House is 2300 sq foot and built 7 years ago. Attic is foam the walls are cellulose I believe.

Ac is a Comfortmaker and I have had it worked on at least 4 seasons. It eats capacitors and the latest is that it quit cooling.

Teck found a pin hole leak in the evap coil and charged with freon to 5 lbs. as a bandaid.

House is now cooling, but still humid. AC has been repaired for 24 hours and running at 73F.

My house has always been humid in the 60-70% range and I never have been able to figure out why.

What is your current interior humidity?

Mine is 52 right now.

Humidity is removed by the air being cooled below dew point and then reheated. When the air is at dew point, the molecule is at 100 percent rh. This air will now squeeze out the water like a sponge and deposit that as condensation on your coil. More dehumidification for every degree below dewpoint you can get that cold air.
A bigger coil can help remove more rh. Colder air does more for this.
Your AC is about to [censored] out on you. A pin hole leak is just going to grow.

Mine is at 84 rh now at 71 deg outside rh is 91

I will add, the better your house is insulated, the higher your rh in your house. Ambient heat load is required to remove rh. If your AC cycles off often, you will build rh unless you are cooling to 45 degree supply air, which is doubtful, because you do not have the reheat factor.

58 here

Is it possible the unit is oversized? To big of a unit short cycles and dont have time to get the humidity out.

A lady just posted on our subdivision face book page about humidity level in her new house she had just built. Builder was trying to BS her saying 60-65 percent Humidity was normal. Normal If you want to grow mold. Humidity in my house yesterday was 49 according to my thermostat with outside Humidity at 80 percent.

Most units are undersized or on the borderline of being undersized. Fan speeds are ran high to move air to compensate for being undersized or near. Which causes high humidity. You hear the stories about houses being to tight this and that. A properly sized unit with returns sized correctly, set up right will knock a lot of humidity out of the air. I’ve had fan speed dropped on a couple houses I’ve lived in to get humidity down.

It’s humid here on the coast but if your AC system is right it will knock the humidity.

I’m not an AC expert but I spent my whole career doing process control in Refineries, Chem Plans etc. Principals are all the same. So is common sense.

They probably oversized the unit and it’s not running enough. Foam houses are tricky.

Mine shows to be 49% right now T-stat set at 77 during the day will drop later on the program.

Still at 68%. AC has not come on yet today. Was set for 73 overnight and the Ecobee changes to 75 at 7AM. Sitting at 74 still.

Foam insulated homes don’t need the same size AC that non-foamed homes do. We are in a foam insulated home, and when the HVAC guy sized the AC/heat pump, his recommendation was way smaller than what I was expecting. I thought it would be way too small. It was dead on perfect. I keep the place at 71 degrees, and the humidity in the house runs at about 50%.

In the much larger home we had in Houston, I had problems getting the humidity down to around 50%, so I bought a dehumidifier - a big one. Once I got the water out of the drapes, carpet, and such as that ( it was a lot of water), I only had to run the dehumidifier every now and then. Nobody could tell me what size dehumidifier I needed, so I bought the biggest I could find.

Here in the country I bought a Honeywell dehumidifier for my barn workshop. Don’t buy a Honeywell. The thing was junk. A sensor went out, it could not be replaced, so I’d have had to buy a new one. Don’t buy a cheaply made dehumidifier.

At 70% humidity, there’s moisture in everything. It’ll take a while to get it out. Speaking from experience.

indoor, main room (30x40?) with 2 4 tons on 2 thermostats set at 72. this sensor gets some window heat.

Temperature
77.0°F
Humidity
57%
Dew Point
60.6°F
Feels Like
77.1°F



outdoor,

81.7°
Dew Point
74.9°F
From Yesterday
1.5
°F
Feels Like
88.1°F
humidity
80%
From Yesterday
5%

the foam is trapping the humidity

[quote=butch sanders]the foam is trapping the humidity [/quote

Is the foam on the ceiling or rafters?

51% here full foam wall and attic