Bridging the Energy Performance Gap: Why Passive House is the Ultimate Solution

The construction industry has long been grappling with the challenge of creating buildings that perform as efficiently as their designs promise. One of the most significant challenges is the Building Energy Rating (BER) performance gap—the discrepancy between the predicted energy efficiency of a building, as outlined in its BER assessment, and the actual performance once the building is occupied. This gap can have far-reaching implications, leading to higher energy bills, increased carbon emissions, and occupant discomfort.

In the quest for a more sustainable built environment, Passive House has emerged as the gold standard, offering a robust solution to closing the BER performance gap. But what exactly is this gap, and how does Passive House design address it?

Understanding the BER Performance Gap

The BER system is widely used to assess the energy efficiency of buildings based on factors such as insulation, air tightness, heating systems, and renewable energy contributions. However, studies consistently show that many buildings underperform once completed and occupied, with actual energy use up to 50% higher than predicted.

This discrepancy is known as the performance gap and can occur due to several reasons, including:

• Poor construction practices that deviate from design specifications.

• Lack of proper installation of key energy efficiency features.

• Behavioural factors of building occupants.

• The limitations of BER assessments, which rely on static assumptions rather than real-world variables.

In many cases, the BER assessment represents an idealised version of a building’s energy efficiency, often underestimating the impact of heat loss, air leaks, and inefficient heating systems. This gap between theory and reality not only undermines the purpose of energy certifications but also weakens efforts to achieve national and global sustainability goals.

Why Passive House is the Solution

Passive House is not just a design standard—it is a philosophy rooted in rigorous attention to detail and a holistic approach to building performance. Passive House principles prioritise occupant comfort, energy efficiency, and durability, addressing many of the causes of the performance gap at their core.

Here’s how Passive House effectively closes the BER performance gap:

1. Rigorous Airtightness Standards

Airtightness is one of the most critical factors in achieving a truly energy-efficient building. Uncontrolled air leakage is a major contributor to the performance gap, leading to unnecessary heat loss and higher energy consumption. Passive House buildings are designed to minimise air leakage to an industry-leading level, typically aiming for an airtightness of 0.6 air changes per hour (ACH) or less. This drastically reduces the heat loss that often undermines a BER assessment’s predictions.

2. Super-Insulation

While many buildings meet minimum insulation standards, Passive House buildings go beyond the basic requirements by incorporating unbroken super-insulation. This results in dramatically lower heat loss through walls, roofs, and floors, ensuring that buildings retain warmth and reduce reliance on heating systems. The high level of thermal comfort achieved in a Passive House is often unattainable in buildings with standard insulation, particularly those that experience construction shortfalls.

3. Thermal Bridge-Free Design

Thermal bridges—points in a building’s envelope where heat can escape more easily—are another significant contributor to the performance gap. Even minor inconsistencies in construction can lead to heat loss and condensation, undermining energy efficiency. Passive House design eliminates thermal bridges through meticulous planning and construction techniques, ensuring a continuous and well-insulated building envelope that performs as expected.

4. High-Performance Windows and Doors

Windows and doors are often weak points in the thermal performance of a building. Passive House design specifies triple-glazed windows and highly insulated doors to ensure minimal heat transfer. This prevents the common issue of windows becoming a major source of heat loss, a problem that can frequently widen the BER performance gap in standard buildings.

5. Mechanical Ventilation with Heat Recovery (MVHR)

Ventilation is key to maintaining indoor air quality without compromising energy efficiency. Many buildings rely on traditional ventilation methods, such as opening windows, which can result in significant heat loss. In contrast, Passive House buildings use MVHR systems that extract heat from outgoing stale air and transfer it to incoming fresh air. This system significantly reduces the need for space heating and maintains a consistent indoor climate, eliminating the risk of poor performance due to inadequate ventilation systems.

6. Real-World Performance Verification

One of the defining characteristics of Passive House buildings is their verified performance. Passive House certification involves both design-stage calculations and post-construction verification, ensuring that the building meets stringent energy performance criteria in real-world conditions. This focus on verification ensures that the building performs as predicted, unlike standard BER assessments, which may not account for construction deviations or occupant behaviour.

Passive House: A Proven Track Record

The success of Passive House in closing the BER performance gap is not theoretical; it is backed by a track record of real-world performance. Numerous studies and post-occupancy evaluations have shown that Passive House buildings consistently meet or exceed their predicted energy performance. For instance, buildings certified to Passive House standards often achieve actual energy savings that are in line with or better than their calculated energy use.

At MosArt, we’ve seen this first-hand. Our advanced simulations and post-occupancy evaluations reduce the performance gap in energy-efficient buildings to 10% or less—far below the industry average of 50%. This is a testament to the power of Passive House as a reliable, proven solution.

The Future of Energy Efficiency: A Passive House Pathway

As the construction industry faces increasing pressure to deliver truly sustainable and energy-efficient buildings, the Passive House standard provides a clear and achievable pathway. By addressing the root causes of the BER performance gap—airtightness, thermal bridging, insulation, and mechanical ventilation—Passive House design ensures that buildings perform as promised, offering real value to occupants and delivering on energy efficiency commitments.

In a world where energy efficiency and sustainability are more important than ever, Passive House represents not just an option, but the ultimate solution to the performance gap challenge.