Towards low carbon homes ? measured performance of four Passivhaus projects in Scotland

This paper will describe the results of a 2-year monitoring programme of 4 Passivhaus dwellings in Scotland. The dwellings, part of a group of 8 houses, are built in a rural location in the South of Scotland to Passivhaus standards for private rent. Construction uses an offsite timber panel system. The dwellings rely on solar thermal hot water heating, backed up by a small biomass stove, which both feed a hot water cylinder. Ventilation and heating is via a Mechanical Ventilation Heat Recovery (MVHR) system, with a post heater from the water store. In theory therefore these buildings are zero carbon in terms of space and water heating. The dwellings have been monitored for a two-year period, gathering detailed data on internal environmental conditions, and energy use, including sub-metered electrical use, along with qualitative data from interviews with the occupants and design team. The wood fuel sources have also been tested for energy content and carbon factors. Other fabric tests such as thermography, u-value testing and airtightness have been conducted. This paper will report on the results of these tests and monitoring and describe the performance of these buildings in practice. In general the performance is very good, but significant differences in occupant behaviour are noted that can affect this, and the importance of incidental gains from non-regulated energy use from electrical consumption, which may undermine the zero carbon targets and which can contribute to overheating, are discussed, as is the relative performance of the MVHR system.