My new home came with a fresh air intake system which I have never had in any home I've lived in. I have been noticing that it runs for a certain amount of time after my furnace or A/C runs. Currently the weather is really cool and humid (50-75 F with 70-95% RH), so my A/C or furnace do not run much as it is to help dehumidify the house. My master bedroom has been consistently around 55-60% humidity for weeks, and sometimes at night it can spike as high as 63%.

It seems like with outdoor air being humid, when the furnace or A/C does run to bring down the humidity, the fresh air intake then brings the humidity back up. Are there any solutions to this other than turning off the fresh air intake completely or running a dehumidifier during this type of weather?

Dehumidifier would be the only solution I can think of.

Thanks for the thread topic, about to move and it has an Aprilaire system also so I will be aware of this issue

That's a good point. I wasn't told how it works by the builder. I think mine may be set to 30 minutes. I'll see if setting to 15 minutes helps.

Changing my intake to 15 minutes did nothing last night. It was 64 degrees outside and 99% humidity all night, so the A/C wasn't running. In the morning my master bathroom was 62% and the master bedroom next to it was 60%. Most of the rest of the house was around 58%.

Are these humidity levels just expected with weather like that?

First I've heard of this fresh air intake for residential. Commercial has had it for a long time, but that's different. Most residential has enough natural infiltration that you don't need a fresh air intake. When you turn on the fart fans or the kitchen exhaust, do you also have to turn on a fresh air fan to make up the exiting air? No. Why not? That's because the air being pushed out of the house is easily brought in elsewhere through infiltration. Who needs a dedicated fresh air intake fan? F'k, just put a timer on your fart fan and punch that every once in a while and you'll have all the outside air brought into your house you could want.

I don't know man, apparently it is to remove pollutants since the house is sealed up better than older houses. I'm kind of annoyed by it. I never thought my old house had humidity issues, but now I'm just obsessed with monitoring it now.

It's becoming the norm with tightly sealed homes that pretty much require a ventilating dehumidifier

El_duderino said:

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It's becoming the norm with tightly sealed homes that pretty much require a ventilating dehumidifier

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Why is the home tightly sealed? To reduce the amount of air coming into the home for heating and cooling energy savings. So, tightly seal the home, but then pay for a fan to deliberately bring hot and cold air into the home that has to be cooled and heated? Makes sense.

I would NOT recommend bringing in "fresh" air as they call it...I don't know where you live but bringing in 100 plus degree humid air in Houston from the prevailing southeast winds in the summer makes ZERO sense. 50% of the population has some type of respiratory problem....asthma, allergies etc. Y'all would be shocked by the number of calls we get regarding this issue...anyone remember the big dark cloud a couple years back that drifted from the refineries all the way across Houston from the SE to the NW? now add that mess to the HOT HUMID air..I tell everyone to close it off.

I'd assume that fresh air ventilations would be used during the mild months, not peak summer or winter

Try turning it down. Or just turn it off.

It's a newer code thing (well not that new 5 to 10 years now I guess) in new construction. Basically not a terrible concept to try and keep interior air from getting stale and unhealthy. But like many things they allow very poor implementation and dumb controls. So that cheap option is what most builders install.

Your issue, plus the thing coming on and blowing 110 or 20 degree air into the house are common complaints. With the dumber controls there are not a lot of adjustment options.

If I had one, I imagine I would turn it off a lot of the year.

I'm actually going to have an ERV system installed in my house here pretty soon. My whole family is sick all the time. I'm starting to think it's our indoor air quality.

Are your humidity levels good? If too high or low it can cause health issues.

Do your research and get a good one, not the builder grade crap.

What is a decent humidity range? Every time I check my thermostat it says like 50-55%.

Pretty sure 50 to 60 is considered normal. Personally I like 50 to 55.

Of course, it is going to vary depending on your location and the exterior conditions and time of year.

Yeah I'm thinking an ERV will do the trick. I live in a sixty year old house.

We prefer 40-45%. When it's gets below 40% inside it feels COLD when it's warm and humid outside.

The key with fresh air intake is to hook it up to a control device that will only turn it on when the outdoor air isn't too hot or humid. You'll probably need to add this if the builder didn't install it, but it's all low voltage wiring, so it should be doable and not dangerous.

What model is your fresh air intake unit?

I bet the manual has wiring diagrams that shows how to hook it up to an IAQ sensor or similar. It could also be interlocked with you AC unit, to only bring in outdoor air when that thing runs.

Also where are you located?

They're putting them in nearly all new homes. We have one and I can confirm you should keep the damper unplugged during the summer heat. We all do that here in Houston. Makes zero sense for a fresh air intake with our humidity levels. It's great in the winter as my ecobee can use it to cool off the house if I need it to.

I don't seem to have these issues that you're having but the fresh air intake on my house is massive!!!! I've got two 4x7 sliding glass doors that not a one of my four kids knows how to close behind them!!!! We also have great entertainment around supper time when I bust out the salt gun to kill flies and season my wife's low salt cooking! I'm a blessed man I tell ya!

On a serious note, I agree with 88, close it off. Unless you're running it through a dehumidifer and UV light all you're doing is taxing your AC and causing allergies.

Being honest, 60% humidity happens during certain times of year even in our best houses and the solution is to lower your thermostat a couple degrees. Mine averages 50-55 most all year but this fall I've seen it in the 60s a couple times (insert door open image) and I just let it run to 68 degrees and it came on down in a day or so.
Good luck!