Hello,

We are in the late stages of a custom build, we are doing the general contracting ourselves which has gone relatively well so far.  We have radiant throughout and and had our local Maxxon dealer to a Therma-Floor overpour 10 days ago.  Our drywaller started working 5 days ago and we fired up the in floor heating system 2 days ago with lots of anticipation and excitement.

Unfortunately this turned into a bit of a nightmare and I'm looking for some advice from others.

Basically, we discovered yesterday a LOT of mold on our pine windows from excess condensation, presumably from the floor releasing water as the heat was started.  Very frustrating, it seems the black mold has permanently stained the pine, in some cases quite badly.

Of more concern though is the floors.  This morning I went to the house to discover what appeared to be a fuzzy white substance on the floors.  The white substance clearly traces out the tubing layout very clearly.  I spent most of the day trying to clean this up.

Is it mold?  I read something somewhere about Efflorescence being released from concrete floors that can look like mold also.

Any advice/information would be great!

don't know about the mold, but i would get some fans on in the building, open it up Doors & windows and turn the heat up, delivered water temp up to dry it out,
You have a lot of moisture in the house, the heat should help dry it out once the water is expelled from the slab.
Dan

It's effloresence, not mold on the floors. The moisture being driven from the concrete is bringing hydrates & salts with it, which crystalize. Once the slab is fully "cured" and dry it'll stop unless significant moisture (from groundwater/vapor leaks in your PEX) continues to pass through it.

Run a dehumidifier in the space to keep the RH under control as the slab cures and you'll stop mold from forming elsewhere. Under 60% RH air reliably inhibits mold growth. If anyone in the house has dust-mite allergies, under 50% RH is even better.

Concrete can hold quite a bit of water, but heating it will dry it out. It's usually better to have a substantial curing period before applying the heat, but schedules & weather don't always mesh perfectly, eh?

Thanks for this.  It's definitely Efflorescence and not mold as you mentioned.  As you mentioned, things have not unfolded perfectly for timing, but I guess it's hard to have everything unfold perfectly.

My basement slab has been curing for over 2 months, so there's no moisture problem down there with the radiant heating.  I would have loved to wait a month after the Therma-Floor to allow it to cure and harden before work continued, but we need to get this house done soon.

When it comes to mold I would recommend having a professional mold test completed when in doubt. Mold can cause a litany of medical conditions. The last thing you want to do is breathe in mold spores. If you have more questions regarding indoor toxins please feel free to check out our site.

www.airmd.com

Ok, I'm a noob and all, but did the dry waller set up house exhaust fans? My understanding is the drywall mud introduces a great deal of moisture. The whole house should have been vented during the process to pull it all out.