Originally Posted by Quattro
I don't understand this. High efficiency furnaces use outside air for combustion only...you don't need "extra" air just to heat your house. Air is circulated through the supply and return system. These big pipes dousing the basement in frigid air really sounds counterproductive.
I agree with you! But the history was:
1. Combustion air was sucked in thru the air leaks in older homes
2. Next, people became concerned(read $$$) and put large ducts for cold outside air near their furnaces
3. Next, they realized this was bringing in too much extra cold air so they enclosed the furnace into a box and ducted the cold, outside air to it.
4. Next, furnace makers made ducts for combustion air conect directly to their furnace.
So... Some people are still back at #2, which works and might be fine for unused basements but it could be better with a little work.