OttoWagner-ArealPlus - Feasibility study for a certified plus-energy-district-renovation of the listed Otto-Wagner-Area

The Otto-Wagner-Areal in Vienna is a large-scale Art Nouveau ensemble of worldwide significance, whose characteristic pavilion buildings are arranged on a park-like hillside. The original use as a hospital will be gradually abandoned from 2020 on and with the settlement of the Central European University, a university campus will be created on a part of the site. The buildings will be adapted to the future requirements of office and university use, student housing and remaining medical facilities.

In a project team under the consortium leadership of Schöberl & Pöll GmbH and the project partners Central European University, Institute for Architecture and Design of the Vienna University of Technology, LANG consulting and the OeAD-Wohnraumverwaltungs-GmbH, a feasibility analysis was carried out within the framework of this project, the aim of which was to provide a well-founded decision-making aid for an internationally trend-setting renovation of a historic areal under the following aspects:

• Reduction of final energy demand of the entire areal by 90% compared to the existing situation
• Provision of remaining final energy demand by renewable energies on site
• Economic analyses by consideration of life cycle costs.

From a methodological point of view, the focus was on a well-founded energetic and structural survey of the existing building (with the help of inspections and the use of suitable tools), coordination with the Federal Office for the Protection of Historical Monuments, development and evaluation of a catalog of measures (also with the use of adequate tools) and the conduction of economic feasibility calculations with a life cycle perspective.

The feasibility analysis came to the conclusion that the redevelopment of the complete Otto-Wagner-Areal can be implemented in Plus-Energy-Standard in compliance with the protection of historic monuments using the appropriate know-how. Final energy demand can be reduced by more than 90 % compared to a typical refurbishment under monument protection requirements ("Baseline Sanierung"), whereas primary energy demand can be reduced up to 75 %. With a special focus on the use of highly energy-efficient user devices and further optimization of the other areas, the Plus-Energy-Standard could also be achieved when including the user equipment in the energy balances.

The following measures must be implemented for a Plus-Energy redevelopment of the Otto-Wagner-Areal:

• Insulation of the roofs and floor slabs as well as internal insulation of the external walls
• Optimization of the box windows and installation of a sun protection between the window sashes
• Minimization of thermal bridges
• Optimization of air tightness
• Highly efficient ventilation systems with heat and moisture recovery
• Highly efficient hot water preparation and use of flow-optimized fittings
• Heating and cooling via efficient surface systems
• Installation of a highly efficient lighting system
• Use of highly energy efficient equipment in all areas of use
• Installation of photovoltaic systems on the roof surfaces

If the site is supplied by an efficient heat pump system via near-surface geothermal collectors or deep borehole heat exchangers, final energy demand is lower compared to a supply with a district heating/district cooling system. From a primary energy point of view, energy demand is lower with a district heating/district cooling system compared to a supply with a geothermal heat pump system (by applying the usual conversion factors from final energy to primary energy).
The implementation of the innovative Plus-Energy renovation concept has higher investment and planning costs compared to a conventional renovation, but when viewed over a comparative period of 15 or 40 years, the Plus-Energy renovation has the lowest total costs (sum of investment and operating costs). Furthermore, additional benefits (so-called "Co-Benefits") of a Plus-Energy-Redevelopment have to be considered.

Project management

Schöberl & Pöll GmbH

Project or cooperation partners

• Central European University (CEU)
• TU Wien – Institut für Architektur und Entwerfen
• LANG consulting
• OeAD-WohnraumverwaltungsGmbH

DI Klemens Schlögl
Schöberl & Pöll GmbH
Lassallestraße 2/6-8
A-1020 Vienna
Tel.: +43 (1) 726 45 66/14
Fax: +43 (1) 726 45 66/18
E-mail: klemens.schloegl@schoeberlpoell.at
Web: www.schoeberlpoell.at