One of the best, and easiest ways (especially in a full log structure) to add more thermal resistance (r-value) to a structure is to increase it in the foundation level.
Typically, the majority of a foundation wall is going to be under ground, so by adding more insulation to the outside of the wall, we are neither effecting the usable space on the interior, nor are we changing the aesthetics of the home from the exterior. A perfect example of this is adding rigid insulation board to the exterior of a foundation wall. The addition of 1-2 inches of rigid foam can make or brake compliance with energy codes.
Another great way to add r-value to your foundation level is with insulated furring walls. This is a perfect method to use if you are planning to finish off any of the lower level. As a standard, most finished rooms in basements are going to incur the addition of furring walls anyway so as to give a much more cozy feeling to the room (rather than looking at bare concrete). By insulating these furring walls, we jump that wall from an R-0.8 or less to an R-13 or more.
Yet another method of adding thermal resistance to your foundation is to plan it out in advance and use some of the great foundation products that have come on the market.
1. ICF (Insulated Concrete Forms)
ICF’s are a nice way to gain r-value in a concrete wall. They basically work by using foam insulation as the concrete form that would be used to pour the concrete wall into. The only difference is while standard forms get removed once the concrete has set; the ICF’s get left in place and provide foundation insulation. ICF’s come in varying sizes and thicknesses, thus providing varying r-values.
2. Precast concrete walls
Precast concrete walls are pre-made in a factory setting, based on your home plans. They are then shipped out to your job site and set into place with a crane. An advantage of precast concrete walls is that you get not only the rigid foam insulation build directly into the wall, but most precast concrete walls are designed in a “stud wall” style using concrete studs for the strength of the wall. This means that you can also insulate between the concrete studs just as you would between wooden studs.
With so many options to choose from, there is no reason why a foundation should be the weak point of the thermal envelope.