Experimental and numerical thermal performance assessment of a multi-layer building envelope component made of biocomposite materials

• Published in: Energy and buildings Vol. 214; p. 109846
• Main Authors: Arregi, Beñat, Garay-Martinez, Roberto, Astudillo, Julen, García, Miriam, Ramos, Juan Carlos
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01-05-2020; Elsevier BV
• Subjects: Air gaps; Anchoring; Assemblies; Biocomposites; Biological materials; Biomedical materials; Building envelope; Building envelopes; Composite materials; Construction materials; Deviation; Energy consumption; Fabrication; Framing; Heat flow meter method; In-situ measurements; Insulation; Lightweight; Mathematical models; Monitoring; Multilayers; Numerical models; Performance assessment; Prefabrication; Prototypes; Thermal bridges; Thermal conductivity; Thermal resistance; Thermal resistance; Building envelope; Biocomposites; In-situ measurements; Heat flow meter method
• ISSN: 0378-7788; 1872-6178
• DOI: 10.1016/j.enbuild.2020.109846

•Thermal performance is assessed for a wall module from bio-based materials.•Numerical models are compared to measurements from a full-scale prototype.•The effect of framing profiles on thermal resistance is specifically investigated.•A workmanship defect is linked to a 5x increase in additional heat flow of profiles.•When suitably mounted the component achieves a U-value of 0.27–0.30 W/m²K.
Building envelope systems are rapidly evolving, driven by increasingly stringent requirements for limiting energy consumption. Current trends favour lightweight, prefabricated wall assemblies with high levels of insulation, which have been shown to be particularly sensitive to thermal bridging through anchoring and framing elements. This paper presents a self-supporting multi-layer wall component made from bio-based materials, where novel biocomposite profiles are used instead of conventional metallic frames. The thermal performance of the proposed solution is calculated from numerical modelling and characterised through in-situ measurement of a full-scale prototype. For the plane areas of the wall with continuous insulation, theoretical calculations are broadly in line with results from experimental monitoring (7–15% deviation). Additionally, an area along a framing profile was specifically monitored, and it was found that the numerical model overestimated thermal resistance with a deviation of 121%. The presence of air gaps between the rigid insulation and framing elements, linked to the fabrication process of the prototype, was identified as a plausible cause. A subsequent explanatory numerical assessment, considering the effect of such cavities in the numerical model, provided results that are consistent with measurements from the experiment and previous literature. The study aims at demonstrating the insulation levels achievable with the use of novel bio-based materials of low thermal conductivity, and more generally, contributing to a better understanding of the thermal performance of framed lightweight insulated assemblies in service conditions, by monitoring and modelling the impact of thermal bridges and workmanship at framing elements.