Assessment of the Thermal Performance of Non-residential Building Envelope Prototype Specimens Insulated with Porous Cementitious Nanocomposites Containing Phase Change Materials, Using a Hot Box Apparatus

Abstract

The NRG-STORAGE project aimed to develop innovative, energy-efficient cementitious foams (NRG-Foams) as a sustainable alternative to conventional insulation materials for non-residential building envelopes. NRG-Foams were designed to balance thermal insulation and heat storage capacity while maintaining volume stability and mechanical integrity. The base material consists of a highly conductive cement paste with air bubbles that provide insulating properties. Enhanced heat storage performance is achieved by incorporating microencapsulated phase change materials (MPCM). This study evaluates the thermal performance of wall prototypes constructed from masonry bricks or concrete, insulated with NRG-Foam panels containing MPCM volume fractions ranging from 0% to 20%. Key thermal indicators—including thermal transmittance, decrement factor, time lag, periodic thermal transmittance, energy savings, and dynamic thermal resistance—were assessed using a NETZSCH HotBox Test Chamber TDW 4040 under both steady-state and dynamic conditions. While thermal performance improved progressively with increasing MPCM content, reaching a maximum at 20% MPCM, it did not surpass the performance of specimens with standard insulation materials. Nevertheless, the findings highlight significant potential for further optimization, particularly with higher MPCM volume fractions. Such enhancements could enable NRG-Foams to outperform conventional insulation materials, especially in long-term thermal analyses conducted under more realistic conditions. In addition, the influence of issues encountered during the experimental procedure on the thermal performance assessment of NRG-Foams is also discussed.