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Ask the Energy Expert
Energy Expert

About "Ask the Energy Expert"

Craig Muccio runs FPL's Conservation Research & Development Program and crunches the numbers to figure out how you can save by managing your energy use.

Your questions on energy-related topics can be submitted anytime to our Ask the Energy Expert blog. Just click here to submit your question, and if chosen, it will be answered here

How to prevent mold using a humidistat

What is your opinion on using a humidistat as a means of controlling mold?

That’s a great question, Roger, and one that many customers raised in response to my recent post on how to save energy and prevent mold when away from home. No one wants mold inside their home, so finding ways to prevent it in Florida’s muggy climate is of interest to many of our customers. Why it happens Mold can begin to take root inside your home when the relative humidity (RH) exceeds about 68 percent. A humidistat, which directly controls indoor relative humidity, is one way to prevent mold. Dehumidifiers and some central air conditioners have a built-in humidistat that tells the system to dehumidify the air to a desired point. Setting your humidistat or dehumidifier Set the controls of your humidistats and dehumidifiers to 58 percent RH to maintain acceptable humidity, since some humidistat sensors are inaccurate by as many as 10 percentage points. Better ways to control mold If you don’t have a humidistat, another way to control mold when you’re away is by programming the A/C to run at 72 degrees for just two hours before sunrise and at 88 degrees the rest of the day. But what if you don’t have a programmable thermostat? In that case, set the A/C at 77 degrees for condos or apartments and 80 degrees for single family homes and townhouses. (Remember to have the fan switch set to auto.) If you live in Florida seasonally or leave for extended periods of time, the most economical way to prevent mold in a vacant home is by using stand-alone dehumidifiers instead of A/C. Use one for every 1,000 square feet. Visit FPL.com to learn what settings that are best when you’re away. We also recommend repairing any leaks around doors, windows and in your A/C ductwork, which will help minimize the amount of moisture getting into your home. We also offer a duct system testing and repair program. We’d like to know if this helps, so feel free to leave us a comment below. Remember to refer any of your customer service questions or concerns to FPL.com/contact.

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Comments [113]

Walter Graef // September 24, 2011

I have an electronic air filter in my air handler which works only if the fan runs continuously. Yet your answer to the humidistat vs mold question says to leave the fan on auto.

I’m confused.

lisa jackson // September 24, 2011

I didn’t no about the air conditioner degrees for mold in my apartments, thanks for the information about the mold in our apartments.

Francis Teta // September 24, 2011

He failed to answer the question that FPL highlighten in their email.

Patricia Burnett // September 24, 2011

This info on controlling humidity in the home and preventing mold was of great help. Thanks a bunch!

cynthia b feerick // September 24, 2011

this was great. it was short and to the point with references for additional info/help.

Edna Welch // September 24, 2011

We have used a humidistat since 1999. We leave for Maine in late May and return in October. Our manufactured home has never had a mold problem, also our electric bills are much lower than many of our neighbors who close up for the summer to head North. We also make a point of leaving all closet doors open so that air can circulate. Great tip!

David Scott // September 24, 2011

I would like to coment that we set our humidistat at 65 and thermostat at 80 and have had no mold in our house, when we are home we have our thermo set on 79 and are comfortable with a fan on when we are in the room

Stewart // September 24, 2011


I recently came back from a 6 week trip after I rented my condo and was horrified to find mildew all over my bedroom dressers and in spurious places around the condo. I thought the central air had failed. Why wooden dressers and a few soft furnishings?

I needed an an AC tune-up so I called the tech and he looked at my thermostat and said “there’s the problem!” It was set to ‘on’ not ‘auto’ as you recommend. He said that raises the humidity by 20%! The renter had fiddled with it not knowing the consequences.

My AC filters hadn’t been changed for a while and I had the system set to hold at 82F but most say 80F is best so, a combination of high humidity, lowered airflow and dark rooms gave rise to the problem. Cleaned up in no time but quite a scare – I am from England and we don’t have AC there.

No need for a humidistat or dehumidifier if the air is working well – I have my place checked once a week to see what the hygrometer says the humidity is and I have my agent istructed to drop the temp from 80F if it goes to 61%.

