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  1. #1
    Join Date
    Nov 2014
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    Question Increasing Humidity in Winter

    Hi All,
    First time poster, long time reader. I've been on an adventure to target 45% humidity in the winter and would appreciate some advice.

    Our home is a 1,500 sq. bungalow home in the midwest. It was rebuilt in 2010 with new gas furnace in the original unfinished basement. Energy audit at 50/cfm reads 3,195 which isn't the best but isn't the worst.

    We were getting 10-12% humidity in the cold winter months heating the house to 70, so we had a Generalaire 900 bypass humidifier installed on the hot water line (17GPD). This put us in the high 20%, low 30% humidity. The way it was installed it would only kick on with the furnace and not with the blower. The gas furnace wouldn't run very much so the humidifier wasn't able to put enough humidity out.

    I recently had a Nest v2 installed which could control the humidifier and run it with the blower independent from heating. It is about 25 degrees outside now and I set the Nest to 70 degrees and 45% humidity. It is able to reach about 43% on the main floor and 2nd floor with the blower and humidifier running 24/7. (the basement is 50% humidity @ 63 degrees). I don't have a variable speed fan and I recall a huge spike in electric running the fan 24/7 in the summer.

    I'm wondering if I should call this mission accomplished or take some more steps to reduce the amount of energy being used. The energy audit company offered no guarantees and wanted thousands of $$$ to do things they couldn't even say what impact they would have. The few hundreds spent on humidifiers and thermostats have been less risky.

    Would anybody call this mission accomplished and close the case?
    Could a bigger humidifier put out more humidity in less time?
    Is putting $$$ toward attacking 3,195 cfm worth the effort?

    Thanks in advance for any advice on which direction to go from here.

  2. #2
    Join Date
    Jan 2008
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    Your furnace isn't running much because it's too big.
    A properly sized furnace will run long cycles, and let the humidifier do it's job.
    45% can cause problems in some regions.
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  3. #3
    Join Date
    Jun 2003
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    I suggest that a 150 watt 200 cfm duct fan will move as much air through the humidifier as a 500 watt furnace blower. Thus you will get the humidification and save 350 watts of electricity per hour verses the furnace blower.
    With the duct sucking from an open space and blowing the humid air into the supply side of the furnace, no need to operate the furnace fan.
    Keep us posted.
    Regards
    TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  4. #4
    Join Date
    Mar 2009
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    Mount Holly, NC
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    "Midwest" covers a LOT of climates, but most are frigid in the winter. Winter humidity can MUCH better be controlled when infiltration is reduced. If ANY ductwork is in unconditioned space, running the blower reduces the humidity in the space, by drawing in unconditioned air through negative pressurizing the home. I recommend getting any and all penetrations in the attic space to the living space, hermetically sealed. Then seal all wall and light openings in the rest of the structure. See how much better the humidifier works after that.
    The TRUE highest cost system is the system not installed properly...

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  5. #5
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    Mar 2009
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    Mount Holly, NC
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    You may want to investigate an hrv system, to control the direction of infiltration and regulate the temp of the ventilated air in the home.
    The TRUE highest cost system is the system not installed properly...

    Find a HVAC-Talk Contractor by clicking here

    Click below to BECOME a pro member
    https://hvac-talk.com/vbb/forumdispl...ip-Information

    Do you go to a boat repairman with a sinking boat, and tell him to put in a bigger motor when he tells you to fix the holes?

    I am yourmrfixit

  6. #6
    Join Date
    Aug 2003
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    In your OP I picked up you clearly have comfort and energy management goals in mind. You even get specific regarding indoor humidity levels. Therefore, if you showed me your energy audit, and further told me your comfort goals, I would interpret the results of your audit along those lines.

    While you expressed dismay at the suggested costs to retrofit your home for energy savings, you did not disclose what those suggestions are. I can say right here that concentrating on air sealing your house returns much more pronounced results than most any other recommended measure common from energy audits. That you've spent much time here focusing on indoor humidity levels bolsters my point. The ONLY reason indoor humidity levels become drastically low in winter is because the house is doing a poor job keeping indoor air separated from outdoor air! The basic function of a house is to be an environmental separator, and most of our wood frame homes don't do that as well as they can with even modest effort to seal them up.

    In the long run I would rather arrange things so the building enclosure/envelope does the majority of the environmental separation, with the HVAC assisting in a much less energy intensive fashion. If you had a truly well insulated, air tight house, it would not need a lot of heating or cooling, but it would need fresh air exchange for human health reasons. In my experirence, the tighter a house is, the more indoor humidity levels stay elevated, without a humidifier.

    This airtightness I speak of would also include the HVAC ducts, since if they are in attics or unconditioned basements/crawl spaces, they are part of the environmental separation boundary. If they leak, they defeat that separation to a degree.
    Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.

