A long-term monitoring study on the thermal comfort and durability of a straw bale Passivhaus cottage

Abstract

The built environment sector accounts for 40% of the UK's total carbon footprint; bio-based construction materials can play an important role in reducing the whole-life carbon of a new build. Straw bale construction is one of the most promising bio-based methods of construction, due to its availability and material properties. Among the declared benefits of straw bale construction are the internal regulation of heat and moisture and the ability of the fabric to dry out. This paper presents a long-term monitoring study aimed at understanding the indoor temperature and moisture balance of a straw bale cottage built in the UK to a near Passivhaus level. The study lasted 6 years, monitoring the temperature and relative humidity of the indoor and outdoor environments, and in ten locations within the straw bale walls. The analysis has shown that the indoor environment achieved thermal comfort throughout the monitoring period, even when the building was used intermittently. Also, an analysis of surface temperatures and a mould growth risk analysis identified very limited mould growth risk within the building fabric. This paper shows the potential of straw bale low-energy construction in providing thermal comfort and a durable building fabric while minimising the whole-life carbon of buildings.