Hi Paul,

In the commercial and industrial sectors where facilities are more finely tailored to the specific needs of each business, and where the choice of alternative sites is more limited and relocation to a new facility is considerably more complicated and costly, I see your point, but I'm not so sure the same can be said of our homes. The residential real estate market is much larger and more fluid, and there's a far greater range of product to chose from; consequently, if your needs or personal circumstances change (e.g., a divorce/separation, birth of a new child, kids move out, etc.) it can be easily exchanged for another. In any event, tearing down an existing structure and rebuilding from scratch involves a large commitment of capital, all of which must be secured upfront, whereas improving the thermal efficiency of a home can be accomplished over an extended period of time, as and when funds permit -- for a good and growing number of us, there's really no other option. In addition, some of us simply prefer older homes to new construction, for a variety of reasons, not withstanding their various deficiencies.

Secondly, although upgraded homes may never achieve the same level of technical performance, as you start to narrow the gap, it becomes pretty much a moot issue. I use this same argument when comparing air and ground source heat pumps -- it doesn't really matter if a ground source heat pump is twice as efficient as its air source counterpart if the home heating costs of one is $50.00/year and the other is $100.00. At some point, good does become good-enough. Along the same lines, if I can't afford to replace my old, leaky windows with new, high performance, low-e/argon units, a couple of inexpensive 3M window kits might very well do the trick -- my heating costs may be a little higher, but it's affordable and it could free up funds that could be better spent on other efficiency improvements that will generate a much higher return at the margin.

Cheers,
Paul