Optimum humidity for home during Michigan winter?

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Old 12-21-08, 10:03 AM
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Optimum humidity for home during Michigan winter?

Hi. I've read through most of the posts, and this question seems to have been discussed before, but I'm looking for various opinions to decide what to do next.

I had an Aprilaire 700A installed in Oct-08 for $500 (incl. the cost of the unit). I have a 2100 ft2 ranch (no basement), that is fairly well insulated, enough to keep the temp at 64 F and be comfortable. The return air duct has no fresh air intake. The humidifer is hooked up to a cold water supply, and blows the moistened air into the hot air output stream of the furnace. I took off the cover during operation and confirmed the fan is working fine, and also that the water flow is unobstructed (I can see the output water flowing into the drain). The filter is only a few months old, and looks fine. The humidifer is set up in Manual mode and is set to 7 (max, not the 8: test mode), and runs when the furnace is in operation (which is about 4 times per hour).

The outdoor temp here in Michigan has been 20 F or so for the past week. With the furnace cycling on 4 times per hour and the humidifer running during those times that the furnace is running, the indoor humidity tops out at 33% or so. With this humidity, my family's skin is extremely dry, we are shocking each other (and the dog, who's practically a walking static electricity weapon). Everyone is blaming the humidifer as being a waste of money. For what it's worth, there is no sign of any condensation on the windows (and I wouldn't care if there was).

Are we unreasonable to expect 45% or so during these cold (20 F) days of winter? Wouldn't that be a more comfortable humidity level?

To achieve 45% humidity, I'm not sure what else we can do. Hook up a hot water line? Re-wire to run with the fan motor on? How much would these changes realistically increase our home's humidity? It's not worth doing if it's only going to bump us up to 36%-38% or so.

Thanks in advance for everyone's advice & input.
 
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Old 12-21-08, 08:16 PM
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With 20˚, 35% is ideal, but no higher than 40%.

The hot water may help, but going back to your furnace on about 4 times an hour, what is the avg run time you get on it?
 
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Old 12-22-08, 06:25 AM
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I haven't done a detailed measurement, but I would estimate that the furnace comes on about 4 times per hour, each time running about 10 minutes.
 
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Old 12-22-08, 06:28 AM
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Originally Posted by Jay11J View Post
With 20˚, 35% is ideal, but no higher than 40%.

The hot water may help, but going back to your furnace on about 4 times an hour, what is the avg run time you get on it?
Thanks Jay. When you say 35% is ideal, how can that be? Seriously, we are statically charged up all the time, our noses are dried out, and our wood furniture is hurting. Why not 45%, like we had in the fall?
 
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Old 12-22-08, 06:31 AM
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What do you have for t-stat? (Make and model)

Do you know if your return ducts in the attic are sealed with duct mastic, or the like?
 
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Old 12-22-08, 06:44 AM
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Originally Posted by OldNGray View Post
Thanks Jay. When you say 35% is ideal, how can that be? Seriously, we are statically charged up all the time, our noses are dried out, and our wood furniture is hurting. Why not 45%, like we had in the fall?
When you look at your manual, chart for your humidifier settings, you'll see the ideal settings for outdoors temps.

If you go any higher your windows are going to start getting frost/wet area on it, and when the temps get really cold, you are going to have a lot of frost on it, and also you are going to have other cold spots in the home that you may not see, and can lead to water damage from the high humidity.

Right now, it's -15 here, and I have an outdoor senor on ours. The humidity is around 30%, and I would not dare go any higher since I still have a couple of old windows in our home. Yes it is some what dry, but I've seen it get as low 10% in homes that don't have a humidifier.
 
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Old 12-23-08, 02:47 PM
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Originally Posted by Jay11J View Post
What do you have for t-stat? (Make and model)

Do you know if your return ducts in the attic are sealed with duct mastic, or the like?
T-stat model is White-Rodgers Comfort-Set III, part # 37-5748A.
 
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Old 12-23-08, 03:32 PM
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Ideal humidity is 35-55% maintained year round. Humidity will vary among rooms, with bathrooms, kitchen, and laundry being higher. You can check humidity levels in individual rooms with hygrometer (sold where thermometers are sold).

If higher humidity is required, you can purchase humidifiers. I have one in the bedroom and one located centrally downstairs in my rental. It is important to monitor humidity in bedrooms. That's where you tend to spend most of your time.
 
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Old 01-01-09, 04:21 PM
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I see some posts on humidity levels and measuring with hygrometers. Last month i posted after successfully installing a HE220 humidifier, to maintain humidity during the winter and help protect a new hardwood floor from drying out. Reading some of the advice here beforehand made the install go well.

