Humidity issues

Paycheck · Jun 16, 2025

Looking for suggestions on how to lower humidity in the house.
12 year old house, 2 story 3200 sq ft. I’ve been here 5 years. New HVAC systems (two systems, one for each floor) 3 years ago(Bosch). 2 years ago I had the crawl space encapsulated and dehumidifier installed. Humidity stays around 50% in there. During the summer, the rest of the house wants to stay around 65% humidity. Can’t get it lower without running AC continuously. The crawl space does have some knee walls that need to be insulated. There is batt insulation in the floor above the crawl space, but it is cheap builder quality and not well done (batts are pushed up into the spans between joists and paper side against floor). No mold or water damage is noted in crawl space. I had one contractor tell me the lousy insulation is causing the issue and I should remove it (paper side should not be against floor). Original encapsulation folks said it didn’t need to be removed. I’m having trouble getting good info on what to do here. I’m tempted to pull out the old and see what happens. I don’t want to have to install a dehumidifier and run a drain line in the house.
On a side note, my floors in the house tend to run cold in the winter (and I hate cold feet).

Looking for suggestions, ideas, better questions to ask, and a few smart *** comments (gotta keep things entertaining

).

In central NC, btw

Immediate question is will removing the crappy insulation help?

PCustoms · Jun 16, 2025

So your crawlspace is encapsulated and dehumidified to 50%

Your interior is typically 65% with no dehumidifier.

What is your question?

Paycheck · Jun 16, 2025

How to lower the humidity in the house. I added that to the original post. Thanks.

PCustoms · Jun 16, 2025

Paycheck said:
How to lower the humidity in the house. I added that to the original post. Thanks.

I would run the AC or get a dehumidifier

Paycheck · Jun 16, 2025

PCustoms said:
I would run the AC or get a dehumidifier

I'm currently keeping the AC at 72-74 degrees. Don't want to run it colder. I understand that just running the fan only won't help (might make it worse). A whole house unit is an option, but since I have two separate systems would I need two dehumidifiers? A stand alone unit is nice, but I would want to set up a proper drain (no bucket brigade at 0 dark thirty). I'm hoping for a less expensive option before I go the whole house route.

bonneyman · Jun 16, 2025

Most newer (post 2010) are latent heat removal machines. The manufacturers figured out they could more easily reach the gov SEER ratings by switching to refrigeration that removed more moisture from the air than the older units. (Moisture in the air holds ALOT of heat). So - when humidity is high - their capacity is being used to remove that excess moisture. So your newer units should be able to do the job.

But I can understand you not wanting to run your units alot, as that bill could be excessive. Better use of your money is going through the house and sealing any air leaks that allow moist air in. Cheaper to prevent moisture infiltration than have to fight to remove it later. Also check the duct system. Just a little leakage in the ducts can have major impact on temp and humidity readings in the home.
Anything you can do to prevent excess heat infiltration can help as well. Window tinting, new weather stripping, shrubbery or bushes planted strategically to shield from sun, more insulation in and around the living space. And reduce opening doors to a minimum. Supermarkets have air doors at their entrances for a reason.

Paycheck · Jun 16, 2025

bonneyman said:
Most newer (post 2010) are latent heat removal machines. The manufacturers figured out they could more easily reach the gov SEER ratings by switching to refrigeration that removed more moisture from the air than the older units. (Moisture in the air holds ALOT of heat). So - when humidity is high - their capacity is being used to remove that excess moisture. So your newer units should be able to do the job.

But I can understand you not wanting to run your units alot, as that bill could be excessive. Better use of your money is going through the house and sealing any air leaks that allow moist air in. Cheaper to prevent moisture infiltration than have to fight to remove it later. Also check the duct system. Just a little leakage in the ducts can have major impact on temp and humidity readings in the home.
Anything you can do to prevent excess heat infiltration can help as well. Window tinting, new weather stripping, shrubbery or bushes planted strategically to shield from sun, more insulation in and around the living space. And reduce opening doors to a minimum. Supermarkets have air doors at their entrances for a reason.

