Energy Modeling: Structure, Strengths and Loopholes

RealLifeLEED is (sadly) back from his glorious vacation, but is happy to continue bringing the best in obscure LEED resources to you hardcore in-the-trenches AP's. Today I'm letting you know about an interesting article written by PhD and ASHRAE Fellow Stephen Kavanaugh about the strengths and loopholes associated with energy modeling, specifically related to ASHRAE 90.1:

Rating High Performance Buildings: What Architects and Owners Should Know

This article brings up a good point about the ASHRAE model, specifically that it won't necessarily be a good representation of the actual energy use! Kavanaugh cites a study that found LEED building's modeled and actual energy use differed by an average of 62%!!! The small graph on the page indicates that it's a roughly 50/50 split between over and underestimations.

It's important to understand what is included in the energy model, and how you shouldn't guarantee the client anything about reduced electricity bills. Though the building is modeled to have low energy use, an owner with a penchant for ice-cold workspaces or a retailer who loves open front doors could ruin the best intentions of your designs.

I personally had little knowledge about what's included in the models until I took a VERY useful USGBC half-day workshop entitled "Understanding Energy Modeling in LEED for New Construction Projects". It was amazing to me how quickly you can use free modeling programs to setup a rough baseline building and play with different features and conservation measures to see where you stack up. The final model will need to be completed by someone who knows what they're doing, but early simulations can provide some interesting insights for amatuers.

Energy modeling problems or helpful hints? Please share your thoughts by leaving a comment!


Anonymous said...

Welcome back Real Life Leed team..we were waiting for your valuable posts

Urban Harvester said...

I don't understand how the Energy Cost Budget Method is misleading for expected energy efficiency for LEED projects when it isn't allowed for EAc3 qualification. You have to use the Performance Rating Method... is this method also inaccurate? I can see the problem with HVAC systems, but I don't understand the point with energy simulations.