CityCalc - Calculation Tool for Energy-Efficiency in Urban Planning

To assess the energy performance of urban planning projects in early design stages with low input and evaluation effort within the project CityCalc, an easily applicable planning and evaluation tool has been developed.

Short Description




Starting point / motivation

As current energy planning and assessment tools for early design stages (urban planning, architectural competitions) are focusing on individual buildings, the interactions of buildings such as mutual shading and shadowing due to the surrounding objects are not taken into account. Although a great variety of tools for solar design are available, most of them are not suitable for architects and early design stages.

In future it will be of increasing importance to quantify the passive and active solar gains in order to fulfil ambitious legal and funding requirements and to implement future-oriented building concepts (e.g. passive house , zero energy, zero carbon or plus energy standard).

Contents and Objectives

Within the research project CityCalc, an easily applicable energy planning and assessment tool for urban planning projects in early design stages and for the analysis of the existing building stock has been developed. CityCalc focuses exclusively on energy efficiency - the reduction of energy demand - with the best possible use of site-specific energy sources (gains from solar thermal and photovoltaic plants, wind energy, combined heat and power). In order to ensure a simple, user- friendly application for architects, a three-dimensional geometry and data acquisition and an interface to energy calculation software have been developed.


The assessment is based on the established algorithm of the Austrian energy certificate, fol-lowing OIB directive Nr. 6 (OIB, 2015). The practical implementation is done with the calcula-tion algorithm of the widely-used calculation software ArchiPHYSIK (ArchiPHYSIK, 2017), whose developer A-NULL Bauphysik GmbH is partner of the research project.


The developed planning and assessment tool is a prototype that has been tested and validated in selected architectural competitions and projects within the research project.

Findings of competitions accompanied within the research project and feedback from im-portant stakeholders of the Austrian architectural competition scene, showed that with CityCalc an important gap in the area of planning and assessment tools has been closed. Based on the clear design, CityCalc enables the assessment of architectural projects without major efforts in early design stages (like architectural competitions, preliminary design). With-in architectural competitions the research team recommends CityCalc to be used only in de-sign approval (by the competitions adviser), as inputs done by participants of the competition have high risks concerning failures. To reduce the effort for competition advisers only a small amount of competition projects should be assessed with CityCalc (e.g. only projects of the second competition stage).

Prospects / Suggestions for future research

To enable unlimited use by third parties and to guarantee a software solution working after the end of the research project, a commercial business model for CityCalc was planned.

In case of that project partner A-NULL Development GmbH took over CityCalc in his product portfolio. With the end of the research project CityCalc is available as commercial solution. Requirement for the use of CityCalc is the license of the building physics software Archi-PHYSIK.


Discussions with important stakeholders and experts of the Austrian architectural completion scene pointed out, that it is of interest to implement economic aspects (like construction and maintenance costs) and additional sustainability indicators (like the ecological assessment of the construction) into CityCalc. The project team plans to integrate some of these aspects into CityCalc in a future research project.


Project Partners

Contact Address

AEE - Institute for Sustainable Technologies (AEE INTEC)
Heimo Staller
Feldgasse 19
A-8200 Gleisdorf
Tel.: +43 (3112) 5886-3648 200
Fax: +43 (3112) 5886-3648 200 DW 18