There are several different ways to build a house, each having their own advantages and disadvantages. The most common approach is called ‘stick-built’, which refers to the 2x dimensional lumber used to construct a wall. Stick-built walls, which are comprised of the dimensional lumber, sheathing, and insulation, are normally assembled at the location of the structure being built. An alternative approach to building residential and light commercial structures are called SIPs (or what are sometimes referred to as tiny house SIP panels).
There are three different types of insulation I considered for my tiny house;
Spray foam – I thought this might be the best choice since it has a high R value and there would be no leaks (since it is sprayed in to all the nooks and crannies). The reason I ultimately decided against it is because this is not a DIY solution and thus likely much more expensive.
Fiberglass – I’ve worked with fiberglass before and it is fairly inexpensive and very easy to install. The problem is it doesn’t have the highest R value (~ 3.4 per inch).
Styrofoam Boards supplemented with spray foam – This is a little more expensive than fiberglass (I’m not sure exactly what the comparison is) but has a much higher R value of 5 per inch. This was my choice because I thought it was the next best thing to pure spray foam and it was something I could do myself.
After working with the Styrofoam boards I think my decision might have been flawed, and in hindsight would have chosen differently. The first and most important reason is that while the R value of the Styrofoam is much higher per inch, the boards that I am using are 2 inches thick, thus giving me an effective R value of 10. If I were to use fiberglass, I would fill the entire wall cavity and thus have an effective R value of 12. Couple that with the ease/speed of installation (the boards are a huge pain and mess to work with) and the lower cost I think fiberglass would be the way to go for warmer climates (my TH is headed to Florida). For colder climates I think I would spring for the spray foam insulation.
This is something that needs to be done right the first time since it isn’t easy to change out. I would love to hear any opinions.
Fun fact: While researching R values I read that 1 inch of insulation is equivalent to 30 inches of concrete!
UPDATE: I have since worked with the styrofoam more and experimented with different cutting tools (circular and hand saw) and no longer find it as difficult to work with. I also got a better tool (Hilti) to inject the foam into the cracks. In addition, if I had used 3″ foam my R value concerns would be alleviated as well.
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