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Old 08-10-2020, 03:15 PM   #1
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ongoing humidity problem


Hi guys and gals,
I've had a previous post about taking refrigerant out of my heat pump.
We still have the ongoing humidity problem.

to recap :
Crawl space is regular one, not encapsulated.
Humidity problem was said to be from a blocked up evaporator coil (this was fixed)
Humidity level in crawlspace is ongoing as well as in the house. Encapsulation is recommended when it did not need to be encapsulated it before.
Crawl space temp is dependent on if the heat is on or the a/c is on.

Summer right now and the crawlspace is the same temp as the house.
In winter, you will sweat under there.
2 sump pumps have been checked and working fine (had them there for years, and just replaced one)
crawlspace is dry, except for sweating insulated duct work dripping down on the plastic vapor barrier.

What is the normal crawlspace temp ?

I'm thinking it is leaks in the duct work under the house, due to a few things.
One fell off when the hvac company was working on the evaporator coil.
They have been back a few times and said they "taped up some leaks" around the joints of the duct work.
The duct work was install at least 16 + years ago, and at that time the house only had a ac unit (not heat pump)
No one around here seems to be able to perform a leak test on the duct system.

Any ideas ?
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Old 08-10-2020, 04:16 PM   #2
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Re: ongoing humidity problem


Since it's happening in the winter too, it has nothing directly do with a/c.

possible having windows open when the system off is keeping the humidity in check.

possible there's excessive humidity in the crawlspace and there's a return air leak which wasn't there before.

Check your downspouts and eavestroughs. Make sure grading is proper so water drains away from the house.
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Last edited by user_12345a; 08-10-2020 at 04:26 PM.
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Old 08-12-2020, 12:13 PM   #3
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Re: ongoing humidity problem


Quote:
Originally Posted by Talar View Post
Hi guys and gals,
I've had a previous post about taking refrigerant out of my heat pump.
We still have the ongoing humidity problem.

to recap :
Crawl space is regular one, not encapsulated.
Humidity problem was said to be from a blocked up evaporator coil (this was fixed)
Humidity level in crawlspace is ongoing as well as in the house. Encapsulation is recommended when it did not need to be encapsulated it before.
Crawl space temp is dependent on if the heat is on or the a/c is on.

Summer right now and the crawlspace is the same temp as the house.
In winter, you will sweat under there.
2 sump pumps have been checked and working fine (had them there for years, and just replaced one)
crawlspace is dry, except for sweating insulated duct work dripping down on the plastic vapor barrier.

What is the normal crawlspace temp ?

I'm thinking it is leaks in the duct work under the house, due to a few things.
One fell off when the hvac company was working on the evaporator coil.
They have been back a few times and said they "taped up some leaks" around the joints of the duct work.
The duct work was install at least 16 + years ago, and at that time the house only had a ac unit (not heat pump)
No one around here seems to be able to perform a leak test on the duct system.


Any ideas ?
You did not mention weather where you live (outdoor temperature/relative humidity) and that's a big deal, especially in the summer time.

Duct leakage, on the supply side, is making air quality in the crawl space better. Though, duct leakage from the crawl space into the return duct is not improving the air you are breathing. That needs to be fixed it there is an issue!

I'll tell you about my experience:
I live in NC, where a typical summer day temperature is 85 to 95F and humidity is 75 to 100%. A crawlspace is the norm where I live because of rolling hills and hardly any naturally flat land, so there aren't as many slab on grade. Because of the underlying granite/quartz, basement excavation is costly, though basements are not unusual.
I built my house in 2006 with a typical vented crawlspace and a vapor barrier that covered the entire earth floor. I installed foundation vent fans to "improve" air flow through the crawl space (this was a BAD mistake)

The first summer after we move in every time the AC came on I noticed a musty smell coming from the ductwork, which is in the crawl space. When I went down and looked I found moisture everywhere and some mildew starting to grow on moist surfaces.

I started reading everything I could to learn about this issue. I found there are three things that have to be controlled in order to keep the crawlspace dry.
1. Moisture vapor coming in from the earth. The vapor barrier has to be continuious. The vapor barrier works even better if turned up the foundation because masonry wicks moisture. It might be best to have a lid without drainage opening on the sump pit.
2. Moisture that comes in as liquid, like rain coming in if drainage around the house is not sloped correctly, leaking pipe or gutters, or dripping condensate from the air conditioner drain pipe.
3. Moisture that comes in as humid air through foundation vents condenses on surfaces (this was my problem).

I solved my problem by>
a. I sealed the foundation vents by placing 1/2 foam board inside the vent that is held in place with adhesive spray foam from a can. I relocated those foundation vent fans so that they circulate air inside the crawlspace, but do not bring outside air in.
b. I completely recovered the earth and foundation with 6mil polyethylene sheet. I used a termination bar at the top edge of the vapor barrier along the masonry foundation. Lapped joints in the vapor barrier are lapped 6". One CMU (concrete block) at the top of the foundation is left exposed for termite inspection.
c. I removed my sump pump/pit completely and extended the drain pipe beneath the footing to daylight. I filled the hole with gravel and put teh vapor barrier over that. (if this can't be done, put a lid on the sump pit)
d. After stopping incoming vapor from earth and through vents, and also controlling flowing water, I put a 70 pint per day dehumidifer inside the crawl space. (I've since added a second backup dehumidifer since the first one I purchased did not have the automatic on that is necessary after a power failure).

