Is there a way to prevent wooden furniture and wall from getting moldy in non ac home

[Michael Yadfar]

I live in an 1870 farmhouse in southeastern PA that I bought 3 years ago, and don’t have AC. The house stays comfortable so I don’t feel I need it, but mold is an issue. Upstairs is usually fine, but downstairs basically all my wooden furniture starts to get moldy when it’s humid. There are also some renovated sections of the house that have drywall instead of plaster so I get mold from the floor to maybe 4’ up the walls. The house is mostly non insulated and I don’t have an AC system, so I keep most the windows open in the warm seasons. The house has a half basement with a concrete floor and a dirt floor crawl space. The house is frame with asbestos siding. I live on top of a hill so I don’t have any issues with water in the basement. I’m thinking of installing a ductless AC system next year just because of the mold, but what did they do before AC?

[Stan Calow]

Why not put in a dehumidifier? Less expensive and more effective than AC.

I think in the old days, they just lived with it.

[Charlie Velasquez]

Mold abatement was one of my responsibilities when our schools shut down in the summer without air conditioning. Dehumidifiers were the only energy efficient method. We closed outside air dampers, set up a couple commercial units in large open spaces, then ran the air handlers for 30 minutes a day to circulate that dry air. Air management is key. Hook them to discharge in a drain someplace so it/they run 24/7. Depending on air management, you may need more than one. Ours cost about _$25/unit/month for the commercial units (electricity).

[Brian Elfert]

I bet changes made to the house to "modernize" it are causing the mold issues. It isn't the same house as in 1870. Strangely enough, older houses with lots of air leakage are usually the houses that don't get mold due to all the air exchanged through all the leaks.

[Jim Becker]

Dehumidifier for now and the MiniSplit for permanent. It will provide you with very economical AC and heat compared to other methods in our area, too. Focus the rest of your efforts toward air infiltration and insulation improvements where you can.

[Bill Dufour]

Some minisplits have a dehumidify setting. Not really sure what that means. No need in my climate
Bill D

[Bill Dufour]

last time I painted the bathroom I used a special anti-mold additive. Not the usa made chemical that only lasts a few years. I got it from England and it contains silver which will last as long as the paint. cost 10-15$ for a dose which treats about one gallon. only use it on the final coat. use bleach tsp or whatever to kill the mold before painting.
Bil lD

[Kev Williams]

Some minisplits have a dehumidify setting. Not really sure what that means. No need in my climate
Bill D
Not an authority by any means, but whenever an AC compressor is running the evaporator temp gets below dewpoint temps and attracts moisture in the air. The dehumidify setting *I believe* runs the blower fan continuously while intermittently cycling the compressor just to collect moisture, as opposed to lowering air temp. Cars with AC will cycle the compressor when running the defroster to collect the moisture from breathing...

[Alan Rutherford]

We got a Frigidaire portable dehumidifier about 3 years ago for our 2-story 1750 sf house in Florida. The AC handles the humidity well as long as it's running, but there are days (too few of them) when it's not because the outside temperature is comfortable although the humidity seldom is. The dehumidifier will take the humidity from 60-65% to 50% in several hours. It can be connected to a drain. We haven't done that and it collects about 2 gallons and needs to be emptied about once a day at most. Less often if we have not let the humidity get high. An AC is less efficient at humidity control than a dehumidifier so keep that in mind if that's your primary objective. However, if the AC lets you keep the windows closed, you might have solved your problem.

[lowell holmes]

Window air conditioner?

[Alan Rutherford]

... what did they do before AC?

In Baltimore in the 1940's-50's we just lived with it. AC didn't exist. Summers could be pretty miserable. I was too young to be aware of the details but I'm sure if something got moldy it either got cleaned or got ignored. Nobody had drywall.

[Michael Yadfar]

My only concern with a dehumidifier is wouldnt there constantly be moist air constantly coming through the open windows? Or are dehumidifiers effective enough to make up for this?

[Mark Bolton]

Sadly your answer is likely no. Nothing. The unfortunate fact is that even with HVAC installed (if you could) you will likely never get away from mold behind furniture pushed back against exterior walls. The simple fact of the matter is there is just not enough air flow/air movement to overcome the moisture infiltration from and old school exterior wall with no ability to upgrade its envelope efficiency to a level that even modern HVAC and keep up with.

