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  1. #1

    High Humidity in Home and Wont maintain Temp

    Hello, I first off want to thank everyone in advance for the effort to possibly help me with my issue. I will start off by telling you that I have a 70,000 btu lennox 95% furnace and 2 ton 17 seer ac with 2 ton down flow coil recently installed all new within last 12 months. When first installed I have no complaints as of yet about furnace side of system. The AC side of system is another story. I will first say we are dealing with consistant high humidity and will not maintain set temperature in home. We have had original installers out 3 different times looking into the issues. First time was out and said they adjusted blower speeds and adjusted and checked freon levels and was satisfied with readings. Within a week we were noticing exact same issues once again and called service again. Second time came out and checked return ducts for leaks in attic and did not notice any and again checked filters, valves, and freon and took readings and adjusted blower again. I was getting about 15 degrees temp drop from return to supply when they left and said with new puron won't get much better. Problem was never fixed and within weeks had service back out with Lennox representitive. Checked all equipment again and same old routine but decided this time my super heat numbers were a little high and decided to change a valve hooked to a little copper line that was next to a big one. The big copper line was cold and little one was cool and they said the valve would fix that and allow for colder temps. So while part was on order I was also told by service my roof could be some of issue not properly insulated and crawl space had a lot of holes in plastic. I decided to take care of my end and had all soffit removed and cut out and baffles installed in rafters with vented every other soffit on eves. I had a gutter replaced to take water away better and completely cleaned all old plastic out of crawl space and replaced with all new 10 mil from wall to wall. Doing all this did me no good with humidity or maintaining temp. New valve came in and they came out and installed and adjusted and set to their numbers according to lennox and book and now little copper line is getting warm and getting a temp drop of about 18 degrees and they adjusted blower again. After about 12 hours of running I noticed little copper line lost all its heat and felt cool again and but big line was cold. I let go until next day and noticed around noon line was not as cool a little warmer. Line continues to fluctuate and always warm and cool up and down. All in all nothing has changed any humidity issues and maintaining temp. I agreed to pay for a energy audit to determing hopefully the problems. The audit found the ducts were leaking in crawl space very bad and I had infiltration rate of 5.2 ach/29%nach. Recomended ducts to be sealed and foam on rim joist to seal up crawls space and 6" fresh air installed into return. HVAC agreed to come back and seal up all ducts and boots in floor and I am going to seal the rim joist and crawl walls with closed cell foam. As of today humidity is still up to 65% and outside humidity is 40% with outside air temp of 86 and my indoor on thermastat was set to 70 but raised to 74 on its own. When I put a thermometer by vents it says it's comning out of vent around 60 or 61. The little copper line is still getting cool and warm and we are constantly dealing with humidity and maintaining temps. I almost feel like with the ac running it is actually causing my humidity to go up because if I shut it all off and open windows the humidity will slowly come down. Even if I just run the blower it seems to raise some humidity levels. I am about tired of it all and desperate for some opinions on what to try next. My home has never had issues before. Now blower is set to lowest setting and all ducts are sealed to their best opinion and roof is ventilated with soffit and baffles and ridge vents, all shower fans vent directly out and so does dryer. On average the temps around here has been higher than normal this year but our highest temps have been in upper 90's with humidity of 70-75%. On them days house would raise to 78-80 easily and humidity would be lower 70's. I am desperate for any advice. Please help!!!!!!!!!!

  2. #2
    Forgot to mention my attic was also just recently filled with 15-18" of blown cellulose insulation and walls were re blown in with same. So house is well insulated. Thanks

  3. #3
    Also has is 1300 sq ft.

  4. #4
    Join Date
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    Quote Originally Posted by arianna02 View Post
    Second time came out and checked return ducts for leaks in attic and did not notice any

    OH BOY, HERE WE GO. IF THEIR FIST DOESNT FIT THROUGH THE HOLE? EVERY PLACE THERE IS AN UNSEALED SEAM THERE IS LEAKAGE. IF IT WOULDN'T HOLD WATER IT WON'T HOLD AIR.

