Mineral wool vs hemp vs sheep wool batt insulation
I have been using Hempitecture hemp batts for insulating my new shop. I like working with it. Doesn’t stink, doesn’t make me itch, and their manufacturing plant is close to me. However, 10% of it is poly fibers which are used as a binder. Cutting it takes a lot of diligence so all those small fibers don’t blow out into and pollute my landscape. And I’m bothered that the company is secretive about its flame retardant, saying only that it is non-toxic.
I’m not convinced I want to use hemp batts in my house…primarily due to the lack of transparency on the flame retardant. So, I’m looking at sheep wool and mineral wool batts. I’m pretty sensitive to formaldehyde though so am not sure mineral wool would be best for me.
Sheep wool batts seem intriguing as there’s a company that doesn’t add anything but boric to deter insects.
I’ve worked with fiberglass batts enough to rule it out with certainty.
I’m only interested in batt insulation and only those I’ve mentioned: Hemp, mineral wool, and sheep wool.
I’m in a cold and dry climate zone.
What are the pros and cons of these three insulations? Which would you suggest and why?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
My preference is mineral wool, and has been for some time. I don't like natural fiber products here due to risk of critters and stuff growing in them. Hidden stuff like insulation is something best handled with a material that isn't likely to harbor pests -- ever -- at least not as a food source. You'd need to check about formeldehyde, but I seem to recall reading that that isn't an issue with mineral wool batts (don't quote me on that though :-)
I do suggest you look into Dow Corning's "Pure Safety" R15 high density fiberglass batts though. This stuff was made specifically to be non-allergenic. I know you mentioned you don't want to work with fiberglass, but in my own (limited) experience using this particular product, it was very different from fiberglass I'd worked with in the past. It's white in color, soft, and very non-itchy. I was pretty impressed with it.
Bill
Would you consider damp sprayed cellulous or the new wood fiber batts?
“Hemp Fiber Insulation
Hemp fiber is composed of roughly 90% hemp fiber and 10% polyester binder. Hemp fiber typically has added boric acid, which is a flame retardant with some known health risks.”
https://buildingclean.org/products-and-health/product-sector-guidance/insulation#:~:text=Hemp%20Fiber%20Insulation,with%20some%20known%20health%20risks.
Walta
In terms of global warming potential (GWP) mineral is much worse than fiberglass, hemp and I think sheep's wool. Cellulose batts are a far better alternative. That's something to consider.
Ecocell and TimberHP are 2 companies that make cellulose batts. They have SDS sheets on their websites, with full details about the various chemicals used. I won't offer an opinion about that as you know your concerns and are better able to evaluate the information.
Scroll down to see a non-comprehensive list of insulations and their GWP. https://www.greenfiber.com/blog/embodied-carbon-and-the-built-environment-get-the-facts
I would caution against making a decision on any product based on ONLY ONE issue related to "greeness" of a product. Often when considering the entire system, or the product over it's useful lifetime, what at first appears to be most green is not. I'm not necassarily saying that's the case in this specific example, but it comes up enough to be a concern.
Bill
"ONLY ONE"
I agree. But when one of the important ones hasn't been mentioned I figure it's helpful to point it out.
Yes it is dangerous to make a decision on only one factor, but fiberglass is superior to mineral wool in many factors:
1) Price
2) R-value/inch
3) GWP
And unfaced fiberglass does not catch on fire either (it will melt at temperatures around 1000 degF, however).
Thanks for the replies, everyone.
Re Dow Corning's Pure Safety insulation: It's priced similarly to wool which, I ruled out after posting due to the high cost...primarily due to shipping.
Re Ecocell and TimberHP: Wasn't aware of them. Look great but, with no local dealers, shipping makes it cost prohibitive.
Re spray in insulation: I'm doing this myself so was wanting to keep it simple with no extra tools/machines needed, hence batts.
Since posting, I've been told the local hemp manufacturing place has temporarily stopped using a flame retardant. If that is indeed the case, it would seem to make a sense for me to use hemp, since that was my biggest gripe with it. They are only a few miles away too, and their prices are actually less than I was planning to spend on rock wool.
When it comes to man-made insulations...it seems to be a "pick your poison" world.
Dean,
"When it comes to man-made insulations...it seems to be a "pick your poison" world."
Which I think is why it makes sense for environmentally sensitive people to locate the air-barrier inside the insulation, limiting their exposure.
I agree -- the air barrier should effectively "seal out" any dusty-type stuff from the insulation. The only thing that could migrate through normal air/vapor barriers would be certain volatile solvents, and those tend to be very limited in insulation materials if they're there at all.
If the OP really wants a barrier to anything in the insulation, use 1/2" foil faced polyiso on the interior behind the drywall, and tape the seams with foil tape. Now you have a near hermetic barrier that even volatile solvents won't be able to get through.
I think people overreact to risk associated with insulation materials. There is likely to be more offgassing from furnishings within the home than from insulating materials. Some people have written about insulating materials, so people think about those, but think of all the other stuff inside a typical home that people don't think about simply because it's never been hyped up.
BTW, for the OP, I'd be reluctant to use certain flammable materials in a house that did not include a flame retardant. Cellulose insulation especially comes to mind. I'm much less familiar with hemp materials, but if it's something that could easily catch on fire from a small flame and support the fire, I wouldn't use it. You don't want to use any materials in your construction that are more likely to ignite and burn than the wood framing, and it takes more than a brief exposure to small ignition source to get framing lumber to start burning.
Bill
"I think people overreact to risk associated with insulation materials. There is likely to be more offgassing from furnishings within the home than from insulating materials."
I'm not that concerned with offgassing while living in it (given all my other material and furniture choices). I'm the one handling every material in this place though...and I just don't like working with stinky stuff, smelling it and breathing in its dust particles while cutting, etc. I do wear a mask but it's not practical or desirable for me to wear it all the time... and stuff can remain in the air and be stirred from the ground. I haven't a good reason to not avoid that which offends my nose and gives me headaches.
Thanks for everyone's thoughts on this.
Gotcha. My biggest issue has always been itchiness with the stuff, which was WAY worse with old school fiberglass than it is with the new stuff, and the new fiberglass and mineral wool are similar in that regard, with a bit of an edge (less itchy) for mineral wool. I haven't worked with hemp, but always imagine it to be a little like a hay bale, which I have worked with (not for building though). Denim is comfy stuff to work with, but expensive.
My personal recommendation for any of the stuff is to wear a full tyvek suit with footies and a hood, and tape the sleeves to your leather work gloves. That will very nearly eliminate any issue with itchiness. Wear a real respirator (the kind with detachable filters) if you have a big job to do, since these work a lot better than the basic dust masks for larger jobs. Full face respirators are best here, since they keep dust out of your eyese too. Note that you only need the particular filter cartridges for insulation, not the fancy ones for solvents.
Take a shower immediately after the job, and get out of the tyvek suit outdoors, then put it immediately into a trash bag. Tyvek suits are cheap, so don't try to reuse one for multiple days of work since you'll just end up tearing them.
Do that stuff and the itchy dusty nastiness of insulation is pretty much eliminated.
Bill
Blow in equipment can be rented.
Note that boric acid is not just for flame retardancies it also deters insects and rodents
Walta