Energy performance of net-zero and near net-zero energy homes in New England

Objective: To investigate the energy performance of net-zero energy homes (NZEHs) and near net-zero energy homes (NNZEHs) in New England. NZEHs produce at least as much energy as they consume on site in a year, while NNZEHs are designed to come close to net-zero. Methods: We gathered construction and occupational statistics on 20 homes; measured 12 months of energy consumption, cost and production data; developed custom models to predict consumption and production; and compared measured performance to modeled predictions. Results: Six out of ten NZEHs achieved net-zero energy or better, while all the NNZEHs achieved an energy density (kW h/m(2)/person) at least half as low as a control house; measured energy consumption averaged 14% below predictions for the NZEHs and 38% above predictions for the NNZEHs; and generated energy was within +/- 10% of predicted for 17 out of 18 on-site PV systems. Conclusion: Even in cold New England, these types of homes, using very diverse systems and designs, can meet or exceed their designed-for energy performance, though actual performance varies widely. Practical implications: Architects, engineers, and policymakers now have quantifiable evidence in support of increasing energy conservation requirements and renewable energy incentives in residential building codes in New England. (C) 2013 Elsevier B.V. All rights reserved.