Home Energy Improvement Index
Dave Bohac, P.E.; Jenny Edwards; Carl Nelson; Isaac Smith
The Center for Energy and Environment has developed a home energy efficiency index for use with its residential energy program, targeted at cost-effective retrofits for existing homes.
The purpose is to help increase implementation of major energy upgrades by providing homeowners with a simple yet quantitatively robust indication of their current status, and their potential for major energy upgrades. The simple visual design can also add value to a program marketing campaign.
The key features of the index are:
Results use a fixed scale from 0 to 100 points. All homes can achieve a perfect score.
A score is based on the cost-effective upgrades relevant to the specific style and age of house, and points are assigned using the relative energy savings of different measures.
Upgrade recommendations are divided into near-term and long-term options.
The index uses a prescriptive approach. The Minnesota version focuses on five upgrades that are the major determinants of a home’s heat loss.
- The index, while reliable, requires minimal field staff time to gather data and can be generated quickly with fewer than 20 inputs about the home’s current condition.
CEE used the SIMPLE Model, developed by Michael Blasnik and Associates, to evaluate the energy savings of five key residential upgrade measures for Minnesota homes: heating system efficiency, wall and attic insulation levels, air sealing, and window panes. Based on CEE program experience and analysis, these represent all of the potential cost-effective measures in the vast majority of Minnesota homes (other climates will include a different set of prescriptive measures). The relative savings change based on the style of home, and the point system adjusts accordingly. For instance, older homes have narrower wall cavities than newer homes, and will have lower savings potential—and therefore points—from insulating empty walls. We call this a “prescriptive approach with quantitative weighting,” and points are determined in the following way:
Total points for each of the five measures are fixed for a given style and age of home; each measure is ranked based on its relative importance to home energy savings.
Remaining points for each measure will depend on a home’s current state (e.g. existing furnace efficiency or insulation levels).
We are currently finishing a report that summarizes the Energy Index and our experience with the first 800 scored homes. Check back soon for results.