Humidity seems way too high

[dan sw fl]

A BLOWER DOOR TEST will address the Root Cause of high humidity IMO.

https://energyconservatory.com/appli...-of-buildings/

One would anticipate a Very Tight home is the problem.
THIS TEST will reveal just HOW TIGHT.
__ Determining a Specific infiltration rate IS YOUR NEXT BEST STEP.

_ ? _ CFM 50
_ _ ? _ ACH50

[pidgeynerd]

A BLOWER DOOR TEST will address the Root Cause of high humidity IMO.

https://energyconservatory.com/appli...-of-buildings/

One would anticipate a Very Tight home is the problem.
THIS TEST will reveal just HOW TIGHT.
__ Determining a Specific infiltration rate IS YOUR NEXT BEST STEP.

_ ? _ CFM 50
_ _ ? _ ACH50

I found the blower door test result that was done as part of my final home inspection in Sep 2017. It only has an ACH50 result as 2.01. Is this good or bad? It was marked "pass". What should I do if I don't have a CFM50 result?

[teddy bear]

I found the blower door test result that was done as part of my final home inspection in Sep 2017. It only has an ACH50 result as 2.01. Is this good or bad? It was marked "pass". What should I do if I don't have a CFM50 result?

Here is good summary of blower door test. Your home is demonstrating how a very air tight home works. On a cold windy day, this home gets by without mechanical fresh air. But with the calm winds or stack effect pressure, this should be mechanically ventilated when occupied.

https://www.homeconstructionimprovem...-test-results/

Also keep in mind that you have exhaust devices that need make-up air to function properly. A fresh air change in 4-5 hours is usually adequate.

Most of us want a house like you have because the home seldom over-vents which is ideal.

After getting the a/c adjusted to max the dehumidification during sensible cooling runs, install a 155 pint per day dehumidifier (like an Ultra-Aire XT155H) with the fresh air option. Connect the dehumidifier return to the open part of the home plus an 8" fresh air duct connected to exterior of the home. The supply of the dehumidifier ideally is routed to the a/c cold air duct. Include a DEH3000 controller to provide fresh air when occupied and maintain the desired %RH. A/c setup and dehu connections are critical.
With these changes, you will be pleased with the indoor air quality, comfort, and low cost of conditioning the home.
Keep us posted.
Regards Teddy Bear

[coolcoil]

Update----

I just read that having your fan switched to "on" is actually bad for reducing humidity. I switched it to auto, let's see if that makes a difference.

Doesn't anyone know if this is a legit problem with on vs auto on the fan?

Yes, it is. Here is an excellent article on the topic. Read the comments too. A lot of very knowledgeable people contributed.

https://www.energyvanguard.com/blog/...-Make-You-Sick

[teddy bear]

Yes, fan "on" will make your indoor %RH higher during short cycling a/c cooling and high outdoor dew points. Fresh air ventilation makes your indoor %RH higher when the dew point high is higher. Occupants make indoor %RH higher. This is true if you do not a method of supplementing your a/c's dehumidification.
The most important part of the info shows that this a/c setup was not able to maintain <50%RH with the fan "auto" mode at any time. The Mean %RH was 58% at best.
If this a/c was setup ideally to remove moisture with 370 cfm of air flow through the cooling, removing 3 lbs. of moisture per ton or a .75/.25 S/R ratio, The removal 10 lbs. of moisture with a 3 ton a/c during peak cooling would reduced the moisture levels to <50%RH. In other words with an ideal a/c setup, would provide a much better overall humidity results.
Adding a small whole house dehumidifier to a whole house dehumidifier will provide provide a steady 48-53%RH.
Here is why I am make a case for being to maintain 50%RH throughout the 3 mild seasons of the year.
A healthy, comfortable home must have a steady, filtered fresh air change
in 3-5 hours depending on the pollutant levels and oxygen needs of the family when occupied. Also the a/c system needs some dry time interrupt the growth cycle of biologicals in the damp cool ducts supply cool air to the home.The other benefit is the mixing of hot/cool areas of the while the t-stat is satisfied

The author of the sited article is recent times is recommending dehus in green grass climates.

In summary:
Get the a/c setu to provide a 75/25 S/R ratio. This will get to<50% any time the a/c is operating More than 30 minutes an hour. Can be single or VS a/c.

Add a adequate sized whole house dehumidifier, like Ultra-Aire sized to your desired humidity levels during evenings and rainy days
Include the fresh air option if you want adequate fresh air change during calm winds and mild temperatures with closed windows and occupancy.
This new thinking for most in the a/c trades. Good duct work and a moderating tight home is needed. This is needed in green grass climates to handle current weather variables and the meet the demands of our current customers.
Why not? It is comfortable, healthy but cost a little more.
Discussion?
Regards Teddy Bear

[teddy bear]

A couple homes dehumidifiers.
The year long data is from a house near Houston.
No fresh air and fan "auto".
The FL. house is the for March this year with fresh air when occupied. The two high days had the patio doors open during the day.
Data from Netatmo
Regards TeddY Bear

[pidgeynerd]

