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Old 11-05-2013, 07:52 AM   #1
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Whole House Humidifier Settings


Hello all,

I installed a Honewell bypass humidifier over the weekend and am trying to figure out how to set it properly. I know you are supposed to set it according to the outside temperature, but it seems like the humidity is too high. I live in the Detroit area and the outside temp has been ranging from the low 30's at night to the upper 40's during the day.

According to the instructions I should set the humidistat to 40 when the outdoor temp is above 20 degrees. I did this, and there is condensation along the bottom of the windows. Is this always an indication of too high of a setting?

I did purchase a digital hygrometer to measure humidity, but I wonder if it is accurate. It said the house was at around 60% humidity, which if true, is definitely too high. I turned the humidifier down to 30, and the hygrometer fell to 54%. I also noticed that at 30 the humidifier isn't even currently running.

How much does the outdoor humidity affect the inside of the house when the furnace is running? The humidity in the area was around 55% yesterday.

Thanks for any advice.

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Old 11-05-2013, 08:51 AM   #2
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Whole House Humidifier Settings


those cheap digital hygrometers are usually inaccurate. I tell my customers to set them between 30-35 as anything over that in a cold climate will cause windows sweating. even with high end triple pane low e argon windows mine will sweat at the bottom occasionally. sweating is also caused by airflow over the window. has poor airflow over the bottom so it gets coldest there and hits the dewpoint and sweats. old poor quality windows and poor airflow and drapes etc cause that too. try 30-35 %.

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Old 11-05-2013, 10:01 AM   #3
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Also depending on the unit you may have the ability to connect an outdoor temp sensor to run it in automatic that lets the controller calculate and apply the correct setting. And if you have a high efficiency gas furnace you can easily install the ODT sensor in the intake pipe (as close to the outside wall as possible). Much simpler than making another wall penetration. I got this tip from one of the pros here on DIY and ran mine this way.
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Old 11-05-2013, 12:11 PM   #4
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those cheap digital hygrometers are usually inaccurate.
I wondered about that. As a test, I left it outside for a couple of hours and compared it to the weather report for my area. The humidity display matched the weather report for the area exactly. I'm not sure if this is a good test, but I do have a little confidence in the device now.
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Old 11-05-2013, 12:28 PM   #5
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Whole House Humidifier Settings


I doubt it as you would have to be near the weather station where they take their readings. You can buy reasonably priced ones from refrigeration or Hvac supply houses or possibly Graingers. made by UEI or Cooper and in a stick/thermometer form.

http://www.superiorvalueproducts.com...22_p_1826.html
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Old 11-05-2013, 12:34 PM   #6
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How much does your place leak air? In other words, how well are the areas around Windows, Doors, receptacle boxes sealed, along with weatherstripping used around doors? How much insulation is in the attic?

Do you also have dampers on your vent for the bath, and dryer, to stop outside air from getting in, when those units are not running?

Remember, humidity changes, depending on what is going on the house. I find my humidity ranges from 51-63% upstairs, with avg. room temp anywhere from 66-71, downstairs in the basement, ranges from 47-64%, with temps down there from 59-66. These are all Winter temps.

I have no moisture on my windows, the room is comfortable right now, with the thermostat set at 67f, due to outside is 53f.

As for adding in a whole house humidifier, it is more of a band-aid then anything, same as using a dehumidifier. You definitely do not want indoor humidity below 45%, nor do you want it to stay higher than 67% for a long period of time.

BTW, what do you have your thermostat set at right now, for daytime and night time settings?
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Old 11-05-2013, 12:41 PM   #7
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all depends on where you live and how cold your climate is. the colder the climate the less humidity the air can hold before windows sweat. my experience is that at lower than 30% you will get nosebleeds and static from carpets etc. 35 is ideal in my climate. really have to try what is comfortable and works 4 U in your climate. hit 40% and you will get mold growing on cold walls in my climate.
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Old 11-05-2013, 02:22 PM   #8
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How much does your place leak air? In other words, how well are the areas around Windows, Doors, receptacle boxes sealed, along with weatherstripping used around doors? How much insulation is in the attic?
The windows and doors are sealed well, but the attic could use better insulation. This is the to-do list, as we recently put a new roof on and had a baby.

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Do you also have dampers on your vent for the bath, and dryer, to stop outside air from getting in, when those units are not running?
Yes we do.


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As for adding in a whole house humidifier, it is more of a band-aid then anything, same as using a dehumidifier.
Don't take this the wrong way as I appreciate your response, but how is a humidifier a band-aid? Isn't a furnace going to dry out the air no matter what?


