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Thread: Help with old house musty smell

  1. #1
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    Help with old house musty smell

    I live in the DFW are of Texas. Warm humid climate. Our house was built in 1966 but was remodeled in 2013 or so. We completely gutted the house down to the studs. Our exterior walls are spray foamed, roof line spray foamed and run our 2 ton heat pump in a "semi-conditioned" attic. The smell was pretty strong and we tried to address the smell in 2016. We spray foamed the under side of our pier and beam with 2" of closed cell spray foam. This was a MAJOR help. I have a feeling the spray foam guys missed a corner of the house as our "crawl space" goes from 18" a the shallow part to about 30" at its tallest.

    I have been watching a couple humidistats, one in the kitchen and one in our closet where I think they missed the spray foam. We hang out in the 50-60% range. Lower end when the heat or a/c run, upper end when its a nice spring day and nothing is running.

    Any suggestions on trying to get rid of the rest of the smell? Im thinking a whole home dehumidifier may help or an ERV to constantly exchange fresh air.

    We cannot find any sources of mold or mildew. Im not sure if this is residual moisture that isnt going away because the house is fairly well sealed.

  2. #2
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    Blower door test to locate location of poorly sealed foam.
    BIg No on the ERV as it brings in moisture without removing any. A ventilating dehumidifier is a much better choice, perhaps coupled with a scheduled use of a bathroom vent fan.
    Try to keep the house at a low positive pressure.
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  4. #3
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    A steady flow of filtered, fresh air, and maintaining <50%RH is the start. Any damp spot for more than 24 hours will start the mold growth. This could be condensation on a cold air supply duct.
    Start by checking the temperature of the cold air leaving the cooling coil. You need cold enough to remove moisture from the house but not cause condensation on the cold air supply duct. 52^F-54^F is needed for good humidity control during high sensible cooling loads. Also the indoor %RH should be <50%RH during hot times of the day. Evening and rainy days need supplemental dehumidification during low/no sensible cooling (evenings and rainy days).

    +55%RH indoors elevates the odors in the home. <50%RH while providing a fresh air change in 4-5 hours will the home. Damp spots must be removed. The positive pressure helps stop damp spots from forming areas of the home where air infiltrates. Roof leaks and rain leaks around windows also may cause the problem. Water leaks in the crawlspace or around slab joists or under carpeting on concrete are also problem areas. Lowering the indoor dew point helps all of these. Over cooling also can cause condensation in the coldest surfaces. Warmer, drier materials in the exterior shell of the home reduces this problem. +75^F, <50%RH is target to reduce moisture problems in the exterior surfaces of the home in areas with high outdoor dew points.

    After getting your a/c working well, get whole house dehumidifier with a filtered fresh air ventilation option that will pressurized your home with a fresh air change in 4-5 hours. Suggest an Ultra-Aire +100 pint per day dehumidifier.

    Further question welcome.

    Regards Teddy Bear
    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. #4
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    Thank you both for your answers.

    Teddy Bear, I was hoping your were going to jump on here and share your knowledge. I had a feeling that was going to be the answer and your golden rule would apply. I will try and find a local contractor that sells Ultra-Aire. I have been looking at their products for a couple years as Matt Risinger on Youtube is a Texas guy and also highly recommends them.

    THanks
    Tim

  6. #5
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    One quick question...talked to a contractor today and he brought up a point I hadnt thought about. His concern was bringing in exterior air when its 100*F outside. Any concerns?

    Also I found it funny I called 4 places on Ultra Aire's website (SanteFe) and two didnt even know what brand I was talking about, one said they can get the product but dont normally install it and the last place wanted $3500-4000 to do the job. I know I can get the unit online for $1700 shipped to me. $1800-2300 seems steep for an install. I may be installing the thing myself.

  7. #6
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    And how often is it 100* outside?

  8. #7
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    Quote Originally Posted by 8mpg View Post
    One quick question...talked to a contractor today and he brought up a point I hadnt thought about. His concern was bringing in exterior air when its 100*F outside. Any concerns?

    Also I found it funny I called 4 places on Ultra Aire's website (SanteFe) and two didnt even know what brand I was talking about, one said they can get the product but dont normally install it and the last place wanted $3500-4000 to do the job. I know I can get the unit online for $1700 shipped to me. $1800-2300 seems steep for an install. I may be installing the thing myself.
    I am including a cooling load calculation. 100 cfm of fresh air during 100^F 75^F outdoor condition is about .5 ton per hour. This be about .5 KW. At $.12 per KWH equals $.06 per of fresh air. The cost declines by +50% during evenings and rainy days.
    Might be $75 for the season for real indoor air quality and comfort in your home.

    Yes a large home with Ultra-Aire 120 is about like your quote. A small unit like a Ultra-Air 70H would be half of that.

