Our project is below 5,000sf which makes it automatically not eligible for an ENERGY STAR rating. There are two distinct space types, office + K-12 classroom. Based on this information, the project team is required to use option 1 from the offline LEED calculator. The calculator determined the combined benchmark source EUI to be 179.
This is where I get confused, or the math part of my brain is not working today. The project team is striving to reach a target of 35% better than the benchmark. If I calculated this, the project building should aim for a target of 116 ( 179 *.65). The calculator, on the other hand, determined the project building should be 86. I'm scratching my head on this....Does the calculator take into account other variables?? Thanks.
Jenny Carney
Vice PresidentWSP
LEEDuser Expert
657 thumbs up
November 20, 2011 - 10:42 am
The calculator is set up to show the percentile change in consumption, not percent reduction, which is why it seems like the math isn't working. Energy Star, and the Case 2 calculator, both work on the use of percentile points.
If you imagine a bell-shaped curve distribution, the distance between one percentile point on the curve and the next varies depending if you are near the top, along the steep sides, or down in the tails. Which means you can't just calculate the percent reduction (where the EUI difference between a reduction 35% to 36% is the same as from 36% to 36%) and have it equal the same amount of change in the percentile points.
Which is a confusing way to say that if you want to set a target EUI for your building, decide on the percentile you want to hit, and then adjust the EUI input in the calculator until is shows that you've hit your goal.