you can likely modify one to fit, the cheap cardboard and fiberglass
the downside is it will decrease airflow and may raise heating and
a friends wife has too many birds, their dander clogs the furnace
he blocked completely the air return from the bird room.
no more troubles
I have seen them used where a furnace is in an attic or crawl space,
and the filter would be much more accessible in the dwelling unit.
Whenever I have seen them, they are on systems where there is only one
return grille, and they are standard size filters. Of course, since
this is the ONLY filter on the furnace, it isn't any more restrictive
than a filter that was at the furnace.
Mcmaster-Carr sells them. http://www.mcmaster.com page 601. I'm not sure
they are available in the smaller sizes. You better make sure you can find
the filters to fit before you buy them. As others mentioned it will affect
the balance of your system as the filters do restrict the air flow.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.