Building Energy Technology: Assessing Net Zero Energy Buildings

Fraunhofer Center for Sustainable Energy Systems

Image of a net zero energy building evaluated by the Fraunhofer CSE research team.

Project Motivation

Zero net energy buildings (ZNEBs) are experimental structures with zero net energy usage, balancing extreme energy efficiency with on-site energy generation. ZNEBs achieve this distinction by any number of improvements, some cutting edge, some mundane. Improving the building’s envelope through additional insulation, installing high-performance windows, or airtight construction can substantially reduce utility bills and improve comfort. Advanced technology like energy monitoring systems give occupants real-time feedback of how they use their electricity. Roof-mounted solar panels can offset the home's energy needs and even feed power back into the grid. 

 

But not every improvement delivers the same results, and for homeowners and builders with fixed budgets, the biggest challenge is to balance energy savings with capital costs. To address that challenge, the Building Enclosures team turned its attention to high-performance houses in the Commonwealth of Massachusetts, setting up a sophisticated monitoring operation to analyze these structures in detail. 

 

A Whole-Building Assessment

The main objective of CSE’s research was to determine whether claims about the energy efficiency, comfort, and health benefits of the various energy-saving and -producing measures used in these buildings were supported by measured field data. To achieve this, CSE researchers set up an ongoing monitoring effort, using a range of sensors to evaluate indoor comfort, temperature, humidity, carbon dioxide levels, and electricity consumption at the circuit level over the course of more than one year. Shorter-term evaluations of a wide range of indoor pollutants were also carried out.

 

NZEHs are designed to consume as much energy over the course of a year as they produce using on-site renewable energy sources. We monitored and analyzed the energy consumption of the two homes at the circuit level, and also evaluated the quality of the indoor environment in detail.

 

A Building America Project

CSE's ZNEB assessment work was one of several research projects undertaken by a Fraunhofer CSE-led research team under a task order from the US Department of Energy's Building America Program.