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Community and Q&A

Minisplit air handling

Jon Lane | Posted in Mechanicals on

I have a new home now for 8 months that has 3 stories and 1 mini split unit on each floor. I have noticed that there is an abnormally large amounts of dust in the home. I had an idea that this dust was from not having enough air movement in the home. Has anyone else experienced this or have any suggestions when using mini split systems?

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  1. GBA Editor
    Martin Holladay | | #1

    Dust comes from a variety of sources: dirt that comes into the house on people's shoes, wood ashes that become airborne when wood stoves are cleaned, and particulates that accompany polluted outdoor air. Needless to say, the ductless minisplits aren't responsible for the dust.

    Of course, forced-air heating and cooling systems include filters, and these filters remove some of the dust that is found in the air that is pulled into the return air grilles and circulated through the house. The amount of air pulled through the typical forced-air system is probably more than the amount of air that is pulled through your three (filter-equipped) ductless minisplit units.

  2. Jon Lane | | #2

    That is my thinking that there is not enough air movement in the home. Each story has an open floor plan, about 460sqft on an average tightly built home (icynene in the roof, zip board sheathing with fiberglass batts in the walls) . Also there are bath exhaust fans on each floor. My partner is constantly sneezing in the top story and I see an enormous amount of dust soon after cleaning the room. I have been happy with the performance of the mini split here in the south for the summer and our mild winter so far. I guess what i am trying to find out is should I have more fresh air movement or exhaust on each floor? My old 1917 house with a heat pump didn't seem near as dusty as this new one.

  3. GBA Editor
    Martin Holladay | | #3

    It's not about air movement (assuming that my theory is correct). It's about filtration.

    I advise that you use a vaccuum cleaner to reduce the amount of dust in your house.

  4. Jon Lane | | #4

    Great advice, we are using and using a vacuum all the time.....
    I guess I just don't know enough about proper air movement in a tight home. Do you think the mini split provides enough air movement or would you suggest an ERV or something of that nature? Thanks for your input!

  5. GBA Editor
    Martin Holladay | | #5

    If all you want is air movement, you can install a ceiling fan. Air movement alone won't remove dust or clean the air.

    The purpose of an ERV is to introduce a measured amount of outdoor air into a house, while simultaneously exhausting a measured amount of indoor air. This type of ventilation system is used so that indoor air doesn't get stuffy, and in some cases (especially during the winter) to reduce indoor humidity levels.

    While ERVs include filters, their main purpose is not dust removal.

  6. T Shepp | | #6

    A vacuum cleaner can be a notorious source of dust (bags). I got a new hepa filter vacuum and it solved my problem...You don't say if it is a central vac or other.

  7. James Morgan | | #7

    If you don't live along a dirt road with the windows open a lot the greatest source of dust in your house is likely to be disposable paper products. Paper kitchen towels, disposable tissues, bathroom tissues, especially the softer, fluffier, more absorbent kind, all give off clouds of tiny cellulose particles when pulled from the box or roll - wave some around in a shaft of sunlight and you'll easily see what I mean. So ironically the tissues your partner uses for his/her sneezing may be part of the problem. Kitchen and nasal tissues have easy substitutes - yes cloth hankies are not as convenient and that takes some getting used to, but may be well worth it. Bathroom tissues may be more of a hurdle, there are options like the washlet etc., on the other hand the volume of use may be much lower and the tissue has a short life in the open air before heading down the drain.

    The other major source of dust is likely to be fibers from new carpets and furnishings - if this true in your case it is likely to get better in time as the looser material is gradually removed. Filtration and evacuation may alleviate the problem but as always, prevention is better than cure. Look to the source.

    Oh and by the way, those tiny particles contain not just cellulose but also the bleaches and other chemicals used in their manufacture. The tighter the house, the more significant these issues become.

  8. Robert Hronek | | #8

    I would think that you have a tight house and should have less dust. Dust in the house is either left over from construction or is being introduced in to the house through various products. It should not be a result of air leaks as you would find in an older house. Pets, open doors and window all play a part but are likely a small part.

    Look at the dust. Is it white? White dust it drywall dust. Drywall and concrete dust are very fine and pass through standard air filters. You will need a HEPA filter to remove. Do you have any duct work? Duct work in new homes will contain a lot of dust that takes years to work out.

    The finer the dust the longer it stays in the air and the deeper you breathe it in to your lungs. This can lead to health problems.

    I would use a HEPA vacuum to thoroughly clean the home. Clean on top of cabinets and in the nooks and crannies of the home that may have dust left from construction. You can get a HEPA filter for a shop vac.

    A couple of room air purifiers located around the house can help. I like Austin room air purifiers for the long life of the filter and it has a large amount of activated charcoal to absorb gases.

  9. Bob Irving | | #9

    A ducted hot air system blows dust that accumulates in the ductwork around the house, while an unducted minisplit is only recirculating air around the actual unit. It cannot produce dust, so it's only blowing around what is already there. Do you have a ventilation system? Any woodstoves? Any device that could bring in dust?

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