    Keep us posted on what you do and the results.

    Regards Teddy Bear


    Name:  cooling cost per hour hot day.png
Views: 241
Size:  103.4 KB
    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"

  9. #8
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    Thanks teddy bear.. we got the unit installed today and its up and running. After seeing your load calc, it makes total sense to have fresh air over a few bucks a month. I just poked up in the attic and notice that the drain line on the dehumidifier is condensating though. Any thoughts on that? The P trap is dripping ever so lightly and the under side of the pvc has a little water all the way down to where it ties in with the a/c drain. Im assuming is condensate as all the pvc joints look glued well.

  10. #9
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    One more thing.. While I havent measured it, I can feel the humidity is high in the attic. We also had an ERV installed to bring in fresh air. Its a Panasonic Intellibalance and we have it running at the 100cfm which if my math is right puts us at air changes about 2.5hrs. 2100sqft house 8' ceilings. 60cfm puts us closer to 4.5hr air changes.

    Anyways, I believe the condensation is happening on the drain lines due to the high humidity in the open cell spray foamed attic. So how to lower the humidity? I was thinking I could put a damper on the fresh air intake on the dehumidifier (its currently capped) and draw in attic air as its filtered air. The intellibalance can vary the intake vs the exhaust air so we can create a negative or positive air pressure in the house.

    Any thoughts on the best way? Small dehumidifier (portable) in the attic?

  11. #10
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    Put closed cell foam on the drain from the dehumidifier, You can buy closed foam tubing and cut to fit from the dehu to the a/c connection. What is the a/c return and supply temp/%RH?

    After we get the house working well, we may be able to use some of a/c-dehu drying on the attic.

    We need to comfirm that we getting the a/c--dehu working to gether to get <50%RH during long sensible cooling runs.

    Keep us posted and thanks for the support on the dehumidifier.

    Regards Teddy Bear
    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"

  12. #11
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    So I have some initial numbers though Im not sure on the accuracy as they are just cheap hygrometers. I orderd a Testo hygrometer so hopefully I will have better numbers Wednesday.

    Inside house: 74*F 59%
    Attic: 80.4*F 60% (felt worse yesterday though no actual readings)
    Return: 75.6 50% (this is blended air from the house air return and the Ultra Aire)
    Supply: 54.1F 89% (this makes no sense to me why its reading so high on humidity. The a/c ran for about 45 min when this reading was taken. The hygrometer was placed in the closest air register)

    Hopefully a more professional meter will give more accurate results. The first 3 numbers made sense, the supply air makes no sense to me.

  13. #12
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    Quote Originally Posted by 8mpg View Post
    So I have some initial numbers though Im not sure on the accuracy as they are just cheap hygrometers. I orderd a Testo hygrometer so hopefully I will have better numbers Wednesday.

    Inside house: 74*F 59%
    Attic: 80.4*F 60% (felt worse yesterday though no actual readings)
    Return: 75.6 50% (this is blended air from the house air return and the Ultra Aire)

    How does the house air get mixed Ultra-Aire? House air should get sucked (returned) to the dehumidifier. The dry air from the dehumidifier should be supplied to the a/c supply. How is your dehumidifier return to the house?


    Supply: 54.1F 89% (this makes no sense to me why its reading so high on humidity. The a/c ran for about 45 min when this reading was taken. The hygrometer was placed in the closest air register)

    This a great number for air coming from the home to the a/c and being cooled by an a/c and supplied to the home. The dew point point of the air has been reduce by 11^F. Cooling air raises the %RH to near 100% RH as moisture is removed.

    Hopefully a more professional meter will give more accurate results. The first 3 numbers made sense, the supply air makes no sense to me.
    I am concerned that the dehumidifier supply must not go to the a/c return before the cooling coil?


    Thanks again for your effort.
    REgards Teddy Bear
    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"

  14. #13
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    Thanks again for the info Teddy Bear

    The ultra aire has its own dedicated return duct in the hallway to pull air from the house. Its supplied into the return side of the a/c. The home air and the dehumidified air are mixed in the return plenum of the air handler for the a/c. There was no space on the supply plenum to add a 10" duct so we went with an alternate method per Ultra aire's installation guidelines. The air handler fan always runs when the dehumidifier runs regardless of if the a/c is running.

    Im going to have to do more research of dew point in relation to humidity. I always assumed less rh should come out of the supply than what went in but it seems to be the opposite.

  15. #14
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    Quote Originally Posted by 8mpg View Post
    Thanks again for the info Teddy Bear

    The ultra aire has its own dedicated return duct in the hallway to pull air from the house. Its supplied into the return side of the a/c. The home air and the dehumidified air are mixed in the return plenum of the air handler for the a/c. There was no space on the supply plenum to add a 10" duct so we went with an alternate method per Ultra aire's installation guidelines. The air handler fan always runs when the dehumidifier runs regardless of if the a/c is running.