I am planning on getting more blown in insulation in the attic spaces. It's not the best and has compacted over the years.

fitter30 · Jun 16, 2025

RH flows from higher to lower. If rh is 65% @ 70° as temp rises rh will drop. Don't say where your at. Call your electric company see if they offer a energy audit that includes a blower door test there usually reasonable. That test will tell how tight the house is. If the ac unit is oversized its not running long enough to pull rh out. Bath rooms need timers on the exhaust fans to run at least 30 minutes after a shower or bath. Kitchen hood needs to run when cooking. My house has a encapsulated crawl space 50 pint dehumidifier and 50 pint in the space Ozark Missouri. Have replaced all the windows and doors used window spray foam in all the electric boxes. House isn't insulated very well. House needs to be under 50% to be healthy. Need a probe type thermometer measure temp of return air at filter and 18"-24" from ac coil in furnace what is the difference? Should be 18° - 24° normal is 20° ac should be running for at least 20 minutes. AC units the air temp is the easier part the rh is where the work is.

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Paycheck · Jun 16, 2025

fitter30 said:
RH flows from higher to lower. If rh is 65% @ 70° as temp rises rh will drop. Don't say where your at. Call your electric company see if they offer a energy audit that includes a blower door test there usually reasonable. That test will tell how tight the house is. If the ac unit is oversized its not running long enough to pull rh out. Bath rooms need timers on the exhaust fans to run at least 30 minutes after a shower or bath. Kitchen hood needs to run when cooking. My house has a encapsulated crawl space 50 pint dehumidifier and 50 pint in the space Ozark Missouri. Have replaced all the windows and doors used window spray foam in all the electric boxes. House isn't insulated very well. House needs to be under 50% to be healthy. Need a probe type thermometer measure temp of return air at filter and 18"-24" from ac coil in furnace what is the difference? Should be 18° - 24° normal is 20° ac should be running for at least 20 minutes. AC units the air temp is the easier part the rh is where the work is.

https://www.amazon.com/Century-Countdown-Digital-5-10-20-30-45-60mins-Required/dp/B0184OYJN2/?tag=atomicindus08-20

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Actually I'm in the process of scheduling the blower door/duct leak test. Did it on my last house, should've had it done here when I moved in. In the Raleigh area.
The higher to lower bit is one reason why I'm curious about pulling the batts in the crawl space.

Codyboy · Jun 17, 2025

Been there 5 years and new units? More tonnage than than the previous units?
Was there humidity problems before?

I had an issue with my old unit and the blower speed wasn't right. The house got cold really quick but never ran long enough to actually do anything with the humidity issue.

mm08822 · Jun 17, 2025

fitter30 said:
RH flows from higher to lower. If rh is 65% @ 70° as temp rises rh will drop. Don't say where your at. Call your electric company see if they offer a energy audit that includes a blower door test there usually reasonable. That test will tell how tight the house is. If the ac unit is oversized its not running long enough to pull rh out. Bath rooms need timers on the exhaust fans to run at least 30 minutes after a shower or bath. Kitchen hood needs to run when cooking. My house has a encapsulated crawl space 50 pint dehumidifier and 50 pint in the space Ozark Missouri. Have replaced all the windows and doors used window spray foam in all the electric boxes. House isn't insulated very well. House needs to be under 50% to be healthy. Need a probe type thermometer measure temp of return air at filter and 18"-24" from ac coil in furnace what is the difference? Should be 18° - 24° normal is 20° ac should be running for at least 20 minutes. AC units the air temp is the easier part the rh is where the work is.

https://www.amazon.com/Century-Countdown-Digital-5-10-20-30-45-60mins-Required/dp/B0184OYJN2/?tag=atomicindus08-20

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By ac unit, do you mean the vap coil is too big?

u3b3rg33k · Jun 17, 2025

Paycheck said:
How to lower the humidity in the house. I added that to the original post. Thanks.

introduce less moisture (people add moisture, so does allowing uncontrolled airflow into the building).
remove the moisture (dehumidifier), control the ventilation (air sealing, ERV for balanced ventilation).

batt insulation will have no effect on moisture unless it's wet from leaks.

Paycheck · Jun 17, 2025

Codyboy said:
Been there 5 years and new units? More tonnage than than the previous units?
Was there humidity problems before?

I had an issue with my old unit and the blower speed wasn't right. The house got cold really quick but never ran long enough to actually do anything with the humidity issue.