Anyway, after the humidifier install I was still concerned about the humidity levels as I had two digital sources (an unused thermostat and portable cool mist humidifier) that both gave what I thought were lower readings than actual (26-30%). I thought this because the difference in humidity is noticeable when entering the house from being outside and I do have some minor condensation on the windows. So I did go out and picked up two different models of manual hygrometers, and both relatively cheap too. One was originally at 0% in the packaging, the other around 15%. I initially set them out beside eachother and later moved to seperate rooms. Both of these manual hygrometers stabilised and report similar humidity levels of 40-45%. (The ideal level for the hardwood and comfort for no static, dry lips/noses, etc. that I was intending with the humidifier install).
But the digitally measured levels are both 15-19% less than this. Do you know why this would be the case, always thought digital would be more accurate? Could the digital ones not be reporting relative humidity like the manual hygrometers but another humidity class?

Thanks for any thoughts on this.
 
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Old 01-01-09, 09:39 PM
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It is hard to say which hygrometer is correct without comparing them to one that has been calibrated.

In cold climates it is the structure that is used to set your humidity level, not a % reading.
The sweat forming on your windows tells you that you are approaching your home's maximum humidity level.

Jay has some good info on this in his posts!
 
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Old 01-02-09, 07:35 AM
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How accurate is your Hygrometer. Do this test. Place warm water and a couple of table spoons of salt in a plastic Ziploc bag. Put meter in bag making sure meter does not get wet. Wait 24 hours and check the RH should be 75%.
 
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Old 01-02-09, 07:53 AM
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Originally Posted by airman.1994 View Post
How accurate is your Hygrometer. Do this test. Place warm water and a couple of table spoons of salt in a plastic Ziploc bag. Put meter in bag making sure meter does not get wet. Wait 24 hours and check the RH should be 75%.
Humm. I didn't know how or knew if you could do that.. I know about ice and water to check your temps. How much water are we talking about? 1/2 cup??

Learn something new everyday!
 
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Old 01-02-09, 09:35 AM
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I have been working with humidity for a long time and I too learned something ..............now I can take the day off!

Understanding Relative Humidity and the Hygrometer

HYGROMETER ACCURACY CHECK

All that's left to do is find out why 75%.
 
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Old 01-02-09, 10:17 AM
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Looks like Greg hooked me up!
 
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Old 01-03-09, 12:52 PM
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Thanks for the tips guys!
As with Jay's reply and not knowing the amount of water, I tried the ziploc bag with 1 cup of water and 2 tblsp of salt. Reading after 24hrs was 88%.

I'm now going to try that quicker test in the link from Greg, with the wetted salt in a bottle cap. That should allow me to get both hygrometers in the bag and tested at the same time.

Interesting humidity theory and yes, you can learn something new everyday!
 
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Old 01-21-09, 12:40 PM
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Cool

All old houses, and 99% of new construction, are poorly done. Most builders are ignorant and careless, and people are still not practising proper super-insulation techniques. I'm willing to bet that your house is none too tight.

With that said, your problem will be being able to put enough moisture into the air to raise and maintain the humidity level at 35%-50% at 68-72 degrees (or whatever you like) for a healthy indoor environment. What is happening is that your house has no proper vapor barrior on the inside of the outer surfaces, and the moisture is going out as fast as you put it into the air.

The reason is that leaky exteriors allow air to seep in and out, and the warm interior air is rushing to the outside cold air, carrying the moisture with it. Worse, that which does not go out thru the air passages, is dampening, or wetting down, the insulation and causing it to hold less dead air and thereby decreasing its insulation value. Hence the problem with common building practices.

I live in a little apartment right now and have my humidifier going 24/7. It can't keep up. Still, like you, I have little choice. The windows get wet, even with double-pane design (not that such is the best). While I don't have to worry about any damage caused, you do if you own the place. Insulating shades can help, as can sheets of insulation board placed over the inside of the windows and doors at night. A lot of hassle, but maybe worth it for you.

Don't worry too much about the humidity guage you purchase; just get a decent one as rated by your research on the Internet and contacting the manufacturer. But any is better than none. It doesn't matter so much the accuracy as matters the consistency of measurement as a relative reference point for you.

But more importantly, your body will tell you when things are right if you sleep well, there is no static in the house, your skin has no dry spots, and you don't get respiratory problems. Watch out for the beginnings of black mold. It can start behind things set against walls or where air is not being circulated. Basically, no mold equals no problem.

The only long-term solution would be retrofit of the whole building. Something to think about.

Best of luck with your problem. I hope this helped a little.
 
 

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