https://passivebase.com/Build a clearer understanding of the details behind whole-building performance.enhttps://passivebase.com/articles/why-large-buildings-can-have-a-lower-n50/https://passivebase.com/articles/why-large-buildings-can-have-a-lower-n50/A large building can have a lower n50 even when its leakage per square metre of envelope is no lower. The reason is geometric: n50 divides the airflow at 50 Pa by the test volume, while q50 divides that same airflow by envelope area. A building with less envelope area per cubic metre therefore gets a lower air-change rate for the same area-normalized leakage. The number describes the chosen denominator as well as the envelope’s leakage. [1] [2]Mon, 12 Oct 2026 00:00:00 +0000https://passivebase.com/articles/why-an-external-dimension-psi-value-can-be-negative/https://passivebase.com/articles/why-an-external-dimension-psi-value-can-be-negative/A negative Ψ-value from an external-dimension calculation does not mean heat travels from outdoors into the building. Ψ is a difference between the heat flow calculated through a junction and the heat flow assigned to the adjoining plane elements. Changing the reference dimensions changes that subtraction, so the residual can change sign while the underlying modelled heat flow stays the same. The conversion below is illustrative, not a measured or published junction result. [1] [2]Mon, 12 Oct 2026 00:00:00 +0000https://passivebase.com/articles/what-a-gap-between-positive-and-negative-pressure-results-reveals/https://passivebase.com/articles/what-a-gap-between-positive-and-negative-pressure-results-reveals/A gap between pressurisation and depressurisation results can reveal that airflow through the tested envelope differs by pressure direction, or that test conditions and measurement variation contributed to the difference. Field and research reports describe direction-dependent airflow through leakage paths and around door and window seals, while measurement guidance explains why repeated readings can vary. The gap alone cannot distinguish these explanations or identify a component. Compare the paired pressure-flow curves, baseline readings and site observations before treating a component explanation as more than a hypothesis. [4] [2] [1] [3]Mon, 12 Oct 2026 00:00:00 +0000https://passivebase.com/articles/how-sigma-ua-psi-l-and-point-bridges-combine/https://passivebase.com/articles/how-sigma-ua-psi-l-and-point-bridges-combine/The direct transmission heat-transfer coefficient combines three contributions: ΣUA for plane elements, ΣΨL for linear junctions and Σχ for point bridges. Each contribution is expressed in watts per kelvin (W/K), so the terms can be added. The sum is meaningful only when the areas, U-values and bridge calculations use compatible boundaries and represent each heat flow once. Ground heat transfer and transfers through unconditioned spaces or to adjacent buildings may be separate terms in the broader transmission coefficient. [1]Mon, 12 Oct 2026 00:00:00 +0000