The HERS rating of a standard new home is by definition 100. Any rating lower than 100 represents the percentage improvement in energy efficiency over the typical new home. In other words, a new home with a HERS rating of 70 performs 30% better than the average new home.

The Unity Home that recently came in with a HERS rating of 34 is 66% more energy efficient than a typical new home! The impressive efficiency of a Unity Home translates into attributes that directly affect the quality of life of the building’s occupants: comfort, quiet, health, low maintenance and predictable, affordable operating costs.

Another rating system that has been widely adopted is the Environmental Protection Agency’s Energy Star for Homes program, which grew out of the EPA’s Energy Star Appliance program. As with most green building rating systems, Energy Star for Homes has evolved as building codes have become more stringent and building practices have improved. Version 3 of the Energy Star for Homes program, which took effect in 2011, requires (among other things) that a HERS rating be established for each home.

The rating is one of several factors used to establish compliance with the program. While the Energy Star for Homes program has had an admirable impact on raising awareness and increasing efficiency in the home building industry — and many state and utility incentives are based on it — Unity has tended not to emphasize the program, simply because they believe that more rigorous standards are necessary and achievable.

Many people are familiar with the LEED rating system, which stands for Leadership in Energy and Environmental Design. Originally conceived in the mid-1990s by the United States Green Building Council (USGBC), the LEED system has over the years become one of the most widely-used green building benchmarks in the US. The LEED system has evolved to include programs aimed at specific building types and construction scenarios. Unity’s sister company Bensonwood has built eight LEED-certified homes to date, and many more that are considered LEED certifiable.

The stringent Passive House standard originally developed in Germany has gone from being a fringe player in the US to garnering increasingly broad support. The first Passive House built by Bensonwood in Vermont in 2010 demonstrated the wisdom of using off-site construction techniques to clear such a high bar. A key to the performance of Passive Houses is the air-tightness requirement of 0.6 ACH50, a standard that Unity hits regularly with its homes (ACH50 is “air changes per hour” at a depressurization of 50 Pascals).

The US Department of Energy program known as Zero Energy Ready Homes (ZERH) takes a holistic approach to establishing standards for homes that would be considered “ultra-high performance” from a conventional perspective, but what at Unity is called as “typical.” Unity homes are designed, engineered and built to be Zero Energy Ready: with the addition of a modest solar electric system, they produce as much energy as they consume.

While the Zero Energy Ready capability of Unity Homes is impressive, some green building thought leaders suggest that this standard does not go far enough. The Living Building Challenge is based on the notion that buildings should not just have a net zero impact on the environment; rather, they should be net positive in terms of energy, water and waste, and they should contribute to the resiliency of the communities in which they are located. Bensonwood recently provided the engineered timber structure to a new building at Hampshire College that has been designed and engineered to meet the criteria of the Living Building Challenge.