Had 2 whole whole dehumidifiers (Aprile Air) installed 3 weeks ago.

One side of the house, it meets the required number (55%) and stops running.

The other side of the house (with fresh air intake)...its working much harder. Almost on all the time to try and meet that 55% number. There is a fresh air ventilator installed on this side, to help reduce the amount of hot/humid air the system brings in.

Wondering if this is normal operation - meaning, one of the dehums running almost constantly to keep the humidity in check.

Some basics:

- Spray foam home.
- Single story, 2 units. One dehum per air handler. Installed in attic space.
- Correctly sized units
- New build (under 5 years)
- Tight house (probably too tight, thus the need for the dehumes)

I suppose that I anticipated them running, then stopping for an extended period of time. But the constant running has me wondering if I have a moisture intrusion somewhere that is causing the machine to work all day/night to keep the humidity in check. Or is it going to take time to dry out a house that has been overly humid for a few years?

I am assuming these are not single speed hvac units since this a foam house ?


Variable speed units ?

What size in tons are the units and how many total square feet ?


What part of the country is the house located in ? North ? Gulf coast ? West coast ?

On the hvac units, is the fan set to auto or to on ?

We have a new foam house(1yr old) only one air handler/unit. Smaller house 2250ish. And we keep ours at 40-45% and doesn't run that much with our Trane thermostat. When I swapped with a ecobee for a while we could never get below 55% and ran all the time, so went back to the Trane and all works fine again. Could be a programming/settings:compatability thing that is causing the issue.

With the lower humidity was able to keep cool setting 3 degrees higher than what we normally have it set and still gets a bit chilly from time to time.

Why not just turn off the fresh air intake system?

I have one in my newly built home, and it constantly just adds outdoor humidity that I don't want. I just turned off at the controller in the attic. Haven't had any issues with air quality. Not sure why I even need it.

So that means spray foam insulation? I don't have that.

House is foamed. Very tight. Thus the intake plus the ventilator on the intake to control for temp/humidity of the intake air

Ok, didn't want to derail your thread, but it seemed like something that could be making the dehumidifier work harder. I read that some fresh air intakes can be set to operate only when the outdoor humidity is within a certain range, but not sure if that makes sense for your setup.

Yes, that's what the ventilator does.

Just trying to figure out if dehumidifier running all day is normal operation

It is when you have the equivalent of a window cracked letting outside humidity into a sealed structure

Gotcha. So you're saying the fresh air intake, even though moderated by the ventilator, is the reason my dehumidifier runs nearly non stop?

Don't mean to derail. Has anyone DIY'd an aprilaire install? Seems straightforward.

I can get you photos of our install. It was pretty straight forward, given the power supply needs were already in the attic space, tied in the drain line to the AC drain, etc. The device was set on a stand that we made, plus a pan with a kill switch incase water collected in the pain.

So far Im really happy with them. Just trying to get dialed in with the fresh air and my HVAC. But they dropped our humidity numbers way down. Don't know that I'ld spray foam a house if I build again.

That'd be awesome!

Where are you located?

We are in the process of building halfway between Dallas and Houston and everyone (A/C Contractors) have sworn to me that we don't need a dehumidifier and I am nervous as a cat about it. Same situation as you with a tightly foamed house.

I am in the motherland and if you are fully foamed, like we are, all guidance we are aware of is you need a dehumidifier. Ours came standard with the foam package, also heat pump was standard.

Hill Country.

Even here, the house cannot dehum itself during the spring and fall. House too tight. Weather just right. No air movement with hvac…bad humidity.

Do it when you build so the entire hvac system can be set up with dehumidifier in place.

There is a huge lack of knowledge (from the general hvac industry) about sizing hvac and controlling humidity in foam homes.

I'm not sure id foam again. At least not under roof decking. Maybe a rock wool style there, foam in the walls.

Do a dehum. You won't be sorry.

One thing I was reading about was that with a new home, your humidity may be higher in the first year because things like your lumber and foundation are still letting off moisture from the newness of the wood or curing of the concrete.

I'm not in a foamed house, but the insulation is still really good. In the spring or fall when it's in the 60s outside, the humidity can get up to 60-63 for days in my house since the A/C or furnace aren't needed. I have to use a portable dehumidifier during that time. I certainly don't keep my fresh air intake on, and I've had no issues.

The only thing I wonder is if I need that fresh air intake for my natural gas furnace to run properly so it gets enough oxygen. The whole A/C and furnace setup is in my attic if that makes a difference.

Heres the photo:

Still haven't really figured out why one end of my home stays more humid than the other end. A bit of a mystery, and I'm not sure where or how to figure it out. I'm going to assume the fresh air intake - even with the ventilator system in place - is mostly responsible.

Side of our house of more humid than the other as well. We don't have spray foam but it is a pretty tight newer build. Only thing I can come up with is that the side with the AC unit is more humid than the other but that doesn't really make sense. We are looking at whole home dehumidifiers.

What humidity levels are you seeing in your home?

I need to measure a bit more but in the noticeably more humid rooms it's 68% when the AC is running. I'm using a cheap hydrometer/thermometer that I used for incubating eggs.

TikkaShooter said:

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Heres the photo:

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Thanks!

Have 3 of the Aprilaire units tied into each of our 2 stage Carrier systems in a spray foam house and the humidity control is super dialed in. All of it is controlled by our Ecobees and the humidity readings are within a few percent of each other max.

3 dehumes for 2 units?

What size dehumes?

3 dehumidifiers into 3 two-stage units...

They are E100Vs.