Types, Benefits, and Installation Techniques

Insulation can be tricky, depending on climate zone, local building codes, off gassing, and R-Values. I’ll give the description of each and my recommendation at the end of this section. 

Batt Insulation – we’ve all seen this. Typically, it is pink insulation that may or may not have paper glued to one side of it. This was the standard for years, and, though the off-gassing isn’t horrible, the R-Value is less than optimal – the max R-Value in a 2 by 6-inch wall is R21. Unfortunately, batt insulation leaves an air gap around wires, pipes, ducting, etc. For this reason, it is very difficult to make batts “form fit” when there are items in the way. 

This image represents the difference between Batts and Blown Cellulose around items in the stud cavity. You can see how the cellulose product is packed tight around each item vs the batts.

Cellulose 

For most people this is insulation typically blown into attics, and is referred to as Net and Blow, when in walls. With this product the R-Value for a 2×6 wall is R-24, which is currently 3 points higher than the 2021 code of R-21. It is worth mentioning that blown cellulose from 20-plus years ago would settle in the walls, eventually leaving a gap of a few inches to a foot at the top of each stud cavity. This would be a dramatic reduction in energy efficiency, however, that problem has been solved by modern-day cellulose technology, which does not settle. 

Closed Cell Spray Foam – this product goes on wet and dries very hard. The R-Value cannot be met by any other product. In a 2×6 wall with 5 inches of closed cell foam, you get an R-Value of 35. It can also be sprayed in the attic, and about 9.5 inches will give an R-Value of 66. There are three specific challenges with closed cell foam.

1. It’s very expensive – roughly 2.5 times cellulose insulation 
2. The off gassing of closed cell foam is quite significant and can remain for several years, especially in warmer seasons. If you suffer from multiple chemical sensitivity (MCS) this is most likely not the product for you. 
3. When this product is sprayed directly onto the inside of wall sheathing or underneath side of roof sheathing, it can create a major dewpoint problem, which allows condensation to form between the closed cell foam and the plywood. 

The damage cannot be seen, but the mycotoxins (basically the off gassing of mold), will find their way out of the wall system, eventually. In addition, several roofing companies and suppliers are voiding the warranty when this product is sprayed in the attic directly on the plywood. There are some exceptions to this. If you use a air gapping system on the wall or in the attic (foam baffles installed), the air gap thwarts mold growth by allowing air flow and, thus, the moisture to move out of the system. This air gap still needs air flow, so venting at the top of the roof down to the eaves is crucial. Standing seam or corrugated roofs with “Dens Deck” also provide an air gap. 

Rockwool / Mineral wool – This is a great product that many people choose for healthy home insulation. However, there are draw back which we’ll discuss below. 

Don’t be fooled by the two different names, these are the same products with two commonly used names. However, wool is certainly a misnomer. Rockwool is made of basalt rock and recycled slag, which is a metal smelting biproduct. It is a great fire-retardant material. It is often used in floor, wall, and exterior insulation applications. It’s easy to cut and install. Rockwools R-Value is 4 per inch, which means with 5 ½” inches you can reach R-22. Rockwool has the least amount of off gassing as it’s very close to zero. 

My concern with rockwool is that like batts, but more severely, it doesn’t conform around wires, pipes, etc. Almost all pictures of it look like the one below, without anything in the wall, which is never reality. I think there are other products which are just as safe regarding toxicity but are much better for insulating your home.

Exterior insulation – I am a huge fan! Especially when used with an air gap. Exterior insulation greatly increases the R-Value of your home and helps to eliminate the dewpoint problem. Rockwool is an option and assuredly the less-expensive option, but my favorite is the Zip System, with Polyiso insulation attached to the inside of the plywood. Polyiso insulation has minimal off-gassing compared to other products. 

Other forms of insulation – like Rockwool or Polyiso (continuous rigid insulation) can be attached to the outside of the sheathing. 

Below is an image using Rockwool

The image below depicts Polyiso (rigid insulation) with wood battens over it, so you get the benefits of exterior wall insulation and the necessary air gap.

Exterior wall sheathing Zip System

My favorite option for mold sensitive, allergic, or CIRS-afflicted people is the Zip System with 1 inch or more of Polyiso on the exterior, and Knauf cellulose for the stud cavities. Knauf has the safest and least amount of formaldehyde. With this combination of technologies, you can reach between R-27 with ½” Zip insulation and R-36 with 2” Zip insulation. 

As clarification, all these options will add cost to your project, and your budget is important.

Make sure the bids you receive are clearly defined and meet the health needs you have for your remodel or new home.  

One last point. In the Blueprint above, I mentioned avoiding OSB when at all possible, in a wall system. However, the Zip System with insulation on the interior side the sheathing seal the OSB and do the best job at keeping the unhealthy formaldehyde out of your living space.