Cheap builder quality units. They had issues and I elected to replace both with the Bosch units. They are sized correctly (3 tons each, each floor is a tad over 1500 sq ft) I don’t know what size the old units were. In my case I wish I had more airflow. Takes forever to cool/heat the house (might be an insulation problem). But that is a good point, something to add to the list to check.

Innovate1 · Jun 17, 2025

Less insulation will cause the AC to run more - that will pull out more humidity (all other things (mainly air leakage) being equal). But your power bill will be higher. How much does your AC run - amount of run time to amount of off time? If the AC is too big (BTUs or tons) it will cool the air quickly without removing much humidity. Sounds like air leakage issues. Maybe water leaks somewhere you may not know about - leaky roof or plumbing?

TRWham · Jun 17, 2025

Paycheck said:
Cheap builder quality units. They had issues and I elected to replace both with the Bosch units. They are sized correctly (3 tons each, each floor is a tad over 1500 sq ft) I don’t know what size the old units were. In my case I wish I had more airflow. Takes forever to cool/heat the house (might be an insulation problem). But that is a good point, something to add to the list to check.

This is the opposite of what you need. If you slow the blowers, it reduces the coil temperature and allows the units to remove more humidity. It also leads to longer run time for a given dry bulb temperature set-point so you get even more dehumidification.

u3b3rg33k · Jun 17, 2025

TRWham said:
This is the opposite of what you need. If you slow the blowers, it reduces the coil temperature and allows the units to remove more humidity. It also leads to longer run time for a given dry bulb temperature set-point so you get even more dehumidification.

not necessarily on the inverter units. The BOVA/B units target an indoor coil temp and will adjust their compressor output (25-110%) to maintain that.

I believe there's a dip switch on the condenser that will lower indoor coil temps for better drying.

PCustoms · Jun 17, 2025

Paycheck said:
They are sized correctly (3 tons each, each floor is a tad over 1500 sq ft)

That's not really how units are sized though....

IMHO you should worry less about the insulation/air sealing (as this is a minimal part of the humidity puzzle) and let the system run. If you set it to 70F and turn it on what do you get to?

What are the outdoor temps and humidity when you are mid 70's and 65% inside?

TRWham · Jun 17, 2025

u3b3rg33k said:
not necessarily on the inverter units. The BOVA/B units target an indoor coil temp and will adjust their compressor output (25-110%) to maintain that.

I believe there's a dip switch on the condenser that will lower indoor coil temps for better drying.

You can get there either way, but regardless, the sensible heat ratio must be lower if your main goal is to reduce humidity. If you increase compressor capacity while maintaining airflow, you have increased total capacity, and that is not really going to help if you are already driving the dry bulb lower than you want in an effort to wring out water. Dry and warmer beats cold and wet every time.

u3b3rg33k · Jun 17, 2025

TRWham said:
You can get there either way, but regardless, the sensible heat ratio must be lower if your main goal is to reduce humidity. If you increase compressor capacity while maintaining airflow, you have increased total capacity, and that is not really going to help if you are already driving the dry bulb lower than you want in an effort to wring out water. Dry and warmer beats cold and wet every time.

However you go about it I don't think OP is getting a dryer house without a compressor running somewhere. if the air handler has a low airflow feature, the bosch is a good pairing, because it can reduce capacity to not ice itself up.

it would appear some of the BVA airhandlers have the feature, so OP would need to have that unit already, and get a thermostat that supports the feature.

Jeepster04 · Jun 17, 2025

I'm surprised you have humidity issues inside of the house. What are you using to measure the humidity and are you sure its accurate? My house is small and my A/C is sized appropriately, but I have no issues keeping it in the 50% range inside of the house with a cheap dehumidifier in my crawl space and its absolutely not sealed up at all. It stays around 65-70% RH in my crawl space but its in the low 60F temps. Are your bathroom vents vented outside? Do you always use them when taking showers? Anything else in the house causing moisture?

The paper on the insulation should always face the living space, so paper towards the floor is correct. No, removing the insulation WILL NOT help with your issues.

justinjoyal · Jun 19, 2025

Paycheck said:
They are sized correctly (3 tons each, each floor is a tad over 1500 sq ft)

What exactly tells you they are sized correctly ?

For example, my system is sized correctly and I cool roughly 2900 total sq ft with a 2-ton heatpump. So saying it is sized correctly based off of square footage is meaningless.