VERY Intersting article, just a tad too late for me (but I am now an AC / humidity expert!)



Stan Robnson // September 24, 2011

I appreciate the insight on the humidistat. I will use your suggestions.

However, I was frustrated when trying to find the headlined article as it was “buried” at the bottom of the page and not really immediately evident. Please put the headlined article at the top of the page.


Jay Hecht // September 24, 2011


Bob Lang // September 24, 2011

A few observations:
Humidistats sometimes stick “ON” and the home gets too cold. One malfunction destroys many days of energy savings. See later comment on “too cold is dangerous also”.

RH is moisture AND temperature related. You need a safety buffer on the humidistat not only because of inherent inaccuracy, but also because the same air during the day when the house may get up to 90 will have a higher RH when the temperature at night is in the mid-70′s

Too cold is not only expensive but dangerous. When dewpoints are in the mid 70′s during summer you don’t want your temperature too near the dewpoint. Just like there is a temperature gradient through your walls from outside to inside, there is a “moisture gradient” through your walls – from high moisture outside to lower moisture inside. breaks in the vapor barrier/insulation make it worse. Too cold of a temperature can cause localized condensation (and mold). Do any of your vents blow directly on outside walls? These walls can be much cooler than the room and, even though the air is dry, they can have problems behind the wall.

Air flow and circulation is important to prevent mold. Large pieces of funiture, mirrors, etc that are tight to the wall can prevent dry air circulation and lead to localized “pockets” of high RH and mold. keep large or impervious items away from the wall to improve air flow.

Variability in humidity has to be accounted for. Is there a room at the end of your ductwork that gets less circulation? Is it surrounded on three sides by outside walls that allow more humidity to “seep” in? Does it have tight windows and doors? You have to control humidity for the worst spot in the worst room to be safe.

Is your AC unit properly sized. If you got sold a bigger unit than necessary, it can cool your house too fast, without removing enough moisture (think about the cold humidity of a cave). A smaller unit running longer will generally remove more moisture. If you have two AC units, set the more energy-efficient unit a degree lower than the second unit. It will run longer and remove more moisture, but the second one will kick in occasionally. Consider the sun’s path over your house – will one unit run more in the morning, and one in the afternoon?

Gerard Kleiman // September 24, 2011

cRAIG why are “experts” always giving general advice, and not specifics. I am a general contractor in Florida, very much into energy conservation.

You state to get a stand alone dehumidifier if you are not home for extended periods of time. Do you realize how quickly the tray fills up with water. You would have a flood in a few days.

secondly, you advise to put the a/c on 72 for 2 hours in the AM. The setting will only have value based on what the a/c was on all night. You do not evaluate that.

Also, efficiency of a/c and de-humidifiers are critical factors.

Do you really think in hot humid Florida in the middle of summer with humidity at 100 and temp at 96, you say putting the a/c on 88 for 22 hours//will keep mold out N e V E R H A P P E N!!!!!!!!!!!!!!!!!!!!

thank you Gerard Kleiman

jim padden // August 16, 2012

Dehumidifiers can be set on a counter top to drain into the sink or toilet. Also, some of them have a small pump to lift the condensate to a sink.

e kosina // September 24, 2011

great info on humistat especially the part of lowering to 58% instead of the recommended 68%.
thank you.

sharon royal // September 25, 2011

I think your newsletter tips are helpful. I’m going to read the archives to see what I’ve missed.

Nick Abbatiello // September 25, 2011

Seasonal Occupants can use a humidistat, wired in series, with their thermostat control to their AC unit. The thermostat can be placed on 77F and the humidistat set for 58%. If the temperature is above 77F and the humidity is below 58%, the AC will not run and cool, which is okay since it won’t support mold. As soon as the humidity goes above 58% AND temperature above 77F, the AC will run.

I also use a back-up plug-in dehumidifier with a drain tube to a plumbing system drain and set if for about 62% in case the main AC unit malfunctions.

This keeps my electric bill to a minimum when away.

Finally, I have family members check my place from time to time to really make sure.

Ken Staber // September 25, 2011

Good tip on humidistats and dehumidifiers. Before retirement, I was an Energy Educator and Energy Home Inspector for Pa Power and Light Co. Your program is pretty good. I enjoy your tips and other money saving information you distribute.

