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  1. #1
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    Dehumidifier recommendation for mold prevention in basement

    I have a quad level house with 4 levels:
    • 754 sq. ft. basement, with stairs leading to:
    • 686 sq. ft. family room, with stairs leading to:
    • ~754 sq. ft. living room & kitchen, with stairs leading to
    • ?? sq. ft. bedroom areas (top level)
    • ?? sq ft. attic
    • Total home area 2,160 sq. ft.


    The bedrooms, living room and kitchen are ducted to a SpacePak ESP-3642D unit located in the attic. Basement and Family room (main level) are NOT ducted with any HVAC. For heat I have a boiler + baseboards. I don't have a furnace.

    The basement does not have any vents really, aside from the clothes dryer vent.
    Basement humidity is high during summer months - about 80% R.H.
    I have had some flooding in the basement, and there was some mold growth.
    I also have some mold growth in the master bedroom (top floor below the attic), likely due to moisture build up from the shower, where humidity stays around 70-75 R.H. even with the air conditioning.

    I need to keep humidity low in the basement and the master bedroom and I am looking for a HVAC system/component recommendation.

    My current focus is on the basement, and I am considering getting a permanent dehumidifier to be installed in that space. I am also considering a dehumidifier for the upper levels.

    I am currently running a portable Frigidaire FAD954DWD in the basement, which brings humidity down to 50% R.H. in that area. In the long run, I am considering using a "whole house" dehumidifier in the basement, and using either a portable dehu in the master bedroom, or install another whole house unit in the attic for the upper levels.

    One option I am leaning towards at the moment is using the Frigidaire in the master bedroom to lower humidity there in particular, and installing a Ultra-Aire 98H venting dehumidifier in the basement + possibly installing a vent to draw fresh air into the basement from the outside into the unit. I don't know if I should or should not vent it, but bringing fresh air into the basement sounds like a good idea, and 98H is capable of doing that.

    I have also considered other models such as Aprilaire 1870 and Ultra-Aire 120H. I want to stay under $2000 for the dehu and not have it be very loud, since my basement is mostly finished and can be used as a living/hangout space, and 98H seems to be a good fit.

    Is my current plan a good direction to pursue? Do I need to consider other systems, units, or direction?

    P.S. The Family room (level above the basement) gets hot during summer and currently there is no A/C there. I am looking into various options as well. I am currently running a portable A/C unit there, but have also been considering something like a wall-mounted air-conditioning system the likes of MSY-GL12NA & MUY-GL12NA 12,000 BTU/H, or similar, since main A/C does not reach that level at all.

    My HVAC needs seem to be a bit complex afterall!
    Last edited by dennismv; 08-28-2019 at 04:18 PM. Reason: more info

  2. #2
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    Start with a small home cheapo model, set it up with a drain, give it a few days and see what happens!

  3. #3
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    Talk to the Ultra-Air people. They can advise you and help you choose a model that matches your situation.
    AOP Rules: Rules For Equipment Owners.

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  4. #4
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    Quote Originally Posted by pecmsg View Post
    Start with a small home cheapo model, set it up with a drain, give it a few days and see what happens!
    Thanks! I have been running the Frigidaire FAD954DWD with a drain for over a week now and the humidity in my basement went down from 80% RH to 50-54% RH. Current reading is about 54% RH.
    I am using the Abbeon Certified Hygrometer (Model HTAB-176) for humidity readings where the hygrometer is 10 feet away from the unit. I have not calibrated the hygrometer for a few years since its purchase, so it may be off.
    Frigidaire FAD954DWD itself reports 32% R.H. but I am not sure how much I can trust that reading ... or the other one, but I trust the Abbeon to be more accurate.

