MCDA assessment of multi-layered envelopes. Case of additive and multiplicative convolution

Abstract

The Multi-Criteria Decision Analysis (MCDA)has been proposed for the choice of the “best” multilayered assembly in terms of its thermal resistance, mass and cost assessment. In the general case, the multilayered assembly can consist of the bearing layer and the insulation layer. In some cases (autoclaved aerated concrete (AAC), hempcrete, etc.) it could be enough to erect the external wall of the building without any additional layer of insulator which meets the National Code`s thermal resistance requirements. As a basic consideration of current research as a bearing layer such materials were taken – clay brick, AAC and hempcrete. As an insulator, two types of material were taken – Rockwool and expanded polystyrene (EPS) as commonly used in Ukraine. As key influence criteria were taken into consideration as follows: the u-value of the envelope W/m2K, the cost of the wall material, UAH/m2 and the mass of the wall kg/m2. All possible com- binations of single-layered and multilayered assemblies the initiated types of materials, which met Ukrainian ther- mal resistance requirements have been created and the calculus of the proposed criteria was performed. The analysis of obtained result revealed that the “best” case of multilayered assembly depends on the method which was applied for the MCDA assessment. Thus, in the case of additive criteria convolution, the “best” alternative is AAC with EPS insulation as well in the case of multiplication convolution. All the above-mentioned highlights that the engineer on site or decision- making person should avoid the temptation to choose the wrong “best” alternative in the erecting of MCDA-evaluated multilayered walls. As well the additional factors of influence should be taken into consideration in terms of compared criteria and assessment methods respectively.