Energy-Saving Design: Investigation of the Thermal Performance of Rammed Earth Residential Buildings
October 20, 2015
Earth Dwellings Australia, with the the University of Western Australia and the Department of Housing are investigating the ACTUAL performance of rammed earth houses. “Numerical and experimental investigations available in the literature show contradictory results. Factors such as hydroscopic behaviour, that is the ability of the wall to control indoor humidity, and how the house is used by residents are not adequately treated in current decision frameworks and policies. ”
Two identical houses have been built in Kalgoolie, both are rammed earth except one has insulated panels inside the rammed earth. There are sensors placed throughout the houses and walls measuring temperature and relative humidity. There is now a website showing details of the project and preliminary results. The aim is to measure the thermal performance of occupied rammed earth houses.
The preliminary results make very interesting reading. “Although insulation is effective at separating the inner and outer parts of the walls, comparing results for the monolithic and insulated houses shows something quite unexpected. There is no real difference between the room or ceiling temperatures in both houses. Both houses show a roughly steady internal temperature of around 20 to 25 degrees even when subjected to a sudden cold snap which occured on the 15 November 2014. Although the temperatures in the walls dropped, this heat was successfully transferred in to the house so internal air temperatures remained largely unchanged. Some questions therefore need to be asked about how these houses perform, specifically why the inclusion of insulation does not affect air temperatures inside the house. A possible explanation might be that the non-rammed earth part of the houses’ envelopes around the kitchen, bathroom and the roof, are ultimately controlling internal temperature. Another might be that thermal bridges in the insulated rammed earth walls where the insulation was not present, for example around windows, allowed heat to bypass the insulation entirely. These questions are being investigated as part of the ongoing project.”