0 Helpful?

Rockboard [mineral wool] or polyiso?

I'm planning a new house. I've been thinking in terms of 2 3/4" of polyiso on the exterior of the walls. However, I'm now thinking that dense rockwool board *might* be better at least from the standpoint of the wall being able to dry to both the outside & inside. I kinow I'd be giving up some r value, but perhaps I could just up the thickness ? I'm in climate zone 4 Western NC in the mountains. Probably using zip sheating under either insulation board.

Asked by Roy Goodwin
Posted Jun 12, 2014 8:08 AM ET
Edited Jun 12, 2014 9:03 AM ET


2 Answers

Select your preferred way to display the comments and click "Save settings" to activate your changes.

To read the accounts of two projects with mineral wool insulation on the exterior side of the wall sheathing, check out these articles:

Installing Roxul Mineral Wool on Exterior Walls

Wrapping an Older House with Rock Wool Insulation

You might also want to read:

Installing Mineral Wool Insulation Over Exterior Wall Sheathing

Answered by Martin Holladay, GBA Advisor
Posted Jun 12, 2014 9:02 AM ET


I'm in Upstate SC and did exactly that on our new house. We put 2" Roxul Rockboard wrapping the entire exterior. I chose Rockboard, because I could not easily get Comfortboard. The big box stores have to order Roxul Comfortboard in large pallets and wait for a full load before they order. They estimated 6 weeks for a shipment. I got Rockboard easily from ATS Acoustics online in less than a week. I think Rockboard and Comfortboard are the same product. Here is the GBA post talking about the 2 products:

Patrick Walshe's blog, http://agreenhearth.com, has a good discussion on using mineral wool.

My blog has some information as well. http://greenvillegreen.blogspot.com/2013/10/cozy-mineral-wool-sweater-on.... You could hit the mineral wool insulation under labels and see the posts on how we used the Roxul.

Answered by Lucy Foxworth
Posted Jun 12, 2014 1:20 PM ET
Edited Jun 12, 2014 1:21 PM ET.

Other Questions in Energy efficiency and durability

ZIP R-Sheathing Climate Zone 5?

In GBA Pro help | Asked by Joseph Yount | May 12, 15

Is there spray-foam insulation without harmful chemicals?

In Green products and materials | Asked by Susannah Shmurak | Dec 1, 15

Heating and finishing a basement in a well-insulated house

In Green building techniques | Asked by Denis | Dec 1, 15

Pros and cons of Grace Ice and Water compared to Tyvek Drainwrap

In General questions | Asked by James Timmerberg | Nov 29, 15

Which adhesive for sub-slab vapor barrier seams?

In Green products and materials | Asked by Josh | Dec 1, 15
Register for a free account and join the conversation

Get a free account and join the conversation!
Become a GBA PRO!