Did I write this? Sorry, no. ;-) We have the same problem and have for years. There are discussion threads on this topic, and I'll be following yours for any new advice.

Good luck!

Forgot about searching will check other posts

I can't suggest a solution because there are too many unknowns. I have no firsthand experience with your exchanger so don't know what type filtration is has. Mini splits are known to have poor provisions for filtering air so they might be part of the problem. Home occupants contribute to air pollution at various rates. Large amounts of dust comes home with people working in dity inviroment,kids and dogs. Carpet vs no carpet plays a role. Circulating air through Merv 8 or higher filters should help a lot but it's up to you figuring out how that's possible with your ac units and air exchanger.

Retired , empty nesters, no pets, 90% harwood floors filters on air exchanger just foam type. thats all manufacturer sells

Under those conditions I wouldn't expect dust to be a problem so you undoubtedly have poor filtration or abnormal introduction of dust. Have you inspected laundry drier exhaust for leak or backdraft? Do you have a woodworking shop? Makeup air is quite common but "exchangers" are normally found in a restaurant , bar , pet store, repair facility , gym and other places with unusual amount of air pollution. Why is it necessary to have an exchanger in your home?

You didn't say how M. splits are filtered and I'm not familiar with your exchanger so I'm at a lose. Foam is a sorry air filter but if that's how system is designed I'm not the one to say change it. Sorry but there's nothing here to go on.

"Makeup air is quite common but "exchangers" are normally found in a restaurant , bar , pet store, repair facility , gym and other places with unusual amount of air pollution. Why is it necessary to have an exchanger in your home? " The "V" in HVAC stands for ventilation. In my experience it's the part of the acronym least understood by HVAC contractors and designers, too. The OP's VanEE exchanger is either an energy-recovery ventilator or heat-recovery ventilator, the use of which is indicated (and may be mandated depending on local codes) for "tightly" constructed homes. It's part of a ventilation strategy to maintain indoor air quality and occupant health.

The problem is we find the house very dusty. Can anyone suggest a solution?

There is dust / dirt in all air that is untreated / unfiltered. The air outside is primarily the source air. You don't live in your house without letting that air in. Every time the door opens you let it in.

Surfaces that show it? While carpet can produce some, most of the time this surface does a good job of hiding it. Until 30 years later you remove it and see all the dirt. So alot of hard surfaces in the home is going to show the dirt much easier than if your house was full of carpeting.

Things that add to these kinds of problems: as said before pets, people who smoke, a household with alot of people. More traffic in the house stirs up the dust / dirt. Air filtration is a way to get rid of it by changing those air filters. An often big contributor to the dust problem in a home is the clothes dryer. When you do laundry your clothes shed and if that dryer vent has a problem (or the house has a problem that causes this waste to come back into the house) the more the dryer is operated in a week the greater the problem can be.

Open style everything: Due to design features of a house you may have decided on style choices that create more work for you. There's this new fad going around of having open faced cabinets in the kitchen. Little did these designers know that by taking the cabinet doors off the cabinets they've now have incorporated a new era of dust bunnies.

Open up your cabinets fad: Looks pretty or Looks Deceiving? The maid tells you I ain't dusting the pantry.

You may have a problem you may not: Every house has dust, excessive dust is going to be quite hard to determine. How much is too much? This figure is going to vary due to an assortment of criteria that is influenced by the list that causes excess.

klem1

No workshop and drier vent is tight. Regarding the mini splits they are manufactured by Fujitsu one of the largest manufacturers in the world so I assume their filters are adequate.

Because new homes are airtight Air Exchangers (HRV, hear recovery ventilation) are required by law in all new homes built in Canada. I have attached a photo of the filter from my VanEE HRV. The manufacturer only makes this foam filter and doesn't have a recommendation for an alternative.

One thought I have is to see if there is a manufacturer of filters that makes custom sized HEPA filters. Would this help?

two new comments came in as I was typing this AM and they addressed HRV,

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Would installing a better quality filter possibly help?

Do an experiment. Turn off the air exchanger and clean the surfaces and areas where you notice the most dust. Now you have no dust. Leave the system off for a couple days. Or however long it takes until you normally are noticing dust builup. If the dust problem is reduced you've found the primary source. An air box large enough for a 4 or 6" by 24x24 or the metric equivalent filter can be ducted into your air exchange system. MERV 8-13 filters replaceable a couple times a year may do the trick.

VanEE offers a variety of different filters including MERV 13 and HEPA depending on the specific model exchanger. Check with the VanEE about options they offer which might better meet your needs before adding anything custom to your system.

I found a manufacture that makes custom HEPA filters at a reasonable price. I am going to order a set and test them. I will use the regular filters for an month, dust, and install the new filters and compare.

In most cases I would say don't expect overnight change but going from foam to HEPA is so dramatic that overnight difference can be expected IF the problem is with that system rather than other possibilities discussed.

VanEE advised that a HEPA filter would restrict air flow and possibly burn out motor