is seal off selected spaces that are dedicated to the return air system for your furnace. Since the joist space is available in homes that are why it is used instead of buying full sheet metal duct.

The picture shown your panning as it is and it looks good. You could actually leave it alone and clean it out with damp rags on flexible rods with the added use of a vacuum. You have many options available.

Thanks, when the time comes I'll pull down one sheet of panning and try to clean the rest from there. I'll only pull down more if necessary.