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  1. #1

    Energy Rater needs advice on controlling RH

    So I'm new to the biz and I'm experimenting on my own home. I have 2300-2500 CFM infiltration rates on a 1400 sq foot home and duct blaster couldn't even reach 25 Pa w/ 2 return registers on a split HVAC system. I NEVER run my unit during spring and fall causing high RH during those times. I just got a Lowe's bought 70 pint units which only does a room at a time and struggles to maintain below 55% without running all the time (is ES and i JUST bought it). what are my options? i plan on sealing duct work this weekend but mind you, ducts are undersized (per a local reputable HVAC guy) and I plan on air sealing. So once I tighten a little, what stepr do you all recommend to control the RH?

  2. #2
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,188
    Your house infiltration numbers are high. Until you stop the house leakage
    RH will be sucked into your house thru these leakage sites, when you run your
    system and the house goes negative.
    You should reduce your leakage to close to your square footage, so you have
    a bit of sealing to do first.

    Joe of buildingscience.com & I had a long discussion about stand alone dehumidifiers
    in conditioned spaces. I was curious about how much sq ft one dehumidifier could handle
    we decided on 2000 sq ft. Locate your dehumdifier centrally in your house and let it run
    to lower RH once you do your sealing work.
    best of luck
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  3. #3
    Join Date
    Aug 2003
    Location
    Central Kentucky
    Posts
    6,247
    Quote Originally Posted by energy_rater_La View Post
    Your house infiltration numbers are high. Until you stop the house leakage
    RH will be sucked into your house thru these leakage sites, when you run your
    system and the house goes negative.
    You should reduce your leakage to close to your square footage, so you have
    a bit of sealing to do first.

    Joe of buildingscience.com & I had a long discussion about stand alone dehumidifiers
    in conditioned spaces. I was curious about how much sq ft one dehumidifier could handle
    we decided on 2000 sq ft. Locate your dehumdifier centrally in your house and let it run
    to lower RH once you do your sealing work.
    best of luck
    Great advice to get going in the right direction!
    Have you set up a Google alert for Carbon Monoxide yet?
    Click here to find out how.

  4. #4
    Join Date
    May 2007
    Location
    Dry as a bone Tucson
    Posts
    4,344

    2300-2500 CFM infiltration

    You must have an evaporative cooler on your house to get those rates or all of your windows are open. Try turning off the cooler and/ or closing all of your windows. That should solve your humidity problems.
    Some Talk, Some Do
    "keeping condensing pressures low and evaporator pressures high"
    "Some customers are more interested in comfort than energy savings"
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  5. #5
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,444
    Where are located? What are the outdoor dewpoints? How many are in the home? Is there a basement/crawlspace in the home? I assume your air flow is with a blower door test. Some resid. dehus are not very good. 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"

  6. #6
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by ACFIXR View Post
    You must have an evaporative cooler on your house to get those rates or all of your windows are open. Try turning off the cooler and/ or closing all of your windows. That should solve your humidity problems.
    Wondering the same thing.

    Are you sure about thse numbers?

  7. #7
    "Where are located? What are the outdoor dewpoints? How many are in the home? Is there a basement/crawlspace in the home? I assume your air flow is with a blower door test. Some resid. dehus are not very good. Regards TB "

    Columbia, SC. 2 but now 1 in the home. vented crawl (part of the problem I know). Yes air flow is with a blower door test; not sure what you all meant by evaporater cooler. I am sure about the leakage rates.

    Energy Rater LA - but what about once I get my leakage rates down? stand alone dehumid, whole house, or maybe an ERV and slow the compressor down (pretty sure I have a variable speed)? Of those 3 what would you say?

    I understand your point about the stand alones...neg pressure with any leakage in the house and a stand alone is only going to be part of the problem; hence my post!! thanks for the input thus far

  8. #8
    Join Date
    Apr 2002
    Posts
    11,808
    your blower door is measuring the 2300 to 2500 CFM when the home is being depressurized by 25 to 50 Pa I assume. Otherwise your numbers sound crazy making people think of swamp coolers.

    Maybe you are as bad as 0.75 ACH from infiltration and then made worse by duct leaks

    your first step is stop the leakage, or spend money on bandaids like dehumidifiers and humidifiers, and constantly pay an unneccessary energy penalty
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  9. #9
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,188
    first....stop the air leakage.
    the stand alone will work and covince you that your home
    needs dehumidification help.
    it is an affordable investment while you educate yourself
    and gather the money for the cost of a whole house dehumidifer.
    then offer it to the a/c company as a prelude to increasing thier
    whole house systems.

    and btw...it is snowing here..sceond time in twenty years!
    stay warm!
    and welcome to the biz...oh, and post more often!
    The cure of the part should not be attempted without the cure of the whole. ~Plato

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