Just had flooring insulation done and now home is more humid and hotter than ever

Full disclosure: I have no experience with your exact scenario.


That said, you can't just spray foam parts of an old house without forethought. You need a legitimate building scientist type contractor. Who did the work and who did you consult?

What sort of ventilation do you have, what is the attic insulation like, and what is your HVAC setup?

If the humidity in the house is worse now, you may be drawing in outside air. After reading the other post, I'd consult a different HVAC company.

Old houses were leaky. When you start sealing them up you can bring about secondary issues with negative pressure sucking in outside air.

ETA: your return air ducting is the first thing I'd be looking at. Make sure you're not drawing in attic air downstream of the filter. Assuming your air handler is in attic.

Don't want to freak you out... but I had my house inspected for mold before. It was only minimal, but inspector mentioned how spray foam was the biggest cause of mold in the houses he looks at.

I would treat it as an emergency to figure out what's going on.

is your crawlspace open? if not, why the need for insulation?

quote:

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is your crawlspace open? if not, why the need for insulation?

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1901 home. Original flooring. No layers between wood and the ground below. Hundreds of small gaps and holes allowing moisture and heat/loss of heat in the exchange. Was what was recommended. I even posted the LSU book on it in the OT.

Maybe so, we did what was recommended consistently.

You likely have a duct leakage or otherwise air unbalance issue since it doesn't sound like you have a grossly oversized unit. Foaming the underside of a home can cause issues if not done correctly but it should've only helped with air leakage and humidity issues.

A crude test is to run the a/c and/or blower fan, then crack open a single exterior door or window and put your face in the crack to see if you feel air sucking in (or out). The wind shouldn't be blowing or any bath vent fans,range fans, or clothes dryers be running that would de-pressure the home. Repeat the test throughout the day to see if results stay similar. Sometimes the leakage is so bad that it makes the door slightly harder to close when a/c blower is on.


Now that you've gone the foam route and aside from the unresolved humidity issue, make goddamn sure you have water leak detectors installed near every water source. Under sinks, behind fridges, toilets...anywhere a small leak can go unnoticed for weeks or months. The water can go under the flooring and go sideways for a long ways.

So, think of living in an ice chest. That's basically what this type of insulation does. I'm no expert like someone else said, but there are things that must be considered like bringing in fresh air and other ventilation to prevent this issue that you're having. You'll have to consult with a legit HVAC expert to solve your problem.

Are you short cycling? The insulation could’ve made the home a little too efficient. Meaning the AC doesn’t cycle on long enough to remove excess humidity from the air before reaching the desired temp. If you have a smart-ish thermostat, dig in the settings. There may be a humidity control setting you can play with. When enabled, it does something like overcool a to a bit below the set point (maybe like 3 degrees) until humidity is in check.