Seite - 51 - in Water, Energy, and Environment - A Primer

affordable ZEHs can be built with standard construction techniques andoff-the-shelf equipment.’ A word about cost: today ZEBs cost more to build than traditional office buildings and homes, but not much more – perhaps 5 to 10% for new construction – but this gap is closing rapidly. Part of this extra cost is recovered via reduced energy bills. In the future, the zero energy building goal will become more practical as energy efficiency is emphasized, the costs of renewable energy technologies decrease (in the way that solar PV costs have decreased significantly in recent years) and the costs of traditional fossil fuels increase. The recent surge in availability of relatively low-cost shale gas thanks to fracking will slow this evolution, but it will eventually occur. In addition, in the US, DOE has established two goals for residential and commercial buildings: create energy systems integration solutions that will enable marketable ZEHs by the year 2020 and commercial ZEBs at low incremental cost (relative to traditional buildings) by the year 2025. These objectives alignwith theEnergy Independence andSecurityAct of 2007 (EISA),which calls for a 100% reduction in fossil-fuel energy use (relative to 2003 levels) for new Federal buildings andmajor renovations by2030. SomeadditionalpointsaboutZEBs/ZEHs:whileanindividual building or home may use an average of net zero energy over the course of a year, it may demand energy from the grid at other times when peak grid demand occurs. In such a case, the grid must still provide electricity to all loads, and a ZEB may not necessarily reduce the required power plant peak capacity. In addition, current definitions of ZEBs/ZEHs do not mandate aminimum performance level for heating and cooling the building shell, thus allowing oversized solar PV systems to fill the energygap. A further consideration is that the energy consumption in an office building or home is not strictly a function of Energyoptions 51