Granular PCM-Enhanced Plaster for Historical Buildings: Experimental Tests and Numerical Studies

Eleonora Baccega,Michele Bottarelli

doi:10.3390/en15030975

Abstract

The construction sector is among the major players responsible for global energy consumption and therefore related emissions, both because of the constantly increasing indoor air quality standard which requires increasingly higher energy demands as well as the great share of historical buildings which are now obsolete and are not up to date with current regulations. Phase change materials (PCMs) applied on the building envelope represent a feasible possibility to improve the performance of existing buildings, also the historical ones, increasing their thermal inertia without violating any legal restriction or causing further alterations to the structure. More specifically, focus of this research was on the addition of a granular paraffin PCM into a lime-based plaster. Experimental tests at lab scale and numerical simulations with COMSOL Multiphysics were carried out to characterize the plasters realized, namely one reference lime-based plaster and one with incorporated 10% by mass of granular PCM (named REFp and PCMp, respectively). The behavior of these plasters applied on the exterior side of a wall was then simulated and compared in terms of temperatures and heat fluxes. However, considering that the estimated thermal conductivity of the reference lime-based plaster was lower than the values found in literature, the simulations were carried out considering an additional plaster, namely a lime-based plaster (renamed LITp), whose properties were found in literature and considered quite representative of a consistent share of existing historical buildings. Great improvements were observed from the application of PCM into the plaster, with reductions of the incoming energy between 9% and 18%.

Highlights

The building and construction sector is the greatest energy-consuming sector [1] with a great share of the primary energy supply deriving from fossil fuels [2]
Considering that the estimated thermal conductivity of the reference lime-based plaster was lower than the values found in literature, the simulations were carried out considering an additional plaster, namely a lime-based plaster, whose properties were found in literature and considered quite representative of a consistent share of existing historical buildings
For what concerns the first simulated wall, namely the two-brick-thick wall, on the basis of the total incoming energy between the brick layer and the inner plaster the PCM plaster (PCMp) brought about a reduction of about 9% and 18% if compared to Reference plaster (REFp) and Literature plaster (LITp), respectively

Summary

Introduction

The building and construction sector is the greatest energy-consuming sector [1] with a great share of the primary energy supply deriving from fossil fuels [2]. The constantly increasing demand for thermal comfort inside buildings is leading to greater energy requirements for ventilation and air-conditioning [5] which, without any improvement to the actual scenario, is estimated to increase by 80% till 2050 if compared to 2010 levels [6] The causes of this are to be found first of all in the change in people’s lifestyle, where living standards are higher and higher with a consequent rise of the internal heat gains due to the electrical equipment, in the impact of the urban heat island effect especially in crowded cities, and lastly in the decrease of the cost of the cooling equipment [7]. Among the methods that nowadays are used to improve the building envelopes’

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Conclusion