Application of the Moisture Potential Theory in Assessing the Heat and Moisture Regime of Building Envelopes

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Abstract

The review of existing mathematical models for humidity conditions was carried out. Methods giving an opportunity to calculate moisture transfer in the sorption zone of humidification and in the supersorption zone are described. The features of calculating moisture distribution using the theory of moisture potential are shown. The new discrete-continuous method for calculating the moisture state of a fence is proposed, which makes it possible to determine the unsteady-state moisture regime using an analytical expression without using various numerical methods. Two formulas for a single-layer and a multi-layer building envelope are derived. The formula allows us to determine the distribution of moisture potential in various sections of building envelopes. The effectiveness of the method is proven by comparing the results obtained with calculations using non-stationary and engineering quasi-stationary calculation methods. The humidity regime of a single-layer enclosing structure in the city of Moscow made of aerated concrete blocks, as well as a two-layer enclosing structure with a clay brick base and silicate brick cladding was calculated. It is shown that the calculation results using the proposed method are both quantitatively and qualitatively close to the distribution obtained using the non-stationary calculation method for both single-layer and multi-layer enclosing structures. The method is recommended for use in engineering work, because it gives a possibility to take into account the inertia of moisture in the building envelope.

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About the authors

K. P. Zubarev

National Research Moscow State University of Civil Engineering; Scientific-Research Institute of Building Physics of RAACS; RUDN University

Author for correspondence.
Email: zubarevkirill93@mail.ru

Candidate of Sciences (Engineering) 

Russian Federation, Moscow; Moscow; Moscow

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2. Fig. 1. Comparison of the results of calculating a single-layer enclosing structure using individual methods of the theory of humidity potential in January: 1 – humidity regime determined by the non-stationary me thod; 2 – humidity regime determined using the proposed discrete-continuous method; 3 – humidity regime determined using the engineering method

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3. Fig. 2. Comparison of the results of calculating a two-layer enclosing structure using separate methods based on the theory of humidity potential in January: 1 – humidity regime determined by the non-stationary method; 2 – humidity regime determined using the proposed discrete-continuous method; 3 – humidity regime determined using the engineering method; 4 – boundary between layers

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