    I was also told by service my roof could be some of issue not properly insulated and crawl space had a lot of holes in plastic. I decided to take care of my end and had all soffit removed and cut out and baffles installed in rafters with vented every other soffit on eves. I had a gutter replaced to take water away better and completely cleaned all old plastic out of crawl space and replaced with all new 10 mil from wall to wall. Doing all this did me no good with humidity or maintaining temp.

    I agreed to pay for a energy audit to determing hopefully the problems. The audit found the ducts were leaking in crawl space very bad and I had infiltration rate of 5.2 ach/29%nach.

    CFM50?

    Recomended ducts to be sealed and foam on rim joist to seal up crawls space and 6" fresh air installed into return.

    HUH?


    HVAC agreed to come back and seal up all ducts and boots in floor

    SAME GUYS WHO SAID THERE WERE NO LEAKS?

    and I am going to seal the rim joist and crawl walls with closed cell foam.

    MAKE SURE THEY LEAK TEST BEFORE LEAVING. BEST WAY TO FIND AND CURE THE LEAKS IS WHILE THE RIG IS STILL THERE. FLORESCENT SPRAY PAINT MAKES LEAKS OBVIOUS.

    When I put a thermometer by vents it says it's comning out of vent around 60 or 61.

    AT WHAT RH, HIGH OR LOW...

    The little copper line is still getting cool and warm and we are constantly dealing with humidity and maintaining temps. I almost feel like with the ac running it is actually causing my humidity to go up because if I shut it all off and open windows the humidity will slowly come down. Even if I just run the blower it seems to raise some humidity levels.

    AN UNDERSTANDING OF DEW POINT, PSYCHROMETRIC CHART, AND INTERPLAY OF TEMP AND RH WILL HELP HERE.

    Now blower is set to lowest setting and all ducts are sealed to their best opinion and roof is ventilated with soffit and baffles and ridge vents, all shower fans vent directly out and so does dryer. On average the temps around here has been higher than normal this year but our highest temps have been in upper 90's with humidity of 70-75%. On them days house would raise to 78-80 easily and humidity would be lower 70's. I am desperate for any advice. Please help!!!!!!!!!!
    So what happened to your duct and homes leakage numbers after things were sealed up? Can you get cfm50 number for house leakage before and after? What's up sealing duct leaks then adding a 6" hole?
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  5. #5
    With adding a 6" fresh air after sealing supply ducts also have me confused. The ducts were taped and sealed yesterday and have not noticed any difference. The hvac company does not do the blower door test a 3 rd party is coming back out after i get foam sprayed also. Im not sure what cfm50 is. The only numbers i do know is what they recorded originally. As far as my RH at vents with supply temp at 60-61 rh is up around 80%. This morning its 72 outside with outside humidity outside 65% and my inside RH is 61%.

  6. #6
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    The little valve is called a thermostatic expansion valve, it regulates the flow of refrigerant into the evaporator coil. It's possible it failed again. Maybe some trash is floating around in freon lines. I always put the filter dryer right in front of the evaporator coil is reduce failure in case something is floating around in there. It is also very important that the system was evacuated properly, which depending on situation could take some time. The valves are very prone to failure if a little bit of moisture is left in system. If valve is failing, coil could start to ice up, which could be causing you excessive humidity problem. The evaporator coil could be bad as well. Maybe half working. Really can't tell from here. You might need to get another company out to evaluate the issue and get a fresh set of eyes.
    I like DIY'ers. They pay better to fix.

