Area 12
Building materials and building thermal physics
Air conditioning is the largest tertiary-sector electricity load. Phase-change materials, bio-based insulation, coupled transfers.
Context
Reducing the cooling load is the most cost-effective energy efficiency measure in the tertiary sector, and it is decided entirely in the physics of the envelope: conductivity, inertia, coupled heat and moisture transfer.
Yet the available hygrothermal models and passive solutions were developed for temperate or hot-dry climates. In a hot, humid climate with low diurnal temperature swing, several founding assumptions collapse.
Open questions
What the literature does not settle
Phase-change materials: what melting temperature and enthalpy are optimal when the diurnal temperature swing is small? Does latent storage retain any value outside desert climates?
Bio-based insulation (coconut fibre, rice husk, earth–fibre composites): how do thermal conductivity and diffusivity vary with moisture content, and are these properties stable under sustained high humidity?
Coupled heat–moisture transfer in massive earth walls: are hygrothermal models calibrated in temperate climates transposable, and where do they fail?
Physics of comfort in humid conditions: what quantitative relation between operative temperature, humidity, air velocity and actual cooling load?
Passive radiative cooling coatings: what net gain under an equatorial overcast sky, where the atmospheric window is partly closed by water vapour?
Feasibility
Guarded hot plate, hot box, hot-wire conductivity meter, instrumented test cells: the equipment is largely built on site.
Methods and facilities
- Thermal conductivity and diffusivity measurement versus moisture content
- Instrumented test cells under real conditions and calibrated hot box
- Calorimetry of phase-change materials
- Hygrothermal simulation of walls and buildings
- Spectral emissivity measurement and radiative balance under overcast skies
Target outcome
Reference thermophysical data for bio-based and raw-earth building materials and passive design rules that cut the tertiary sector's largest electrical load.
Simulated production chain
Production of bio-based insulation and phase-change materialsFrom the manufacturing process to the costed cooling savings on a real building.Related areas
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Indium-free transparent conducting oxides, iron-based soft magnetic materials, dielectric ceramics.
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Computational physics
DFT, molecular dynamics, multiphysics simulation: electronic structure, phonon transport and point defects.
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