Most HVAC retro-fits into older homes have to do a lot of rough justice with regards to duct sizing and placement when it comes to the space available and access available. This means prime register locations are not available due to structural issues and the like.

Taking away the HVAC component and trying to deal with it without AC or with window units/mini splits, would mean you would have to have so much internal air movement it would be like a wind tunnel inside your space to move enough air to dry the space between the wall and the furniture. Beyond that the HVAC would likely just never keep up.

Its one of the burdens of an older uninsulated home with a poor envelope. Your main option is to simply live like they did in the times when the home was constructed. Free standing furniture. Not against exterior walls. And just deal with it.

[Jim Becker]

Mark, one of the benefits of the MiniSplit with multiple indoor units is that there is zero ducting and the interior units allow for even conditioning throughout a home when the design is valid. This is idea for older homes where retrofitting with duct work isn't achievable or has serious "side effects". An alternative is the small duct, high velocity systems, but MiniSplits are so incredibly efficient compared to a "standard" high SEER AC system that they are often used instead of the small duct/high velocity setup and are far easier to install.

You are correct about the envelope...which is why I mentioned infiltration and insulation up above.

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Michael, dehumidification units kinda need a closed space, so open windows isn't going to work.

[Mark Bolton]

Mark, one of the benefits of the MiniSplit with multiple indoor units is that there is zero ducting and the interior units allow for even conditioning throughout a home when the design is valid. This is idea for older homes where retrofitting with duct work isn't achievable or has serious "side effects". An alternative is the small duct, high velocity systems, but MiniSplits are so incredibly efficient compared to a "standard" high SEER AC system that they are often used instead of the small duct/high velocity setup and are far easier to install.

You are correct about the envelope...which is why I mentioned infiltration and insulation up above.

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Michael, dehumidification units kinda need a closed space, so open windows isn't going to work.

As I said, even with mini-splits and high velocity (rarely used because they can be very VERY VERY persnickety) trying to overcome a very old, porous, envelope, is extremely difficult. Trust me. You simply cant move enough air to make the interior space livabile (your comb-over will be standing straight off the top your head) and you cant pull enough moisture out of the air behind a piece of furniture pushed fairly tight to the wall. Any HVAC installer worth his salt will inform you of these pitfalls and if not your being duped.

The "zero ducting" advantage of a mini-split speaks directly to a reasonably constructed envelope (hence them coming from Asia and the EU who arent slobs like those of us in the US). They are basically a high efficiency window rattler. Period.

They will never, EVER, EVER, move enough air 20' away from the unit to overcome moisture accumulation behind furniture pushed against an exterior wall, in a porous home, even if its directly below the unit. Just wont happen.

[Michael Yadfar]

I’m not talking about just furniture against the wall, like literally everything, including my kitchen set in the middle of the room has this issue

[Jim Matthews]

I would suggest a low tech, passive approach using some sort of desiccant. I had good results in my Adirondack basement with what amounted to mesh bags filled with pumice.

https://www.mcmaster.com/desiccant-packs/

[Mike Soaper]

The moisture has to be coming from somewhere, i'd try to find/control the source before trying to manage it with a dehumidifier or AC

"I get mold from the floor to maybe 4’ up the walls." " The house has a half basement with a concrete floor and a dirt floor crawl space"

My guess is the moisture is coming up either from the basement or crawlspace or both. The water source might be from gutter downspouts or a spring.

To check to see if the moisture is coming from the concrete slab or crawlspace floor i'd place a large sheet of clear plastic on the those floors and check for condensation under the plastic.

As I understand it some crawlspaces are vented and others are encapsulated to manage moisture .

[Peter Kelly]

I grew up in a 1600s stone farmhouse in Glen Mills PA with minimal AC and never experienced the mold issues the OP describes. Has to be water infiltration of some sort, could even be an improperly vented dryer backing into the living space.

[Jim Becker]

That's a good point...I've had moisture issues with the back wall of the 250 year old stone portion of our home. Part of my solution has been to get more sunlight exposure to that area as well as attending to improving the gutters and other water pathways. The moisture has to be coming from somewhere and it's either from below, from above or through the wall from the outside. The level of moisture that causes wetness and mold isn't likely coming from the air as I think about it more. The source needs to be determined.