Mold, Humidity and Dehumidifiers

[Bertilak]

Anyone have experience dealing with household mold or with dehumidifiers?

I get gray-black mold on:

• Wood surfaces, especially if it is bare wood w/o a hard finish
• Walls with flat paint
• Leather (e.g. shoes left sitting around unused)
• Wicker
• Fabric (upholstery)

My house is 2400 sq ft. with central air fed via ceiling vents. House is on slab -- no basement.

What I have done/learned so far:

1. I contacted Texas state department of health. They tell me there are two kinds of license they issue: mold inspector and mold remediator. Neither is allowed to do both jobs to avoid conflict of interest.
2. I contacted a couple of inspectors and they are *very* expensive (over US$500).
3. One inspector was very helpful and said my description (as above) almost certainly means I have a humidity problem. He suggested I get a humidity meter from Wal-Mart. I found a good one for only 8 bucks. The humidity meter reads not only current humidity but also high and low measurements.
4. The inspector said anything over 55-60% could encourage mold. I found that my house goes between 60% and 75% -- mostly on the high end!
5. Before any of the above, I already suspected humidity as the problem so cranked the air conditioner down a couple of degrees so it would run longer.Since I still average somewhere around 70% humidity it apparently isn't doing the job I hoped it would. As far as I can tell all that did was raise my electric bill $60.

So it seems I need a dehumidifier. This is where I really need some advice! They have a wide price range and even the larger ones (70 pt/day) only claim to cover about 1400 sq ft.

Anyone know a bit about these things? I am concerned about noise and having to constantly empty the water bucked and maybe even then not having enough capacity to get the job done.

 

[raisindot]

Wow. If you're getting mold on surfaces you can see, you're probably getting it on interior surfaces you can't see, such as inside interior walls. This is where the real mold problems occur.
My guess is that a lot of this mold may be the result of leaks in your roof or siding that are letting moisture into the house, or water vapor coming through the foundation rather than just environmental humidity. My house (near Boston) is extremely humid (no central air) but I don't see any mold on surfaces.

A dehumidifier will generally take care of water vapor in one room. You'll rarely find a commercial model that will take care of an entire floor. I've got a Sears model that I got for around $150. I have it going day and night. It's loud, but I keep it in the basement, where most of the humidity is. Generally, it runs for about 18-20 hours before it needs dumping. Many models do come with a tap in back allowing you to attach a house that can spill the water into a ground trap of some kind so you don't have to constantly empty it.

Keep in mind that running these things is very expensive. I estimate it accounts for around $20 a month of my electric bill. I've also read that when used in a basement it's not good to keep it going all the time because once it gets rid of the ambient humidity it starts to draw vapor from underneath the foundation.

In your situation, there might be whole house dehumidifiers that are more powerful or are attached to your furnace or something. It would really suck to have to be running many individual units in a house. Then again, your mold problem seems a lot more severe than a humidifier might be able to cure.

Jeff in Boston

 

[David37]

I would try to work on getting the air conditioner doing it's job better first. You can clean the evaporator coils (inside the home) with soap & water. If you have mold on the walls you probably have it in the coils too. You are breathing this stuff. It will cake up on the coils and limit the area that is doing the cooling. More cool area means more moisture gets removed and more volume of cooled air going to the vents. With the unit breaker off, I'd get some scrubbing bubbles or simple green & douse the coils, take a water hose and wash thru the coils, preferably opposite of the normal air flow. makes a mess I know, get some towels & try to be as neat as you can. There is a drip pan that catches the condensated water & moves it either to a sewer vent or outside the home. This needs to be clean too, it will have mold & algae in it. Oh yeah and replace your air filter. After everything is clean, you could put a fungicide in pan, like a pool chlorine tablet busted up. An A/c guy would have the tablets made for a/c units. After a good deep cleaning, I would suggest doing the same thing to the condensor (outside unit) except it doesn't get the chlorine tablets, you'd need to remove the sheet metal panels to do a better job with the water hose. After all that, if your unit was healthy before, it will deffinately be in top shape now. It will run cooler, it will remove more moisture from the air, it will catch this condensate & remove it from the home properly. Since you have a mold problem now, I would suggest a UV light unit be installed in the evaporator unit. This is supposed to sterilize the air as it passes thru the unit, also it prevents mold, mildew & algae from growing on the coils. A good A/C guy can do all this for you if you're not inclined to using your elbow grease, and if you still wanted a dehumidifier, the A/c guy is the goto source for those questions as well. I am nothing more than an A/C hobbyist, but love to read up on it. I hope that helps you out...

 

[ackvil]

I use a dehumidifier in my basement-garage in hot, humid Florida. I use a Delonnghi which has a pump that sends the water to the outside. It does a decent job and we do not have a mold problem.

However, it is not as good as AC.

