Helmut F. O. Muller1*, Jorg Schlenger1, Andreas PreiBler1, Heinrich Muller2, David Fiedler2

1 Chair of Environmental Architecture, Department of Architecture and Civil Engineering, Baroper Str. 301

2 Chair of Computer Graphics, Otto-Hahn-Str. 16,

Dortmund University of Technology, D-44227 Dortmund, Germany
Corresponding Author, helmut. mueller@tu-dortmund. de

Abstract

This paper describes a building energy evaluation method developed by the named chairs in co­operation with the Chair of Building Process Management, Dortmund University of Technology, in 2007-08. The method aims at an energy assessment of fa? ades of public office buildings in Germany. The evaluation aspect of energy considers the overall energy demand in reference to the EU directive 2002/91/EG as well as embodied energy and Global Warming Potential (GWP) of the building elements used. The aspect of energy, being dealt with in this paper, is integrated in a comprehensive assessment system covering economy as well. The basis of the energy assessment is a dynamic energy simulation with the computer program TRNSYS, applied for a defined room with four fa? ade orientations. The user of the assesemnt system has a quick and simple access to the results of the TRNSYS simulations by an EXCEL-Tool.

The fa? ade systems, which vary from convetional load bearing external walls to high-tech curtain walls, are classified by a “morphological box”; a table with 23 parameters and up to 6 options per parameter. The design parameters under consideration include shape, dimensions, material, construction, and functional properties of fa? ades. For the TRNSYS simulations the morphological varity of the fa? ade systems was reduced to a manageable number of 6 physical parameters, relevant for energetical properties. Each of these parameters was varied by five equidistant steps within an appropriate bandwidth.

The EXCEL based tool gives access to the overall primary energy demand index for a number of 150,625 possible fa? ade variations. Additionally there was developed a free choice of interpolation for properties by regession analysis. Thus an unbounded design variety can be evaluated quickly, based on a limited number of elaborate simulations. The main influences of fa? ade design on overall primary energy demand can be derived. Thus the energy assessment can be used for comparison as well as for optimization.

Keywords: assessment, energy, fa? ade, evaluation

1. Introduction

The method was developed as a framework for a specific assessment system to be used by a German federal institution in early design stages [1]. Various types of fa? ades for both new office buildings and renovated ones had to be included in this project. The assessment tool gives no absolute energy and cost values but specific indices for a relative comparison only.

The fa? ade technology considered varies from conventional load bearing external walls with window openings to high-tech curtain walls for high-rise buildings, fulfilling a performance spectrum from minimum building standards to high quality and low energy solutions. The evaluation aspect of energy performance is considered by an overall energy demand for heating, cooling, ventilation and lighting with reference to the EU directive 2002/91/EG as well as embodied energy of the fa? ades and Global Warming Potential (GWP) of the building elements used.