By Adam Cohen
Passivhaus is the world’s strictest standard for building energy performance, and the most effective path to achieving net-zero energy use buildings. Unlike other green design standards, Passivhaus brings a laser-like focus on operating energy, which over the lifetime of a traditional building, quickly exceeds embodied energy (the energy used in the production and transport of construction materials, and the construction process itself).
Passivhaus buildings achieve overall energy usage reductions of 60 – 80% (and space heating and cooling demand reductions of 90%) through a combination of five strategies:
- Superinsulated, airtight, thermal bridge-free envelope – minimizes heat transfer through surface conduction and air movement.
- Balanced ventilation with energy recovery – provides 100% fresh air, preconditioned through high efficiency heat exchange.
- Efficient mechanical systems – decrease energy demand and internal heat gains.
- Passive elements – utilize building orientation and shading to optimize natural light and solar heat gain.
- Readiness for renewable integration – allows building to achieve net-zero energy by way of photovoltaics, solar thermal, geothermal, wind power, etc.
Unlike “check box” style green certifications like LEED, Passivhaus is entirely performance-based. Builders and Certified Passive House Consultants work together in Passivhaus design and construction to ensure that buildings perform to specification. To achieve Passivhaus certification, three key metrics must be met:
- 1.4 kWh/ft2 or 4.75 kBTU/ft2 annual heating and cooling demand
- 11.1 kWh/ft2 or 38.1 kBTU/ft2 annual total primary energy demand
- 0.6 ACH @ 50pa of air leakage
Besides the obvious advantage of reduced operating costs through lower energy use, Passivhaus high performance buildings set a new bar for building in the 21st century:
- Increased occupant comfort – by eliminating drafts and maintaining a maximum temperature differential of 4°C/7.2°F between the warmest and coolest indoor surfaces.
- Improved indoor air quality – through a constant, controlled supply of filtered, fresh air.
- Little to no marginal cost – increased costs to achieve the Passivhaus standard can be offset by downsized HVAC equipment; investment payoff occurs in 7 – 10 years.
- Passive resilience – as a result of their low-energy design, Passivhaus structures can maintain superior comfort over traditional buildings even in the event of power outages or other unforeseen circumstances.
- Potential for carbon neutrality – low energy demand, integrated with renewable energy technologies, can lead the way to a sustainable, carbon-free future.