concerned about formaldehyde in plywood subfloor-safer alternatives?

Not sure if this is the best forum to put this in, my apologies if somewhere else would be more appropriate.

We started putting down subfloor for our eventual hardwood floor a couple days ago. I am not thrilled with the solution my partner has chosen for this, as it is far less than "natural", but I also don't know what other option we have since our house is slab above grade in a very humid climate and I do not want mold, as I am highly allergic. Anyhow, he has put down plastic sheeting with some fancy styrofoam panels and then tongue in groove plywood above that. While I don't like the first two layers at all, the plywood and it's formaldehyde off-gassing is what worries me most. I know it is phenol formaldehyde as opposed to the more dangerous urea formaldehyde, but both of us are experiencing respiratory irritation. I have been searching for information about how harmful this truly is and finding conflicting information, with some saying it will be reduced to levels found in nature within weeks and others saying it will continue to off-gas for as much as 10 years at levels above "normal". I go to great lengths to keep toxic gick out of my life whenever possible, so the thought of having half the floor of our sanctuary off-gassing a carcinogen, potentially for years to come, is extremely upsetting, to say the least. Especially since this is our sleeping and yoga space. Thus far, I have not been able to find a real alternative to the plywood, though. I know there is formaldehyde free plywood, but it sounds as if it is not rated to be used a subfloor.

I guess what I am wondering is:
1. Does anyone know how harmful this plywood truly is? Am I overreacting? I am extremely good at overthinking.
2. Is there a safer (and sane, see below) option than the plywood?
3. Since this stuff is already in our home for the moment, other than ventilating with fresh air, is there anything we can do to reduce the irritation?

I think it's important to understand that we are living in our house as we work on it and right now, it is a crazy cluster jumble and it is making life very difficult and stressful. Especially since we also have a cat with asthma. While I want to ensure that we are making the best choices for our health in the long term, to protect health in the short term, upheaval of our living space needs to be minimized. Part of the reason he chose plywood is cause it will have to serve as temporary flooring until we can put in the hardwood floor. We had hoped to avoid this kind of madness by staying in our tiny house while we fixed this house, but the department of making people sad threw a wrench in that.

Obviously, it would have been preferable if this had been figured out before the stuff was in the house. My partner has far more construction experience than I and thus has been making most of these decisions. He researched the materials, but reached a conclusion that since it was phenol formaldehyde, which seems to be considered acceptable by most, it was okay. To his credit, I know he is beyond overwhelmed and just trying to get our home to be sane and functional. He also said if this is a real issue, he will tear it out, lame as that would be.

Thank you!

I think that when we mix mediums it is going to be non-ideal.  A wood tongue and groove floor is a traditional thing to do when the floor is over a crawlspace or basement. When a floor is ground connected it is more in line to stick with ground connected compatible materials, mass materials like slate or tile.  So you are wanting to put a wood floor over a slab, ground connected mass.  Likely what he is doing is the only way you can realy do it, .  If I had a cement slab floor I would use a penetrating sealer ( and I have done this and it dries and then does not outgas) then for a floor covering slate or other tile.  No outgassing.  They also make floor tile now that looks rather like wood flooring,  it looks very nice over the whole house.

I used this in our studio that has a concrete slab, and no more effervescence.  I have a ton of allergies and chemical sensitivities, including to molds.  I have no problems having used this product on the concrete slab in the studio.  So I could see it worked as we had no sealer for years, and then sealed with this and with a below grade room and over 80 inches of rain, no effervescence or moisture with this product.  I even put it over the cement grout in rock foundation walls that are on one part of the room, transparent and peneatrating.  

https://www.radonseal.com/product/110.html   this one I used is for an older slab, they have another product for newer slabs https://www.radonseal.com/product/100.html

For people that are going to float a wood floor over a slab I recomment this over plastic sheeting as this will actually seal and keep all moisture out, the plastic sheeting is not sealed to the concrete and there could still be migration up.  

here are some examples of wood look tile, about $2/sq ft  https://www.homedepot.com/b/Flooring-Tile-Porcelain-Tile/Wood/N-5yc1vZb97mZ1z0jipd

and US (vermont) quarried natural stone, this is very hogh quality slate, it doesnt peel away like cheap imports, about $5/sq ft http://www.vermontslatedepot.com/floor.html

Construction is full of irritants. Many things including simple dust could be causing it. Personally I’d be more worried about the styrofoam, simply because Plywood subfloor is in virtually every modern building I’ve ever lived in, but styrofoam hasn’t been. I’m just a cabinet maker so I don’t know the chemistry. I do know the materials that irritate me most are press boards (which you will find in most furniture, cabinets, and trim pieces), carpets, glued, paints, and upholstery. Dust can be bad to just because you never know what’s in it. I know mold gets a lot of attention, but good air flow and careful plumbing should prevent it. I built my house with straw, mud, and wood, because my wife was “chemically” sensitive. Which was lucky because after retiring from cabinet making I’ve become sensitive to all the crap I use to breath everyday.
In older homes locally subfloors were just pine or fir boards. A simple solution would be no subfloor, just build it out of hardwood.

Thank you, Sue! Yes, I agree this is certainly non-ideal and can see why tile makes sense in this context. That is our plan for the other half of the house. Perhaps I should have mentioned the choice of wood floor is not merely an aesthetic one. We noticed that in the winter, the slab got super cold and it was not feasible to do yoga on, which is something we really need. Also, in the warm times, because the slab is cooler and we don't have central air, we get condensation on the slab. We have already had mold issues and seeing as we have lots of wood furniture, I'd be concerned it would become a mold farm with that stuff on a sweating tile floor. So we decided that insulating this part of the floor was the way to go, even though I don't love the materials. I can live with most of it, just not sure about the plywood.

I wish we had known about that sealer! That sounds like a great solution. How much odor was there while it dried? Unfortunately,  I don't think we could use that now without moving out for several days and we have too many other obligations presently to handle that right now.

Heather Olivia wrote:Thank you, Sue! Yes, I agree this is certainly non-ideal and can see why tile makes sense in this context. That is our plan for the other half of the house. Perhaps I should have mentioned the choice of wood floor is not merely an aesthetic one. We noticed that in the winter, the slab got super cold and it was not feasible to do yoga on, which is something we really need. Also, in the warm times, because the slab is cooler and we don't have central air, we get condensation on the slab. We have already had mold issues and seeing as we have lots of wood furniture, I'd be concerned it would become a mold farm with that stuff on a sweating tile floor. So we decided that insulating this part of the floor was the way to go, even though I don't love the materials. I can live with most of it, just not sure about the plywood.

I wish we had known about that sealer! That sounds like a great solution. How much odor was there while it dried? Unfortunately,  I don't think we could use that now without moving out for several days and we have too many other obligations presently to handle that right now.

I dont recall any or much odor.  Go check reviews for the product.  I had no problems with it.

If your insulation is sheets that are not attched to the  slab I am not sure that it will save you from condensation or mold. I have used insulation boards for a similair reason in 2 wall spots ( shower that is agaisnt an exterior wall, so heat from shower could cause condensation on inside of the cold exterior wall)  and I make sure the boards ( thermax, 3inch, policyano...whatever) are flush agianst the cold surface and I attach and fill in cracks to glue it to that cold surface, spray foaming all edges so no warm moist air can contact that cold surface .  Maybe he has them held down well and there is no space on the edges in your case, but if they are just lying there and there are spaces between and on the edges of the room, it could be that your mosit warm air will contact that cold floor and condense etc....