It started off as a super-energy-efficient residential design standard in Germany. Passivhaus Design is an extremely tight building standard, minimizing outside air infiltration at every possible opportunity. Less outside air entering a structure means the HVAC cost is diminished, not having to condition large volumes of outside air – cold air in the winter and hot/humid air in the summer.
Many modern houses are now built with “house wrap,” a kind of shrink wrap around the entire perimeter of the building shell. This greatly decreases infiltration and exfiltration through the building envelope. Passivhaus does much more, striving to seal every opening both against airflow. Passivhaus standards also seal breaks in the insulation caused by typical structural and design practices.
What began as an idea has become a major trend, especially in Europe. The Passivhaus standard has now become common for buildings of every type, including hospitals. Why? Because electricity rates in Europe are on average 50% higher than in the U.S. That means the payback (cost of the project divided by the annual energy savings) for energy conservation projects is 50% faster.
All U.S. buildings would do well to adapt the Passivhaus “superinsulation” standard.
An airtightness standard is more complicated because the people inside the structure use up oxygen and breathe out carbon dioxide, meaning fresh air must be delivered to the occupied spaces via forced ventilation. This requires a complicated system of electronic controls, dampers, sensors, and fans – both for ventilation and exhaust air.
The American standard is to have a fixed air exchange rate for different areas, depending on the occupancy and activity level. A more efficient solution is for a carbon dioxide sensor to adjust the fresh air ported into the building via the outside air ducts.
Either way, every occupied space needs a carbon dioxide alarm (similar to smoke alarms) to warm people whenever the carbon dioxide levels increase above healthy norms.
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Excerpted from Going Green, available as an eBook at this list of eBook retailers online.