In my furnace (ruud ubhc-17j14sfa), there is a permanent, washable filter. It was there when we moved in 2 years ago. The house is about 10 years old now. The filter is pretty simple, more like a strong mesh. I don't just want to replace the filter as the it might effect the airflow going to the furnace and cause issues, or have the furnace work harder.
Does anyone have experience with this? would it be ok to replace it with a higher MERV rating without causing any issues?