10 years IBN building – our experience with the building

A brief introduction to the IBN building

We extensively renovated a one-story, circular-segment masonry building built in 1955 (a former grocery store), adding a wood frame upper floor and a glazed stairwell. Based on the holistic approach of building biology, it was important to us to create a distinctive architecture, to integrate the structure with the environment, and to focus on health and sustainability.

Our flagship project was realized as a plus energy or passive house (EnerPHit standard for the modernization of old buildings) with planners, craftspeople, and building materials mainly from the region.

1 Technical drawing
2 Building before renovation and addition
3 Main entrance (southwest)
4 Side entrance (northwest)
5 Garden side (east)
6 Multipurpose room on the ground floor
7 Large office space on the top floor

Building materials

All of the materials used, including the finishes and furniture, have stood the test of time. So we would do everything exactly the same or very similar to what we did before.

8 The old façade with its large shop windows had to be completely replaced with a wall made of unfilled perforated bricks + ETICS
9 Installation of foam glass insulation in the base area
10 Ready-to-install wood frame construction elements for the upper floor
11 Holes in natural fiberboard for installation of blown-in wood fiber insulation
12 Finishing plaster work on a window reveal
13 Completed installation of clay board on the wall and natural fiberboard on the ceiling

Heating system

For the central heating system, we combined a primary pellet stove with viewing window with a 400-liter buffer tank and wall and floor heating elements. The indoor climate is excellent, the temperature-controlled floors are only 1 to 2 degrees warmer than the indoor air, even in winter. Due to the low flow temperatures (< 30°C), we have no problems with the wooden floors. By using passive solar energy, we can turn off the heating completely from about mid-March to mid-October, and in some years even longer, depending on the weather. The annual heating requirement is about 4,500 kWh, which is about one and a half pallets of pellets (= one and a half tons). If the pellet stove should break down, we can heat the water in the buffer tank with our photovoltaic system in emergency mode.

The pellet stove has a viewing window facing the meeting and exhibition room, so that the fire can be experienced with all the senses. The burning noise is relatively loud at a higher power setting due to the integrated fan. If the ambient noise level is to be very low, the power can easily and immediately reduced via the integrated display, or the pellet stove can be switched off completely. In winter, we empty the ash from the pellet stove about once a week and use it to fertilize the garden.

The fine particulate matter in the outside air from pellet stoves is generally much lower than that from wood-burning stoves, for example, and our energy consumption, and therefore our production of fine particulate matter, is very low. Nevertheless, we are monitoring the market for the possibility of retrofitting a particulate filter, but no concept has convinced us yet.

Instead of encasing the 400-liter buffer tank in plastic insulation, we built a box made of wooden battens and gypsum fiberboard around it and insulated the resulting cavity with ≥ 40 cm (16 in) of blown-in wood fiber insulation.

Today an alternative to the pellet stove would be an air-to-water heat pump combined with our photovoltaic system. However, this requires electricity, and more than 10 years ago, when we had to decide on a heating concept, the share of renewable energies in the German electricity mix was only about 25%, which was definitely not enough for us. It is now over 50% and will (hopefully) continue to rise further.

14 Pellet stove with viewing window
15 Installation of floor heating pipes
16 Wall heating pipes before clay plastering

Ventilation

In order to gain experience with ventilation systems and to make measurements, three different central ventilation systems with heat recovery were installed for three different areas of use (office, multipurpose room, model apartment). All three ventilation systems work well, especially since they can be operated with preset values for air temperature and air quality via the displays that are easily accessible to all employees.

The optional carbon dioxide control works perfectly. The air exchange rate is automatically increased (based on the Building Biology Evaluation Guidelines SBM) when the carbon dioxide level reaches 1,000 ppm at the latest.

A ventilation system with humidity recovery is installed in the multipurpose room. In winter, the air humidity there is on average about 10% higher than in the other rooms.

Our ventilation systems have been a blessing during the coronavirus pandemic. Because (preheated) air is blown in from several supply air vents on one long side of the building and blown out on the opposite long side, no one sits or stands in each other’s breathing air, even during meetings.

Laboratory tests for mold spores in the ventilation systems show no abnormalities.

We change the filters in the ventilation systems ourselves about once or twice a year.

