Hi tuifeathers,

I'm no expert but we are using a "green consultant" for our house (in our location some kind of green rating is required for new residential construction). We are using a mineral wool board for the exterior insulation and open cell spray foam for the interior insulation. There was a long discussion about whether we would prefer dense pack or damp-spray cellulose on the interior -- that would have been the first choice of the green consultant. Second choice would have been the JM spyder(?) blown fiberglass but apparently the installers around here were not familiar with that and we did not want to be guinea pigs.

You might also post your question on the Green Building Advisor site.

Good luck!

most open cell foams these days use water as a blowing agent, so after they off gas right away, they are typically fine.
blown cellulose or fiberglass is another good (and better) option than the batts.

I do question why the expense of open cell in the attic yet batts in the walls? Its like putting a cooler lid on a cardboard box....

." Our builder generally uses open-cell foam in the attic space and batted fiberglass in the exterior walls."

I'm on the same page with your builder conventional insultation for walls..... just make sure that air tight drywall approach is used for interior.
costs of foam pay back for roofs much faster than walls
and as roof gets the brunt of heat/cold gain it makes
economic sense to spend more in this area.
plus it makes non issues of builder errors,
keeps ductwork in semi conditoned space.

mix of chemicals for spray foam when done correctly
with water based sprays offgass quickly.
even chemically sensitive clients I've worked with in
the past have been ok after 2-3 days after open cell install.

local to me we have an insulation company that does an excellent rock wool install for walls. R-15 wet applied.
use the drywall air tight install .
as walls are air tight to exterior, and with air tight drywall approach air tight to interior..what is between the two barriers is contained within that space.

best of luck.

Just used Roxul in the home my sister built and using it in ours next. Mold resistant, fire resistant, and quiet. Easy to install, texture similar to loaf of bread so it's easy to cut then just stand it in place and it holds itself up. When done moisture barrier over wall. We used R-23 for the northeast winters. Very impressive and roughly 30% more expensive. Also I believe it may offer a tas rebate.

Here is a link that might be useful: Roxul Insulation Brochure

Ibewye, were you able to find Roxul lengths other than 47"?

Thanks for all the great advice! I'll let you know which way we decide to go and how it works out!

Toxicity of building products (including insulation) is meaningless compared to your ventilation strategies.

Follow ASHRAE 62.2 or the new BSC ventilation guidelines if you care anything about indoor air quality and the best practices to achieve it.