This paper reports on six Technology Strategy Board funded projects that are examining the performance of a range of new build low energy houses throughout Scotland. These are two- year monitored projects that capture quantitative data on energy consumption and environmental conditions including air quality, but also qualitative data through interviews and surveys with occupants and designers. The projects (n=26) have a number of varying characteristics, including different types of construction and design intention, including some Passivhaus, and more mainstream social housing. The paper will examine and compare early observations of comparative performance in respect of air quality. Factors include occupancy and ventilation behaviours, but also include room volume, openings, and mechanical systems. The study identifies trends in terms of high temperatures and CO2 levels, particularly in bedrooms overnight.