Since our office is located in the city, it often gets noisy outside. It’s nice to have good indoor air quality even with the windows closed.

Good to know: In summer, the ventilation system draws in warm air from the outside. At that point, we turn off the heat recovery system and also turn off the ventilation systems completely, at least during the day, and instead switch to intermittent ventilation by opening and closing windows.

The central ventilation unit on the upper floor is located in the open kitchenette next to the offices. This unit is relatively loud (about 50 dB) under normal operating conditions, but we can close the door. If quiet operation is important to you, you should not install central ventilation units in common areas or design walls and ceilings to enclose them with sound insulation.

17 Ventilation system: central ventilation unit on the upper floor
18 Disc valve at a height of about one meter for the supply air
19 Spiral ducts on the ceiling with openings for the exhaust air

Water

The drinking water pipes are made of stainless steel. Due to the low demand for hot water in an office, it is heated nearby in two on-demand water heaters and two under-sink storage tanks. After about 6 years, the under-sink tanks began to leak and had to be replaced. That’s why we now do without one of them.

A 6,000-liter cistern collects rainwater, which we use for toilet flushing and irrigation. As a result, our consumption of drinking water is very low. However, during two hot summers, the (then warm) rainwater in the cistern “shifted” and smelled musty. Since then, we have watered more often in summer so that the water in the cistern is replaced more often by fresh rainwater.

20 Installation of the water cistern with filter and overflow in a trench
21 Drinking water and rainwater distribution – rainwater pump at right

Electricity

To keep our electricity consumption low, we have made sure to use energy-saving devices such as computers, other appliances (e.g. refrigerator, ventilation units), and lighting.

There is a photovoltaic system on our roof (about 60 square meters, about 7,500 kWh per year), the electricity from which we use ourselves as often and as well as we can. We also use it to charge electric vehicles. What we do not use is fed into the public grid.

After five and a half years of operation, the inverter broke due to a lightning strike. Our homeowners’ insurance paid for the replacement.

Since we produce more energy per year with the photovoltaic system (about 7,500 kWh) than we consume with the pellet stove (about 4,500 kWh), we can describe the IBN building not only as a passive house, but also as a plus energy house. It should be noted, however, that this designation (for almost all passive houses) is only correct if the whole year is considered, but not only the winter months, i.e. the heating season.

In order to reduce electromagnetic pollution as much as possible, the entire electrical installation (including the photovoltaic system) is shielded. In addition, all computers and servers are wired, eliminating the need for a Wi-Fi router in the building. All employees are required to put their smartphones and other mobile devices (e.g. smart watches) on airplane mode or turn them off. In addition, the lightweight wood frame construction on the upper floor is shielded from radio frequency radiation with a stainless steel mesh that is mounted on the outside behind the wood siding. It feels really good!

22 Photovoltaic system
23 Photovoltaic system inverter

Light

The entire building is extensively glazed to maximize natural daylight. This means that artificial lighting is rarely needed, even in winter and/or on cloudy days. Nevertheless, a professional lighting designer was hired to design the artificial lighting system. As a result, we enjoy a great atmosphere and lighting quality throughout the building. Electromagnetic pollution and flicker from lighting systems have been reduced as much as possible.

Adjustable external blinds help prevent unwanted heating of the interior and glare at workstations when the sun is shining. Their slats are shaped (patented!) to deflect the outside light onto the whitewashed ceilings, providing indirect and glare-free natural daylight to the workstations.

Where there is light, there is also shadow: One disadvantage of large-surface glazing that we did not take into account is the fact that on hot days (e.g. with an outside temperature of 35°C and an inside temperature of 24°C) the surface temperature on the inside of the glazing, even on the side of the building facing away from the sun, is about 30°C, which is practically equivalent to wall heating. To avoid this, the windows would have to be temporarily insulated from the inside in summer, which is hardly realistic. On hot days, therefore, special attention must be paid to solar control and proper ventilation during the day (keep hot air out) and at night (ventilate well).

24 Daylight-redirecting external blinds
25 The artificial lighting in the multipurpose room can be adjusted to mimic natural light. At noon, the light color is bluish.
26 … in the evening, the light color becomes more reddish and the illumination level decreases.

