A Neil Armstrong moment: That’s when you realize that some unremarkable event is actually the result of a long, arduous, and purposeful process.
We at Bergmeyer recently had one of those Neil Armstrong moments. We finally got a look at how one of our project’s post-occupancy energy use compared with its designed energy use. There it was: actual performance versus design intent. If your firm has signed the AIA 2030 Commitment, you’ll understand why this felt a bit like walking on the moon.
Each year, we record the energy use intensity and lighting power density for every project we design and compare our whole-firm numbers to a declining scale that will get us to zero by 2030. But those numbers are not for actual energy use. They’re theoretical. And as we dutifully and optimistically send those numbers to the AIA every year we wonder: how do our projects actually perform?
But getting actual energy performance data wasn’t as easy as it sounded. After many false starts and frustrating meetings, we have succeeded – with lessons learned. So if you’re thinking about doing your first post-occupancy energy use analysis, consider this advice:
1. Pick the right project: For our first venture into POEs, simpler was definitely better. We used a small, owner-occupied built-to-suit office building as our beta project. Something where the energy use sectors looked familiar (think ASHRAE Advanced Energy Design Guide) and where the building users were the same people who paid the utility bills. That disqualified a lot of our retail and restaurant projects (as tenants in their spaces) and our university projects (too many different parties involved in building finance and operations).
2. Pick the right client: The first several clients we asked to share actual energy use data were reluctant. It was either “our electricity costs are not a problem” or “that information is private” or “we don’t want to be your guinea pig!” The right client for us turned out to be one that understood our mission. The willing client, Historic Boston Inc., is an organization committed to strengthening Boston’s neighborhoods through historic preservation. The building – the Eustis Street Fire House – was built in 1859 in Boston’s Roxbury neighborhood. It was gutted to the structure and historic exterior shell and adaptively-reused as HBI’s headquarters.
We simply asked HBI if we could use their energy use data to help us learn and become smarter. They kindly agreed.
3. Find a good data aggregator: We used WegoWise. They’re a web-based utility tracking and benchmarking company that is committed to using data and analytics to promote building energy efficiency and mitigating the effects of climate change. Good people to have on your side.
4. Don’t flub the math: The first data you get will not be in a useful form. Our first report from WegoWise was about 30 months’ worth of raw energy use numbers. To begin, pick a twelve-month baseline period. Then convert those kilowatt hours of electricity into BTUs, divide total BTUs by 1,000, and divide again by floor area to get kilo-BTUs per square foot per year. Gas use is recorded in “therms”, which also needs to be converted to KBTUs/SF/yr and added to the electricity use. Now you’re apples-to-apples with your energy modelling results.
5. Don’t fear the results: Our beta project performed pretty well in year 1. Our energy model described a designed intent Energy Use Intensity (EUI) of 74.02 kBtu/sf/yr. The actual first-year performance data was 76.64 kBtu/sf/yr: only 3% higher than designed. Pretty remarkable given the number of variables involved the gut renovation of a historic property. And we were still 5% more energy efficient than benchmarked New England buildings. Not bad.
But at 42 kBtu/sf/yr., our AIA 2030 Commitment target was quite a bit lower than even our designed EUI. And our year 2 WegoWise data is showing a mysterious 10% increase in overall energy use . . . which of course gives us an opportunity to go back to our gracious, mission-driven clients to understand the reason for the increase. And to get even smarter.
That’s the story. OK, it’s not nearly as big a deal as that historic stroll from Apollo 11 at Tranquility Base on July 20, 1969. But still. It was one giant leap for Bergmeyer.
This post originally appeared on the blog of Principal Mike Davis, FAIA