Lessons from post occupancy evaluation and monitoring of the 1st Passive House in Scotland

This paper describes an investigation carried out to understand the performance in practice of the first certified Passive House in Scotland and associated low or zero carbon technologies LZCT. The aim was to provide some useful feedbacks on actual performance in order to inform and hopefully improve building industry processes and policy. Monitoring was carried out on three dwellings on the west coast of Scotland. All dwellings are within 250m of each other with similar orientation and occupancy but were built to different standards representative of: 1950’s Scottish building standards; 2010 Scottish building standards; and Passive House standards. The Passive House included mechanical ventilation with heat recovery (MVHR), air to air heat pump and solar thermal hot water heating LZCT systems which are in general being encouraged for new build and retrofit. The monitoring was carried out over 1 year and included indoor environment (RH, CO2, T), outdoor conditions (Solar, T, RH), energy use (Watts, kWh), operation schedules, and hot water system temperatures (T). In parallel with the monitoring, the Passive House and associated LZCT were investigated by inspection and observation and by comparison with both the Passive House Planning Package (PHPP) and the recommendations of the Certified Passive House Designer course. There were many interesting findings from the investigation, these included: lower and more consistent CO2 levels in the Passive House than in the houses without MVHR; poor layout and ducting of MVHR system giving poor energy performance and condensation problems; poor controls and specification of air to air heat pump giving poor space heating performance; poor control of solar thermal hot water system reducing performance; lack of occupant understanding of operation and maintenance for the LZCT systems. The lessons learned are relevant to all future implementations of these LZCT systems in the building stock both new build and retrofit. Possible improvements in industry and Passive House processes are discussed