The Home Energy Rating (HERS) Index is an industry leading metric of a building’s energy efficiency. As the index and its methodology are widely known and respected, it provides a solid metric for calculating not only the energy usage of a given home, but also the savings generated by various energy efficiency measures. For example, a home that scores 70 on the HERS index is 30% more efficient that one which scores 100. And the home which scores 50 on the index is 28% more efficient that the home which scores 70.
In terms of actual scores, the average new home today scores right about 100. In contrast, the average home for resale in the US scores 130, which makes sense when one considers that newer homes tend to be constructed with newer, more efficient materials and techniques. Going further down the scale (i.e. more efficient), LEED* certifications (probably the most well-known green certifications), begin at around 85. And, the Architecture 2030 standards aim for a score of 50 by the year 2030. For another data point, the current Passive House standard comes in at 20. Finally, at the very end of the scale, a building that uses no energy or produces the same amount of energy it consumes scores a 0.
Thinking about the points on the scale, we feel that Passive House deserves a special mention. Even a forward looking specification such as Architecture 2030 aims for a 50% improvement in energy efficiency. And, remember, that target is for something almost two decades way. On the other hand, Passive House, scoring about 20, represents an 80% improvement in energy usage from today’s reference house. And this is something that is achievable today! Considering that buildings consume 49% of all the energy consumed in the US, the potential for energy savings and a reduction in the carbon footprint are staggering. Passive House and other forward looking standards are literally decades ahead of their time.