I've consulted several HVAC contractors on this subject and received
widely ranging answers so I've turned to you folks for some expert
I currently use 3M's new 12 MERV 1" premium filter and my furnace fan
is set to 'auto'. I'm very satisfied with the filtering I'm currently
getting with this filter. I'm in the process of adding an HRV and will
be running the furnace fan on low at the continuous setting year-round.
Some contractors have suggested upgrading from a 1" media filter to a
5" media filter to improve airflow, theory being the 3M's I'm currently
using are too restrictive now that I'll be running the fan
My concern is that the 5" media filters typically have a lower MERV
rating and I'll lose some filtering effectiveness.
Should I be concerned about airflow restriction with the 3M filters
based on continuous fan operation and is there any other benefit, aside
from reduced filter change frequency, to switch to a 5" media filter?
The one upside that I've considered is that if I add a 5" filter to my
system I can use the 1" slot for a charcoal/carbon filter to improve
odor/gas removal - any thoughts?
I appreciate your responses.