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  1. #1
    Join Date
    Jan 2010
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    10

    Comfort Questions Related to Humidity - Please Help

    Hello All!

    I have a 5 year old 2,000 sq ft house with zoned heating and cooling. We have 2 80% gas furnaces (not sure on the size) and two 2 ton 13 sear air conditioners. The systems are builders grade train systems.

    We live in St. Louis and have been frustrated by the comfort of our home during the spring/summer/fall seasons. We feel that there is too much humidity in the home (confirmed by chips and other things going stale). I think it is related to the sizing of the system and also general seasonal challenges with the humid stl climate.

    I have considered two new systems like the advanced bryant/carrier systems, but feel that they will not ultimately fix my problems (plus cost is an issue and the systems function fine now).

    My question and thought surrounds the addition of a whole home dehumidifier and 2 humidifiers for winter months. Do you think I could control the humidity of the home and keep it at 45% all year with a Honeywell Vision IAQ thermostat? Can you tie one whole home dehumidifier to both systems?

    What do you guys think about this? What other method would you recommend to control humidity all year round in a climate that is both very dry in the winter and extremely humid in all other seasons.

  2. #2
    Join Date
    Aug 2009
    Posts
    1,127
    Both your summer and winter issues have primary causes that you could address, primarily that your home is leaky. You should collect some data first before making any expensive decisions. Instead of potato chips, buy a cheap digital thermometer with a humidity readout. Around $15 at the big boxes or online.

    Second, get a home energy audit with a blower door test. That will identify exactly where your issues lie, and they will give you a breakdown on solutions, estimated costs, savings, and how long to break even on your upfront costs.

  3. #3
    Join Date
    Nov 2008
    Location
    Biloxi, Ms.
    Posts
    176
    There is a real sharp dealer in your area. Call "Academy Air" and ask for Terry.

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,437
    Quote Originally Posted by timsmsu View Post
    Hello All!
    in St. Louis and have been frustrated by the comfort of our home during the spring/summer/fall seasons. We feel that there is too much humidity in the home (confirmed by chips and other things going stale). I think it is related to the sizing of the system and also general seasonal challenges with the humid stl climate.

    I have considered two new systems like the advanced bryant/carrier systems, but feel that they will not ultimately fix my problems (plus cost is an issue and the systems function fine now).

    My question and thought surrounds the addition of a whole home dehumidifier and 2 humidifiers for winter months. Do you think I could control the humidity of the home and keep it at 45% all year with a Honeywell Vision IAQ thermostat? Can you tie one whole home dehumidifier to both systems?
    ll other seasons.
    You appear to understand the problems, while some here may not. A little backroung for the rest.
    All homes should have a minimal amount of fresh air changes when the home is occupied to purge indoor pollutants and renew oxygen. Most experts suggest an air change in 5-6 hours as a minimal amount of fresh air when the home is occupied all year. Experience says you have the most fresh air change during cold windy weather and inadequate fresh air change during warm calm weather. The signs of excess fresh air is extreme dry in winter and damp during the rest of the year, like yours.
    During cold weather, the outdoor dew point (moisture level) is very low.
    Large homes with 2 occupants with adequate fresh air will be very dry dispite adding .5 lbs of moisture per hour per occupant. Small homes with +4 occupants will be wet, needing more than the a fresh air change in 5-6 hour to keep the home dry. How many in what size home is the issue. Air tightening a home will raise the indoor %RH. Adding occupants raises the %RH. Adding a humidifier will raise the %RH. In cold climates +35%RH during <20^F outdoor temps should be avoided. You should avoid condensation on cold surfaces like windows. Calculations can be made to estimate the fresh air change rate based on outdoor dew points and the number of occupants. If you are able to able to maintain 68^F, 35%RH with 2 adults, you getting 70 cfm of 20^F dew point fresh air infiltration. If lower %RH, air tighten or humidify.
    Looking at higher outdoor dew points problems,
    During the rest of the year, the outside dew points vary from 50^F-80^F. Like during winter, occupants add .5 lb moisture per occupant to their homes. Unlike the winter, during +60^F outdoor dew points, the home is +60^F dew point plus moisture from the occupants are damp.
    In addition, a healthy home has the 70-100 cfm of fresh air to purge indoor pollutants and renew oxygen. A properly setup a/c with a moderate-high cooling throughout the is able to remove the on 2-5 lbs. of moisture per hour to maintain <50%RH.
    During evenings and rainy days with low/no cooling loads a/c is unable to remove the mositure from the occupants and fresh infiltrating/ventilating air, dehumidification or reheat are methods of maintaining <50%RH. The a/c industry initially suggested variable speed a/c and a few now are offering real whole house dehumidifiers.
    The whole house dehumdifier is able to supply fresh air if/when needed while supplementing the a/c with maintaining <50%RH during the spring/summer/months with or with out cooling loads. I worked with Ultra-Aire whole house dehu for +15 years developing the concept of whole dehumidification and fresh air desired.
    Search my past posts for more info than you want.
    This week in Cape Coral we have high outdoor dew points without any cooling loads. We experience these conditions throughout the green grass climates at different times of the year. I am attaching a pictures of an indoor outdoor % meter showing some of our typical conditons and 80-100 cfm of fresh air ventilation. This amounts to 2-3 lbs. per hour dehumidification load to maintain <50%RH.
    Open to questions or comments from all. Congratulations on your open thinking on the problem of comfort and indoor air quality.
    Regards TB
    Attached Images Attached Images  
    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"

  5. #5
    Join Date
    Jan 2010
    Posts
    10
    Thanks everyone! We have great windows and a very well built house. We do have two areas where fresh air enters the home. We have a 900cfm kitchen hood and a fireplace directly across the room. on cold windy days you can feel the cold air blowing in through the exhaust vents. The house is sealed well, but there is definitely air entering there.

