Passive [Aggressive] House

Passive House (PH) is a building standard that enhances energy efficiency, thereby reducing our ecological footprint. Though it is currently only a voluntary measure, architects have an obligation to address worldwide climate trends that are directly related to the built environment. In a recent World Economic Forum survey, world leaders were asked to identify their concerns across the globe. The most alarming was climate change, rated significantly higher than issues such as weapons of mass destruction, the water crisis, and large-scale migrations.

So, where does that leave architects?

Human energy consumption is a major component of global climate change, and approximately 30% of this energy is related to how we build and utilize buildings. By ensuring our architecture is responsible, energy-conscious, and takes advantage of every tool at our disposal, we can lessen human impact on the environment.

A Heated Planet

The world was at its hottest 55 million years ago during the Paleocene-Eocene Thermal Maximum (PETM) period. Scientists believe ocean-generated methane caused temperatures to rise so high that life could not survive around the Equator. It took thousands of years for the Earth to cool down again. For perspective: our current carbon production is 100 times more per year than what it was during the PETM. Since 1950 alone, we've more than doubled the amount of atmospheric carbon. We can expect at least a two degree rise in temperature over the next 50 years, alongside melting sea ice and rising sea levels of over 200 feet.

  • The need for Passive House design by SMMA's Anthony Iacovino, Senior Project Architect.

Passive House Explained

In 1988, Dr. Wolfgang Feist built the very first Passive House building in Darmstadt, Germany. The house abided by five basic principles: extremely well-insulated glass and doors, highly efficient but small HVAC equipment, airtight construction, maximized thermal bridges, and highly insulated exteriors. Inspired, Dr. Feist compiled these principles with his own energy model for public use, now called the Passive House Planning Package (PHPP).

Pictured: Dr. Wolfgang Feist and the first Passive House project.

The need for Passive House design by SMMA's Anthony Iacovino, Senior Project Architect.

Tightening Buildings

Whenever the wind blows, air infiltrates the average building envelope. Therefore, traditional houses are typically drafty. To combat this, Passive House says architects must make structures tighter by creating two barriers against the wind: one on the outside and one on the inside. All penetrations, such as windows and doors, must also be completely sealed when closed.

To determine if the building is tight enough, Passive House requires meeting 0.6 air changes per hour at 50 pascals of pressure. This requirement ensures that under normal conditions, only 6/10ths of the total volume of air escapes in an hour’s time. Testing for this objective is best done as soon as possible to be able to make any necessary corrections.

The need for Passive House design by SMMA's Anthony Iacovino, Senior Project Architect.

Insulate, Insulate, Insulate!

Passive House insulation standards are massive compared to current insulation practices. To start, the outside of the building needs to be completely intact and waterproof, including the wind barrier and any exposed surfaces. The inside barrier is where we consider the insulation: walls need a high R-value (R38), meaning the insulation has high thermal resistance. This also means the walls need to be thick and dense to accommodate additional insulation. Passive House then categorizes and tallies each load or heat source, calculating the total heat demand through all heat gains and losses. 

The Principles at Work

SMMA has already begun applying Passive House standards, focusing on two of the most important principles: airtightness in building enclosures and high-performance glazing. For our Winchester High School project, we transformed a thermally inefficient structure by going beyond what was required by code. Our design team increased insulation on the roof, wrapped the parapets with wall insulation, and placed a new veneer system on the outside. All layers are currently intact and reach R36, establishing a solid and efficient foundation for the future of the school.

Hover over the image below to see how SMMA applied Passive House standards:

The Need for Triple-Glazing

Passive House requires a 0.14 U-value for glass windows. U-values measure how well heat passes through building materials. They are calculated by BTU/hr-sq ft °F, with The British Thermal Unit (BTU) being the primary unit for heat energy in the United States. The lower the U-value, the greater the resistance to heat flow.

Achieving low U-values resides partially in the implementation of triple-glazing. A typical piece of glass has a value of around 0.75, and on our more focused projects we can achieve a value of about 0.35. This comparison reveals how nearly impossible it is to reach a 0.14 value with just two sheets of glass, forcing us to weigh all options. Solar orientation is also extremely important in this instance, since we can strategize where we place windows and how we use them for heat.

The need for Passive House design by SMMA's Anthony Iacovino, Senior Project Architect.

Lower Costs, Better Solutions

Passive House is not unlike typical construction when it comes to cost. Though extreme efficiency comes with a high initial cost, there is a point where the efficiencies allow you to downsize the mechanical system, in turn lowering the total project cost. As we work with clients, designers must make sure we are not paying more for a high-performing building to reap the benefits of Passive House’s lower energy costs.

SMMA is in a unique position regarding Passive House. We have the in-house ability through talented architects, engineers, and designers to take the less prosaic solutions and transform them into well-designed and beautiful solutions, separating ourselves from the rest of the market as a firm that truly understands environmental responsibility and impactful design.