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Case Studies: Waldsee BioHaus Environmental Living Center


Project name: Waldsee BioHaus Environmental Living Center

Location: German Language Village of the Concordia Language Villages Bemidji, MN

Web sites:,,, Passive House Institute US, Passivhaus Institute

Architect: Stephen Tanner, INTEP, LLC

Builder: Zetah Construction General Contractor, Bemidji, MN

Building size: 5000 sf

Building use(s): Environmental Center for experiential learning and living with an apartment and student dormitory for up to 28 people, and classroom for similar capacity.

Completion date: August 2006

Ratings and awards:

  • Minnesota Environmental Initiative Award in the category of Air Quality and Climate Protection, May 2007
  • 2007 Nominee for the World Clean Energy Award in the construction category. It is a newly created awards program to recognize global achievement and innovation in integrative use of energy efficiency and renewable energy.
  • First Certified PassivHaus (Passive House) in North America, April 2006
    Germany's Passivhaus Standard is an energy conservation and renewable energy use standard. The standard is a quantifiable system which must be proven by use of defined calculation tools and verification by the Passivhaus Institute itself to achieve certified standards.


The BioHaus is part of a larger effort by the Language Villages and Germany's Deutsche Bundesstiftung Umwelt, Europe's largest environmental foundation, to create a "Transatlantic Green Bridge" between Germany and the United States. The BioHaus promotes a dialogue and exchange of sustainable building components and technologies as well as encourages cooperative work on the development of innovative educational curricula on the subject of sustainability with emphasis on sustainable building. Through innovative curriculum development, specifically around the topic of sustainable building design in Germany, Waldsee's new BioHaus fosters the transfer and exchange of environmental education across the Atlantic between the U.S. and Germany and back. The BioHaus also features innovative and technologically cutting-edge building systems and components. Designed by Intep, the Minneapolis-based architectural and consulting company specializing in high-performance and sustainable construction, The BioHaus is a cutting-edge environmental learning center. In tune with the philosophy of the Language Villages, learning by immersion, this project is based upon the German Passivhaus standards for efficient energy use. The concept of the building is that its design will facilitate learning in all its details of environmental living.

The real beauty of Waldsee BioHaus might not be found in any one detail itself. It might really be in taking a step back and admiring the dimensionality of the entire building itself. From the fun German language and cultural learning environment for kids to the sophisticated sustainable building construction to the overall philosophy behind the Waldsee BioHaus, the design combines two key functional elements:

  1. Private areas containing dormitories and apartment – the base and rear of the building as represented by the blue stucco and its massive feeling walls.
  2. Public areas for gathering, playing and learning – the light, reflective part of the building as represented by the aluminum siding and thinner walls.

The BioHaus design concept is inspired by the vision of immersion learning and explores three different types of inside/outside relationships, establishing a relationship between nature and BioHaus. The architecture of BioHaus helps students experience this first hand. The openings, windows and doors of BioHaus reflect three basic principles of gaining understanding through perspective via the German themes of Durchblick, Ausblick and Einblick. Immersing into a different culture starts with the recognition that a different culture is based on a different perspective and therefore has a different understanding of the world.

  • Durchblick means perspective, vista or view in German, but it also means "seeing through" something. Forest is the main natural element in northern Minnesota through which one walks to enter Waldsee BioHaus. Entering it is accompanied by also "seeing though" the building into the forest.
  • Ausblick also means perspective or vista in German, but it also means "seeing into" the future. The large windows to the south give this sense of perspective to the students using the common room or the studio – the place of learning and experiencing.
  • Einblick means to "see into" or inspect in German, but it also means "gaining insight." The small window to the west in the studio symbolizes this – the places where students would be learning about the environment.

All are stimulating themes to explore while living in Waldsee BioHaus – to foster the learning and experiencing of modern German living, sustainable building design and technology in the German language.

The Waldsee Biohaus project represents a bold leap in residential integrated design. Intent on providing a demonstration of effective energy resource use, the Concordia Language Village (CLV) chose to work with Stephan Tanner to go beyond developing a building that incrementally improves upon current building approaches. Gauged to impact the way we perceive building performance and quality of living experiences, CLV has provided an experiential building for us to learn from in the northern cold climates about taking significant strides with integrated strategies for use of renewable energy.

The first Certified Passivhaus project in North America, and one of a growing trend in building design on the continent, this approach is well established in Europe. Similar to how LEED provides standards for design and construction, Passivhaus standards provide environmental considerations in the design process. The similarities stop there, as Passivhaus operates strictly on measurable building performance criteria that go well beyond the requirements of LEED. Passivhaus requires stringent integration of passive design strategies, energy use in relation to floor area, and envelope detailing for tightness and insulation.


