Friday, January 6, 2012

Sustainable Construction Options For Exterior Walls


As I mentioned in my last posts, we are finally building our cabin. Over the next few posts, we'll tell you all about the options we are choosing for our cabin. 

While ICF walls (insulated concrete forms) are, in my opinion, the best choice for exterior walls, especially in large houses, based on insulation value and structural integrity, we just could not allocate the funds for ICF for this project. The materials are very expensive compared to conventional mthods. Since this is a cabin, not a full-time home, we may never see the ROI (return on investment) from the insulation/energy savings. Of course, ICF provides more value than just energy savings; they also provide excellent sound buffering and is not flammable. The latter is so important in a semi-arid region. However, it is hard to put a dollar value on those. 

Another good choice for exterior walls are SIPs (structurally insulated panels). These consist of foam sandwiched between plywood. These are manufactured to precise measurements at the factory and then later assembled on site. These are a great choice for the same reason as ICF- high insulation value and structural integrity. Plus, there is very little waste. However, the dimensions must be perfect (ie: plans drawn by an architect) and assembly requires both an experienced crew and a crane. There's no way we could have gotten a crane down our road and since we wanted to avoid paying an architect, this option was not feasible for us.

So, while our exterior walls are not filled with concrete, they are much better than regular walls because they are extra thick. Instead of building with 2x4's on 16" centers (meaning that the wall's studs are placed every sixteen inches), as is conventional construction methods in most new neighborhoods, we chose to build with 2x6's on 24" centers. Studies have shown that this method actually doesn't cost much more than conventional 2x4 on 16" centers, and it's just as structurally sound. Plus, thicker walls will allow us to put more than the usual amount of insulation. The same amount of insulation value as ICF or SIPs without the extra cost. 

More insulation means it will take less energy to heat or cool the space. And, that's sustainable! 

We haven't made the final decision on what kind of insulation to use, but we are really leaning towards spray foam.  We'll talk more about these options in a later post.