    Quote Originally Posted by kdean1 View Post
    Talk to the Ultra-Air people. They can advise you and help you choose a model that matches your situation.
    I talked to Ultra-Aire and the rep was concerned that the basement is opening up to the first level (there is no door or barrier) and thus any dry air will escape the basement and mix with the other air, making it a harder job for the dehumidifier to keep the air dry.
    The rep suggested Ultra Aire MD33 to fit seamlessly with the wall and require no ducting and will cover 1200 sq. ft. so it might work as an option.
    But if I can do ducting (and I believe I can), another option is the 98H dehu, as it has duct collars, but the rep didn't know if I wanted to go that route.
    As far as ducting he suggested that I can use it as a standalone unit with a T or Y connection (I lost him here though)
    He suggested going with Ultra-Aire may be a better option for me than the Santa-Fe product line.
    I asked about venting or not venting the unit, and the rep did not make a suggestion one way or another, it seems to be entirely up to me if I wish to vent it or not.

    Recommendations also seem to depend on who you talk to... I talked to Dri Eaz and they've suggested PHD 200 Crawl Space Dehumidifier.
    Aprilaire will recommend Aprilaire products.
    I am a bit confused as to which direction to take (not so much the vendor choice, but the type/capacity/form factor of units and where to place them).
    Kind of a overall system design to where I will likely be happy with it and won't have to take it out or change it out at a later day.
    Or a "no, don't do that" if I am thinking of something that will not be beneficial.

  5. #5
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    Quote Originally Posted by dennismv View Post
    Thanks! I have been running the Frigidaire FAD954DWD with a drain for over a week now and the humidity in my basement went down from 80% RH to 50-54% RH. Current reading is about 54% RH.
    I am using the Abbeon Certified Hygrometer (Model HTAB-176) for humidity readings where the hygrometer is 10 feet away from the unit. I have not calibrated the hygrometer for a few years since its purchase, so it may be off.
    Frigidaire FAD954DWD itself reports 32% R.H. but I am not sure how much I can trust that reading ... or the other one, but I trust the Abbeon to be more accurate.
    Sounds like its doing its job!

  6. #6
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    I am assuming that all reasonable efforts have been exhausted as far as keeping out the water/moisture ?
    remember, with electronics; when its brown,its cooking and when its black, its done!!!

  7. #7
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    Quote Originally Posted by micdundee View Post
    I am assuming that all reasonable efforts have been exhausted as far as keeping out the water/moisture ?
    Mostly, yes but there might be a few more efforts in store...

    The timeline is as follows:
    there was flooding due to sump failure resulting in mold growth
    sump was fixed, and there have been no more flooding, so mold issue will hopefully be contained.
    There is still an issue of some moisture seeping through concrete on the floor when it rains, that has not yet been addressed, and more insight is needed (i.e. detecting the source of moisture more exactly and sealing).

    Aside from that, the basement is not sealed off the main level, so any air is free to enter in and out of the basement via a door frame (door has been taken out for ease of everyday access).

    Suppose I seal off any moisture leaks inside the basement walls & floor, there is still an issue of air entering through the doorway and that air is pretty humid during the summer, although I haven't measured just how humid that air is on the main level.

    I am thinking some air movement and ventilation in the basement will help. I could perhaps consider a fan in there to aid in circulation and see if it helps instead of a dehumidifier.

  8. #8
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    Any circulation can help but it does sound like the dehumidifier is doing its job, if the sauce of water cant be corrected a 2nd dehumidifier may be needed from time to time. Good to have a backup anyway!

    Basements are a constant battle of moisture finding a way in and mechanical means of removing it! You stated you went from 80% down to 50+% that's fine. As you address the moisture infiltration that % will continue to go down. 50% or less is acceptable!

  9. #9
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    pecmsg, thanks

    I thought that humidity had to be lower, say 45%-ish, but if 50% and some is okay then yes, the Frigidaire is doing its job and I like the continuous drain option - there are no water buckets to empty.

    Would you then expressly recommend NOT getting a whole-house dehumidifier in my case?