Dave Hoke // September 25, 2011

Very helpful
Thank You

James Shenkberger // September 25, 2011

The information was very helpfull.

Joanne Calafiura // September 25, 2011

I use a humidistat when I am away for the summer. My apartment is fresh-smelling and mold-free when i return.

Dolores O'Connell // September 25, 2011

I understand about setting the humidistat @ 58 when away for extended periods of time. What setting is recommended for daily use? Our A/C is on almost constantly and we keep the humidistat set to “on” with no degree indicated. Thanks for your advice.

Douglas // September 25, 2011

It easy to comment on things you agree with..
I believe humidity control should be as much a part home design as temprature. (wherever you choose to build)Lots of benefits in addition to mold control.

Gary Meeks // September 25, 2011

We have a manufactured home 1620 sq. ft. While away for the summer I leave the humidistat set at 60 and the air set at 80. At five years now it seems to be working.

Gary W. LeBlanc // September 25, 2011

Thank you for the update on mold/humidistat

Paul // September 25, 2011

About the humidistat controlling mold. Yes it does , years ago I would install humidistats in the condos on the beaches for the snowbirds. They would be gone for long periods of time and some would come back that have left the A/C system off and had a cave type look with walls furniture drapes fully covered with mold. So I suggested a humidistat so as to run there A/C systems less to save money on there bills as well as to prevent mold from forming which could cost thousands to remediate. Don’t forget if you leave your home to have your air system checked out before you leave. Because if your condensate from your drain pan overflows it can yield as much as twenty gallons of water per day. Or you my want to hire a service company to check your system for proper operation at certain times so as to give you some piece of mind. I have been in the HVAC business for 36 years now and highly recommend this if your going to be gone for any length of time.

Tom Emborsky // September 25, 2011

what if I have a programable thermostat and a humidistat? How should I set them for extended periods away from home? They are wired in parallel.

Bernie C. // October 25, 2011

78 deg and 58 % is fine ….parallel wiring is the way to go…..if in series you are using the devices as a low limit control ( both the humidistat and thermostat have to be “made “.) to get temp control and/or humidity control.

mrs D Lewis // September 25, 2011

I live in a town house I go away 2-3 month’s at a time I set my a/c thermostat on 82 degrees. what temperature setting should I set my humistat on 65?? more or less Thanks

Bill Grab // September 25, 2011

But dehumidifiers have to be emptied periodically and if you’re not there for nine months of the year that’s pretty hard to do.

Jane Bell // September 25, 2011

Is there a benefit to using a dehumidifier in a garage during the summer if the garage is opened and closed several times a day?

Dale Dickinson // September 25, 2011

This article was very helpful for us, because we do leave our house for five months in the summer. We do have a humidistat, but still have found mold in far corners. We have set the humidistat at 65, and air conditioner at 80.

Howard Cohen // September 25, 2011

I am a snowbird and leave humidistat at 60%, and temp. at 75. Does thermostat have to be set, as well? Mine is not programable, and I was told. it therefore cannot be used should not be used with humidistst. Is that correct?

Mark // September 25, 2011


A few additional comments about preventing mold in a Florida home.

Install an outside exhaust fan for bathrooms with a shower. The fan should be at least 120 cfm, if not the airflow will not be strong enough to push the air outside. The duct should be as air tight as possible to prevent leaks of air in the attic.

An old home AC unit coil above the fan will accumulate debris on the fan side of coil. Cleaning this debris is difficult and can be expensive. Compare costs with a new installed coil. From exprience, an A coil is better for removing moisture from the air than a Z coil. On larger systems an A coil can be obtained by special order.

New AC systems are more efficient. In Florida, home heat is of less importance, I recommend a basic electric heat strips for the few days we heat our homes. I prefer a standard non-heat pump system for my Florida home. If you live near the coastline, you will be fortunate to have ten years of use for your AC system.

I recommend to lower temperature to 72 at night and 78 during the day.

My well insulated concrete block house cools down at night and holds the coolness until 2-3pm in the summer afternoon. Then the AC modulates until the the programmed night temperature.

