CH-12-032 -- Passive Houses: What May Happen When Energy Efficiency Becomes the Only Paradigm? PDF

Buildings need to be energy efficient. Nobody doubts that. However, when it becomes the sole paradigm, unwanted consequences may be the result.

In this paper, the case of a passive house is discussed; this house was declared uninhabitable less than two years after the inhabitants, a family of five, moved in. The enclosure consisted of a timber-framed façade finished with a brick veneer and a pitched tiled roof, both with U-factor 0.13 W/(m²·K)/0.023 (Btu/[ft²·h·°F]), argon-filled, low-e (layer with low long wave emissivity covering the cavity looking glass surfaces in double or triple glazing) triple glazed timber windows with average U-factor 0.74 W/(m²·K) (0.13 Btu/[ft²·h·°F]) and a floor-on-grade, annual mean U-factor 0.16 W/(m²·K) (0.028 Btu/[ft²·h°·F]). A balanced ventilation system with heat recovery supplied the fresh air, while a heating coil in the supply duct after the recovery unit cared for heating. Supply air first passed through a ground tube before entering the recovery unit. Airtightness should have been such that n50 did not pass 0.6 h-1.

Soon after moving in, the inhabitants complained about degrading health. On-site measurements showed the indoor air was quite polluted, while relative humidity was remarkably high. A closer look revealed stagnant water in the ground tube, a too-low fresh air supply, an inadequate design of the ventilation, heating, and domestic hot-water system, and an oriented strand board (OSB) air barrier inside the enclosure that turned quite humid at the rain-side during summer and acted as effective UF-source that way.