If a dirty (clogged) filter makes an hvac work harder, does having a thicker (ex: allergen blocking) filter make an hvac work harder?

one of those HEPA filters that reduce allergens in the air also reduces the amount of air that moves through the air handler! Just as if it was a clogged dirty filter. get yourself one of those washable electrostatic filters that you can adjust for size and by the carbon pad put the electrostatic filter in first and put the carbon filter pad over it. This shouldn't reduce your air flow one little bit and it will catch almost every bit of the allergens in the air

household disinfectants with towel dispensers can make effective dust filters,,a DIY project, dry a couple, unfolded out flat on a bath towel to dry

use duck tape,carefully trimmed to seal the edges,measured to the lgth & width of the filter already there,the unit does work a wee bit harder with a fine filter,, but they are quite effective when regularly cleaned or replaced,

Yes - puts more of a load on the blower motor - but can't tell you how much. Our experience: we had a new furnace put in - which required some ductwork anyway - so we asked the HVAC contractor if it would be a good time to install an electrostatic filter, or just provide for one of those thicker (like 3 to 4 inch) filters. Their reply was that it would shorten the life of the blower - to stick with a standard 1" thick replaceable filter - to NOT use one of those permanent, washable filters - but to use the pleated replaceable filters which have more surface area, and are available in a variety of grades (standard, anti-allergy, anti-smoke, etc).

Who knows how much extra load there is with thicker filters - but, looking at the blower motors, our old unit had a big 1/3 horsepower motor . . . . the new one has a much smaller "hi-efficiency" motor, ie overengineered made-to-last vs marginal.

Yes but you will never notice the difference. However, since it filters out more dust it will need to be changed out more often. Check your filter periodically and change it when ever it needs it.

Filters are rated and one is supposed to use those ratings when switching to a new/different type. So if done properly, the unit will still have the same airflow.

If done improperly, then airflow is restricted, and they are a number of issues that can result. From improper airflow.

True somewhat, but not work harder, as the fan motor doesn't care much unless it overheats. The issue is reduced airflow by a more restrictive filter. Clogged and micron filters are the same and most fan motors have a heat cut-out circuit so no worries.

yes the indoor fan will eventually run over amps and trip its over load . ive found this many times with filthy dirty blocked up filters along with loss of airflow of course.

If it's dirty and clogged, yes.