Smart membrane or vapor retarder for mineral wool
I hope this question can help others who are working with mineral wool in the future so feel free to edit my question so it’s easier to read through.
Back in 2015 I was educated on using Mineral Wool thanks to GBA. I had to special order the product and every tradesmen working with me questioned me wondering what the heck the product was and why I would spend so much more on it. I tried to explain the pros and why it was a better product but I truly don’t think it registered with most besides the HVAC contractor. At that time the cost of it was double the price of paper faced fiberglass insulation.
Today, now four years later, the only product available *Still through special ordering only* is actually more than double the cost by a tiny amount; it comes out to be about 103% (as in 100% = 2x the cost of fiberglass) more expensive per square foot to purchase R23 mineral wool vs R21 paper-faced fiberglass. That’s a hard pill to swallow, folks. When most home builders only use the R value as a determining factor, they see that they will never get their money’s worth with that much of a cost difference. It seems they think it only would ever make sense for the homeowner to be the one requesting it because they have done their research and know it’s a superior product.
Now this is a bit disheartening but just provides a little background. I’ve yet to see it used by any home builder in our area besides myself. So when I go to try and discuss the use of a smart vapor retarder, you can imagine the looks I get. Anyways, back to the point of this question. What is the suggested moisture blocking, or vapor retarding method now in 2019 and moving on when using a mineral wool insulation?
I personally used CertainTeed Smart Membrane, but I have noticed that is getting more expensive by the day. I have also read articles online that are arguing it’s not worth the added cost or time (to properly install and seal things up). http://www.ntcinsulation.com/the-insulation-lab/smart-vapor-barriers-are-they-really-that-smart
GBA did an article on smart membranes back in 2013 but those links are now invalid and there are more products out there.
Where should home builders look for proper methods in this day? Are smart membranes fading out like “vapor barriers” did in the 80s and 90s? If a builder is not air-sealing with something like Zip Sheathing, and/or just taping regular 7/16″ OSB seams, what is the suggested product or technique of sealing when using mineral wool for the exterior wall insulation? I would like to see GBA do an article similar to the one in 2013 but perhaps with current products and various methods. Seeing some test results of those rather new products in 2013 would also be enlightening I think but that is always an idea for the future testers out there. For now I’d just like to discuss the options with those who are actually familiar with mineral wool unlike the local builders or local home building material stores.