Keywords: heat transfer, moisture transfer, buildings, mathematical modelling, software, GUI.

Building heat and moisture simulation tools have been available for a long time, aiming at various analysis issues such as indoor air quality, comfort, energy and etc. However, most of the simulation themes are energy consumption related such as commonly adopted programs TRNSYS [1], DOE-2 [2] and the recently developed EnergyPlus [3]. Moreover, most of the simulation tools are hard and time-consuming, thus expensive to use [4]. A recent survey has shown that moisture damage is one of the most important factors limiting a building's service life. Unfortunately, models for such topics are lacking.

Modelling moisture transfer in buildings requires that a simulation program adequately addresses fundamental heat and mass transfer processes through the solid materials of building envelopes and indoor air. In fact, there is still a lack of knowledge that defines the heat and moisture transfer problem well. The complexity, plus the importance, of the modelling work leads to the following fact: even though there is a great variety of not only model methods but also the number of models, only a few well-documented computer codes have been introduced. Until the 1980s, there was no commercial computer code available [5].

Recently, the situation has been improving. However, an overall calculation of heat and moisture transfer in buildings with control applications is still lacking. Therefore, the development of a precise model for buildings is necessary, which is the main objective of the program HTMB (Heat and Moisture Transfer in Buildings) [6]. This paper describes some of the new features concerning the general program structure, models, performance, integration, GUI (Graphical User Interface) design and other programming issues in HMTB.

The software HTMB has a modular structure that allows sections of the program to be accessed independently. An example is the module of heat and moisture transfer in envelopes which can be used as a completely independent program for studies of heat and moisture transfer for structures. The software has been tested with our measurement and has shown satisfactory performance.

HMTB has made the following new contributions in the area of building simulation software. Firstly, HMTB allows the user to simulate a number of processes with control applications that recent programs in the literature cannot do well. These include: Moisture generation rate; Unheated building control; Night heat building control. Secondly, its friendly GUI allows users to work with a 'simulation view' of a building simulation process. In building the GUI, we have set up the objectives as: Creating a safe experimental-data-interchanging tunnel; Allowing a user to construct a wide range of structures, from 1D structure to a complex multiple-storey building, in a easy and graphical way; Allowing a user to visualise results data in a modern way. Such a GUI is not very common in building software. Hence, it is believed that the program would be an aid in enhancing energy efficiency and solving moisture problems of buildings through accurate design of envelope structures and their operational control.

1

Klein, S.A., Duffie, J.A., Beckman, W.A., "TRNSYS - a Transient Simulation Program", ASHRAE Transactions, 82, 623-633,1976.

2

Winkelmann, F.C., Birsdall, B.E., Buhl, W.F., Ellington, K.L., Erdem, A.E., Hirsch, J.J., Gates, S., "DOE-2 Supplement, Version 2.1E", Technical Report LBL-34947, Lawrence Berkeley National Laboratory, Berkeley, CA, USA, 1993.

3

Crawley, D.B., Lawrie, L.K., Winkelmann, F.C., Buhl, W.F., Huang, Y.J., Pedersen, C.O., Strand, R.K., Liesen, R.J., Fisher, D.E., Witte, M.J., Glazer, J., "EnergyPlus Creating a New-generation Building Energy Simulation Program", Energy and Buildings, 33, 443-457, 2001. doi:10.1016/S0378-7788(00)00114-6

4

Hien, W, Poh, L., Feriadi, H., "The Use of Performance-based Simulation Tools for Building Design and Evaluation", Building and Environment, 35, 709-736, 2000. doi:10.1016/S0360-1323(99)00059-1

5

Kohonen, R., "Modelling and Calculating Moisture Transfer in Building Materials", in "Proceedings of Heat and Mass Transfer in Building Materials and Structures", Chaddock, J.B., Todorovic, B. (Editor), Hemsphere Publishing Corporation, 3-20, 1991.

6

Viljanen, M., Bergman, J., Grabko, S., Lü, X., Yrjola, R., "Ensuring the Long Service Life of Unheated Buildings", TKK-TRT-100, Helsinki University of Technology Publications, 1999.

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