    Whole-house dehu sounded like a good idea to me for the all features that I'd get, but whether it is worth the expense, is a fair question.
    If I do-it-myself it will cost me equipment and parts and time & research, and if I have a contractor install one it will be $3-4K for install in my area.

    As far as the features and perks that I'd get, my thoughts with the Ultra Aire 98H or similar were that I could set it up in the basement long-term, or permanently, and set up a few ducts above the drop ceiling to aid air circulation and maybe even vent in fresh air in from the outside and then "live in a vented air utopia of a basement". But if a whole-house dehu is really not necessary then I can certainly keep the $2-4K and use it elsewhere.

  10. #10
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    Quote Originally Posted by dennismv View Post
    pecmsg, thanks

    I thought that humidity had to be lower, say 45%-ish, but if 50% and some is okay then yes, the Frigidaire is doing its job and I like the continuous drain option - there are no water buckets to empty.

    Would you then expressly recommend NOT getting a whole-house dehumidifier in my case?

    Whole-house dehu sounded like a good idea to me for the all features that I'd get, but whether it is worth the expense, is a fair question.
    If I do-it-myself it will cost me equipment and parts and time & research, and if I have a contractor install one it will be $3-4K for install in my area.

    As far as the features and perks that I'd get, my thoughts with the Ultra Aire 98H or similar were that I could set it up in the basement long-term, or permanently, and set up a few ducts above the drop ceiling to aid air circulation and maybe even vent in fresh air in from the outside and then "live in a vented air utopia of a basement". But if a whole-house dehu is really not necessary then I can certainly keep the $2-4K and use it elsewhere.
    By all means I prefer a Whole house dehumidifier if your in an area where mild temps and high humidity are the norm.

    For just a basement that stand alone unit does the job. Tighten some of the leaks and it will do better.

  11. #11
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    Quote Originally Posted by dennismv View Post
    I have a quad level house with 4 levels:
    • 754 sq. ft. basement, with stairs leading to:
    • 686 sq. ft. family room, with stairs leading to:
    • ~754 sq. ft. living room & kitchen, with stairs leading to
    • ?? sq. ft. bedroom areas (top level)
    • ?? sq ft. attic
    • Total home area 2,160 sq. ft.


    The bedrooms, living room and kitchen are ducted to a SpacePak ESP-3642D unit located in the attic. Basement and Family room (main level) are NOT ducted with any HVAC. For heat I have a boiler + baseboards. I don't have a furnace.

    The basement does not have any vents really, aside from the clothes dryer vent.
    Basement humidity is high during summer months - about 80% R.H.
    I have had some flooding in the basement, and there was some mold growth.
    I also have some mold growth in the master bedroom (top floor below the attic), likely due to moisture build up from the shower, where humidity stays around 70-75 R.H. even with the air conditioning.

    I need to keep humidity low in the basement and the master bedroom and I am looking for a HVAC system/component recommendation.

    My current focus is on the basement, and I am considering getting a permanent dehumidifier to be installed in that space. I am also considering a dehumidifier for the upper levels.

    I am currently running a portable Frigidaire FAD954DWD in the basement, which brings humidity down to 50% R.H. in that area. In the long run, I am considering using a "whole house" dehumidifier in the basement, and using either a portable dehu in the master bedroom, or install another whole house unit in the attic for the upper levels.

    One option I am leaning towards at the moment is using the Frigidaire in the master bedroom to lower humidity there in particular, and installing a Ultra-Aire 98H venting dehumidifier in the basement + possibly installing a vent to draw fresh air into the basement from the outside into the unit. I don't know if I should or should not vent it, but bringing fresh air into the basement sounds like a good idea, and 98H is capable of doing that.

    I have also considered other models such as Aprilaire 1870 and Ultra-Aire 120H. I want to stay under $2000 for the dehu and not have it be very loud, since my basement is mostly finished and can be used as a living/hangout space, and 98H seems to be a good fit.

    Is my current plan a good direction to pursue? Do I need to consider other systems, units, or direction?