Paycheck · Jun 23, 2025

justinjoyal said:
Innovate1 said:

Less insulation will cause the AC to run more - that will pull out more humidity (all other things (mainly air leakage) being equal). But your power bill will be higher. How much does your AC run - amount of run time to amount of off time? If the AC is too big (BTUs or tons) it will cool the air quickly without removing much humidity. Sounds like air leakage issues. Maybe water leaks somewhere you may not know about - leaky roof or plumbing?

Click to expand...

It tends to run quite a while to change the temp more than a couple degrees. I do have weak airflow in the far parts of the house, but it still takes a while. I'll have to time it and post.

PCustoms said:

That's not really how units are sized though....

IMHO you should worry less about the insulation/air sealing (as this is a minimal part of the humidity puzzle) and let the system run. If you set it to 70F and turn it on what do you get to?

What are the outdoor temps and humidity when you are mid 70's and 65% inside?

Click to expand...

It will get to 70, just not quickly. I've been running both at 72-74 this month to see what happens. Humidity is still 64-66% when they run. Right now it's 93 degrees with 60% humidity outside. Both thermostats set to 74 and holding, downstairs humidity is 64% and upstairs is 65%. Crawl space is 84 degrees and 41%.

Jeepster04 said:

I'm surprised you have humidity issues inside of the house. What are you using to measure the humidity and are you sure its accurate? My house is small and my A/C is sized appropriately, but I have no issues keeping it in the 50% range inside of the house with a cheap dehumidifier in my crawl space and its absolutely not sealed up at all. It stays around 65-70% RH in my crawl space but its in the low 60F temps. Are your bathroom vents vented outside? Do you always use them when taking showers? Anything else in the house causing moisture?

The paper on the insulation should always face the living space, so paper towards the floor is correct. No, removing the insulation WILL NOT help with your issues.

Click to expand...

Ecobee thermostats backed up[ with thermopro sensors. I have a portable AC unit in my garage and it's showing 84 degrees and 56% (90 outside). The humidity difference there is interesting. 12 year old house, baths properly ventilated. I got a third opinion from a large crawl space company and they said pull the insulation. Since it's poorly done I think I'll remove it and see what happens. I can always put something better back in.

justinjoyal said:

What exactly tells you they are sized correctly ?

For example, my system is sized correctly and I cool roughly 2900 total sq ft with a 2-ton heatpump. So saying it is sized correctly based off of square footage is meaningless.

Click to expand...

For example, my system is sized correctly and I cool roughly 2900 total sq ft with a 2-ton heatpump. So saying it is sized correctly based off of square footage is meaningless.

I'm going by the one ton/500 sq ft rule (courtesy of YouTube U). Also going by what my HVAC company says. What measure do you use? I have roughly 1750' upstairs and 1550' downstairs. Both units are 3 ton.
And I believe the dip switch that folks have mentioned has been switched.
Thanks for all the input and questions folks!

PCustoms · Jun 23, 2025

Paycheck said:
I'm going by the one ton/500 sq ft rule (courtesy of YouTube U). Also going by what my HVAC company says. What measure do you use? I have roughly 1750' upstairs and 1550' downstairs. Both units are 3 ton.
And I believe the dip switch that folks have mentioned has been switched.

Thanks for all the input and questions folks!

Google manual J

Paycheck · Jun 23, 2025

Innovate1 said:
Less insulation will cause the AC to run more - that will pull out more humidity (all other things (mainly air leakage) being equal). But your power bill will be higher. How much does your AC run - amount of run time to amount of off time? If the AC is too big (BTUs or tons) it will cool the air quickly without removing much humidity. Sounds like air leakage issues. Maybe water leaks somewhere you may not know about - leaky roof or plumbing?

It tends to run quite a while to change the temp more than a couple degrees. I do have weak airflow in the far parts of the house, but it still takes a while. I'll have to time it and post.

Paycheck · Jun 23, 2025

PCustoms said:
That's not really how units are sized though....

IMHO you should worry less about the insulation/air sealing (as this is a minimal part of the humidity puzzle) and let the system run. If you set it to 70F and turn it on what do you get to?

What are the outdoor temps and humidity when you are mid 70's and 65% inside?