Effective energy use solutions:

  • Compact footprint and volume: The two-story design with a nearly square footprint, results in a compact building form with a low surface area to volume ratio.
  • Zoning interior spaces and activities for effective daylighting and passive solar gain.
  • High performance building envelope.
  • Energy-standard-based-design using the German Passivhaus standard.
  • Ground to air heat exchange system for the fresh air intake and a high efficiency heat recovery system.
  • Low energy use mechanical equipment and appliances.
  • The western half of the lower level of the structure is tucked into the slope with an earthen berm, gaining natural insulation from soil temperatures.

Orientation: South

Daylighting strategies: Optimal Zoning: The location of spaces used mainly during the day were given priority in regard to access to daylighting. Dormitories were located on the lower level and oriented toward the east and the apartment on the upper level is oriented to the north (bedrooms) and east (living/dining room). Service areas like toilet rooms, showers and mechanical room on the lower floor are compact and centrally located for minimal and efficient mechanical installation needs.

Passive Heating and Cooling Strategies:

  • This current design for the Waldsee BioHaus is optimal for an effective use of daylight and solar gain in the winter. Common Room and Studio are oriented toward the south with additional transom lights along the north wall.
  • Passive Heating achieved primarily through large south facing window area and a high performance envelope.

Shading of structure:

  • Appropriately sized overhangs.
  • Cooling achieved through the use of large motorized exterior blinds (Warema) that cover all south facing windows and doors.

Envelope: The building envelope is highly insulated. Specific attention was paid to insulating throughout the slab floor to the ground, exterior walls to the roof including windows and doors. A new insulation technology, Vacuum Insulation Panels (VIPs), were used on the upper floor for the roof and exterior walls with aluminum cladding and were juxtaposed to the traditional insulated stucco walls, allowing these insulation approaches to be showcased for educational purpose. A flat roof form was selected for this design with an extensive green roof. In the summer the green roof design and the vegetation on the roof serves to retain rainwater and establish a heat buffer. In the winter time the flat roof form allows snow to remain as an additional insulation blanket on the roof.

Wall thickness:

  • o Below grade: 20" total thickness: 12" ICF plus 8" EPS
  • Wall type A: 20" total thickness: 2" x 12" stick frame filled with icynene spray-in insulation plus 8" EPS
  • Wall type B: 8" total thickness: 2" x 6" stick frame with icynene plus 2" Vacuum Insulation Panels (VIP's)

Insulation R-values:

  • Walls
  • Below grade walls: R 55
  • Above grade
    • Wall type A: R-70
    • Wall type B: R-70
  • Roof: R-100
  • Slab: R-55

Building tightness:

  • Pressurization and Air tightness: Blower Door Test Passivhaus standard is n50 (50 pascal) <0.06 h-1 (In terms of the number or air changes per hour)
  • Test Results at n50: 0.18 h-1
  • BioHaus has been pronounced as one of the tightest building envelopes in the U.S. by one of the pioneers of Blower-Door testing, Gary Nelson, Vice President of the Energy Conservatory in Minneapolis who performed the pressurization test.


  • Optiwin/Mueller Dreiholz Triple Pane Windows: German wood framed windows certified for Passivhaus standard.
  • R value: R-8 approximately
    • R= 1/0.129 BTU/hr.ft2 °F (U.S.) = 7.7519379 BTU/hr.ft2 °F
  • Average U-value for entire window (frame + glazing):
    • Uw = 0.73 W/m2K (metric)
    • Uw = approx. 0.129 BTU/hr.ft2 °F (U.S.)
  • U-value for (triple pane)glazing:
    • Ug = 0.60 W/m2K (metric)
    • Ug = approx. 0.106 BTU/hr.ft2 °F (U.S.)
  • g-value (perpendicular radiation) = 0.52 similar to SHGC in U.S.

Air barrier: Sto-Guard air/moisture barrier system. Sto-Guard is a continuous, structural and durable air barrier.

Climate control systems:

  • The need for a ventilation system and high air quality required 100% fresh air insuring that indoor air not be re-circulated, a ground to air heat exchange system for the fresh air intake and a high efficiency heat recovery system.
  • AWADUKT Earthtube system: 100m long tube at 9 ft. below grade brings the fresh air to the ventilation system while pre-tempering the air by ground to air heat exchange.
  • Highly efficient (85%) air to air heat recovery and 100% fresh air ventilation system from Lüfta, Germany controlled by Staeffa Controls (Siemens) Talon System.
  • System One Control is the Minneapolis based company which provides, designs, installs and programs the control and monitoring system of the BioHaus.
  • A total of 6 loops in three 120 ft. deep wells (2 loops/well) supplies heat for distribution by the radiant floor heating system, using a ground source heat pump system from REHAU North America.
  • Ground source heat pump: 25,000 btu capacity

Backup heating/power: The ground-source heat pump system serves as backup for the solar thermal domestic hot water supply.