My crawlspace is real comfortable to be in now, dry and cool!


ps;
Another thing that needs to be controlled properly is the fan that brings air through ducts. The air conditoner needs to cycle on and off in order for condensate to drain properly. When the fan stops frost built up on the coil melts then it drains downward to be collected in a pan inside the air handler, then out through the drain pipe.
I made the mistake of leaving my thermostat's fan at "on" instead of "auto". The fan running continuiously was blowing liquid condensate into the ductwork, not allowing to drain properly.

Last edited by AWWarn; 08-12-2020 at 12:38 PM.
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Old 08-12-2020, 02:05 PM   #4
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Re: ongoing humidity problem


Quote:
Originally Posted by AWWarn View Post
You did not mention weather where you live (outdoor temperature/relative humidity) and that's a big deal, especially in the summer time.

Duct leakage, on the supply side, is making air quality in the crawl space better. Though, duct leakage from the crawl space into the return duct is not improving the air you are breathing. That needs to be fixed it there is an issue!

I'll tell you about my experience:
I live in NC, where a typical summer day temperature is 85 to 95F and humidity is 75 to 100%. A crawlspace is the norm where I live because of rolling hills and hardly any naturally flat land, so there aren't as many slab on grade. Because of the underlying granite/quartz, basement excavation is costly, though basements are not unusual.
I built my house in 2006 with a typical vented crawlspace and a vapor barrier that covered the entire earth floor. I installed foundation vent fans to "improve" air flow through the crawl space (this was a BAD mistake)

The first summer after we move in every time the AC came on I noticed a musty smell coming from the ductwork, which is in the crawl space. When I went down and looked I found moisture everywhere and some mildew starting to grow on moist surfaces.

I started reading everything I could to learn about this issue. I found there are three things that have to be controlled in order to keep the crawlspace dry.
1. Moisture vapor coming in from the earth. The vapor barrier has to be continuious. The vapor barrier works even better if turned up the foundation because masonry wicks moisture. It might be best to have a lid without drainage opening on the sump pit.
2. Moisture that comes in as liquid, like rain coming in if drainage around the house is not sloped correctly, leaking pipe or gutters, or dripping condensate from the air conditioner drain pipe.
3. Moisture that comes in as humid air through foundation vents condenses on surfaces (this was my problem).

I solved my problem by>
a. I sealed the foundation vents by placing 1/2 foam board inside the vent that is held in place with adhesive spray foam from a can. I relocated those foundation vent fans so that they circulate air inside the crawlspace, but do not bring outside air in.
b. I completely recovered the earth and foundation with 6mil polyethylene sheet. I used a termination bar at the top edge of the vapor barrier along the masonry foundation. Lapped joints in the vapor barrier are lapped 6". One CMU (concrete block) at the top of the foundation is left exposed for termite inspection.
c. I removed my sump pump/pit completely and extended the drain pipe beneath the footing to daylight. I filled the hole with gravel and put teh vapor barrier over that. (if this can't be done, put a lid on the sump pit)
d. After stopping incoming vapor from earth and through vents, and also controlling flowing water, I put a 70 pint per day dehumidifer inside the crawl space. (I've since added a second backup dehumidifer since the first one I purchased did not have the automatic on that is necessary after a power failure).

My crawlspace is real comfortable to be in now, dry and cool!


ps;
Another thing that needs to be controlled properly is the fan that brings air through ducts. The air conditoner needs to cycle on and off in order for condensate to drain properly. When the fan stops frost built up on the coil melts then it drains downward to be collected in a pan inside the air handler, then out through the drain pipe.
I made the mistake of leaving my thermostat's fan at "on" instead of "auto". The fan running continuiously was blowing liquid condensate into the ductwork, not allowing to drain properly.
this screams problems. you should not be blowing condensate off the coil into your supply ductwork under any circumstances, nor should you have frost/ice build-up.
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Old 08-12-2020, 03:01 PM   #5
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Re: ongoing humidity problem


Quote:
Originally Posted by u3b3rg33k View Post
this screams problems. you should not be blowing condensate off the coil into your supply ductwork under any circumstances, nor should you have frost/ice build-up.
Parts of what you say is correct.

Condensate should not blow, that is what I said was a problem.

Light frost on a AC cooling coil when the compressor is running is not unusual. It is normal when humid air passes through the coil. That frost melting when the AC fan cycles off is how condensate is created.

Frost buildup that gets heavy enough that it blocks airflow is a problem that needs attention. Either air flow is restricted or refrigerant level is low.

The problem I had was that the fan was running continuiously, not frost buildup. When the compressor cycled off, the fan kept pushing air through, taking moisture from the coil. That was operator error, not a malfunction.

Last edited by AWWarn; 08-12-2020 at 03:22 PM.
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Old 08-12-2020, 05:37 PM   #6
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Re: ongoing humidity problem


A comfort cooling evap coil, should NEVER frost up. If it does, something is wrong.


Condensate is created b the coil's temp being below dew point, and the moisture vapor "condensing", on it.
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Old 08-14-2020, 02:04 PM   #7
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Re: ongoing humidity problem


Quote:
Originally Posted by AWWarn View Post
Parts of what you say is correct.

Condensate should not blow, that is what I said was a problem.

Light frost on a AC cooling coil when the compressor is running is not unusual. It is normal when humid air passes through the coil. That frost melting when the AC fan cycles off is how condensate is created.

Frost buildup that gets heavy enough that it blocks airflow is a problem that needs attention. Either air flow is restricted or refrigerant level is low.

The problem I had was that the fan was running continuiously, not frost buildup. When the compressor cycled off, the fan kept pushing air through, taking moisture from the coil. That was operator error, not a malfunction.
this is an incorrect assumption. your coil should not have a surface below 32F. AC systems produce condensate continuously, cycling off is not required.
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