 

[Wilpar76]

I would try to work on getting the air conditioner doing it's job better first. You can clean the evaporator coils (inside the home) with soap & water. If you have mold on the walls you probably have it in the coils too. You are breathing this stuff. It will cake up on the coils and limit the area that is doing the cooling. More cool area means more moisture gets removed and more volume of cooled air going to the vents. With the unit breaker off, I'd get some scrubbing bubbles or simple green & douse the coils, take a water hose and wash thru the coils, preferably opposite of the normal air flow. makes a mess I know, get some towels & try to be as neat as you can. There is a drip pan that catches the condensated water & moves it either to a sewer vent or outside the home. This needs to be clean too, it will have mold & algae in it. Oh yeah and replace your air filter. After everything is clean, you could put a fungicide in pan, like a pool chlorine tablet busted up. An A/c guy would have the tablets made for a/c units. After a good deep cleaning, I would suggest doing the same thing to the condensor (outside unit) except it doesn't get the chlorine tablets, you'd need to remove the sheet metal panels to do a better job with the water hose. After all that, if your unit was healthy before, it will deffinately be in top shape now. It will run cooler, it will remove more moisture from the air, it will catch this condensate & remove it from the home properly. Since you have a mold problem now, I would suggest a UV light unit be installed in the evaporator unit. This is supposed to sterilize the air as it passes thru the unit, also it prevents mold, mildew & algae from growing on the coils. A good A/C guy can do all this for you if you're not inclined to using your elbow grease, and if you still wanted a dehumidifier, the A/c guy is the goto source for those questions as well. I am nothing more than an A/C hobbyist, but love to read up on it. I hope that helps you out...

+1 - My parents had a similar problem. They upgraded their AC, although not because of the mold issue, and the problem was solved.

 

[BCatl]

Besides the good advice above, if I need to go in depth with a problem, I go to that old fashioned place called the county library, which I support as a taxpayer anyway!

You'd be amazed at some of the books they have that will go deeper into these subjects, and you may hit on a solution. If your local library doesn't have it, they can get the book from one of the other ones in your county.

These places have saved me money because they have at least allowed me to talk to a contractor more intelligently if I can't DIY.

I live in the humid South too so I feel for you. Good luck.

 

[blary54]

I would recommend an AprilAir whole house dehumidifier. This would work perfect for you...but kind of expensive. Hooks up to the furnace and takes the humidity out of the whole house. I have one in my house...its great.

http://www.aprilaire.com/index.php?znfAction=ProductsCat&category=dehumid

 

[Bertilak]

An update and hopefully good info for others with similar situations.

My humidity problem seems to be the result of several factors:

1. The ideal AC capacity for my house would be just under four and a half ton so neither four nor five ton is ideal. I have five ton. This tends to cool the house before proper dehumidification can occur. Dropping to a four-ton unit would leave me under-powered for the hottest days of Texas summer.
2. The indoor blower unit can be configured for several speeds and mine was set to the highest, exasperating the over-capacity situation.
3. The wife had insisted on setting the blower to "always on". This caused recirculated air to pass over the warming and evaporating condensation in the unit, blowing humid air right back into the living space.

Dehumidifiers will not do the job efficiently and one with the needed capacity will be *very* expensive and complex to hook up with an existing AC.

Technically, the best solution is to install a two-stage AC unit with a variable speed blower and a combination thermostat-humidistat. These run at a low capacity until the extra capacity is needed (extra hot and humid days). The variable speed blower adjusts itself to balance out cooling, dehumidification and efficiency. The system will even resort to cooling the house a couple of degrees below the thermostat setting to meet the humidistat setting.

I have proposals from a half dozen AC contractors. These ranged from about $3000 to about $8000 and all but one involve installing a two stage unit with variable speed blower. The cheapest proposal was to replace just the indoor unit with a dual speed blower.

So far I have come very close to solving my problem as follows:

1. Set the blower to auto instead of always-on.
2. Re-configure the blower to use the next slower speed. I was told not to go any lower on this as it might cause trouble in the unit. (freeze-ups?)
3. Cranked the temperature down from 77 to 73.

The above adjustments keep the humidity below 55%, usually around 50%. We still get new mold forming but it is *greatly* reduced. There is mold inside the supply plenum and I think this is getting spread through the house and killing that may completely solve the problem (somewhat of a long shot).

Given all my new knowledge and a handful of proposals I went back to the AC contractor who installed my system. He said that up until two-three years ago almost nobody had one of these fancy new two-stage, variable-speed systems and people have been solving mold problems for longer than that. He re-did some measurements in my house and took things back to the distributor (Rheem/Ruud).

The distributor is supposed to come back with recommendations so I am waiting on that before dropping several thousand on a new system. We are *so* close to having this solved already. But things are just borderline even at 73 degrees, which is too much of a "thermal shock" for me when going to and coming from Texas outdoor temps! Bumps up the electric bill as well.