Yes, fan "on" will make your indoor %RH higher during short cycling a/c cooling and high outdoor dew points. Fresh air ventilation makes your indoor %RH higher when the dew point high is higher. Occupants make indoor %RH higher. This is true if you do not a method of supplementing your a/c's dehumidification.
The most important part of the info shows that this a/c setup was not able to maintain <50%RH with the fan "auto" mode at any time. The Mean %RH was 58% at best.
If this a/c was setup ideally to remove moisture with 370 cfm of air flow through the cooling, removing 3 lbs. of moisture per ton or a .75/.25 S/R ratio, The removal 10 lbs. of moisture with a 3 ton a/c during peak cooling would reduced the moisture levels to <50%RH. In other words with an ideal a/c setup, would provide a much better overall humidity results.
Adding a small whole house dehumidifier to a whole house dehumidifier will provide provide a steady 48-53%RH.
Here is why I am make a case for being to maintain 50%RH throughout the 3 mild seasons of the year.
A healthy, comfortable home must have a steady, filtered fresh air change
in 3-5 hours depending on the pollutant levels and oxygen needs of the family when occupied. Also the a/c system needs some dry time interrupt the growth cycle of biologicals in the damp cool ducts supply cool air to the home.The other benefit is the mixing of hot/cool areas of the while the t-stat is satisfied

The author of the sited article is recent times is recommending dehus in green grass climates.

In summary:
Get the a/c setu to provide a 75/25 S/R ratio. This will get to<50% any time the a/c is operating More than 30 minutes an hour. Can be single or VS a/c.

Add a adequate sized whole house dehumidifier, like Ultra-Aire sized to your desired humidity levels during evenings and rainy days
Include the fresh air option if you want adequate fresh air change during calm winds and mild temperatures with closed windows and occupancy.
This new thinking for most in the a/c trades. Good duct work and a moderating tight home is needed. This is needed in green grass climates to handle current weather variables and the meet the demands of our current customers.
Why not? It is comfortable, healthy but cost a little more.
Discussion?
Regards Teddy Bear

Teddy, does S/R Ratio stand for Sensible Heat Ratio? I just want to make sure I say the right thing when talking to the contractor.

[teddy bear]

Teddy, does S/R Ratio stand for Sensible Heat Ratio? I just want to make sure I say the right thing when talking to the contractor.

Yes. All a/cs need a significant amount of sensible cooling to remove any latent or moisture frrom a home. Asjust the air flow to the 75% sensible cooling. This will get you 3 lbs. of moisture per ton of cooling per hour.
As you see, during low sensible cooling loads, dehumidification from the a/c.
Keep us posted on your techs comments.
REgards Teddy Bear

[pidgeynerd]

Yes. All a/cs need a significant amount of sensible cooling to remove any latent or moisture frrom a home. Asjust the air flow to the 75% sensible cooling. This will get you 3 lbs. of moisture per ton of cooling per hour.
As you see, during low sensible cooling loads, dehumidification from the a/c.
Keep us posted on your techs comments.
REgards Teddy Bear

Teddy,

Some junior tech came out and didn't know anything about the sensible cooling ratio or how to even adjust it. All he did was lower by fan speed from high to medium. He said this would the AC run longer somehow which would allow for more moisture to be pulled out. My builder is covering the charges for the service so it doesn't matter to me that someone else may have to come out again to look at this.

However, was it a good idea to change the fan speed as a first step? Also, how exactly does one change the sensible cooling ratio? I'd like to know so I can explain/understand it better.

[hvacvegas]

Teddy,

Some junior tech came out and didn't know anything about the sensible cooling ratio or how to even adjust it. All he did was lower by fan speed from high to medium. He said this would the AC run longer somehow which would allow for more moisture to be pulled out. My builder is covering the charges for the service so it doesn't matter to me that someone else may have to come out again to look at this.

However, was it a good idea to change the fan speed as a first step? Also, how exactly does one change the sensible cooling ratio? I'd like to know so I can explain/understand it better.

Dropping the airflow may be the proper thing to do.
You will get more latent removal that way.
The problem is did he lower it too much?

The way to change the ratio is to change the blower speed, as he did. Kudos to him.

Sounds like you have a base model furnace, that limits the amount of modifications that can be made.

[dan sw fl]

INCREASE S.H.R.
by decreasing Relative Humidity.

THE BEST method to > S.H.R. would be to move to Arizona.

[teddy bear]

Teddy,

Some junior tech came out and didn't know anything about the sensible cooling ratio or how to even adjust it. All he did was lower by fan speed from high to medium. He said this would the AC run longer somehow which would allow for more moisture to be pulled out. My builder is covering the charges for the service so it doesn't matter to me that someone else may have to come out again to look at this.

However, was it a good idea to change the fan speed as a first step? Also, how exactly does one change the sensible cooling ratio? I'd like to know so I can explain/understand it better.

After checking the a/c functions, mainly the refrigerant charge/expansion devide and air flow at the condenser, adjust the cooling coil air flow to get the desired coil temperature which controls sensible/latent ratio. The a/c blower speed, air filter restriction and damppering are the main tools techs use. Techs need extended training to do these things. These are just few suggestion for techs to get extended training on.
Your tech may have been right on track. Hopefully, he measured the effect of his adjustments. Some will try anything to see if it helps, not ideal. Like many of us have done, I call it learning it the hard way.
Keep us posted.
Regards Teddy Bear