Sub Floor Part Four – Insulation

409 In this post, we will look at the laborious process of insulating the floor. It took me a few days of work to get it finished properly.  We chose solid core foam insulation by RMAX. After a lot of research and fumbling we discovered that solid core foam has one of the highest R-Values per cubic inch. It is also resistant to moisture and mold and is less attractive to pests then many other types of insulation.  403 414 I did my best to place the cross blocking at even intervals, but most compartments to be insulated were not the same size.  This fact essentially precluded pre-cutting all of the insulation at once. Each individual compartment had to have the foam cut exactly to size.  we used 5 inches of insulation and 1/4 thick shims to completely fill each space.  To create 5 inches of insulation we had to stack three pieces in each space; two at 2″ and one 1″.  There were over 45 large compartments and several smaller ones.  What does all this add up to? I hand cut over 150 pieces of foam to fit unique spaces.  Labor intensive!!! Cutting: The first thing I tried was a hack saw blade. This worked well to cut, but tended to wander and produce a crooked cut. Next I tried the table saw., and even set up a shop vac to catch the dust. Though the pieces were delightfully square and easy to make, one day of the dust in my hair eyes and lungs (even past the dust mask) and I was seeking a new method.  Finally I settled on using a metal ruler as a guide and a Ginsu Fillet knife with a thin blade to do the cutting. Though it required more elbow grease, the cuts were clean and straight enough and the dust was minimal. Installation:  Actually installing the cut pieces was very easy. the foam had enough give that it was a snap to push it down in place. Some compartments had angles and/or bolt heads protruding into the compartment. It was a simple matter to cut a notch in the foam to allow it to slip into place.  I filled gaps with spray foam, and made collages of scrap pieces in the middle of the three layers to get the most for our money. The collage method worked well enough that I came out one full sheet of insulation ahead of my projections! 420 Above my Older son is standing on the mostly completed insulation job.  The wheel well spaces still had glue curing, so I chose not to seal them until the last minute.  In the end it took over 4 days to get this job done.  Why bother with such a laborious method? Why not just lay down the pink fiberglass and be done with it? In the end it came down to R-Value.  I calculated an estimated total R-value of 32.5 for only 5 inches of insulation! The rigid materials which compose the foundation and the 1/4 air space beneath the foam add a couple of points with the foam making up about 95%.  What is so amazing about this fact is that it takes twice the thickness of standard fiberglass insulation to reach this same number.  32.5 R-value is enough to sustain us in light to moderate snow climates, especially with the smaller square footage involved in tiny houses.


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