Department of Architecture and Civil Engineering

On the passive climatic control of earth building materials

At a glance

Funding body: University of Bath
Principal investigator: Andrew Heath
Co-investigator: Enrico Fodde
Researcher: Fionn MacGregor
Dates: 2010-2013


Compacted soils, in their many vernacular forms have been traditionally used as building materials. Recently, sustainability concerns have raised the profile of compacted soil as a construction material in modern applications. This is partly due to passive climatic control exercised by earth materials on indoor environments. Depending on the building envelope configuration, earth materials can provide a thermal and moisture balance between outdoor and indoor environments or buffer against thermal and moisture indoor fluctuations.

While the context of partly saturated soil mechanics has been used to characterise the strength and deformation properties of earth building materials, so far simplified building physics models have been used to assess the climatic control exercised by earth materials. These approaches are somewhat limited in that they assume both a linear rate of moisture transfer and linear moisture storage capacity.

This work proposes an alternative model to simulate the response of an earth building envelope whereby the rates of heat and mass transfer across the earth building material are dependant on the driving thermal and pressure gradients but also, on the available mass (water content) and hence, on their partly saturated condition. Thus, this work aims to rigorously define experimentally the relationship between the water content, flow properties and matrix suction over a wide suction range for some typical earth building materials.