Indoor climate

All employees rate the indoor climate as excellent thanks to optimized ventilation, radiant heat (temperature-controlled walls and floors), and natural, neutral or pleasant-smelling, and moisture-buffering materials (e.g. wood and clay).

But: As mentioned before, we have a passive or plus energy house. And because of the excellent thermal insulation (“thermos flask effect”), it quickly becomes too warm in such a building, especially in summer. Examples:

• If the sun shines into the building and you forget to close the daylight blinds (e.g. if you are away for the weekend), the indoor temperature rises by about 2 degrees Celsius within half an hour, so that the indoor temperature can rise from about 22 degrees to over 30 degrees in one morning or afternoon and then drop very slowly without ventilation.
• Even if the ventilation system is not turned off in summer when outside temperatures are high, it will quickly become too warm.
• Even if there are more people in a room than usual (e.g. at a team meeting or a presentation), their body heat can make it too warm.

We have often had to switch from winter conditions (heating on, maximum heat recovery from the ventilation system, daylight blinds raised to use passive solar energy, etc.) to summer conditions (heating off, heat recovery from the ventilation system off, blinds down, etc.) from one day to the next. This is the case, for example, in February or March when it is still wintry cold and overcast one day and spring-like warm and sunny the next; and vice versa in October or November.

Ultimately, everyone in a passive house has to think and act quickly on some days in spring and fall and on hot days in summer in order to maintain a comfortable indoor climate. We have written instructions for this, which are posted upstairs for all to see. Alternatively, everything could be controlled automatically (like in a “smart home”), but this would involve additional installation and maintenance costs and would not always meet individual requirements.

Noise control / acoustics

The sound insulation to the outside and to the neighbors is also excellent thanks to the triple glazing.

The soundproofing of the dowel laminated timber ceiling (including 11 cm of crushed limestone) is good, but not perfect, which we have consciously accepted. By simply retrofitting a suspended ceiling, the sound insulation of the dowel laminated timber ceiling could be significantly improved.

The acoustics on the ground floor are excellent due to the acoustic joints in the dowel laminated timber ceiling and the large amount of paper (library, printed matter). The acoustics on the upper floor are somewhat reverberant due to the large area of glazing. Long-pile, sound-absorbing wall hangings and large acoustic elements between the desks, which were developed in-house and are made of coconut fiber filling and sheep wool felt, reduce the reverberation. To further improve the situation, we would need to install additional acoustic mats and/or panels, such as sheep wool felt, on the ceilings.

Life cycle assessment

In 2014, Viktoria Eva Maria Schuster completed a life cycle assessment entitled “Sustainability Assessment (LCA and LCC) for the Partial New Construction of the Institute of Building Biology + Sustainability IBN Office Building” as part of a bachelor’s thesis at the Rosenheim University of Applied Sciences in the Interior Design program. The summary reads in part: “The result shows that the sustainability rating of the IBN building is very positive.” Experts who regularly conduct sustainability assessments have confirmed to us that they have never had a sustainability assessment with such good values.

Construction and running costs

The building biology way of building and living should and can be affordable. However, we decided during the planning phase that this requirement could not and should not apply to the IBN building for the following reasons:

• Elaborate details due to the circular floor plan, partial demolition, addition of floors, extension, fire protection, etc.
• Additional work because we want to show and test many things in our building under practical conditions.
• Our building, which attracts worldwide attention, should be representative and spacious.

However, the comparatively high construction and renovation costs are quickly amortized by the very low running costs. In recent years, the average annual cost of pellets, electricity, and drinking water has been about €600.

