Concrete’s Role in Passive House Construction

As the construction industry moves toward greener solutions, the push for sustainable, energy-efficient buildings grows. Global energy consumption for buildings accounts for nearly 40% of total energy usage. With stricter legislation, such as the focus on net-zero emissions by 2050, the pressure to build with energy efficiency has led to more projects pursuing Passive House certification. Passive House is an advanced target that goes beyond sustainable materials to construct a building that performs more sustainably—an embodiment of sustainability’s core concepts.

Achieving certification comes with its own set of challenges as it demands precise attention to design, materials, and construction processes. Even small deviations can compromise a building’s energy efficiency and environmental performance. Among these challenges is the use of concrete in foundations and slabs, which impacts both airtightness and thermal performance in significantly different ways than conventional construction.

The 5 Core Principles of Passive House

1. Eliminate or minimize thermal bridging in the building envelope
2. Utilize high-efficiency energy (double- or triple-paned windows and doors) to allow solar gain and mitigate energy loss through glass
3. Reduce space conditioning loads, allowing for minimum equipment to meet loads
4. Create an airtight envelope, preventing infiltration and air loss, with an intention for durability and longevity
5. Capture and utilize heat and moisture recovery in the HVAC system to enhance indoor air quality

Concrete in Passive House Foundations & Structural Systems

Concrete is used widely in Passive House construction due to its robustness and ability to be molded onsite, which can help eliminate gaps and reinforce airtightness. While concrete is typically associated with higher costs, the price difference between traditional and low-carbon concrete options is narrowing, making sustainable choices more accessible without major impacts on budget. Even still, concrete’s carbon intensity and potential for thermal bridging must be addressed in order to adhere to Passive House standards.

The use of concrete can introduce thermal bridging at any juncture where it interfaces with other elements, creating opportunities for significant energy loss.  Incorporating thermal breaks—materials with low thermal conductivity such as foam glass, high-density polystyrene, or structural thermal break pads—prevents this issue by blocking heat transfer through the building envelope. This minimizes cold spots and condensation risks and also reduces the overall space conditioning loads required to maintain indoor comfort, allowing for smaller, more efficient mechanical systems.

Consistent curing is another critical factor, as it enhances concrete's structural integrity and thermal performance. Poor curing can lead to cracking, which undermines airtightness and efficiency. To ensure consistency, contractors must adhere to rigorous concrete placement and curing practices. Proper consolidation, the use of high-performance sealants, and careful detailing at all material interfaces leverage concrete’s strengths while meeting Passive House standards.

Passive House in Traditional vs. Modular Construction

Passive House poses certain challenges and opportunities in traditional versus modular construction projects. Traditional construction allows for greater customization, enabling detailed, site-specific adaptations to meet Passive House requirements. Unlike modular construction, where components are prefabricated under factory conditions, traditional construction enables project teams to adapt building designs and processes in real-time to address the unique characteristics of a specific site. This flexibility helps ensure that the building can achieve the strict energy efficiency, thermal performance, and airtightness goals required by Passive House certification with the right trade coordination.

Modular construction introduces efficiencies that can streamline Passive House projects, as demonstrated by the La Mora Senior Apartments in Yonkers, New York. In combination with prefabrication methods, the team was able to overcome the challenge of maintaining airtightness during transport and assembly while expediting the overall construction timetable. To ensure airtightness, the project team inspected and tested each module prior to installation, requiring close oversight to prevent insulation gaps during stacking. Third-party compliance inspections were used to verify each module’s airtight construction, mitigating risks of insulation damage or gaps. The process also involved performing early blower pre-tests at key stages to identify potential issues, allowing for corrective action before final assembly. This approach balanced the project's accelerated timeline with Passive House requirements, ensuring those standards were met without compromising the schedule.

Passive House standards impose rigorous demands that can necessitate additional inspections and extend project timelines. Project managers can address these expectations by incorporating regular testing and inspections throughout construction, not after delivery, and working with concrete contractors to educate them on potential pitfalls. This proactivity allows for earlier identification of areas for improvement, ensuring that the building meets all certification criteria.

Efficiency & Success in Passive House Projects 

Earning Passive House Certification requires collaboration between all project team members. Early reviews and alignment of project goals and requirements mean all stakeholders are committed to the stringent standards at hand.

Projects like the La Mora Senior Apartments show how Passive House can be integrated successfully with concrete, even given complex methods like modular construction. By performing early blower tests and inspections, the project team ensured that the building met airtightness requirements without sacrificing the accelerated schedule modular construction offered or the structural integrity that concrete provides.

As Passive House continues to grow in popularity, it amplifies the importance of careful planning, technical expertise, and collaboration to meet today’s high standards of energy efficiency. The La Mora Senior Apartments are one example of Passive House projects that show how sustainable buildings can be optimized—efficiently, durably, and sustainably.