For those interested in ICF construction
As an FYI to people interested in building with ICF (Insulated Concrete Forms)...
We just moved into our newly constructed house. We build using ICF partially for sound-proofing and its inherit solid construction, but also for energy efficiency.
Until yesterday we didn't really know how efficient the construction was - we had a modeling done before - but we just received the outcome of our actual Home Energy Rating and here is our number: HERS Score of 41.
This is for a house with a conditioned space of > 5000 sq.ft and without the use geothermal or solar assistance.
While it will be pretty expensive to change the building envelop of house, we still have the option to add solar assistance in a couple years (if and when the prices come down a bit more).
However, the extra price for a geo unit - even after a 30% tax break - combined with the low energy cost of a low HERS score house puts the pay-back period for geo into the 20 yr plus realm meaning that for us that's not an option.
Here is a link that might be useful: HERS Score post on our blog