Twenty years from now, when fuel prices are substantially higher, it will be relatively easy to go back and add some more insulation in the attic. Perhaps it will be less simple, but possible, to improve the foundation Rvalue, and windows could be upgraded, by replacement if necessary. The toughest area to improve will be the walls. The options for walls will likely be the same as those available today, forcing the removal and replacement of siding, or the destruction and renovation of the interior of the shell. Because this component is the most difficult and costly to improve later, I build R-30+ walls and thus I'm always in search of the elusive "easy" way to do this. If one