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BTW, what do you have your thermostat set at right now, for daytime and night time settings?
I run it at 68 during the day and 64 at night.
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Old 11-05-2013, 02:49 PM   #9
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all depends on where you live and how cold your climate is. the colder the climate the less humidity the air can hold before windows sweat. my experience is that at lower than 30% you will get nosebleeds and static from carpets etc. 35 is ideal in my climate. really have to try what is comfortable and works 4 U in your climate. hit 40% and you will get mold growing on cold walls in my climate.
You have to have warm moist air, for mold to grow. If you have cool air, and just higher humidity in the 60% level, you are not going to have mold growing all over the carpet and walls.
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Old 11-05-2013, 02:56 PM   #10
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You have to have warm moist air, for mold to grow. If you have cool air, and just higher humidity in the 60% level, you are not going to have mold growing all over the carpet and walls.
Mold will grow in the 30's (Farenheit).
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Old 11-05-2013, 02:58 PM   #11
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Originally Posted by srelliott83 View Post
Don't take this the wrong way as I appreciate your response, but how is a humidifier a band-aid? Isn't a furnace going to dry out the air no matter what?
Adding a humidifier on a hvac system, same as using a dehumidifier in the basement or main living area, is a bandaid, for when you either have a home that is too air tight, or not properly insulated, but still allows it to breathe. As for your attic insulation, how deep is it right now up there, if you measure it in various areas?

You want a middle point. What you want, is for the house to be able to still breathe, but not hold in the humidity during Winter or Summer, where it stays in the high 60's.

As long as you are between 47-62%, may peak to 65 or 67 after using the shower or dishwasher, you are fine. As for your temps, you should be fine at that temp.

I do tend to bump my unit up or down, depending on how the week may run, by looking at the forecast, then going into the website that controls my thermostat (3m-50 with Cloudbeam wifi radio), and changing the program.

A day like today, I have found it better to just set the thermostat at 67, since the temp is in the mid to high fifties this week. If it gets a little chilly, I just bump up to 68 for a few min's, then bump it back down to 67.

Summer time though, is a different story, when it comes to making sure you still stay around that 47-60% range. As long as you keep the temp at a decent temp, not too high, and humidity at the same range, not only is it better for you, but it is better for any electronics in the home, along with the furniture and woodwork.

I have had to run a dehumidifier after we got our Central a/c. Before we had it installed, downstairs humidity would stay around the low to mid 70's, and temp would be also in the low to mid 70's. Now it stays around the same as the main living area during Summer. Winter it stays lower in temp, but that is only because we have not placed any insulation on the walls, only insulated around the Joist & Rim bay area in the basement.
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Old 11-05-2013, 02:58 PM   #12
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If you have a poorly insulated wall and especially in a corner behind a sofa etc it will get damp as the temp hits the dewpoint then mold grows on dampness. I have had to add HRVs to houses with damp walls and poor circulation as the walls got moldy and the health dept would not allow the health nurse to enter the house. It happens but you need to see it and we have the cold to do it.

Mold will grow on cold damp basement walls easily.
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Last edited by yuri; 11-05-2013 at 03:02 PM.
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Old 11-05-2013, 03:04 PM   #13
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Mold will grow in the 30's (Farenheit).
Only Penicillium type molds grow at colder temps. Those temps have to be no lower than 34f, otherwise it does not grow at all, it stays dormant. Aspergillus mold, which is what you see more common in homes, is what grows at warmer temps. Yes both need the right environment, but having your humidity at 47-60% all the time, is not going to automatically make mold start growing in the structure. You first need to have the spores on surfaces or in the air.

If you keep a clean house, wipe surfaces down all the time, do not leave food laying on the floor, or counters, clean your bathroom with a mold & mildew killing type agent, when you clean, it stays away.

If you do not keep a clean house, it will allow not only mold spores to populate, but also will allow critters in the house. The key is to keep your house clean, stuff wiped down, and you will have no problems.
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Old 11-05-2013, 03:08 PM   #14
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Just to clear up any inconsistency, or wives tales see:

http://epi.publichealth.nc.gov/oee/mold/grow.html
http://www.ces.ncsu.edu/depts/fcs/mold.html
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Old 11-05-2013, 03:09 PM   #15
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I agree and the moldy ones are usually dirty people or someone who cannot clean or afford cleaners etc. I tell my customers that if you have nosebleeds or dry skin bump it up to 35-40% max or the minimum you feel comfortable with. I have never seen one set over 40% where I live so it really depends on your house, air circulation, cleanliness and comfort requirements. Set it unitl the windows sweat and back it up 5% is what I recommend.

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