One thing to note about the professional spray foam is that it is quite expensive. Also, there are concerns about how spray foam impacts indoor air quality. Considering this we started looking into options that are less expensive and are less environmentally harmful. This search led us to Roxul, a product essentially made from rocks. It is fairly inexpensive and since it's made from natural sources, it doesn't have the same environmental and health concerns as some of the other options.
Initially we decided to go with Roxul and started seeking out deals. We were lucky that before we found a great deal we realized that using Roxul as our insulation we would be adding roughly 1500 extra pounds to our Tiny Home (if used to insulate the entire house). We need this house to be road worthy so weight is a real issue. All materials used need to be as light as possible. This fact quickly ruled Roxul out for us.
After deliberation we decided to go ahead and use a standard extruded rigid foam board insulation. The price was right and it was fairly easy to instal (could easily be sawed to size and fitted into place). Between each floor joist we laid 2 pieces of 2” sheets and then one 1” sheet to fill the cavity.
Although we ruled Roxul out as our main source of insulation, we did decide to use a small portion. We created channels around the perimeter to serve as a place for our plumbing and to allow access for inspection and maintenance of our fasteners/connectors.
Since Roxul is very flexible we could easily fit it around the plumbing pipes. This flexibility will also allow us to easily remove the insulation later on if we need to get at the pipes or check the hardware.