Total building energy use:

  • 14,250 btus/ year
  • Total primary energy use is 85% below MN energy code.
  • Passivhaus standard:
    • o Specific space heating < 15 kWh/ m2a = <4,760 BTU/ft2 yr
    • o Specific primary energy requirements <120 kWh/ m2a = <38,000 BTU/ft2yr
  • Performance calculation results:
    • o Specific space heating energy requirement of 13.7 kWh/ m2a = < 4,350 Btu/ft2yr
    • o Specific primary energy requirement of 44.9 kWh/ m2a (14,250 Btu/ft2yr)
    • o Factor of 1.6 of Passivhaus standards


Solar system description and size: The current renewable energy system consists of a solar thermal system providing domestic hot water, assisted by the ground-source heating system that primarily functions to supplement the solar heat gained from the passive solar design. A solar electric system is to be added in the future.

Solar thermal: The German engineered domestic hot water system includes:

  • 12 roof mounted (45° angle) RAUSOLAR flat plate panels
  • Four 119 gallon Superstore Ultra stainless steel double walled tanks with heat exchangers.

Solar electric: A photovoltaic system is planned with an annual energy generating capacity above the electrical need of the Waldsee BioHaus and will be implemented when financing is available. The system will be located on the flat roof of the building in front (south) of the solar-thermal panels. It will be tied into the electric grid to avoid the use of a battery bank.

Solar thermal system cost: approximately $45,000 including installation

Financial incentives/donations: Some in-kind donations were made by the REHAU North America.

Date installation was completed:

  • The system was first installed in the summer of 2006.
  • CLV has since made some modifications to the domestic hot water tank which should be complete by February 2008.

System Designer: REHAU AG/ REHAU North America

Engineer: INTEP Review

Installer: Wes' Plumbing, Bemidji, MN

Estimated amount of energy needed for total hot water consumption: 29,750 kWh/a

Estimated amount of solar contribution to hot water production: 17,780 kWh/a

Percent of building's total energy use provided by solar:

  • Solar Thermal Domestic Hot Water: 60% of hot water demand
  • Solar Electric: Will produce a surplus of remaining power needs for return to the utility grid.

Actual monitored energy delivered by system: Web based monitoring for secure data collection will provide accurate performance of the energy systems.


Integrative planning: Optimized the whole rather than the integrated components, tools were applied for defined data for a particular component or regional climatic conditions.

Modeling software: Passivhaus Planning Package

Design tools: Daylighting, solar thermal hot water system, photovoltaic system, ground to air heat exchanger.


Concordia Language Villages, particularly the German Language Village, Waldsee, wants to provide an opportunity for villagers and visitors to experience modern, German sustainable living, building technology and design. Waldsee BioHaus is a showcase for highly energy-efficient building and a place for environmental education with a focus on sustainable, healthy living. For this project, Concordia Language Villages has partnered with Europe's largest environmental foundation, the Deutsche Bundesstiftung Umwelt, to establish a "transatlantic green bridge" which promotes the exchange of ideas as well as the collaboration of environmental educators across the Atlantic.
Source: Edwin Dehler-Seter
Environmental Education/ Natural Resource Management Specialist
Concordia Language Villages


Integrated Planning from the beginning of the project is crucial and pays off in the end which is reflected in its achievements:

  • Tightest building in North America/Pressurization Test Results: 0.18 h-1
  • Specific heat requirement: 13.7 kWh/(m2a)

Waldsee BioHaus is a good example for how much can be achieved in energy conservation and efficiency when integrated planning as well as commitment coupled with diligence from the local contractors comes together.

When using imported systems or components along with domestic ones it is crucial that special attention is paid that all components are fully compatible with each other. In our case, this has led to modifications in the solar thermal hot water systems and the replacement of the initial domestic hot water tank, which could have been avoided.
Source: Edwin Dehler-Seter

Change in the built environment does not need to be incremental it can be done in leaps, it is not a cost issue it is a social/cultural issue.

There was a lot of instrumentation on this project, and there is a leap of optimization to be made in using fewer instruments.

Window technologies data from local resources do not meet all of the Passivhaus standards, and little things can have an overall impact when working with a project that pushes the building to such extremes of performance.
Source: Stephan Tanner


Sustainable features include:

  • Extensive green roof
  • Low impact and healthy building materials
  • Low-emission building products
  • Simple building design and technology
  • Landscaping with native species around the building
  • Use of locally manufactured and sourced products (85-90%)
  • Project completed by local Bemidji, MN contractors


Video of architect can also be found at:
Images courtesy of Edwin Dehler-Seter, Concordia Language Villages and to Cal Rice, Bemidji.