  7. #7
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    Madison, WI/Cape Coral, FL
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    Quote Originally Posted by arianna02 View Post
    With adding a 6" fresh air after sealing supply ducts also have me confused. The ducts were taped and sealed yesterday and have not noticed any difference. The hvac company does not do the blower door test a 3 rd party is coming back out after i get foam sprayed also. Im not sure what cfm50 is. The only numbers i do know is what they recorded originally. As far as my RH at vents with supply temp at 60-61 rh is up around 80%. This morning its 72 outside with outside humidity outside 65% and my inside RH is 61%.
    What part of the country do you live in?
    Relative humidity in not a good reference to use when comparing outside to inside. Best to use outdoor dew points to see if the a/c is working. 90^F, 40%RH is 65^F dew point. Outdoor air should be infiltrating your home at an air change in 4-5 hours to purge indoor pollutants and renew oxygen. When 65^F dew point air is cooled to 75^F, the %RH rises to 65%RH. Your a/c needs to remove enough moisture to lower the indoor dew point to 55^F which is 75^F, 50%RH. An air change of fresh air in 4 hours is about 50 cfm which need a 1-2 lbs of moisture removed per hour. 2-3 occupants add +1 lbs. of moisture per hour. So if you a/c removes 3 lbs. of moisture per hour and your home is excessively air leaky, you would end up with 50%RH.
    For you a/c to remove moisture from the air the cooling coil must be colder than than the dew point of the inside air. In your case, a 45^F cooiling coil would be ideal to provide <50%RH at 75^F. The amount of air flowing through the coil and the return air temp determines the coil temp. Slowing the air flow reduces the %RH in the home.
    You may not get all this but show it to your a/c tech.
    Go to Lennox if you must to get help.
    Also keep in mind when the a/c does low/no cooling loads and the outdoor dew point is +55^F, supplemental dehumidification is needed. Whole house dehumidifier like the Ultra-aire supplement the a/c to maintain <50%RH during all seasons. They are also designed to supply fresh air when needed.
    Make your self familar with ^F dew point and %RH effect. When the outdoor dew point drops to <45^F, the fresh air infiltration will lower the indoor %RH. Too bad more a/c techs do not understand this.
    Here is a dew point map.
    http://www.weather.com/maps/maptype/...name=undefined
    The areas below 45^F do not supplemental dehumidification.
    Regards TB
    Last edited by teddy bear; 09-14-2012 at 08:51 AM. Reason: add dew point map
    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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    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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    Last edited by jpsmith1cm; 09-14-2012 at 05:53 PM. Reason: non AOP member

  9. #9
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    As much as I want to praise your efforts and plans to fix the building envelope, what you describe in your OP sounds like a/c performance problems. Even with a well insulated, air tight house, if the a/c is malfunctioning the house interior can become too humid. With the weather conditions you reported, and assuming your a/c is sized correctly, you should not have difficulty keeping both the interior temperature and humidity under control if the a/c system is working properly. If your a/c service company has already replaced the expansion valve (TXV) once, it could be because poor installation practices caused it to fail in the first place. TXVs are generally reliable IF they are installed correctly and with care.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  10. #10
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    Bad practices. Brazed without nitrogen, no filter/dryer. I think those guys might have hit on the TXV cause if it's gone again.

    Quote Originally Posted by arianna02 View Post
    With adding a 6" fresh air after sealing supply ducts also have me confused. The ducts were taped and sealed yesterday and have not noticed any difference. The hvac company does not do the blower door test a 3 rd party is coming back out after i get foam sprayed also. Im not sure what cfm50 is. The only numbers i do know is what they recorded originally. As far as my RH at vents with supply temp at 60-61 rh is up around 80%. This morning its 72 outside with outside humidity outside 65% and my inside RH is 61%.
    Oh, so the work's not DONE. Let's see what happens AFTER surgery, when you've been in recovery for a while?

    When that third party comes back, ask them for CFM50. It's a hard number, not a soft number. ACH is like asking you how much you weigh per inch of height. Not only does it not tell much, there is a lot of room for variance. Get before and after. Also ask for duct leakage analysis now that they've been "sealed".

    And find out why they feel you need to randomly pull in copious amounts of high latent air. If they say it's because you need fresh air, ask how you get that spring and fall when the equipment's not running. You supposed to hold your breath during those seasons?
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  11. #11
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    mechanical'al

    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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  12. #12
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    DOE/Steven Winter Assoc has recently completed a study and built standards for spray foam insulating duct in attics. I attended a webinar where the author, Bill Zoeller presented their findings. It was fantastic:

    http://bit.ly/sprayfoamducts

    Early adopters will need to be significantly involved in the process to insure quality, probably having to lead the contractors until these strategies and best practices for implementation trickle to the field.

    Attachment 327661 Attachment 327671 Attachment 327681 Attachment 327691

    You can encapsulate unburried duct. It doesn't meet Challenge Home requirements so you wouldn't design this way, but apparently is a significant improvement for retrofit:

    Attachment 327701

    Here's my spray foam picture album for those interested.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

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