Bottomline, with a new standard 3 1/2 ton Carrier AC and a new multi-variable speed Hayward pool pump, my electric bill is lower by $100 per month.

I hope you have some take away info from my comments.

Thank you.

Dan Howansky // September 25, 2011

I found your comments on using a humidistat very useful. I have a condo in Florida that I use only December thru April. I do have a hunidistat but encounter some mold in the back bedroom and bathroom due to lack of air there. Do you think it would be possible to install a timer to just run the fan to circulate air for a short time each day..

Mark // September 25, 2011


A few additional comments about preventing mold in a Florida home.

Install an outside exhaust fan for bathrooms with a shower. The fan should be at least 120 cfm, if not the airflow will not be strong enough to push the air outside. The duct should be as air tight as possible to prevent leaks of air in the attic.

An old home AC unit coil above the fan will accumulate debris on the fan side of coil. Cleaning this debris is difficult and can be expensive. Compare costs with a new installed coil. From experience, an A coil is better for removing moisture from the air than a Z coil. On larger systems an A coil can be obtained by special order.

New AC systems are more efficient. In Florida, home heat is of less importance, I recommend a basic electric heat strips for the few days we heat our homes. I prefer a standard non-heat pump system for my Florida home. If you live near the coastline, you will be fortunate to have ten years of use for your AC system.

I lower temperature to 72 at night and 78 during the day.

My well insulated 2100sf concrete block house cools down at night and holds the coolness until 2-3pm in the summer afternoon. Then the AC modulates until the programmed night temperature.

Bottom line, with a new standard 3 1/2 ton Carrier AC and a new multivariable speed Hayward pool pump, my electric bill is lower by $100 per month.

I hope you have some take away info from my comments.

Thank you.

Frank // September 25, 2011

It was explained to me by air and heating company that they do not install humidistat anymore in new homes or buildings. They have failed when the switch wore out the little piece of plastic that kicks the device on and off. It was once made of metal now plastic in China. If that means anything. Suggested to leave air on 77–79 which have found to work

dorothy senner // September 25, 2011

For 20 years, my NJ friend has put out filled pie tins of Kitty Litter throughout her Fort Myers condo when she leaves in April to November; she has never had a problem with mold! I, too, do that as well in my condo and so far, so good–no mold. I set my A/C at 84 degrees to go on while I am gone, my friend does not use her A/C at all.

Bret Alan Bower // September 25, 2011

have you ever checked the humidity levels in a home that is left at 80 degrees throughout the summer here in Fla? I believe many of your customers will have humidity problems. In a perfect world it “could” work, but too many other factors have entered into the equation. Dirty filters, incompetent homewatch services, and heavy household dust in areas not thought about often. Older homes that do not have suppy vents in the closets, and also as you mentioned poor seals around doors and windows

Bruno Dugas // September 25, 2011

Thanks for the info. I do not have a humidistat; do you think it a reasonable investment to get one installed?

susan freedman // September 25, 2011

you imply that a humidistat and a de- humidifer are the same thing. a humidistat DOES NOT take relative humidity out of the air. there are only 2 ways to take humidity out of the air – an air conditioner and a de humidifer. a humidistat in no way takes humidity out of the air, than a thermostat makes it cool in the house. An air condition makes it cool in the house. the humidistat contols the thermostat – telling it when to have the a/c turn on. And what in the heck are you recommending a de humidifer to use when people are away!!! it would fill up so fast that it would overflow and then you would have mold in the house. you would need someone to empty the de humidifer every few days. having lived in FL for over 30 years and watching houses for 20 years – i have NEVER known anyone to use a de humidifer. i wouldn’t evern know where to buy one! i believe you need to alter your incorrect advice.

william berroyer // September 25, 2011

The piece on humidity control was very helpful.


jean paul parcel // September 25, 2011

For the last 20 years in Florida as a snow bird, i always use the following program without any problem at all and at a low cost.
Every days set at 86deg. except from 9pm to11pm 78deg and this is what i recommend to all my friends in the park
Have a good day J.P.

Paul Avondoglio // September 25, 2011

Irrespective of controlling mold, is using a humidistat in conjunction with your central a.c. more efficient energy-wise than using a high efficiency central a.c. alone? Please advise. Thank you.

