In August of 2016, we posted a video describing the design and construction of the foundation and floor framing of our High Performance Tiny House in Florida.
Since then, we have made a lot of progress. We've also prioritized the design and construction of an off-grid, "zombie proof" homestead, and its permaculture farm, in the mountains of North Carolina, which kept us from sharing our experiences and shedding our knowledge on the blog! Alas, here is an update. Welcome to today's post!
Where we left off at the tiny house...
Whether you're seeing the video for the first time, or not, you heard me talk about insulating both the cavities and continuously on the outside of the sheathing. What I hope you picked up on, in the video, is that to achieve that continuity with the sheathing, we built the floor in sections, and upside down.
If we had set the floor joists on the masonry foundation wall, first, the sheathing would have been interrupted by the double sill plates on top of the masonry. This detail would have been much more complicated to deal with, but still doable.
By keeping the sheathing continuous, on the outside of the structure, we maintain continuity of our control layers, which gives us a "perfect" enclosure. And, by having continuous insulation, that has the appropriate hygrothermic (drying potential) and thermal properties, on the outside of the sheathing, we've protected the structure from exposure to the elements. This helps prevent LOTS of things that cause building failure (e.g. Rot, Mold, Freeze, Thaw, etc.), not to mention keeps us comfortable inside the house (This is a very good thing).
Rock wool insulation works for framed floor, wall and roof/ceiling.
I've mentioned before why I like building with rocks. While it's not practical to use rocks for everything in the structure of the home, rocks could be the best ways to insulate. From the drying potential, as illustrated in the video below, and described in this blog post from July 2016, to the R-Value that increases as the temperature drops, to the fact that rocks don't burn, there are fewer and fewer reasons to NOT insulate with rocks.
After finishing the floor framing, we were ready for insulation. We started by insulating the cavities with 6" Batts (R-26.4 max at colder temperatures), and then installed the continuous 2" rigid (R-8.8 max at colder temperatures) rock wool insulation on the outside of the sheathing. As I mention in the "perfect enclosure" blog post, the walls and the roof were insulated the exact same way. Four (4") to six (6") inches of cavity insulation, with two (2) inches of continuous rigid insulation on the outside.
In a later post, I will explain the many reasons why using ONLY continuous exterior rigid insulation, with absolutely NO batt insulation in the cavities, is absolutely the most effective and simple way to insulate a building. HANDS DOWN. For now, we'll talk about using rock wool insulation batts in the cavities, too.
Here are pics from the installing the rock wool insulation batts and rigid board, before, during and after, at the High Performance Tiny House (Florida).
For more on designing and building high performance homes, whether they're tiny or "zombie proof", be sure to read more of this blog, and follow along.