A New Path: Outcome-Based Compliance
I bought a car last spring that was rated 29 mpg highway. Now conventional wisdom is a new car will never actually achieve the performance rating given. Those numbers are for comparison only and “actual mileage may vary.”
So imagine my surprise when, after returning from a road trip this summer over which my average speed exceeded 50 mph, I learned that my gas mileage for that trip had exceeded the 29 mpg rating. My actual mileage was 29.2 mpg.
Now, if I hadn’t actually received the 29 mpg I would not have any recourse. I might have taken the car back to the dealer and at best perhaps received a tune up. But I certainly would not have been able to return the car or require one that did meet the 29 mpg target.
The same is typically true with regards to the energy performance of buildings. Typically energy conservation codes provide two methods for complying with that code–a prescriptive method and a performance method. Both methods are based upon a goal of not using more than a certain amount of nonrenewable energy per square foot of building, over a certain time period. The prescriptive method tells the builder exactly how to build the building to achieve compliance, and the performance method permits the builder to vary from the prescriptive design, as long as the estimated energy usage under the proposed design does not exceed that of a standard building built according to the prescriptive method.
In either case, there are no provisions to review and evaluate the actual energy usage of the building after it has been built. The actual outcome of the building’s energy use is not evaluated.
ICC's Green Code
The latest draft (PV2) of the International Code Council's International Green Construction Code, however, will include an outcome-based compliance path as an alternate to the prescriptive and performance based design for energy efficiency currently used by other energy conservation codes. It will also limit use of the prescriptive path to buildings that are under 25,000 square feet.
When a building is built using the new outcome compliance path, it is to be designed, constructed, commissioned, operated and maintained to limit peak net energy demand during the building’s anticipated peak consumption period, and direct and indirect CO2 emissions, so as not to exceed targets that have been chosen by the jurisdiction. These targets are to vary by occupancy, so that a different target might be selected, for example, for an office building in comparison to a factory or storage building.
The intent of this is to ensure that the actual energy usage of the building does not vary from the originally intended target of the relevant energy conservation code. The need for this is obvious. Anytime one makes a decision to proceed with a plan, they need to weigh the estimated cost versus potential benefit. And if it is found that the cost is too great, they do not proceed. If they do proceed, once the plan is in place they need to evaluate the outcome. Was the cost within its estimated range? Has the benefit received been consistent with what was hoped for?
If not, then perhaps they need to go back and make some changes. Perhaps the plan can still work, it just needs some tweaking?
This is a fairly common practice for business people who have to make decisions about investments and reinvestments in their business. So it becomes apparent why such an approach within a code for sustainable construction might be worthwhile. The problem with the approach within the IgCC is that, at the present time at least, it appears to be somewhat incomplete.
The IgCC does give some provisions for evaluating the performance of individual systems within the building. For example, IgCC PV1 requires a commissioning of the energy systems of all buildings that consume energy. Commissioning is defined as a process that “verifies and documents that the selected building systems have been designed, installed, and function according to the owner’s project requirements and construction documents, and to minimum code requirements,” except as noted within the IgCC.
The requirements of IgCC PV1 for the commissioning of the building’s mechanical system call for the development of a commissioning plan, which prescribes the testing of the mechanical system that is to be performed, along with a preliminary and final commissioning report. The requirements for the building’s lighting system are similar, except they add a requirement for a post occupancy report for the re-evaluation of the lighting systems 24 months after occupancy of the building has occurred.
The requirements for the commissioning of the building envelope are not nearly as well developed. The registered design professional responsible for the design of the building is to “provide evidence of building thermal envelope commissioning and completion in accordance with the International Energy Conservation Code” and the IgCC. The commissioning is to include pre-construction documentation, drawing notes that specify the provisions for commissioning, and verification by an approved, independent agency that the building thermal envelope system has been installed in accordance with the approved construction drawings. But the exact requirements under which this is to occur have not been specified, and would need to be determined on a project by project, jurisdiction by jurisdiction basis. The changes made to IgCC PV2 will provide little clarity to this section.
Furthermore, it would appear that the requirements for evaluating the outcome of the building are incomplete. Although post occupancy reports are required to document the performance of certain systems, there are no requirements to evaluate the performance of the building as a whole.
Also missing are any incentives for the building to achieve its targeted outcome. No potential ramifications of a building not achieving the targeted outcome, with regards to the estimated or anticipated energy usage or CO2 emissions, are given. Prior to occupancy the building’s owner, and all who are being paid by the owner, have an incentive to bring the building into compliance with the code so that a certificate of occupancy will be issued, and the building can be occupied. Once the COO has been issued and the building is occupied, what recourse will the code official have is the building is then found to no longer be in compliance with the IgCC, through post occupancy commissioning reports?
While the concept of outcome-based compliance, coupled with commissioning, may have some validity, it is clear that further work needs to be done before concept becomes practical application. Perhaps the next version of the IgCC will provide greater guidance.