I'm told by some HVAC companies via mail flyers and websites (example) that it may be very expensive to retrofit new PVC pipes to update an 80% efficient furnace to a 90% one. Therefore, the logic ...
Just bought a house that had a new furnace installed this summer. Vent number 1 in the image is for the furnace (2 is the water heater and 3 is sump). As you can see in the image, 2 and 3 both would ...