insulation options
There are many options to consider for insulating a conventionally framed home. From the basic industry standard batt insulation to spray foam systems. As different as the insulation systems are, so are the associated costs. Like most people I tend to look for a higher quality product that is cost effective compared to the benefit afforded. It would be nice to have the best of everything in every home, but few of us have the funds available to budget this way.
We also tend to focus on “R” value more so than air infiltration. A better gauge of effectiveness and cost vs benefits of an insulation system beyond code minimum values is air infiltration. That being said I am not a fan of a house sealed so tight that a mechanical system, using energy, is needed to provide minimal ventilation.
In our geographic region (Bend, Sisters, ad greater Central Oregon) batt insulation in the walls and floors, with blown-in insulation in the ceilings (with batt insulation in slopped ceilings) is the standard, and least expensive, conventional insulation system.
At the other end of the spectrum are systems of spray foam insulation, primarily in the ceiling, but also can be used for wall insulation. This system results in a non-vented attic space and very little air infiltration. I’ve used this system in a roof application and it works very well, but is also very expensive compared to most other options.
As custom home builder I’ve found the best option is a combination of blown-in insulation and batt insulation. I use the conventional system, except I replace the batt insulation in the walls with blown-in insulation. This approach costs a few hundred dollars more for a whole house compared to using batt insulation for the walls. But it eliminates air gaps and other potential problems from improperly installed batt insulation. The reports I viewed years ago when first switching to this system stated that blown-in insulation in the walls reduces air infiltration by 38%, and added an extra 1 or 2 points to the “R” value. There are several companies with several types of blown-in wall systems that I’m sure have different properties but all should preform close to the base-line statistics quoted above.
Using the insulation system above with an osmosis paper wrap (Tyvek or similar) will result in a reasonably tight home that will still let water vapor out.