It will get to 70, just not quickly. I've been running both at 72-74 this month to see what happens. Humidity is still 64-66% when they run. Right now it's 93 degrees with 60% humidity outside. Both thermostats set to 74 and holding, downstairs humidity is 64% and upstairs is 65%. Crawl space is 84 degrees and 41%.

Paycheck · Jun 23, 2025

Jeepster04 said:
I'm surprised you have humidity issues inside of the house. What are you using to measure the humidity and are you sure its accurate? My house is small and my A/C is sized appropriately, but I have no issues keeping it in the 50% range inside of the house with a cheap dehumidifier in my crawl space and its absolutely not sealed up at all. It stays around 65-70% RH in my crawl space but its in the low 60F temps. Are your bathroom vents vented outside? Do you always use them when taking showers? Anything else in the house causing moisture?

The paper on the insulation should always face the living space, so paper towards the floor is correct. No, removing the insulation WILL NOT help with your issues.

Ecobee thermostats backed up[ with thermopro sensors. I have a portable AC unit in my garage and it's showing 84 degrees and 56% (90 outside). The humidity difference there is interesting. 12 year old house, baths properly ventilated. I got a third opinion from a large crawl space company and they said pull the insulation. Since it's poorly done I think I'll remove it and see what happens. I can always put something better back in.

Paycheck · Jun 23, 2025

justinjoyal said:
What exactly tells you they are sized correctly ?

For example, my system is sized correctly and I cool roughly 2900 total sq ft with a 2-ton heatpump. So saying it is sized correctly based off of square footage is meaningless.

Paycheck · Jun 23, 2025

Sorry for the duplicate replies. My ability to mutiquote isn't that hot it appears.

Paycheck · Jun 23, 2025

PCustoms said:
Google manual J

Thanks for that. I wonder if that was ever used and if the builder has a copy. I don't know who did the original.

Two Door · Jun 23, 2025

Paycheck said:
Thanks for that. I wonder if that was ever used and if the builder has a copy.

Most likely no and no.

dscheidt · Jun 24, 2025

Paycheck said:
Thanks for that. I wonder if that was ever used and if the builder has a copy. I don't know who did the original.

If it wasn't required when the house was built, the answer is no, it wasn't done. I There are plenty of houses that have woefully oversized units, as built. But there are also lots where it was about right.

f it was required, it should be in the plans. Of course, whether anyone has those is an entirely different thing.

chinboys · Jun 24, 2025

Laws of physics and thermodyanamics are in play here for your relative humidity interior problem.
In short, you have a leaky and perhaps an inadequate insulated house... convection and conduction with some radiation heat transfer are the problems.
Heat always transfers toward the cold (outside to the inside of your home) . And osmosis always drives higher moisture content air into space where there is less relative humidity.

An air door pressurized test will highlight your major air leaks.
An infrared survey will highlight your heat infiltration.

If you could do it all over again...
1. vapor barrier the external shell of the home
2. add maximum insulation to the walls and attic
3. add a vapor barrier on the inside shell of the home (to prevent mold from growing inside your wall cavities )
4. stop all air leaks
5. air circulation, keeping the air handler fan continously on

An oversized AC will short cycle when it needs to run long enough to remove the latent heat (hot air with high relative humidity).
Also the latent heat removal is where the spend in electrical cost occurs.
Once the latent heat is removed is when the temperature will drop (sensible heat) using less energy.

TRWham · Jun 24, 2025

chinboys said:
...
Once the latent heat is removed is when the temperature will drop (sensible heat) using less energy.

That's not how dehumidifying air by mechanical cooling works. It is not the same as condensing steam, for example, which would happen as you describe. In order to remove moisture from air, you must first lower its dry bulb temperature to the dew point, and that is entirely a sensible process. Once the air is at the dew point, any additional cooling will condense moisture, and simultaneously lower dry bulb, wet bulb and dew point.

Paycheck · Jul 14, 2025

Thanks folks for the help and suggestions.
A couple updates.
Blower door test done, it came out better than I thought. Other than some obvious holes that should be fixed shortly it did pretty good.
I found a setting on my Ecobee thermostats that opened up a humidity setting (overcool if I remember correctly). Seems to have dropped RH a couple points.
I suspect the thermostat readings are a bit high, I need to calibrate them with a known device.
My units were set for 3 tons, had the installer come out and set them to 2 tons. We'll see how it goes. They did have pics of the original units and the upstairs was 3 ton, downstairs was 2.5 ton.
I will check with the builder to see if they have a copy of the Manual J.
I will be adding insulation to the crawl space and the attic space (cellulose top off in attic, rim joist/knee wall sealing in crawl space). Remove the fiberglass batts in the crawl space. If I need to replace them down the road, well, that will be down the road.