MICHAEL maiden // September 25, 2011

Do you leave the humidistat at 58 always?

Patricia // September 25, 2011

Is it most effective to have a programmable thermostat? There are no controls on my thermostat for “auto” set. Thank you

jean paul parcel // September 25, 2011

For the last 20 years in Florida as a snow bird i been using the following program, without any problems at all and at a fair price
Every days my programing thermostat is set at 86deg. except from 9pm to 11pm set at 78deg every days of coarse, this is what i recommend to all my friends in the park
p/s no humidistat.
Have a good day J. P.

john kern // September 25, 2011

great info on humidistat and Air Conditioners.

linda Gill // September 25, 2011

Thank you for advice on mold prevention< we are away all summer and keep our air conditioner on at 86 degrees. I hope this is sufficient

Peggy Reeser // September 25, 2011

We own a 46 foot boat that stays in the water in a marina year around. When we are out of Florida for 6 months we put our 2 ac units on humidifier. What setting should they be set on?

William Ramsey // September 25, 2011

So I still don’t know whether a humidistat is a sound investment. We live in a condo year around. We leave our a/c set on 83 during hot season. we are comfortable with this. We leave a/c off and window open to enjoy gulf breeze most of the year. Use heating a little in Jan and Feb. Should we consider a humidistat?

Robyn DeVille // September 25, 2011

Craig,your answers may be useful for north or central Florida; yet it is not accurate for Southwest Florida. The proper humidity for a home/condo should be between 35-50%. Humidistats are unreliable and give a false sense of security. The HVAC should be set at 76-77 degrees. There are multiple other precautions to take that you did not mention that are imperative. I am a licensed mold remediator and given the right conditions; mold growth can start within 3 days. Using proper fitting & good quality AC return filters are a MUST and should be changed a minimum of 30-60 days. Clothes dryer vents must be checked for blockage, vent traps must be emptied after every load; bathroom exhaust fans should be used with each shower/bath and left on a minimum 30 minutes after; when cooking the overhead exhaust fans should be used. I have a list over over 16 items that homeowners should follow. Although your response was good it was far from complete!

John Apo, Sebastian // September 25, 2011

I am seasonal. I have set my thermostat to 79 degrees. Plus we cover ALL the bath and kitchen vents with plastic wrap, the toilet bowl and tank with saran wrap, and all the bath and kitch drains with saran wrap weighted down. All of this to prevent moisture from coming in. We have had no mold problems. Also, you should note tnat with an extended power outage(such as in a hurricane)line connected(24 Volt) programmable thermostats will revert to their default setting, which is HEAT. To avoid this, use a battery operated programmable thermostat.

Dennis // September 25, 2011

What if my 2500 sq foot, two story home needs about 3 dehumidifiers? Would that be more energy efficient than a humidistat connected to my AC? Dennis

George Prytula // September 25, 2011

When I use my two portable dehumidifiers the heat generated is quite noticeable so I wonder if the energy cost is any cheaper than simply turning down the A/C temp setting.
Also, if no one is in the room does a ceiling fan contribute to mold control? Should a ceiling fan be left on when the house is vacant over extended periods?

R Edwin // September 26, 2011

Stand-alone dehumidifiers are not a good choice for someone away from home. They have to be emptied every day. If the controls work properly, they’ll just work until the tank is full, and then shut down – - leaving you with an open tank of stagnant water in your living room. If the controls don’t work properly, someone gone for several months would come home to extensive water damage from the overflow.

Julia McAninley // September 26, 2011

I found it helpful in knowing what I should do when away. thanks.

D Smith // September 26, 2011

Actually, most experts define 50% relative humidity as the point where mold begins to grow inside a building so the ideal is to set humidity controls at or below 50%. Both Trane Corporation and Honeywell now have controls that are probably a little more accurate than those in the past. However, controls are not very useful without the associated equipment to take water out of the conditioned air inside the building. Most HVAC installations unfortunately rely on just lowering the temperature setting(as suggested by the FPL Engineer) to remove moisture in the air. This is not very satisfactory and will usually result in actual relative humidity above the desired maximum of 50% (or even the levels he recommends) in humid climates. Further, attempting to reduce humidity in a very humid climate in this way is a recipe for energy inefficiency since the building must be kept very cold (and uncomfortable) to get the humidity to desired levels. This can be corrected by whole house dehumidifiers which can be purchased by homeowners from Honeywell and a few other manufacturers for integration with a central air conditioning system. Purchasing free standing dehumidifiers will lower the humidity but are not designed to be controlled by controls for the HVAC system.

