Typically over looked in Maine, foundation insulation is an integral part of making your home more energy efficient. The average foundation in Maine has an R-Value of 1, that is the same as a single pane of glass… The 2nd law of thermal dynamics teaches us that heat always flows to cold. So when our home sits atop a foundation with almost no resistance to heat loss it leads to more expensive fuel bills and a less comfortable indoor environment.
We insulated the foundation of this Gray, Maine home (pictured to the left) with fire rated 2″ Thermax polyisocyanurate foam board. Note the cut out of the foundation and the framed daylight wall above which we insulated with dense pack cellulose. This foundation went from R-1 to R-13.5 in just a few hours time. So instead of most of the heat from your furnace or boiler being absorbed by your foundation, it can now travel up into your living space.
We use three types of rigid foam insulation on our poured foundations:
- Fire Rated Thermax (polyisocyanurate) which can stand alone and does not need a fire rated barrier.
- Non fire rated polyisocyanurate, which needs to be covered with a fire rated barrier like 1/2″ sheet rock.
- Extruded foam board, which also needs a fire rated barrier.
For granite or stone foundations we use vetted sub contractors to install 2″ of closed cell spray foam. We do not recommend spray foam for poured foundation walls. While spray foam is a good insulator the added expense, higher rate of installation issues, the need for home owners to vacate their residence for 24 hrs, and the negative environmental impact lead us to use this product only where absolutely necessary.
We often package insulating a foundation with the installation of a durable vapor barrier, aka basement encapsulation.
Below is an example of the non fire rated polyisocyanurate. This basement will be finished with sheet rocked walls and ceiling
