Big Picture: Broad and Surprising Findings

Conclusions

This analysis uncovered two enormous surprises and one big irony. The first surprise is that recent improvements in solar technology and cost make residential PV installations not only viable, but financially lucrative. The second surprise is that many upgrades to the building envelope, historically done in the interest of environmental responsibility, actually return relatively small environmental benefits that are most often outweighed by environmental harms. Conventional wisdom has everyone thinking that the first step is reducing energy demand, and then add solar as a secondary step. Unfortunately, very few homeowners can afford the investments needed to achieve energy savings from building envelope upgrades, and they never get to the solar step; most also do not understand the true costs (and overall benefits) of onsite solar. The outcome is predictable; almost no progress in reducing harmful environmental impacts from the residential sector. 

We need to think of onsite solar as the first priority rather than the afterthought. When household energy use is met by onsite production of cleaner and cheaper solar energy, suddenly the building envelope becomes much less important. Every dollar invested in solar PV has direct, known, and significant impact in reducing environmental harm, at least when displacing fossil fuel-derived energy. That claim cannot be made for any building envelope upgrade, most of which have negative financial return and net negative environmental impact.

The enormous irony is that the answer has been right in front of us, yet seemingly elusive. Because our decisions are too often driven by short term knowledge or interests (immediate costs) without a full understanding of longer term results, we’ve missed the integrated and life-cycle whole. Our focus on the trees in front of us veiled the trees behind and the forest as a whole. In our research we demonstrate that the most responsible environmental choice in most U.S. housing markets is the basic, least-costly, code-minimum house with solar PV providing annual energy needs. Our analysis firmly suggests that the most responsible choice environmentally happens to be the least costly option, not only initially at construction, but operationally through its life cycle and at decommissioning. Another irony is that environmental interests in the industry still advocate robust, premium building envelopes and this, unfortunately, limits action to the wealthy few and drives a belief that nothing meaningful can be achieved except with enormous financial investments.