I have an older Lennox natural gas forced air furnace in my house. It has the hammock style filter cage. My cold air trunk comes off the left side of the furnace and that side of the cage is always filthy.. but the rest of the filter is clean. Seems like a big waste of a large filter. I was thinking about modifying the cold air trunk to use one of the mainstream off the shelf filters.
How do I size the correct thickness of filter? Obviously I can't install a filter larger than the trunk.. so thickness is my only variable.
Also do they make kits to do this? I have no problem working with tin.. just want to make this look as pro as possible.
Other than that.. the furnace still works great.
That's the only pic I have of my furnace.