By Yetsuh Frank, Building Energy Exchange
The development of US energy codes is driven by two primary factors that obscure the advantages of high-performance components and systems. The first is that our codes focus on the performance of individual elements rather than their holistic impact on overall performance of the building, and the second is using the concept of diminishing returns to determine cost effectiveness of individual components.
First, the performance requirements of various building components, whether these be window units or the insulation of exterior walls, are evaluated on a component by component basis with little regard for how these choices might impact one another. For instance, all other things being equal, the selection of extremely high performing windows may allow a project to install less insulation to meet the project’s demands, or vice-versa. Currently our energy codes provide prescriptive criteria for both, without regard to how they impact one another. Under this paradigm, you don’t get to reduce your levels of insulation because of your high-performance windows. Despite the fact that higher performing elements might pay for themselves many times over across their life span while providing far superior comfort, our prescriptive code paradigm masks their cost effectiveness and reduces the chance that they will be considered.
Second, the performance criteria of specific components are generally selected by determining a point of diminishing returns. Take insulation as an example: the first few inches of insulation in an exterior wall assembly are the most critical inches. Moving from a wall with R1 to a wall with R5 provides a huge step forward in performance, both in terms of comfort and saved energy, for very little cost. Moving from R5 to R10 you begin to see diminishing returns on the dollars spent for each unit of increased performance. It is at this point that codes professionals typically determine that it is no longer cost effective to increase the performance of the component in question and set the prescriptive requirements for that element. These criteria are perfectly sensible with regard to the individual component in question, but discourages consideration of those occasions when increasing the performance of a particular component might reduce spending in other areas. In our insulation example, imagine if rather than providing just the code mandated R 10 wall, providing an R 30 wall allowed you to significantly downsize your heating system. In that scenario, increasing the amount of insulation may actually result in spending less money.
The opportunity costs of this paradigm in terms of carbon emissions is significant. Sometimes increased performance can reduce first costs.
Certainly, there is little about our codes that precludes project teams from pursuing holistic solutions that take advantage of the type of synergies described here. And the role of our codes is to act as a backstop, to determine the minimum that must be provided, not to establish industry leadership. But our codes are the central reality of the building industry, setting the tone for virtually all design and construction decisions.
Passive House has been designed to take advantage of the interaction between envelope performance and the heating and cooling systems. The fact that Passive House is seen as such a revelation by so many in our industry speaks to the manner in which our current code paradigm has quietly shaped the way we look at decisions about building performance. Even if something like the full Passive House standard is not adopted as our energy code, it will be a huge improvement if the principles embedded in the standard become our typical approach to design decisions, altering both the cost and performance of our buildings positively.
Postscript: This piece owes a great debt to the work of Amory Lovins of the Rocky Mountain Institute. For a deeper exploration of these concepts we highly recommend Natural Capitalism: Creating the Next Industrial Revolution which he co-authored with Hunter Lovins and Paul Hawken.