The combined effect of heat and moisture transfer dependent thermal conductivity of polystyrene insulation material: Impact on building energy performance

Abstract The aim of this article is to elucidate the combined impact of heat and humidity transfer on the thermal conductivity of polystyrene used as an insulation for building envelope. In building energy assessment, the conductivity of the insulation material is assumed to be constant. This yields inaccurate results, as the thermal conductivity, k-value, of any material is a complex function of many factors, such as temperature, moisture, and density. This dependence has been shown in extant studies and linear variation of the thermal conductivity vs. temperature have been proposed for fibrous materials. Accurate evaluation of building thermal comfort and energy assessment, which requires a precise calculation of the cooling load, and thus the sizing of the HVAC equipment, depends on the accurate determination of the thermal resistance of the building envelope components, the insulation material in particular. The aim of this work is thus to inspect the combined effect of operating temperature and moisture content on the thermal conductivity of polystyrene insulation material and its impact on the energy performance of buildings. The results reveal that the k-value of the polystyrene insulation is significantly influenced by its moisture content at different operating temperatures. Indeed, an 8% increase in the total cooling load calculated at 28 °C and 30% moisture was measured relative to the base case evaluated at 24 °C and 0% moisture.

[1]  Moncef Krarti,et al.  Potential energy savings from deployment of Dynamic Insulation Materials for US residential buildings , 2017 .

[2]  Karolos-Nikolaos Kontoleon,et al.  Dynamic thermal response of building material layers in aspect of their moisture content , 2016 .

[3]  Mohammad S. Al-Homoud,et al.  Variations of Thermal Conductivity of Insulation Materials Under Different Operating Temperatures: Impact on Envelope-Induced Cooling Load , 2002 .

[4]  L. Cremaschi,et al.  Moisture behavior of polystyrene insulation in below-grade application , 2018 .

[5]  I. Budaiwi,et al.  The impact of thermal conductivity change of moist fibrous insulation on energy performance of buildings under hot–humid conditions , 2013 .

[6]  Robert Černý,et al.  Effect of moisture content on heat and moisture transport and storage properties of thermal insulation materials , 2012 .

[7]  M. Khoukhi.  Change of the Thermal Conductivity of Polystyrene Insulation in term of Temperature at the Mid Thickness of the Insulation Material: Impact on the Cooling Load , 2016 .

[8]  A. D. Tran-Le,et al.  Modeling thermal conductivity of hemp insulation material: A multi-scale homogenization approach , 2016 .

[9]  U. Berardi.  A cross-country comparison of the building energy consumptions and their trends , 2017 .

[10]  Hua Ge,et al.  Determination of optimum insulation thickness for building walls with moisture transfer in hot summer and cold winter zone of China , 2015 .

[11]  L. Ye,et al.  The effect of moisture content on the performance of polyurethane insulation used on a district heating and cooling pipe , 1997 .

[12]  M. Khoukhi,et al.  Effect of Temperature and Density Variations on Thermal Conductivity of Polystyrene Insulation Materials in Oman Climate , 2015 .

[13]  Hans Müller-Steinhagen,et al.  Effective thermal conductivity of moistened insulation materials as a function of temperature , 2008 .

[14]  M. Khoukhi,et al.  Effect of Operating Temperatures on Thermal Conductivity of Polystyrene Insulation Material: Impact on Envelope-Induced Cooling Load , 2014 .

[15]  Luisa F. Cabeza,et al.  Experimental study on the performance of insulation materials in Mediterranean construction , 2010 .

[16]  Abdul-Mohsen Al-Hammad,et al.  A Comparison between Actual and Published k-Values for Saudi Insulation Materials , 1994 .

[17]  Moncef Krarti,et al.  Control strategies for dynamic insulation materials applied to commercial buildings , 2017 .

[18]  Y. Çengel.  Heat Transfer: A Practical Approach , 1997 .

[19]  P. Fazio,et al.  Determination of Optimum Insulation Thickness of Exterior Wall with Moisture Transfer in Hot Summer and Cold Winter Zone of China , 2015 .

[20]  Bjørn Petter Jelle,et al.  Traditional, state-of-the-art and future thermal building insulation materials and solutions Prope , 2011 .

[21]  Joseph Andrew Clarke,et al.  A rational approach to the harmonisation of the thermal properties of building materials , 2009 .

[22]  B. Draoui,et al.  The impact of changes in thermal conductivity of polystyrene insulation material under different operating temperatures on the heat transfer through the building envelope , 2016 .