Robert // September 26, 2011

Does the humidistat work independantly from the thermostat? In other words if you have both and it gets hot but not humid will the thermostat take over and vice versa?

Inge Grosso // September 26, 2011

If the power goes out, what happens to the thermostat and humistat temperatures that I have programed? Do they need to be re-set?

nancy whyte // September 26, 2011

Very informative. Wish I’d read this last April when I left my condo. I think I left the AC on around77….hope so. I plan on reading these emails often. Thanks.

Kavanagh // September 26, 2011

Very helpful article, particularly about the difference in humidistats. Thank you

Anthony Randisi // September 26, 2011

I’m a Canadian that recently purchased and renovated a condo in Pompano Beach, FL. This is a vacation home so were away most of the time & I’m very concerned about mold. My contractor installed a new electronic thermostat. Do you think it would have a built-in humidistat or is that usually a separate control?
Anthony R.

sam // September 26, 2011

Very helpful the home inspector did not know.

Craig // September 26, 2011

We are seasonal residents on the east coast of FL and when we bought our condo we had a small mold problem which we dealt with. The mold specialest we used said humidity over 50% breeds mold and we should leave our dehumidifiers set at 40% to 45%. I have one in the open kitchen draining into the sink and the second in the master bath draining into a jacuzzi drain. We leave for 7 months and return to a completely oderless condo. Do we need to have them set that low? We also leave the humidistat on the air handler set the same as the dehumidifiers.

Robert // September 26, 2011

Helpful. Thank you.

Art McMahon // September 26, 2011

Artical very helpful. Thanks.

Lester Basso // September 26, 2011

Your article was very informative for mold control.

What is your opinion with using ultraviolet (UV)light for mold control in the air handler?

Jim Petrarca // September 26, 2011

What can we do if we lose our power during a hurricane for an extended period of time to make sure we don’t get mold.

Joyce A Bancroft // September 26, 2011

We left our mobile home for 8 months this summer for the 1st time and added a humidistat to control the AC. The humidistat was set at 65, the AC at 80 degrees. We did not leave fans or dehumidifier on. All interior doors are open and water sources covered/ turned off. Did we do enough ?

Joanna Garry // September 26, 2011


Barb Uhlman // September 26, 2011

Our AC/Furnace man recently told us that there was a little mold growing in the air handler. He suggested an ultra-violet light. BTW, the air handler is a little over 2 years old, but we are there only seasonally. What do you think of his ($700) suggestion? Thank you in advance.

I will reexamine our settings on the ac and the humidistat. Thanks again.

Janice LaPlante // September 26, 2011

What is more energy efficient to control humidity,
keeping the thermostat above 80 and humidistat at 58-60 or running the air conditioner @72 2hrs/day

Martin Miller // September 26, 2011

If the humidistat is to be set at 58, while I am up north in the summer, what should the setting be for the thermostat? (I am a snowbird living outside of New York City in the summer and in south florida during the winter.)

Ginger Cody // September 26, 2011

very informative. thanks.

Gen Lotto // September 26, 2011

Summetime – thermostat at 10 pm at 75*
until 8 am -stop day time – used fans -

mike // September 26, 2011

working in this business for aprox. 28yrs on the west coast of Florida, humidistat wired in series w/t stat Set temp @ 80.Set Humidistat 60 to 65% fan on auto………no issues

Robert Epstein // September 26, 2011

Your response to the humidistat question is fine as far as it goes — but in a high-rise condominium (with individual A/C units and a central chiller) there is commonly a central duct system exhausting air from the hundreds of bathrooms in the building. So, there is always air from the outside entering the building, and the apartments through the thresholds and other leaks. Shouldn’t this require a different scheme than your two hour a morning suggestion? And what would be the point of checking the A/C ducts? — air leaking from my ducts is still in my apartment. Thank you for your comments.

