Ecobee shows below for indoor humidty level and when the AC is running. Our house just feels way too humid and we've gotten several alerts recently when it exceeds 70%. You can see below that the humidity increases while the ac is running. It spikes and then reduces pretty quickly. That doesn't seem right. I'm wondering if I need my evap coils cleaned, or possibly even a dehumidfier. We bought this house a couple years ago and it had been retrofit with foam in the roof rafters. I'm wondering if they just sprayed the foam and didn't worry about the AC. Is it not ventilating well, or could the AC be oversized now maybe? Anyway, the humidity just gets uncomfortable at points. Have a company coming out to do maintenance next week, just curious y'all's thoughts.

This might be a silly question but is the fan set to on or auto?

Auto

I'd guess they didn't adjust the hvac to match the spray foam. Whole home dehumidifier is also a necessity as well

Edited for the better more experienced responses below .

I left out a piece of info that might be helpful. When they retrofit the foam they DID NOT remove the blown in insulation from the floor of the attic.

Sounds like there's gonna be an insulation vacuum in your future.

Suck the old crap out and get a whole home ventilating dehumidifier.

Anyone got a ballpark cost on insulation removal? I've considered a dehumidifier for a while anyway.

Depends on the layout/size.

I rented a unit for $300. My attics (plural) had a lot of nooks and elevation changes. Took me a day. I hurt for a week.

Somewhere around $1500-2000 for someone to do it.

I'm not opposed to doing myself, er...having my 18yo son do it. Just don't know where the heck to dispose of the old insulation. Seems like a pain to transport all that somewhere.

https://www.thebagster.com/default.aspx

I was in a similar boat. I gutted an old home, spray foamed the entire house, got a variable AC, but I also installed a whole home dehumidifier.

I have the humidity set to 40% in the house. Let's just say we go through a lot of chapstick.

I was quoted around $1 a square foot to remove when I got a quote last year

Spray foam homes and humidity. This is probably my issue as well

That's because a lot of people don't install the proper hvac system for spray homes unfortunately.

What's proper? Like proper sizing? Wondering if I'm over sized. 2 unit home. Single story.

Typically sizing and then it's high humidity with a single stage unit in a spray foam setting. Variable speed and/or dehumidifier are needed with spray foam or any sealed house

Thanks.

You in the biz or just knowledgeable? Or both.

Looking for a good company to come retrofit what I have with whole home dehum

Not in the business. Just had to do a lot of research when replacing my system a few years ago to be able to weed out the garbage installers and guys who still go by the 500sq/ft per ton rule of thumb.

I don't remember who the poster was, but someone on here has experience with DIY dehumidifier install.

Rules of thumb, as noted, are not really a thing any more. However, they can give us clues when we know information like "it's got spray foam now". Can you tell us the sq footage of the home? Single story? Two story? How tall are the ceilings? What are the model numbers on the equipment? Both outside and inside units.

These will give the pros here more info to work with. There's a chance your system just needs to be adjusted a bit. Installers regularly leave things defaulted, I've had it happen on every single new unit I had installed on my residences. I had to go back after the fact and read the manual and make changes. Also, your unit may have trim capabilities or dehum settings to allow it to work better.

El_duderino said:

---

Not in the business. Just had to do a lot of research when replacing my system a few years ago to be able to weed out the garbage installers and guys who still go by the 500sq/ft per ton rule of thumb.

I don't remember who the poster was, but someone on here has experience with DIY dehumidifier install.

---

I did a DIY dehumidifier install. Amazing difference. We don't have foam but plenty of infiltration by humid air in the shoulder months.

If you are in Cypress or the greater Houston area I can help you. I own Wise Guys Heating & Cooling and have helped tons of Ags here. Spray foam and single speed equipment are like 2 trains pulling in the opposite direction. You need a heat load done and then install variable speed equipment. My office number is 713-466-7555 and my mobile is 832-347-0807...class of '88 and my son Dylan is class of '19

Unfortunately I'm not in your area. Do you know any HVAC Ags in the hill country?

Here is my unit:


Some information:

1) We have 2 of these.

2) Approx 4500sq ft

3) Single story home

4) Spray foam insulated - walls (2x6 exterior) and underside of roof.

5) High ceilings in one side of the house - this is the side where the humidity levels stay higher. This is also the side of the home were the unit has a fresh air intake. Pulls in air from an intake vent thats on the screen porch ceiling. Humidity gets bad on this side, Highest I've seen is 72%. Taking this measurement off the thermostat. Not year around issue. Mostly during the spring/early summer. When its humid outside, its humid inside. Dry outside, like after a front in the fall = dry inside.

6) Lower ceilings on the other side. Humidity more under control. Highest Ive seen is upper 60s.

I've had the company that did the install (during the build process back in 2019) come try and make some adjustments to help the system run longer. I assume the adjustment was to increase motor runtime (by slowing it down?) in hopes of running longer to pull more air out of the home. Hasn't worked.

I don't notice any signs of an over humid house. No mold. Towels hung up will dry easily. Only thing I can tell is the house feels warmer than the thermostat says when the humidity levels are up.

Any thoughts or help would be welcome. I know I need a dehumidifier retrofitted into my system - if thats possible. Just not sure if I need 2? Appreciate the input.

So 10 tons combined for 4500 square feet it looks like. I'd say probably 2 Santa Fe 98 dehumidifiers would be suggested instead of 1 massive one, but I'll let the pros take over.

My attic looks a whole lot like the attic in this video. Larger space. But yeah. Similar.

10 tons on 4500 sq ft and its foamed ?

What kind of air filters are you running ?

There are 2 of these. One on each side of the house in the attic.

Ceiling height on the side of the house with tall rooms. This is in a bedroom. Similar height in the living room. This is the side of the house where the humidity is highest on sticky days.

Oh boy. This explains a lot

So how do I fix this? The systems were installed in 2019. So there is simply no way I'm pulling them out.

Any way this (the humidity and the over sizing) can be solutioned by keeping the current units?

Tikka can you call me please. 832-347-0807

Thanks 88. Got the number. Headed out with the family for dinner. Let's connect tomorrow

10-4

Way too much AC. Those are inverter variable speed units or st least they should be. Try running one in the off position with the fan on and the other like normal and see if the house will dehumidify a little. There's nothing wrong with single stage equipment in foam houses when sized right. Fresh air should have also been incorporated in your design and we like to pull that in through a dehumidifier. Good luck as you're in a real jam and it's going to cost you some money to get out of it.