Anyone seen nail corrosion from Roxul?
I’m slowly building my home home and last year I fell for a great price on roxul comfortbatt. I bought what I thought I needed and stacked it in the basement of the dried in house. 8 months later I moved the roxul and was surprised to notice white carrosion and rust on the galvanized Hitachi ringshank nails I used to attach studs to an interior wall sill plate. Nails show carrosion only where I stacked the roxul and no where else in the entire house. I recently learned that roxul has formaldehyde and worry that the off gassing through the plastic wrap is the culprit. I moved the bundles outside on a porch and slit open the ends to off gas. I’m worried that it could still cause problems when I install them in a month. I’m attaching a picture of the nails.
Thanks
Ryan
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Replies
I'm not clear. Are you concerned about formaldehyde exposure or about the corrosion on the nails?
I've used Roxul Comfortbatt in a number of applications and haven't seen anything like you are describing. I'm not sure that formaldehyde even reacts with iron. I'd be a lot more concerned that you have some moisture management problem and that the stack of Roxul prevented air circulation from clearing out the moisture.
I think it is a lot more likely that PT sill plate is corroding your nails. You might check out this lengthy pdf on the corrosion of fasteners by pressure treated lumber
http://www.ggashi.com/wordpress/wp-content/uploads/PT-Lumber-Causes-Steel-Corrosion.pdf
As for formaldehyde exposure, I have always assumed that the Greenguard Gold rating on Roxul comfortbatt meant I was likely getting more exposure from subfloor osb or from pressboard cabinetry than Roxul. I will say that the amount of cat urine odor coming off Roxul can be quite noticeable when you open the package but seems to dissipate quickly. In several years of using it, I have received 1 batch that remained smelly (and it wasn't really the catty odor, more of a burnt odor).
If you have concerns about the initial odor, opening the packages in a garage or other unoccupied space and ventilating may address them. If the smell is a concern with Comfortboard, you can stack the boards quite high in a sort of lincoln log chimney, run a fan over it, and ventilate it to accelerate the initial blowoff. Do remember how much that comfortboard weighs if you do that! (8.0 pcf) However, Comfortbatt doesn't stack well so opening the packages is generally the best you can do.
Ryan,
I think that the key to this mystery has nothing to do with the Roxul. Here's the key: you wrote, "I moved the bundles outside on a porch and slit open the ends to off gas."
What you had in your basement wasn't a pile of mineral wool batts. What you had was a pile of full plastic bags.
Where the plastic bags touched the nail-heads, the bags inhibited inward drying and encouraged rust. In areas of your basement where plastic bags weren't piled against the nail heads, there was no corrosion.
The problem was stacking the plump plastic bags against your wall.
Thanks all. Our basement had a unpleasant oder for the past year and it went away when I took the bags of roxul out.....boy did they smell when I opened them up! I sure hope they off gas faster now.
The basement is quite dry but I am sure there was slightly more humidity near the wall due to lack of airflow The roxul was mostly up about 4-6" away from the wall (no plastic on nail heads)at the bottom of the piles but touching the sides of the studs at the top of the piles. There was no sign of corrosion where I had foam stacked next to the wall nearby. For other reasons I have had some experiments going with the same nails outside in wet mud with copper nails and in contact with pressure treated lumber in a continuously damp environment.....no corrosion! The only time I have ever seen the white powder corrosion like this on galvanized nails is once when I had a bottle of muriatic acid off gas in a shed and from oxalic acid wood bleach over spray. I thought that formaldehyde can change to formic acid in the right environment. I just did a quick Google search and found this article saying that formaldehyde in air is modertly corrosive to galvanized nails. http://manual.ingal.com.au/41.php. I'm thinking I made a nice humid air pocket for the initial off gassing of formaldehyde to settle down into.
Thanks for the post Ryan. I believe there was more to the corrosion you noticed than moisture, since I've never seen galvanized metal show corrosion unless an acid was present. I don't know if it might be formic acid, but it seems suggestive since the effect was only noticed with one product, and one that was not in direct contact. No one wants to imply that Roxul has a problem with formaldehyde, but there are any number of products on the market with problems that are considered negligible only by comparison, not in absolute terms. Personally, I prefer to accept the theoretical offgassing from XPS, which is at least not considered a carcinogen.