The Passive House approach has two advantages in predicting building energy use. First is its physics-based understanding of building science, with modeling tools that accurately account for the flow of energy through all elements of the building, including the thermal bridges that are missed by the checklists of LEED and others. This is why Passive House-modeled thermal energy performance charts so closely to actual performance.
The chart above shows eleven new Passive House buildings and six retrofitted Passive House buildings, all located in Germany. The tall gray bar to the left shows the mean heating energy use for a non-Passive House multifamily building in Germany. The somewhat shorter bar to its right shows the heating energy use of a typical "low energy house",roughly equivalent to Energy Star homes in the US. For the Passive House buildings that make up the rest of the chart, each shows two bars: one blue (modeled performance) and one gray (actual performance). The data demonstrates both the transformational reduction in energy use of Passive House buildings, but also how accurately the Passive House model predicts energy use once the the buildings are occupied.
But even if predicted versus actual performance do not match as closely as these examples have shown, the second advantage that Passive House brings to predictable performance is one of scale. By pushing energy demand down to very low levels, the actual significance of any performance gap becomes almost immaterial. A 25% performance variance for a Passive House project amounts to about 3 kBtu/sf/yr, for example–a rounding error for most projects. But a 25% variance on a non-Passive House building is a big deal, easily amounting to 30 kBtu/sf/yr–a tenfold increase in the “performance gap.”
Passive House design optimizes the light, air, and thermal energy of a building, reducing building energy use by as much as 75%. It’s the world’s most rigorous building energy standard, charting a straight path to zero carbon building. The result is a better way to design and build, with revolutionary performance and predictable results.