Optimising the hygrothermal and structural properties of cob for thermally comfortable and energy-efficient homes in Jordan: an exploration using experimental and computational methods

Haddad, Kamal 2025. Optimising the hygrothermal and structural properties of cob for thermally comfortable and energy-efficient homes in Jordan: an exploration using experimental and computational methods. PhD Thesis, Cardiff University. Item availability restricted.

	PDF - Accepted Post-Print Version Restricted to Repository staff only until 11 September 2026 due to copyright restrictions. Download (13MB)
	PDF (Cardiff University Electronic Publication Form) - Supplemental Material Restricted to Repository staff only Download (201kB)

Abstract

The environmental impact of construction materials, such as concrete and steel, is a growing global concern. Cement production alone generates 8% of global carbon emissions, while the construction sector accounts for 30% of energy use and 27% of related emissions. This highlights the urgent need for sustainable alternatives. Jordan, the geographical context of this research, is highly vulnerable due to its 96.4% reliance on imported energy. Jordanian residential buildings consume 43% of the national electricity, with heating and cooling accounting for 57% of household demand, at an average energy use intensity (EUI) of 91.4 kWh/m2. These challenges underline the need for climate-responsive, low-energy construction strategies suited to the country’s climatic and energy profiles. This research investigates cob, an earthen building material composed of subsoil, water, and natural fibres, as a potential sustainable alternative for constructing climate-adaptive, hygrothermally comfortable, and structurally stable homes in Jordan. Accordingly, a three-layered methodological framework was developed to examine cob at the constituent, material, and building levels. At the constituent level, experimental techniques such as sieve analysis, X-ray diffraction, and scanning electron microscopy were employed to characterise subsoil and fibre components. Drawing on these findings and existing literature, 51 cob mixes were formulated with varying fibre types, fibre content, and water ratios. Material-level analysis was conducted in three sequential phases: initial testing, a variability experiment, and detailed hygrothermal and structural performance testing. Initial tests of proposed mixes assessed bulk density, thermal conductivity, volumetric shrinkage, and compressive strength, offering insights into how material composition affects performance. The variability experiment investigated the influence of sample preparation methods on the material’s performance, leading to the development of 10 optimised mixes. The final phase involved a detailed assessment of hygrothermal performance, encompassing thermal conductivity at various humidity levels, volumetric and specific heat capacities, water vapour transmission properties, moisture buffering capacity, and structural properties. Results demonstrated that cob’s improved thermal performance and excellent moisture buffering capacity iii suggest strong potential for reducing energy consumption and improving occupants’ comfort. At the building level, findings from the material-level experiments were used as inputs in WUFI Pro simulations to assess the hygrothermal performance of cob walls under different thickness and orientation scenarios. These scenarios were benchmarked against Jordan’s building regulations to identify the wall’s configurations. Parametric modelling informed the design of two architectural configurations: cube-based and dome-based, optimised using Grasshopper and Ladybug tools. Optimisation objectives included reducing EUI and maximising thermal comfort while maintaining the floor plan area to 120 sqm. The results highlighted that dome-based configurations outperformed cube-based designs, achieving a 27% reduction in energy use intensity while maintaining 81% thermal comfort, compared to a 3% reduction and 78% comfort compliance in optimised cube-based designs. This research contributes to the knowledge of sustainable construction by developing a methodological framework that links material-scale characteristics to building-scale performance. It offers empirically derived benchmarks for cob mix optimisation, integrates experimental material characterisation with computational research methods, and provides region-specific insights applicable to energy-vulnerable and climate-challenged contexts like Jordan. These findings support architects, researchers, and policymakers in promoting sustainable, energy-efficient, and structurally viable housing solutions.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Architecture
Date of First Compliant Deposit:	11 September 2025
Last Modified:	12 Sep 2025 15:12
URI:	https://orca.cardiff.ac.uk/id/eprint/181044

Actions (repository staff only)

Edit Item