I'll keep ya posted.

Paycheck · Jul 29, 2025

Update. Between finding some better settings on the Ecobee thermostats and setting the Bosch units to 2 ton instead of 3 ton, there has been a marked improvement. With the heat outside I have been able to keep the humidity at 59-60% with temps in the mid to upper 70's. Adding insulation should help as well.
Thanks folks!

Mismail · Aug 4, 2025

Paycheck said:
Looking for suggestions on how to lower humidity in the house.
12 year old house, 2 story 3200 sq ft. I’ve been here 5 years. New HVAC systems (two systems, one for each floor) 3 years ago(Bosch). 2 years ago I had the crawl space encapsulated and dehumidifier installed. Humidity stays around 50% in there. During the summer, the rest of the house wants to stay around 65% humidity. Can’t get it lower without running AC continuously. The crawl space does have some knee walls that need to be insulated. There is batt insulation in the floor above the crawl space, but it is cheap builder quality and not well done (batts are pushed up into the spans between joists and paper side against floor). No mold or water damage is noted in crawl space. I had one contractor tell me the lousy insulation is causing the issue and I should remove it (paper side should not be against floor). Original encapsulation folks said it didn’t need to be removed. I’m having trouble getting good info on what to do here. I’m tempted to pull out the old and see what happens. I don’t want to have to install a dehumidifier and run a drain line in the house.
On a side note, my floors in the house tend to run cold in the winter (and I hate cold feet).

Looking for suggestions, ideas, better questions to ask, and a few smart *** comments (gotta keep things entertaining).

In central NC, btw

Immediate question is will removing the crappy insulation help?

Yes, removing the old, improperly installed insulation is the right move, as it's likely trapping moisture in your subfloor and preventing your dehumidifier from effectively drying out the area. You should also get those knee walls insulated, as they're another direct path for humid air to enter your house.

Paycheck · Apr 28, 2026

A quick update. Started learning more about HVAC and found a couple local home quality pros (along with a few online ones) and have been making progress. Had a Manual J done (thanks for the input folks) and oversized is an understatement. I have two three ton units and I only need one three ton for the entire house. One of the folks I've been working with has the same systems in his house and we made sure the units were reset to two ton (Bosch) and did some tweaking to the Ecobee thermostats that will hopefully help out. During this process I found out that although I have two stage systems, they were only wired up as single stage. Got that corrected as well. Next job is to go through the ducting and make some improvements there. I also added some insulation in the attic and behind one of the knee walls.
The lack of rain here this year has kept the outdoor humidity down so I'll have to wait a bit to see if what we've done so far works enough to keep me from replacing systems.
I appreciate all the help and input!

fitter30 · Apr 29, 2026

Dehumidifier has to set a 40%. 50% RH will grow mold. Your electric company might offer a energy audit that includes a blower door test. This test tell how tight the house is. Humidity RH flows from hi to low just like heat. If te house isn't sealed very well it will pull RH right in and the systems aren't running long enough. Is the crawl space sealed? Could also add another dehumidifier to our duct system or use a portable with a pump to put it in a sink or bathtub. With a probe style thermometer want to take return temp and discharge air temp readings 18" from ac coil. The difference should be between 18° -24° f 20° is normal design.

Paycheck · Apr 29, 2026

Blower door was 2820 CFM@50 Pascals (prior to sealing up a large leak at the fireplace), 6 ACH. Crawl space is sealed and dehu set at 50%. Don't remember the discharge temp (it's been checked, tech didn't mention anything abnormal. Right now, I would be happy with 50% with what I have. We'll have to see how the summer goes and work from there.

fitter30 · Apr 29, 2026

mm08822 said:
By ac unit, do you mean the vap coil is too big?

Hottest days in summer does the units cycle or run almost constantly? By checking the temperature drop across the furnace/ air handler the higher the drop the more RH is being pulled out. Can't go over 24° like to stay in the range of 22°. By dropping blower speed by one speed and give it 30 minutes of run time before checking it.

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