 

[malocchio]

this is very interesting...my daughter and I both have houses in the san francisco bay area...both of us have had our home values reduced by 65 % in the past 4 years.....my daughter has another house in fairburn georgia,and will move there soon...I don't want to be away from my grandkids,so I am thinking of moving there also....I worry about the mold problem as well,especially since we all have allergies....I spend time in the tropics, west and east africa,and have spent a month in jamaica...the mold problem is solved there by building cement houses with cement walls and floors....there are very few cement houses in the u.s,.although it is becoming a little more prevelant....once the mold does start to grow inside a house it is really tough to get rid of...

 

[BCatl]

this is very interesting...my daughter and I both have houses in the san francisco bay area...both of us have had our home values reduced by 65 % in the past 4 years.....my daughter has another house in fairburn georgia,and will move there soon...I don't want to be away from my grandkids,so I am thinking of moving there also....I worry about the mold problem as well,especially since we all have allergies....I spend time in the tropics, west and east africa,and have spent a month in jamaica...the mold problem is solved there by building cement houses with cement walls and floors....there are very few cement houses in the u.s,.although it is becoming a little more prevelant....once the mold does start to grow inside a house it is really tough to get rid of...

Well we have humidity in the South, but mold is actually pretty rare. However, if you have a finished basement, and if water ever get's in that basement and behind the drywall, you could have problems.

It's so important to have a home inspector look at the house before you buy it to see if the basement is prone to water problems. One thing I've learned: never let the real estate agent pick the home inspector. If possible, try to find the home inspector yourself, and make crystal clear to them who they work for.

 

[Bertilak]

I would recommend an AprilAir whole house dehumidifier. This would work perfect for you...but kind of expensive. Hooks up to the furnace and takes the humidity out of the whole house. I have one in my house...its great.

http://www.aprilaire.com/index.php?znfAction=ProductsCat&category=dehumid

Actually, I haven't given up entirely on this approach yet. The story that a whole house dehumidifier was not an ideal solution was given by people who I don't think sell them!

 

[malocchio]

Well we have humidity in the South, but mold is actually pretty rare. However, if you have a finished basement, and if water ever get's in that basement and behind the drywall, you could have problems.

It's so important to have a home inspector look at the house before you buy it to see if the basement is prone to water problems. One thing I've learned: never let the real estate agent pick the home inspector. If possible, try to find the home inspector yourself, and make crystal clear to them who they work for.

yes indeed !! I am always alert with those who work on comission !! lots of good advice on this thread...

 

[Bertilak]

Another update.

In my previous post I said my AC guy was going back to his distributor for advice and this is what they came up with. I also called the company and they were *very* helpful in explaining things to me. I like their story and will be installing an ICM CC750 Comfort Control Center:

From their literature:

2007 Product Showcase Award Winner - "Comfortech Show"
2006 Dealer Design Award - Silver Medallist - "the NEWS"

The CC750 is a variable frequency/variable voltage fan motor speed control that adjusts the output to the motor according to two temperature sensors. One sensor is mounted in the return air duct and the other is mounted in the evaporator coil. A temperature differential between these two probes is monitored based on user-set parameters to create ideal conditions for humidity control in cooling. Other benefits include lower fan noise, warmer heat pump operation, and colder air conditioning operation. When the CC750 is operating in inverter mode, it uses significantly less energy than a fan motor operating at full speed.

Intelligent features are built into the control. It has a ramp up feature that slowly increases the motor speed to eliminate noise, reduce the inrush current, and eliminate the surge of unconditioned/unheated air at the beginning of a cycle. The humidity sensor input works with any dehumidistat to extract the most moisture from the air when the dehumidistat senses high moisture. When a dehumidistat is not used, the cooling cycle is adjusted periodically for maximum cooling and maximum moisture removal with a time cycle.
...
By measuring both the return air and evaporator temperature, the CC series control has direct system feedback and will adjust the blower speed to achieve the desired settings with respect to comfort, moisture control, and energy savings.

Cost will be about $550.

The ICM company also recommended a UV light inside the unit to kill any mold, pollen, dust mites, or other nasties that might accumulate there. I am still considering that but will likely go with it if it is under $200.

 

[bradyarz]

Another update.

In my previous post I said my AC guy was going back to his distributor for advice and this is what they came up with. I also called the company and they were *very* helpful in explaining things to me. I like their story and will be installing an ICM CC750 Comfort Control Center:

From their literature:


Cost will be about $550.

The ICM company also recommended a UV light inside the unit to kill any mold, polen, dust mites, or other nasties that might accumulate there. I am still considering that but will likely go with it if it is under $200.

i'm far from being an expert in the field, but that sounds like a really great idea to me.