First passive-house school reconstruction

Status

finished

Summary

Motivation

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

Contents

The present study investigates the measures required for rehabilitation under passive house standards, such as insulation, reduction of heat bridges, integration of the ventilation system in the existing building, day-light llumination, heat-protection in summer etc as well as costs so incurred by describing the proposed rehabilitation and add-on new building of the 12-class General Secondary School and the 8-class Polytechnic at Schwanenstadt, Upper Austria. The reference basis is the implementation scheme originally conceived which was based on conventional minimum building standards. With this in mind, the research project takes into account all aspects of sustainable and ecological comprehensive rehabilitation integrating advanced rehabilitation methods for maximum energy and resource saving while at the same time substantially increasing occupational quality and functionality.

Objectives

The following objectives should be reached for rehabilitating the old and building the new school while achieving a satisfying cost/benefit ratio:

• High occupational quality: Good fresh air quality in the classrooms, improved daylight situation, considerably improved thermal comfort. Rehabilitation takes place without significant interference with everyday school activities due to prefabrication and short installation time on the construction site.
• Very low energy requirement: Heating heat and primary energy demand according to passive house limit values 90% lower than in the existing building and approx. 75% lower compared with conventional rehabilitation. Lower energy demand in building construction due to use of lightweight timber construction elements and optimisation according to ecological building principles.
• Enhanced building quality: High building value due to sustainable, long-term rehabilitation measures, low life-cycle cost.
• Role-model effect: First rehabilitation 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 such as vacuum insulation, multiplier effect in the general public.
  The objective of the research study is to develop an appropriate rehabilitation concept containing options for further decisions in planning and implementation. The next steps should be further project planning and implementation and to use the project as a role model for other rehabilitation projects.

Planning method

For a holistic assessment of the project, a planning focus going beyond conventional methods is applied and calculation methods are used:

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

Summary of results

The major elements of the rehabilitation concept are increased compactness of the building by integrating the required addition of a new building, opening interior areas for daylight use via fanlights, complete exterior rehabilitation and/or superstructure with an envelope fit for passive house use and of high ecological quality, innovative thermal rehabilitation of the floor cover by using vacuum insulation panels with minimum floor height increase and integration of decentralized, energy-efficient classroom ventilation equipment in the existing building. The results are summarized in the diagram below. Additional costs for com fortable and ecological rehabilitation according to passive house standards were determined at 8 to 13%, depending on the execution version, compared with conventional rehabilitation.

Conclusions

Despite of difficult overall conditions in energy and comfort engineering, rehabilitating the public school at Schwanenstadt to achieve passive house standards is feasible. This results in a forward-looking role-model concept offering a very high energysaving potential for similar projects as well. In the opinion of the authors, additional costs involved amounting to 8 to 13%, depending on the execution version, are justifiable and will pay off due to subsidies and low energy operating expenses and create considerable added value of the building concerning sustainable building quality, user comfort, energy efficiency and effect on public opinion.

Contact

Dipl.Ing. Hans-Christian Obermayr
Obermayr Holzkonstruktionen GesmbH
Johann Pabst Str. 20
4690 Schwanenstadt
Tel.: +43 07673 2257-0
Fax: +43 07673 2257-926
E-Mail: office@obermayr.at