Tiny House Insulation: Efficiency vs. Health

For most of my design/planning process I have been pretty sold on using closed-cell spray foam insulation. Now I’m reconsidering, and wanting go with a more natural alternative if possible.

Closed-cell Spray Foam

Closed-cell spray foam costs more than most other types of insulation (and has to be installed by a professional – so doesn’t jive with a lot of tiny house builders’ DIY thinking), but it has so many benefits:

  • Efficiency – highest R-value per square inch of any insulation material (approx R6-8/inch – great for use in the narrow 2×4 walls most tiny home builders use to maximize space, without having to sacrifice energy efficiency.
  • Air Tight – Adds to effective R-value by filling any and all gaps, to avoid any air leaks, thus creating a very air-tight envelope.
  • Structural Rigidity – dries hard and adds considerable rigidity and strength to the structural walls of the house.
  • Vapor Barrier – acts as a vapor barrier, so no extra membrane needed.
Spray foam installation

Spray foam installation

The downside:

  • Cost! – can be thousands to install – typically 30% or so above other options.
  • Hazardous Materials? –  Though many forms of spray foam have some soy content, they are still predominantly petroleum-based products.

This means spray foams are in no way sustainable, recyclable, or healthy for the house inhabitants. Though most closed-cell foam producers claim there is little or no off-gassing, I’m worried about air quality and potential health effects, not to mention environmental impact in both production and eventual disposal of the product.

Just look at the bodysuit the guy in the photo has to wear to install this stuff — that obviously is not a healthy product. Looks comparable to a uranium leak!


There are many well-known natural insulation materials. Cellulose is probably the most common. Though attractive for those with 6, 8, or 12 inch walls, most natural options are not nearly as efficient per inch as spray foam. But my current 2nd choice behind spray foam is: Natural Wool! Oregon Shepherd produces natural, sustainable, environmentally friendly and healthy wool insulation. Here are some of the benefits they advertise:

  • Fire and vermin resistant
  • Non-toxic
  • Resists mold growth
  • Acoustically superior
  • A naturally “green”, energy saving product
  • Eliminates voids and air pockets common with other insulation materials
  • Reduces air infiltration and increases the “effective R-value”
Natural wool installation

Natural wool installation

Notice the guy in this photo: Plain clothes. No health issues when coming in direct contact or breathing this material!

All these things sound vary attractive to me, but I can’t avoid the importance of a very well insulated house. I know of a few tiny house builders using this natural wool insulation who are located in the Northwest. The climate there is more mild than most of the rest of the country, so I’m wondering how well this wool will work in colder climates, if I end up somewhere with less pleasant winters.

I’m waiting to hear back from Oregon Shepherd about R-value/inch specifics in order to make my final decision. If I can devise a way to use healthy, sustainable products to achieve a similar overall insulation efficiency, then I’m certainly going to go all natural!

What do you use for insulation?

I know many people who have used and have loved spray foam. Anyone using something more natural?


Author: Alek Lisefski