Accurately Measuring Building Energy Use
- Jul 7, 2018 12:59 am GMT
In recent months, there has been some debate about the advantages and potential disadvantages of remote building energy audits.
At the same time, however, on-site audits have also been the subject of recent discussion and scrutiny, albeit in a slightly less publicized manner. Most notably, the U.S. Department of Energy’s Energy Efficient Buildings Hub (EEB Hub) recently used their temporary headquarters, the Philadelphia Navy Yard building, to conduct on-site energy audits using three different providers. The goal? To better understand the variability in audit results for commercial buildings.
The tested building is a fairly standard representation of an office building – 62,000 sq. ft., four stories, standard mechanical equipment and full occupancy across the year.
The results that EEB Hub revealed were enlightening. Contracted to report on energy usage, costs, and recommendations for efficiency improvements, the three auditing teams arrived at distinctly different conclusions for how the building should be upgraded. Only a few measures (such as CFL lighting and condensing boiler upgrades) were universal across all three audits, and the reported energy savings potential ranged from $22,000 to more than $60,000. Measure prioritization and payback times also varied considerably across the three auditing teams.
And this is just one example. In late 2011, the ASHRAE Journal’s article “10 Common Problems in Energy Audits” found that errors such as overestimated savings, poor energy conservation measure (ECM) selection, and missed ECM’s were present in well over half of on-site audits. This past October, an Energy Engineering article titled “Eight Ways in Which a Poor Quality Audit Can Prove Costly to the Building Owner” warned that experience-levels, as well as the strengths and weaknesses inherent in every auditor/auditing team, can lead to varying outputs and degrees of overall accuracy.
How can we take the subjectivity – and therefore the variability – out of building energy analysis? The EEB Hub argues that “standardizing assessment” can play a big role in limiting variability. The argument is that if everyone is using a different yardstick, it’s hard to create apples-to-apples building efficiency comparisons. The Investor Confidence Project, a venture by the EDF and Efficiency.org, is taking a similar standardization approach in creating commercial building protocols to drive larger energy efficiency investment.
I believe that these standardization initiatives can absolutely lead to more reliable on-site results. However, I also believe variability can be limited by starting with the data, as opposed to starting with a person. A remote audit solution, for instance, enables past energy consumption to tell us the story of how a building consumes energy. The process by which we reveal efficiency opportunities is highly analytical, structured and repeatable.
HVAC system use, for example, is determined by hourly-level analysis of consumption data across the entire year, rather than through varied modeling approaches and subjective discussions with the building operator. Savings are reconciled for every hour by end use against the baseline energy consumption, so the seemingly common traditional on-site mistake of overestimating savings is effectively impossible.
It is important to state here that analytics are not meant to fully replace the traditional on-site audit. For buildings with deep retrofit potential, for example, investment grade on-site audits provide a level of engineering and financial rigor that remote analytics cannot reach. In some cases, the two approaches are seen as naturally complementary. However, just as remote audits can be scrutinized for their accuracy, depth, and overall relevance in the world of commercial efficiency, it’s important to recognize where traditional approaches have their limitations as well.
Photo Credit: Building Energy Audit/shutterstock
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