    P.S. The Family room (level above the basement) gets hot during summer and currently there is no A/C there. I am looking into various options as well. I am currently running a portable A/C unit there, but have also been considering something like a wall-mounted air-conditioning system the likes of MSY-GL12NA & MUY-GL12NA 12,000 BTU/H, or similar, since main A/C does not reach that level at all.

    My HVAC needs seem to be a bit complex afterall!
    I would suggest The ultra-Aire 98H with a 6" fresh air duct to the intake of the 8" dehu return. Put a damp in the 6" to increase the fresh air by choking the 6" to more fresh if needed. You need about 80 cfm of fresh air to purge the indoor pollutants and renew oxygen. Try discharging the dry, fresh air into the basement main area. The extra 80 cfm will force the dry fresh air up through the home and leak out of open vents and imperfections. This steady flow may resolve the entire humidity problem throughout the home.
    Thank you for thinking about Ultra-Aire.

    If you need cooling in the mid level of the home, suggest a properly sized mini-split.
    This would be a good start.
    Keep us posted.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  12. #12
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    Quote Originally Posted by teddy bear View Post
    I would suggest The ultra-Aire 98H with a 6" fresh air duct to the intake of the 8" dehu return. Put a damp in the 6" to increase the fresh air by choking the 6" to more fresh if needed.
    Thanks, Teddy Bear, But can you say that again?

    UA98H has:
    A) Optional 6" Fresh Air Intake
    B) 10" Return Air Duct
    C) 10" Supply Air Duct

    I lost you on 8" size, and on bringing more fresh air, and on what it means to choke the 6" (do you mean open or closed)?
    Are you suggesting to use 8" duct and connect it to intake "A"?

    When you say bring in fresh air via a 6" duct, do you mean to have it go into 10" (?) intake "B"?
    Will I need to use a motorized damper option rather than manual for this to work?

    I am also considering UA 120V, as it seems to be a lot more efficient, and form factor may suit me better, even although it costs more. Would you recommend 120V as well or will 98H do better for me as far as dehumidification and ventillation go?

  13. #13
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    Quote Originally Posted by dennismv View Post
    Thanks, Teddy Bear, But can you say that again?

    UA98H has:
    A) Optional 6" Fresh Air Intake
    B) 10" Return Air Duct
    C) 10" Supply Air Duct

    I lost you on 8" size, and on bringing more fresh air, and on what it means to choke the 6" (do you mean open or closed)?
    Are you suggesting to use 8" duct and connect it to intake "A"?

    OK, a 98H has a 10" and 6" return, connecting the 6" to the fresh air is ok for a short 6" flex to the outside for 80 cfm of fresh air when the 10" is connected to the open part of the home. 80 cfm of fresh air is ok for 2,500 sqft. of living area. Upto 3,000 sqft. better to 120 cfm fresh air. Getting more air requires sucking harder on the 6" fresh air duct. Or increasing the size of the fresh air duct. Going up to 8" fresh duct reduces resistance of the fresh air flow. A shutt off damper may be require if you stop the fresh air when the home is unoccupied for partial day occupancy.

    When you say bring in fresh air via a 6" duct, do you mean to have it go into 10" (?) intake "B"?
    Will I need to use a motorized damper option rather than manual for this to work?

    I am also considering UA 120V, as it seems to be a lot more efficient, and form factor may suit me better, even although it costs more. Would you recommend 120V as well or will 98H do better for me as far as dehumidification and ventillation go?
    The UA 120V is also a good choice. For more positive control of humidity with fresh air the larger dehu is good.
    Getting the fresh air to circulate throughout the home, getting a return from the main floor to the dehumidifier located in the basement and supplying fresh, dry air into the basement will effect circulation of the dry, fresh air throughout the two lower levels plus the addition of fresh air will force the mixed air through out the home with some of the air leaking out the top of the home.
    Sorry about the confusion.
    Thank you for your interest and keep us posted.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

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