Energy usage of households accounts for a significant portion of total energy consumption and carbon emissions. Scottish homes today are highly energy consumers emitting on average 3 tonnes of CO2 per house annually and the amount exceeds the UK average of 2.75 tonnes of CO2. Moreover, 26% of the households are actually facing fuel poverty. It is therefore a critical task to efficiently manage and minimise energy usage in housing in order to meet carbon dioxide (CO2) emission reduction and energy consumption cut targets such as 80% overall cuts in carbon emissions by 2080 for the UK, compared with 1990 levels. The study has been undertaken within the Zero Energy Mass Custom Homes (ZEMCH) research network’s demonstration projects - e.g. ‘ZEMCH 109’. The house was intended to be built in South Ayrshire, Scotland, in early 2012, added to the adjacent existing post-council end-terraced house. As part of the project, the Building Environments Analysis Unit (BEAU) research centre has conducted a post occupancy monitoring of the energy and indoor environmental conditions (e.g. indoor air temperature, relative humidity and CO2 levels) in the Scottish affordable home which will also continue even after the construction of the newly built extension and the refurbishment of the existing home. It is important for the successful demonstration of the ZEMCH 109 project that detailed monitoring and post occupancy evaluation (POE) of the exiting NRGStyle home are performed sufficiently in order to investigate the relationship between human behaviour and energy consumption, and the indoor environmental conditions.