On a fascinating tour of green building and design in Germany, organized by the Ecologic Institute environmental think tank with funding from the German government, we saw first hand how the Passivhaus standard for energy efficiency isn't just for houses.
The Passivhaus standard is so stringent, in pure performance terms, that it sometimes leads to dramatic, paradigm-shifting outcomes.
An exciting example of this, which we observed in action, is a Passivhaus school on the outskirts of Frankfurt, the Grundschule Riedberg, designed by 4a Architekten GmbH. This school is so tight and effectively insulated that a classroom in use is typically warmed simply by the heat of the students inside.
Ventilation is sized carefully at the correct low volume exclusively to provide appropriate fresh air. The central heat-recovery heat exchanger that makes the once-through air system efficient is the largest piece in the equipment room, taking pride of place where the boiler would traditionally stand.
Additional heating is provided by a cost-effective wood-pellet heater and distributed hydronically to small radiators in the functional spaces.
In a Passivhaus project, the value saved by avoiding a large central heating and distribution system, and its ongoing fuel costs, is invested instead in triple glazing (and sometimes, on north sides, quadruple glazing), in excellent insulation, and in highly airtight construction. The school we saw was built on a standard budget, using some value engineering in other project dimensions to balance the upfront investment in high-performance construction.
The operable window strategy at Grundschule Riedberg illustrates another example of the simplifying effects of the stringent standard. With so little outside energy supplied to rooms in use, there's only a tiny amount of waste if some of it goes out the window. Users are simply trusted to open the window when they want extra air, and to close the window again if the room starts to chill.
Experience has also suggested a simple strategy for minimizing the use of electric lighting in the highly daylit spaces. Avoiding the complexity of myriad occupancy sensors and their limitations in adjusting finely to varied user lighting preferences, there's a central control system that turns off the all the classroom lights at the end of each class period.
When class starts up again, teacher or students can turn the lights on if they want them. Most often, the daylighting is sufficient, and the lights just stay off.
To a visitor's eyes, the school seems comfortable, lively, creative, and happy, educationally unencumbered by the sophisticated appropriate technology embodied in its vessel.
With all best wishes,
Editor in Chief