Filter box for regular + charcoal filters

I’s like to buy or build an ERV pre-filter box for a max 150 cfm (typically more like 75 cfm) that can accommodate a regular and charcoal filter, with a… I’s like to buy or build an ERV pre-filter box for a max 150 cfm (typically more like 75 cfm) that can accommodate a regular and charcoal filter, with a…Read MoreGreenBuildingAdvisor