Bob Epstein // September 26, 2011

In a high-rise condominium, there are exhaust fans removing air from hundreds of bathrooms. Makeup air comes into the building from the outside, through doors, other peoples’ open windows, and under apartment thresholds. A/C is provided by individual units, perhaps running off a central chiller.

Under those conditions, does your advice about a two hour operation in the a.m. still make sense?
It would be nice if it did, but seems to me a humidistat in series with the thermostat makes more sense. Appreciate your discussion.

Roger & Priscilla Lauzon // September 26, 2011

We are using thermidistat @ 82* and Humidistat
at 66

Fred Kobie // September 26, 2011

This information is way off and it will and has caused more mold damage in our area than any other single cause. This is not the correct way to control the environment and horrible advice. I am an expert in humidity, a/c, mold, among other things and if you call or e-mail I will give you updated information to help but please stop telling people that dehumidistats help control mold in ANY FASHION.

Herb // September 27, 2011

Where can I purchase a humidistat?

T. Martin Radcliffe // September 27, 2011


I put a brand new Amana Air Conditioner System in my Mobil Home this summer. It is an “Energy Saver”
model, as many new A/C units are today. I also sealed the inside of my windows with a clear flim that is cut to shape, tacked on with two sided tape around the edges and then you use a hair dryer to shrink wrap/tighten the flim so as to leave a sealed window instead of the old luver/slat windows that you crank open and closed. They are awful at keeping the cool air in. This was much, much cheaper than putting in new windows, and actualy even more effective. At any rate, together; the new A/C unit and the sealed windows has dramaticly reduced my electric bill this summer. As you can see from my billing records; May, June, July, and August, the hottest months, have been my least expensive bills yet. Thank you for the tips which I got from FPL last year about all of this, which I followed.

Tom Martin Radcliffe

ernest O'Mahony // September 27, 2011

Where can I get prices of dehumidifiers and how long should they run during Summer in an empty house

Sam Preffer // September 27, 2011

As a snowbird I am interested in the propper method to prevent mold while I’m away for the summer months

Cynthia // September 27, 2011

How can a person use a stand alone dehumidifier when they are away for the summer? Someone would have to dump the water out.

Renga // September 28, 2011

Good suggestions

Emiliya Clark // September 28, 2011

I am renting townhouse in Boca Raton and I had 2-3 leaks for last year. After landlord fixed the leaks, another issue came up: MOLD! After long battle with landlord to fix it, they finally got it done. I am not sure if they fix it right way. Please, can you tell me how and where I can get free mold inspection? I worried about my small children and my health.

Condo Life // September 28, 2011

How to control window condensation?

Wallace F Pursiful` // September 28, 2011

This article is very helpful and answered our questions about our humidistats and dehumidifier. Thank You.

dave // September 28, 2011

We have a a/c unit and a humidistat. What is the best temperature to set the thermostat when we leave the house for an extended length of time? Is it ok that the temperature may rise to the high eighties?

Thank you!

phyllis bruck // September 28, 2011

If I use a dehumidifier, do I still have to use my air conditioner at the same time?Thank you.

ron // September 29, 2011

I recently had a new ac and humidistat installed in my Naples, Florida condo. The installation company suggested setting the humidistat at 60 and the AC at 80 when gone for extended periods. Are these the best settings i.e. your response above recmmends setting AC at 72. Thank you for your response.

Karen // September 29, 2011

If I am a seosonal Miami resident and I am gone fore weeks at a time, won’t the stand alone de humidifiers require someone to empty the collected water?

Tony Ruvolo // September 30, 2011

Does a humidstat make the temperature in my house feel more comfortable depending on the setting. Actually we donot have a humidistat in our system…. Thank you

Diana Hutchison // October 1, 2011

I appreciate the tips and newsnotes from FPL. I do practice the humidastat control tips at home and away. Thank you for keeping updates in my awareness.
Diana Hutchison

Ruth Jones // October 3, 2011

I,m very surprised that a dehumidifier is the cheapest way to go while your away. In Mass I run one in the basement in the summer and the electric bill jumps. Also where would the water be going? The one we use here, we either empty the bucket, or set it up with the hose running through a whole we made in the basement door. How does one do this in Florida while your gone for such a long time?

