First rehabilitation project of a public building to reach passive-house standard

Status

completed

Summary

Motivation

Thermally sustainable refurbishment of old buildings is the most significant contribution by far to effectively reduce CO2 emissions as provided for in the Kyoto protocol. This offers a chance to immediately raise the standard of buildings in need of refurbishment in terms of energy efficiency and user comfort. The first refurbishment ever of a public building according to the generally acknowledged and "standardized" energetic prime standard of passive houses should demonstrate the feasibility of a large-scale passive house refurbishment at reasonable additional cost and fulfill a role-model function.

Contents

The present demonstration project investigated and implemented the measures required for refurbishment under passive house standards, such as insulation, reduction of heat bridges, integration of the ventilation system in the existing building, day-light illumination, heat-protection in summer etc as well as costs so incurred based on the refurbishment and the add-on new building of the 12-class General Secondary School and the 8-class Polytechnic in Schwanenstadt, Upper Austria. The reference basis was the refurbishment project originally planned in accordance with conventional minimum building standards. With this in mind, the research project took into account all aspects of sustainable and ecological comprehensive refurbishment, integrating advanced refurbishment methods for maximum energy and resources saving while at the same time substantially increasing occupational quality and functionality.

Planning method

For a holistic assessment of the project, the following focuses and calculation methods were used in addition to conventional methods:

• Alternative preliminary design in line with passive house requirements
• Comparison and evaluation of different ventilation systems
• Analysis of heat bridges occurring particularly in refurbishment measures
• Developing prefabricated timber construction elements for thermal refurbishment
• Analysis of design execution versions by using passive house project package PHPP
• Dynamic thermal building simulation using TRNSYS
• Daylight planning and optimisation with Adeline
• Ecological life cycle analysis of refurbishment versions

Objectives and results

The major elements of refurbishment were an increased compactness of the building by integrating the required addition of a new building, opening interior areas for daylight use via fanlights, complete exterior refurbishment and/or superstructure with an envelope fit for passive house use and of high ecological quality, innovative thermal refurbishment of the floor structure by injecting cellular glass ballast into the cavity below the floor slab and integration of decentralized, energy-efficient classroom ventilation equipment into the existing building.

The objective of this demonstration project was to implement the preceding research study to develop an appropriate refurbishment concept based on passive house standards. This pilot project has a role model effect on other refurbishment projects. The following objectives have been reached for rehabilitating the old and building the new school while achieving a very good cost/benefit ratio:

• High occupational quality: Good fresh air quality in the classrooms, improved daylight situation, considerably improved thermal comfort. Refurbishment took place without significant interference with everyday school activities due to prefabrication and short installation time on the construction site.
• Enhanced building quality: High building value due to sustainable, long-term refurbishment measures, low life cycle costs.
• Very low energy requirement:
  • The heating demand of 14.1 kWh/m²a is 88.5 % lower than in the old building and 82.4 % lower than in conventional refurbishment.
  • End energy demand at 33.6 kWh/m²a, reduced by 76.5 %.
  • Primary energy demand at 59.3 kWh/m²a, reduced by 68.1 %.
  • All parameters below passive house limit values, partly to significant extent. CO2 emissions for energy demand at 10.3 kg CO2/m²a, reduced by 74.7 %. CO2 emissions for "grey energy" in building production were 55 % lower than in conventional refurbishment due to the use of lightweight timber construction elements and optimisation according to ecological building principles.
• Role-model effect, image effect: First refurbishment of a public building according to passive house standards, forward-looking concept in the fields of energy efficiency and modern school buildings. Use of innovative technologies, multiplier effect created, for instance, in the Specification 2008 of Lower Austrian Government Buildings, or Vorarlberg Service Package "Nachhaltig:bauen in Gemeinden" (Sustainable building in municipalities)

Conclusions

Despite difficult overall conditions in energy and comfort engineering, refurbishment of the public school in Schwanenstadt to achieve passive house standards was a true gain for the municipality. This results in a forward-looking role model concept offering a very high energy-saving potential for other refurbishment projects as well. Additional costs of 13 % required for complying with passive house standards, for daylight optimisation and ecological measures, are rather low and will pay off due to subsidies and low energy operating expenses either immediately or without requiring additional grants in a few years. This creates considerable added value of the building concerning sustainable building quality, user comfort, energy efficiency and effect on public opinion. The municipality, students, school operator and teachers are very satisfied with the innovative refurbishment.

Project management

Ing. Dipl.-Kfm.(FH) Harald Weingartsberger
Neue Heimat OÖ, Linz

Project or cooperation partner

• Ing. Günter Lang
  LANG consulting, Wien
• Arch. DI Heinz Plöderl
  PAUAT Architekten, Wels
• DI Bernd Krauß
  Planungsteam E-Plus, Egg
• Ing. Bernhard Gasser, DI Michael Berger, DI Christoph Muss
  team gmi Vorarlberg - Wien
• DI Hans Christian Obermayr
  Obermayr Holzkonstruktionen GesmbH, Schwanenstadt
• Ing. Emanuel Panic