    What was everyones thoughts on using the Honeywell Dehu/humid on a vision IAQ thermostat?

  6. #6
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Quote Originally Posted by timsmsu View Post
    Thanks everyone! We have great windows and a very well built house. We do have two areas where fresh air enters the home. We have a 900cfm kitchen hood and a fireplace directly across the room. on cold windy days you can feel the cold air blowing in through the exhaust vents. The house is sealed well, but there is definitely air entering there.

    What was everyones thoughts on using the Honeywell Dehu/humid on a vision IAQ thermostat?
    900 CFM kitchen hood?!! OMG!!!

    That is part of your problem. In my area, every 100 CFM exhaust eats up 1/2 to 2/3 tons of cooling in peak weather. All that air you exhaust brings in an equal amount of makeup air and associated humidity. Alarm!! Alarm!!
    Remember, Air Conditioning begins with AIR.

  7. #7
    Join Date
    Jan 2010
    Posts
    10
    Yes, the hood is large, but is used 3-4 times a week for 15 -30 min (We have a commercial grade kitchen and love to cook). I realize that this will pull humidity and fresh air in through various parts of the home including the fireplace chimney.

    The current units work just fine in terms of temperature control, but the humidity thing drives me nuts, especially in the spring/summer/fall months. My thought was to add the dehum/hum and vision IAQ upstairs and on first floor to monitor temp and humidity. When upstairs calls for dehum it will activate and remove the right amount and visa versa for first floor.

    thoughts on this idea?

  8. #8
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Some suggestions/Probable causes:

    1. Your equipment is oversized. (Except when you are cooking, then you are undersized.) Get a load calculation done. Put in smaller units if needed.

    2. Get a blower door test done.

    3. Your ducts are leaking or have come apart. Get a duct inspection.

    4. Put your email in your profile so I can send some things I can't post here.
    Remember, Air Conditioning begins with AIR.

  9. #9
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,437
    Quote Originally Posted by timsmsu View Post
    Thanks everyone! We have great windows and a very well built house. We do have two areas where fresh air enters the home. We have a 900cfm kitchen hood and a fireplace directly across the room. on cold windy days you can feel the cold air blowing in through the exhaust vents. The house is sealed well, but there is definitely air entering there.

    What was everyones thoughts on using the Honeywell Dehu/humid on a vision IAQ thermostat?
    Are there anyother suprises like the exhaust hood? I suggest you get $200 CO2 meter and monitor the home to determine the real fresh air infiltration throughout the seasons and equipment operation.
    co2meter.com
    We need the info to size equipment for dehumidification and humidification. My Suspisions are that you get excess fresh air during the heating season and inadequate fresh except when the hood is used in the summer or windy. If you are in the 100 cfm range, you will need 2 lbs. of humidification per hour during very low outdoor dew points. During High outdoor dew points, you will need upto 3 lbs. of dehumidification. For the hours when the a/c is low/no cooling load, the Honeywell 90 pint per day dehu will do. Higher air infiltration or more than 2 occupants will increase the increase/decrease the moisture needs/load. The ducting of the dehu will resolve the coverage issue. There should not be a problem with a occasional short increase in ventilation other than a short term loss of humidity control. Also, any open combustion devices will backdraft even after the exhaust is discontinued because the chiminey is cooled down. This could be fatal to the occupants. Make-up air fresh air ventilation for summer would help. CO alarms and power exhaust furnace/water heater are important. Plug the fire place when using the hood???
    Blower door testing tells about the size of the holes in the home. It does not tell you how much fresh air you are getting with the varible weather conditions like temps/velocity direction of wind, also the operation of the many exhaust devices in the home like hood, clothes drier, and bath fans.
    Very interesting problem. Few realize how little fresh air homes get during calm, moderate weather. Homes that easily kept dry when the outside dew points are high are not getting and air change of fresh air in 5-6 hours which is minimal fresh air for indoor air quality. The end result is that we live in chemical soup during calm moderather conditions. This is hit or miss at best. Two adults in a 2,500 sqft. home should be approx 650 parts per millon to get an air change in 5 hours. Attaching couple photos with wet outside, dry inside, 2 adults, and 90 cfm of make-up air with a 90 pint per dehu removing 2-3 lbs. per hour. We can have weather like this for days at a time. A straight a/c with a whole home ventilating dehumidifier provides fresh air when needed and maintains <50%RH for minimal investment and operating cost. Keep us posted.
    Regards TB
    Attached Images Attached Images   
    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"

  10. #10
    Join Date
    Jan 2010
    Posts
    10
    thanks everyone for all your help. I wanted to include an observation. I noticed, and have noticed in the past a small amount of condensation on the windows upstairs (not sure if only in the winter). It is a band of about a quarter of an inch on the top pane at the bottom by the latch. This is only on upstairs windows. We have 230 cfm remote blowers removing shower moisture on a timer up to one hour. I failed to mention we have a 48 gallon fish tank with a hood.

  11. #11
    Join Date
    Jan 2010
    Posts
    10
    Kevin, I cant figure out how to display my email. harlan_tim@msn.com thanks again

  12. #12
    Join Date
    Jan 2010
    Posts
    10
    Also, I have a meeting with a hvac rep from a big company here in st. louis. I will fill you guys in on his suggestions.

  13. #13
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Quote Originally Posted by timsmsu View Post
    Kevin, I cant figure out how to display my email. harlan_tim@msn.com thanks again
    Go to User CP. Put it in your profile. Don't list it here, the mods don't allow it. See site rules.
    Remember, Air Conditioning begins with AIR.

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