    Im going to have to do more research of dew point in relation to humidity. I always assumed less rh should come out of the supply than what went in but it seems to be the opposite.
    Blowing dry air from the dehumidifier into the a/c duct ahead of the cooling coil causes the a/c coil to remove less moisture equal to the amount the dehumidifier removes. The supply from the dehumidifier should be connected to the a/c supply down stream from the cooling coil. Changing this connection will improve amount of moisture removed when both a/c and dehumidifier operate.

    Glad we found this error.

    Regards Teddy Bear
    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"

  16. #15
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    Well, I was able to get the Ultra aire moved to the a/c supply plenum with a backdraft damper. I was able to move a 6" duct around to the end of the plenum and open up the 6" hole to a 10" hole for the dehumidifier. So now it has its own return in the hallway and properly outputs to the supply side of the air handler.

    I havent tried to get any better readings yet but I still have my concerns. So the warm air from the dehumidifier is mixing with the supply air like intended but Im only seeing 58-66*f air coming out of the a/c vents now. I know its expected to go up but its more than I assumed.

    Also, the dehumidifier has been running for 48hours non stop and we are not making progress on the humidity in the house. Nest thermostat is still seeing 60%. I shut off the ERV for now to see what happens. Really hoping to see the RH drop with the ERV off.

  17. #16
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    Quote Originally Posted by 8mpg View Post
    Well, I was able to get the Ultra aire moved to the a/c supply plenum with a backdraft damper. I was able to move a 6" duct around to the end of the plenum and open up the 6" hole to a 10" hole for the dehumidifier. So now it has its own return in the hallway and properly outputs to the supply side of the air handler.

    I havent tried to get any better readings yet but I still have my concerns. So the warm air from the dehumidifier is mixing with the supply air like intended but Im only seeing 58-66*f air coming out of the a/c vents now. I know its expected to go up but its more than I assumed.

    Also, the dehumidifier has been running for 48hours non stop and we are not making progress on the humidity in the house. Nest thermostat is still seeing 60%. I shut off the ERV for now to see what happens. Really hoping to see the RH drop with the ERV off.
    OK, need the %RH and the temp from the home and the a/c supply. There is about +300 cfm of conditioned air coming from the a/c supplies because of the dehumidifier by-pass throughout the home. It will take a +week to reduce the %RH in the home because of the moisture content of the materials in the home moisture release.

    If both dehu and a/c are working, we are removing +8 lbs. per hour of moisture from the home. Need the inside home and a/c supply temp/%RH numbers. The moisture load from the ERV should be 2 lbs. per hour when the home is at 50%RH.

    Keep us posted.
    Regards Teddy Bear
    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"

  18. #17
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    Ok, used the new Testo and got the numbers:

    House: 72.0F, 54.8% RH, 54.9Ftd, 61.3Fwb
    Supply 1: 56.4F, 70.8% RH, 47.1Ftd, 51.2Fwb
    Supply 2: 63.7F, 60.0%RH, 49.8Ftd, 55.1Fwb

    Supply 1 is closer to the a/c, supply 2 is more blended air from the UltraAire being dumped into the supply plenum. Taking a week to dry out the house makes much more sense now that you mention everything in the house needing to dry out, not just the air.

    THanks again for the help

  19. #18
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    Quote Originally Posted by 8mpg View Post
    Ok, used the new Testo and got the numbers:

    House: 72.0F, 54.8% RH, 54.9Ftd, 61.3Fwb
    Supply 1: 56.4F, 70.8% RH, 47.1Ftd, 51.2Fwb
    Supply 2: 63.7F, 60.0%RH, 49.8Ftd, 55.1Fwb

    Supply 1 is closer to the a/c, supply 2 is more blended air from the UltraAire being dumped into the supply plenum. Taking a week to dry out the house makes much more sense now that you mention everything in the house needing to dry out, not just the air.

    THanks again for the help


    House: 72.0F, 54.8% RH, 54.9Ftd, 61.3Fwb ==55^F dew point

    Supply 1: 56.4F, 70.8% RH, 47.1Ftd, 51.2Fwb == 47^F dew point= only a/c if 1,000 cfm 7.4 lbs.per hour

    Supply 2: 63.7F, 60.0%RH, 49.8Ftd, 55.1Fwb ===50^F dew point= a/c + dehumidier = if 1,300 cfm 10 lbs. per hour


    If we have 1,000 cfm of cool air with a reduction of dew point of 5^F is 9 lbs/hour. of water when the a/c and dehumidifier are operating.

    This appears normal but we are guessing at the air flow.

    Keep us posted.

    Regards Teddy Bear
    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"

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