Indoor humidity above 70%
 

This morning we received an email indicating that our indoor humidity was 76%. Since we are away this month we had our AC set 79. We lowered it to 77 and the humidity fell to 71%. Does that sound too high? Is there something wrong or can this happen from time to time?

It's too high. My thermostat is always set on 78 degrees, and my indoor humidity rarely exceeds 55 percent. Today, it is 44 percent, and it has ranged from 41 to 45 percent during the past 24 hours. And, I don't use any humidity control. I would have it checked by an HVAC company, but you may want to remeasure the humidity with another measuring device first. Is there a window or door opened, or do you have a broken window? Do you have a leak in the house with standing water? Those are some things that could cause high humidity.

Definitely too high and a real mold risk. We keep our A/C at 81 when not there and our humidity rarely exceeds 60%, and if it does it’s only by 1-2%. It’s a good idea to keep a dehumidifier in the home as a cheap insurance policy. We keep one on the kitchen counter during the humid summer months so it can drain into the sink and set it to only run when the relative humidity reaches 60%. Prolonged humidity above 70% needs to be addressed ASAP.

Another possibility is that the condensate drain is clogged and the supply air fan is sucking water into the house.

You’re mixing up Dew Point vs Humidity.

The long and short of it is that a “dew point” below 60 is what most people think of comfortable. The lower the number, the “drier” the air is. A dew point above 60 means more moisture in the air.

I believe you have it wrong
 

I think you have it wrong.
A dewpoint of 60F means that moisture forms on surfaces in your home at 60F. This is uncomfortable and has a relative humidity of 100 % which is high mold condition.

A relative humidity of 60 % means that the water content in the air in that house is 60% of the maximum water content that the air at that temperature can hold.

Probably all the recent thunderstorms?

After my comment I looked further to find comparisons for dewpoint (F) versus relative humidity (% at T)

Dewpoint considerations are consistent with Pondboy's Post
Dewpoint less than or equal to 55F is dry and comfortable range
Dewpoint of 55 to 65 F is becoming" sticky " range
Dewpoint over 65 is oppressive

To try to link dewpoint and relative humidity I found this comparison which includes the units of measure for typical recommended AC settings
If RH is 50% and indoor T = 80F the dewpoint would be 59 F.

Hope thos helps for comparison without having water contents and graphs.

Check the indoor RH again this afternoon when the air conditioning has cycled on/off several times. We had a foggy morning so it’s highly likely that your A/C did not run at all for several hours and the RH came up during that time.

Yes I would consider this too high; do you have a trusted neighbor that can inspect your house? I tend to agree with the above comments about the humidity being too high. This could be a malfunction in the AC system, possibly the thermostat. A backup in the drain line typically causes the AC to shut down. If the neighbor can arrange an inspection of the AC system, I would do that also.

We lowered the temperature and it is down to 67% but that still seems high. We have it looked at on Monday.

High humidity
 

We were snowbirds for a couple of years and had a similar experience with too high humidity.. One reason ours was high , I set the fan to run all the time. HVAC guy told me that’s a problem so I reset it to auto and the issue corrected itself. Hope that helps you.

Humidity too High
 

You may want to check your filters inside your home. Also a lot of people don't realize the outside condensing unit coils may need to be cleaned as well. Check condenser drain line to make sure it's free of debris and draining properly.

Another area to check. Is your air handler accessed from the garage? Check the air handler room for any condensation. I’ve seen bad door seals allow moist garage air into this room. Basically it’s like keeping a window open. The AC will never keep up removing all the moisture.

It is too high, glad you're getting it looked at. A few days above 70% is not a problem, but it can be an issue long term for sure.