Elsa Betton // October 8, 2011

This information is very helpful. I’m in the process of renovating my mom’s condo which had mold all over both due to leaks and from my mother not using her air conditioner.

Bob Moro // October 9, 2011

Interesting article about controlling mold, but I am still confused about the efficacy of humidistads. The article says they can be inaccurate, but seems to endorse them. When I spoke to an FPL representative, he told me humidistadts don’t work and they don’t recommend them. That is consistent with a Florida radio host who specialized in home construction-he said they just don’t work. So I am still a little confused about whether to install one!

Laurence Mizutani // October 13, 2011

I’m still learning from you, but I’m trying to achieve my goals. I definitely liked reading all that is posted on your website.Keep the tips coming. I loved it!

John Ryckman // October 24, 2011

I use the humistat to control humidity and set the thermostat on 75. It really does not matter what the temp is, I just want the A/C to run if humidity gets to high. I also leave some of the ceiling fans on low to keep the air moving. Our condo is listed for sale right now and the folks that work with the agent came in and set humidity was to high. I think was only about 58%. They set the humistat lower and turned off the fans. Their contention was that I didn’t want that moist air being moved around by the fans. That seems backwards to me. I would think I would want that air moving and mixing so that areas of the condo don’t get higher humidity. So what is acceptable humidity and should the fans be left on at all times? Thank you.

Larry Pace // October 31, 2011

We have a condo in Ft. Myers and are there seasonally. We do set the humidistat in conjunction with the proper A/C thermostat settings. We also have a UV light. No problem so far with mold in our 2 years there.
But, I do have a question.
We have been advised to open our cabinet and closet doors and leave all of our ceiling fans (dining, living,and 2 bedrooms) on low speed during any extedned time away. Cost is minimal.
Do you feel this is necessary or an advantage for more air circulation to combat mold?

William G. Sullivan // November 1, 2011

I have a house in Palm Bay that has 150 amp service and I would like to increase to 200 amp service would Ihave to change my service lines coming in from the pole. I want to install a electric tankless water heater I want the one that Bosch makes it is a 125 model an calls for 3- 40 amp lines to it. any help would be welcomed

William G. Sullivan

Nancy shaw // November 1, 2011

This is helpful information that everyone who lives in Florida should have.

Top Rated Dehumidifier // February 1, 2012

Thanks for the wonderful information about the benefits of a dehumidifier. I think one of the best and efficient way to avoid mold problems at home is to get one of the top rated dehumidifiers in the market. I’ve been looking for a few dehumidifier that I find good reviews on the internet and hope to get one very soon.

bob castellanos // April 28, 2013

We leave for the summer(5 months). What should we set our humidistat and AC at? We live in southwest Florida. Last year we got mold in our closets. Please reply. Thank you.

Air Conditioners Brisbane // May 28, 2013

According to me it’s a great question. I really admire to reading your article.

Manny LaFont // June 7, 2013

While at home in Naples Florida what is the ideal
Humidistat setting

Lillian Bosco // July 12, 2013

Yes, this was very helpful especially being a snowbird from Canada.

MARIE // July 24, 2013

I am being told to leave humidistat on “On” all the time. And this is by A/C people. Go figure….Please advise.


Laura // August 11, 2013

My HOA is telling me I can not keep my air at 66 degrees as it is causing condensation to unit below. It is a concrete building with concrete between each floor. They want me to pay for mold resistant paint in unit below. Unit below keeps air at 78. If he would turn his down even just at night wouldn’troblem go away?

black Mold removal // September 6, 2013

Way cool! Some extremely valid points! I appreciate you writing this post and also the
rest of the site is very good.

Joe Gonzales // December 2, 2013

Thanks for this great information. I live in Florida and this is definitely a great info on how I prevent mold.

robert costa // March 21, 2014

How often do you suggest that I have someone check to ensure that my A/C is working properly when my home is vacant. I want to ensure that it is working properly so that I won’t have a mold problem.
Thank you


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