  7. #7
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    A homes air change rate depends on the wind and stack effect and the imperfections in the home.
    During the cold windy weather, Plenty of dry outside air is forced through most homes. Enough fresh air passes through the homes to purge indoor pollutants and renew oxygen.
    During calm wet weather, inadequate fresh wet air passes through the home, making indoor air quality poor. In addition, the occupants are adding moisture resulting in damp except when the a/c is working hard.
    It is not uncommon to need a humidifier during winter and dehumidifier during cool wet weather in the three warm seasons. To complicate the problem, additional fresh damp air is needed during the calm times of the year when the home is occupied.
    HRVs do not normally have good pay back except in extreme cases.
    In green grass climates, a whole house ventilating dehumidifier is a practical way of getting fresh filtered air throughout the home and supplemental dehumidification during the wet cool weather. Units like the Ultra-Aire are the pioneers of this type.
    You may have enough cold weather fresh air and need a humidifier.
    Keep us posted.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  8. #8
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    On face value without doing the math I would consider that blower door number to be in need of serious improvement.
    If the auditor did not express that was a reason for low humidity I would have to question their audit.

  9. #9
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    Using your posted indoor humidity levels. I come up with a rate of .72 ACH. Your currently getting 12.4 gallons per day out of your humidifier. Is it connected to the hot water line at the water heater, or a hot water line that is running close to the humidifier.

    45% at 25F outdoor temp, is a lot to ask of a non powered humidifier.
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  10. #10
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    Quote Originally Posted by beenthere View Post
    Using your posted indoor humidity levels. I come up with a rate of .72 ACH. Your currently getting 12.4 gallons per day out of your humidifier. Is it connected to the hot water line at the water heater, or a hot water line that is running close to the humidifier.

    45% at 25F outdoor temp, is a lot to ask of a non powered humidifier.
    I took the OP's stated CFM50 of 3,195 and came up with a similar ACH natural as you, with some assumptions of course since I don't know the exact house interior volume nor exactly where it is or how well sheltered it is:

    (3195 * 60)/21,000 ft^3 = 9.13 ACH50. 9.13/10.7 n factor = 0.85 ACH natural.

    The "midwest" location, height of the house, interior volume, and shielding were the largest assumptions here. Would be curious what your calc process was based upon interior %RH.
    Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.

  11. #11
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    Quote Originally Posted by Shophound View Post
    I took the OP's stated CFM50 of 3,195 and came up with a similar ACH natural as you, with some assumptions of course since I don't know the exact house interior volume nor exactly where it is or how well sheltered it is:

    (3195 * 60)/21,000 ft^3 = 9.13 ACH50. 9.13/10.7 n factor = 0.85 ACH natural.

    The "midwest" location, height of the house, interior volume, and shielding were the largest assumptions here. Would be curious what your calc process was based upon interior %RH.
    His post of 12%RH before humidifier. And his 43% with stat running fan and humidifier 24/7(wild guess that its running 24/7). Used grains per pound of air, and came up with roughly 145 CFM of exchange.

    I did it on a scratch sheet spread sheet, so not organized to do a good break down of entire calc.
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  12. #12
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    Quote Originally Posted by beenthere View Post
    His post of 12%RH before humidifier. And his 43% with stat running fan and humidifier 24/7(wild guess that its running 24/7). Used grains per pound of air, and came up with roughly 145 CFM of exchange.

    I did it on a scratch sheet spread sheet, so not organized to do a good break down of entire calc.
    Actually, after rereading the OP, I realized the house was two story with what appears to be a non-conditioned basement (63F @ 50%RH). Therefore I guessed the interior volume as 24,000 and reran the numbers with everything else unchanged; got .75 ACH natural, very close to your number.
    Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.

  13. #13
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    Thread Starter
    Thanks all for the thoughtful replies. I figured the house might be 18,000 cu. ft. based on a 750 sq. foot basement at 7' high, and the first and 2nd story (1500sq) at 8 ft high (2nd story is a little bit smaller as it has a dormer not a full floor). I read somewhere that 10 ACH isn't so bad, I recall the energy auditors saying if we tightened up the house we may have to start bringing more fresh air in with a controlled fashion, so you can see between the cost and fighting these two forces, I felt like George Banks from father of the bride where they moved the furniture out, then brought in chairs. (http://www.youtube.com/watch?v=TFNlqU72wpY&t=0m50s)

    I definitely value comfort first and energy. The 40%+ has prevented nose bleeds, but on cold days the humidifier and fan will run 24/7. The auditors recommended we air seal, caulk, and blow more insulation, but because it's a bungalow a good portion of the walls were not accessible for sealing so only 50% could be sealed. The costs ranged from $2,000 to $5,000. I suppose there was just a lack of confidence with no guarantees, if we spent that kind of money to see the number go from 3195 to 2895 I'd be very disappointed.

    I'm actually a bit pleased with the energy usage as of late averaging 30-40kWh a day, the fan appears to be adding a few kWh a day, during the summer I was hitting 70kWh and I blamed the fan so I'm thinking something was wrong there as those days were not even hot. The other consideration is that as it goes into the teens I'll probably have to lower the humidity anyways, I'm looking forward to see what the system will handle.

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