TimberHP or other insulation options?

Hi Permies,

We're building a house. It's not a foray into 100% natural materials by any means at all, but where possible we'd like to use better products.

Our contractor told us about TimberHP, a wood fiber based insulation. Comes in batts and fill. Some type of borate is added (boric acid?) to make it flame resistant to some degree.

It looks like a decent option at first glance. Have any of you worked with it? Is it possible to get in North Idaho?

Should I pursue another avenue?

This is post frame construction with 8' spaces to fill. For the attic, a fill insulation will be easiest.

Thanks!

-Theodorin

PS: Not sure if this is the right subforum for this.

Hi Theodorin,
you're in the right place with your question I would say.
I have worked with this stuff in Germany, under a different brand name,but basically the same.

It has good qualities when it comes to insulation, also it provides some thermal mass (more inertia when protecting the house from heat in the summer) and some noise cancelling due to its mass.
It is quite environmental, mostly renewable and has a lower grey energy footprint than other insulation products.
With the borax its not flammable and animals are less likely to eat it/nest in it.

2 things to watch out for:

1) It will (like most insulation) loose its insulative value when wet. It might also decompose when wet. So keep it dry by not letting water enter from the outside or the house (vapor barrier).

2) It's much more expensive than other options (for example mineral wool) over here. No idea what the builder quoted you for. It's worth comparing though.

I hope someone else will chime in, maybe even someone with experience with the material in your area.

Good luck for the build!

Hi Theodorin,
I too have heard of that product. I have not worked with it specifically, but the company I work for, used that type of product in the expanded building project.

I also can't speak to the availability or price of some of these products, but here are some options that are way better than the pink fiberglass or foam.

Sheep wool batts - can be expensive, treated for bugs and fireproof, does maintain insulation value after drying out if it gets wet.

Blown in cellulose - (available at big box stores) generally made from recycled newspaper or blue jeans. treated for bugs and fireproof. Settles over time... not too bad for attic, but walls maybe not. Not too bad for cost, but can be messy to install. Does not maintain value after it gets wet.

Mineral Wool (rock wool) - (available at big box stores) made from slag from the steel making process. Fireproof and bug/rodent resistant naturally. Installs the same way as fiberglass, so it doesn't throw off builders who are not familiar with the process of other types of insulation. does maintain insulation value after drying out if it gets wet.

Hemp batts - made from industrial hemp fiber (no relation to its cousin plant which is so controversial). Not as familiar with this product, but I've heard good things.

Mycelium insulation - grow your own insulation :), check out this thread about a door, using this type of insulation. https://permies.com/t/myco-door

Hempcrete - my personal favorite, uses industrial hemp fibers mixed with a lime based morter to make a monolithic wall. Its not insulation for the wall, it IS the wall. Provides insulation, helps with humidity, is fairly fireproof, carbon negative, rodent and bug resistant.

Hopefully this will help you go down a rabbit hole about more natural insulation :)

Thank you both for your replies!

I'm interested in RockWool or TimberHP at this point. I have a quote for RockWool, just waiting on hearing back about TimberHP. Mycelium insulation sounds really cool but I doubt it's something I can get in a couple week timeline.

Availability of RockWool has been poor in this area, but did find someone who has it locally. It's much more money than fiberglass, but it sounds like it will be a better product in the long run.

TimberHP has some interesting demonstration videos. One of them suggests that it's better at warding off heat than mineral wool. I don't know if the test is rigged in some way, or if there's a property of R-value that doesn't quite convey this. It's also not the most realistic test to have a heat source directly over insulation. But maybe it's relevant in some way.

Cold is certainly more important to us than heat, although we're hoping to passively cool the home during the summer.

The heat thing is likely just due to higher thermal mass.
Rockwool is definitely preferable to fiberglass. And the wood fiber products are, to me, even a bit more desirable. But of course it comes at a cost.
They say that mineral wool (rock wool) doesn’t produce fibers that are problematic. But I somehow think that maybe in a couple of decades they will find out it does, just like they did with glass wool.
Also the wood product uses less energy in the making and stores carbon in it. In case that’s something you value