CASE STUDY:The Christophorous House - a multi purpose office building with low-energy consumption

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SECTOR: Energy
COUNTRY: Austria

INTRODUCTION
The start of construction was in December 2002 for a multi -purpose office building with low energy consumption for BBM in Stadtl-Paura, Upper Austria.
BBM stands for ( Beschaffungsbetrieb der MIVA ) a non-profit organisation to organise the supply for a developing countries agency. Its main focus lies in ecological water –and energy supply.
This ideological background was the motivation for a innovative and ecological optimised concept for a new building for 40 employees. Due to early involvement of a planning team ( architects, wood-builders, energy-specialists) the decision was made for a multi-purpose office building with storage, retail stores and community service in low energy standard
The minimum parameters to meet the standard of a “passive office building” were set by the Institute for “Passive house” in Darmstadt.
The final (measured) figures proofed to be even better due to careful planning by the leading architects Albert P. Böhm and Helmut Frohnwieser .

Heating Energy Figure: 14 kWh/m²a
Pressure-test- air -change figure: n50 0,4 h -1
Primary Energy Figure : 49 kWh/m²a (including power supply for total house-technic)

Architecture and Construction Principles
The specification of the site resulted in a circular building form that is devided by regular cubic shape to open up the building. The split into two separate main volumes represents the different functions. The main volume is four stories
high and the centre is a glass dome covering the open atrium for all floors
and brings down the light to the first floor.
This serves also as the entrance to the community centre for 100 people. The storage sector is a separate volume located in the south of the core building including packaging and truck-parking.

The core contribution to reach the goals of a “passive-house” standard is trough the use of an innovative wood construction system. The round shape of the building put an extra task to the wood engineers to prevent heat losses.

The main structure is wooden frame. The covering walls are not caring weight.
Due to the round shape and its optimised day light use it was possible to have deeper office spaces than in a regular shape.

The guiding principles of optimised ecological energy use were the main influence on architecture. This was only possible in a holistic planing process staring in a early stage of the project.

Site plan

First floor

Second Floor

Architecture and the guiding parameters by the darmstadt “pasivhause”
institute required a new solution in construction details and building technology.
The following aspects position this office building as a prototype in the wood building industry:

• curved outer walls in “passive house” standard done as prefabricated elements

• The building load of 4 stories of an office building are carried by a wood structure.

• Round columns made out of assorted natural rounded trunks instead of expensive and energy consummating Multi Layer wood.

• The weight of the floors is brought into the wooden structure without steel-connectors.

Energy concept
Buildings for housing use most of their energy for heating. Office buildings use their main energy for light, air-conditioning and computer.
The energy consumption is driven by mainly by two factors:
- the quality of the computer and copy- machines
- user comfort in the office building such as temperature, day-light, light and quality of air.

This results in the fact, that cooling of an office building can be more energy consuming than heating. Therefore a different concept for low energy consumption is needed.
With the help of energy specialist over the whole planning process the dynamic modelling and simulation was done in TRNSYS. This proofed to be influential to architecture, construction method and detailing.

The diagram shows the heating and cooling energy consumption in a calculation, using the worst case climate data of the last 10 years.

Heating and cooling energy consumption for the whole building [kWh/a]
Due to dynamic simulation models the team was successful in achieving parameters of 15 kWh/m²a and even below for the Heating Energy Figure and a Primary Energy Figure for cooling of 49 kWh/m²a. (maximum 80kWh/m²a)
The solution for the heating was a heating pump with earth collectors combined with a highly efficient air supply system including heat recycling. For cooling in summer the system with earth collectors works reverse.
The power supply for the heating pump is compensated with a 80 m² photovoltaik feature.
Recycling of Water

1. The building has a water basin for collecting the rain water. To maintain the quality of the water a circulation pump is used to bring the water to a biological sand filter with plants.
2. Rainwater collector
In case of rainfall the overflow of water from both building roofs will be guide over the sand filter to tank. If the maximum level is reached, the water goes into a drainage pit.
3. Gray Water
The water from the kitchen and the snack bar is collected separately and stored in a grey water tank. A timer brings this water to planted filter basins, and from there is runs to the rain water collector.
4. Rainwater use
From the drain water pit a pump system brings the water to toilets, helps watering the plants, a is extra supply if there is nor enough grey water. The system for the toilets includes a water watch for exact public fees for water use.

The building with its 2000 m² was finished in October 2003. Exact monitoring will help to ensure the quality and to further exchange the knowledge gain in that experiment.

PROJECT CONTACT:
Gerald Leindecker
Institut fur Analytische Structurentwicklungsplanung
Hinterschweigerstrasse 2
A-4600 Wels
Tel: +43 7242 60757
Fax: + 43 7242 60757
Email: g.leindecker@asn-linz.ac.at

Plan and Picture courtesy of
Architect DI Albert P. Böhm A-4020 Linz, Stelzhamerstraße 10
Architect Mag. Ing. Helmut Frohnwieser A-4020 Linz, Beethovenstraße 16