A. Almost Never. The correct size of your HVAC system is based on running a computer generated load using measurements of your home’s interior space. If you put in an oversized furnace it will not run long enough to get to its steady sate efficiency. If you put in an oversized A/C unit it will not run long enough to remove humidity.

A. Yes, as your filter gets too dirty its ability to capture and hold particles decreases and more dust and dirt can come through the filter. It’s important to use a good quality filter, typically in the 8-12 MERV range. Below MERV 8 it does not capture enough particles and above MERV 12 it is too restrictive to air flow.