Construction data

Institute of Building Biology + Sustainability IBN, 83022 Rosenheim

Architects	Architect’s office Martin Schaub with IBN architects Karin Hick and Winfried Schneider
Built in	1955 as a grocery store “Konsum” (ground floor) | 2014 extensive reconstruction, extension, and addition of a glazed stairwell
Usable area	Approx. 250 m2 (2690 ft2) for offices, multipurpose room for consultations, presentations, exhibitions, and others, allergy-friendly model apartment
Foundation	Existing strip foundations and concrete floor slab, thermal insulation of foam glass panels 2×120 mm, 0.05 W/mK
Exterior walls, ground floor (starting from the outside)	Silicate paint, 15 mm lime plaster, external thermal insulation composite system made of natural fiberboard and blown-in wood fiber insulation 0.038 W/mK, existing walls made of hollow concrete blocks partly supplemented with unfilled insulating bricks 0.08 W/mK, base and finishing clay plaster, U-value 0.1 W/m2K
Exterior walls, upper floor (starting from the outside)	Horizontal spruce siding, pre-grayed curved boards mounted on untreated battens, stainless steel shielding mesh, 2 x 100 mm natural fiberboard, 160 mm lightweight wood frame construction with thermal insulation made of blown-in wood fiber insulation, 20 mm natural fiberboard, vapor retarder, built-in furniture or 20 mm clay board, finishing clay plaster, U-value 0.1 W/m2K
Roof (starting from the outside)	Stainless steel standing seam roof, sarking membrane, 18 mm solid wood sheathing, 80 mm ventilated rainscreen, top rafters with 160 mm natural fiberboard insulation in between, 20 mm diagonal solid wood sheathing, bottom rafters with 280 mm blown-in wood fiber insulation in between, vapor retarder, battens, 20 mm natural fiberboard, 5 mm finishing clay plaster, lime paint, U-value 0.09 W/m2K
Interior walls, ground floor	Existing walls made of hollow concrete blocks, partly supplemented with bricks, plastered on both sides with base and finishing clay plaster, partly in combination with wall heating, partly lime paint, partly textured lime plaster
Interior walls, upper floor	Lightweight wood frame construction with thermal and sound insulation made of 120 mm blown-in wood fiber insulation, 20 mm diagonal solid wood sheathing on both sides for bracing, 20 mm natural fiberboard, 20 mm clay board, finishing clay plaster
Floors, ground floor (starting from the bottom)	Existing concrete slab, polyethylene membrane as a vapor barrier, 300 mm dry fill made of mineralized wood chips, 50 mm natural fiberboard, partly with wooden battens in between, partly with floor heating clay panels (Lithotherm) between wooden battens, solid hardwood parquet flooring (robinia and oak), oiled, and natural stone tiles
Mass timber ceiling (starting from the bottom)	Dowel laminated timber ceiling partly with 240 mm acoustic joints, 24 mm diagonal solid wood sheathing as bracing, building paper lining, 110 mm crushed limestone, 20 mm natural fiberboard, floor heating clay panels (Lithotherm) between wooden battens, solid hardwood parquet (ash), oiled, and tiles
Windows and French doors	Aluminum-clad wood windows, passive house-compliant, oiled, U-value 0.66 W/m2K, unheated glazed stairwell with double glazing
Exterior doors	Solid oak doors with cork insulation, passive house-compliant, waxed
Interior doors	Solid spruce framed doors, oiled
Energy standard	Plus energy or passive house standard (EnerPhit for the modernization of old buildings)
Heating requirement	Approx. 4,500 kWh/year (20 kWh/m2)
Heat generation	Wood pellet stove with viewing window and 400-liter buffer tank (can also be heated with photovoltaic power in emergency mode)
Heat distribution	Low-temperature surface control systems for walls and/or floors
Ventilation	Central ventilation systems with heat recovery and carbon dioxide control, partly humidity recovery
Electricity	Photovoltaic system on the roof approx. 60 m2, yield approx. 7,500 kWh/year, electric charging station, energy-saving computers and appliances
Light, lighting	Rooms flooded with light thanks to large areas of glazing, flicker-free and low-EMF LED lamps, partly dimmable and tunable white light
Rainwater use	6,000-liter rainwater cistern for toilet flushing and garden irrigation, infiltration trench for temporary storage
Process water	Stainless steel pipes, decentralized on-demand water heaters
Furniture / interior	Mainly custom-made solid wood furniture, partly combined with waxed linoleum
Design of exterior space	Removal of tarred surfaces, water-permeable surfaces such as soil, gravel, natural stone paving, regional plants, small fountain, willow fence
Additional building biology criteria	Building materials made from plant- or mineral-based raw materials, largely free of harmful substances, largely glue-free construction (e.g. dowel laminated timber ceilings, floors, lightweight wood frame construction, interior doors), healthy indoor climate, best possible reduction of electrosmog (ELF electric and magnetic fields and radio frequency radiation), excellent environmental performance, and much more.
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