Adding insulation in a house saves energy, but with each extra inch, the savings per inch diminishes. At some point, the cost of adding more insulation becomes hard to justify. At this year’s BuildingEnergy conference in Boston, three energy experts explored two questions regarding high-performance houses: At what point are envelope improvements a waste of money? And what metrics should we use to determine when enough insulation is enough? One point to these questions was to determine whether the thick levels of insulation required by the Passive House standard, an approach to superinsulation developed in Germany that is gaining traction in the United States, were justified. Because of the declining cost of PV, all three reached the same conclusion: They are not. The three presenters were David White, an energy consultant from Brooklyn; Marc Rosenbaum, director of engineering at South Mountain Company in Massachusetts; and Rachel Wagner, a designer at Wagner Zaun Architecture in Duluth, Minn. The net-zero approach White introduced a case study of a new construction project in Huguenot, N.Y., a location in climate zone 5 with about 6000 heating degree days. The owners were aiming for net-zero-energy use, where a combination of insulation and site-produced energy create…
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Interesting, but you need to get your units straight. Energy is measured in kWh and power is measured in kW what is stated above makes no sense. All of the numbers above should be kWh except the size of the PVs which are correctly stated as kW.