How Passivhaus Homes Stay Warm in Winter and Cool in Summer

When people first hear about Passivhaus, they often ask the same questions.

• "Will it overheat during summer?"

• "Can I still open the windows?"

• "Do I need heating?"

• "Is mechanical ventilation enough to keep the house comfortable?"

The answer is surprisingly simple. A well-designed Passivhaus doesn't just perform well during winter. It is designed to provide exceptional comfort, healthy indoor air and low energy consumption throughout every season. Unlike conventional buildings, which often struggle with cold draughts during winter and overheating during summer, Passivhaus homes maintain remarkably stable indoor temperatures by combining excellent insulation, airtight construction, high-performance windows, intelligent shading and carefully designed ventilation.

According to Vasilis Giannopoulos, Passivhaus Designer and Internorm Specifications Manager, successful Passivhaus design isn't about one individual product. "Optimal building performance comes from treating the building as a complete system. Windows, insulation, airtightness, ventilation and shading all work together to minimise energy demand and ensure exceptional comfort throughout the year."

Passivhaus homes remain comfortable throughout every season by combining five key principles:

• Excellent thermal insulation

• Airtight construction

• High-performance triple glazed windows

• Mechanical Ventilation with Heat Recovery (MVHR)

• Intelligent solar shading and passive solar design

Rather than relying heavily on heating or air conditioning, these principles significantly reduce energy demand while creating healthier, more comfortable homes.

As energy prices continue to rise and the UK experiences more frequent heatwaves alongside colder winter periods, homeowners, architects and developers are increasingly looking for ways to create buildings that are more comfortable, energy efficient and resilient to our changing climate. Buildings account for a significant proportion of the UK's energy consumption and carbon emissions, making the built environment one of the biggest opportunities to reduce our environmental impact. Improving the performance of our homes not only lowers energy demand and running costs but also creates healthier, more comfortable places to live. This is where the Passivhaus Standard has become increasingly influential.

The , of which Internorm UK is a Patron Member, is the UK's leading independent organisation promoting the Passivhaus Standard, has played a key role in raising awareness of low-energy building design and supporting the adoption of Passivhaus principles across the residential, education and commercial sectors. Through research, technical guidance, training and collaboration with industry professionals, the Trust continues to demonstrate that buildings can achieve exceptional levels of comfort while dramatically reducing operational energy use and carbon emissions.

For homeowners, Passivhaus offers far more than lower energy bills. It delivers stable indoor temperatures, healthier indoor air quality and year-round comfort. For architects and developers, it provides a proven methodology for designing buildings that perform as intended, helping to meet increasingly ambitious sustainability and net zero targets.

As Vasilis Giannopoulos explains: "Passivhaus is not simply an energy standard. It is a design methodology that prioritises occupant comfort, building performance and long-term resilience. When every element of the building works together, the result is a home that feels noticeably different to live in."

Winter is where Passivhaus performs at its very best.The highly insulated building envelope dramatically reduces heat loss, while airtight construction eliminates unwanted draughts. High-performance triple glazed windows allow valuable solar heat to enter the home during sunny winter days while minimising heat escaping back outside.

Mechanical Ventilation with Heat Recovery (MVHR) continuously supplies fresh, filtered air while recovering heat from the outgoing stale air. The result is a warm, comfortable indoor environment with significantly lower heating demand. Many Passivhaus homes require up to 90% less heating energy than conventional buildings.

But perhaps the greatest benefit isn't lower energy bills. It's thermal comfort. Unlike older homes, where cold window surfaces create uncomfortable draughts and radiant cooling, Passivhaus windows remain close to room temperature, allowing every part of the room - including areas beside the glazing - to remain comfortable throughout winter.

One of the lesser-known advantages of Passivhaus is how little additional heating is required during spring and autumn.

Internal heat gains from occupants, cooking, electrical appliances and natural sunshine are often sufficient to maintain comfortable temperatures. Combined with the MVHR system, many Passivhaus homes require little or no conventional heating during these transitional seasons.

One of the biggest misconceptions surrounding Passivhaus is that highly insulated homes become too hot during summer. In reality, the opposite is true. When designed correctly, Passivhaus homes remain remarkably comfortable during hot weather. The key lies in preventing excessive solar heat from entering the building.

According to Vasilis: "Good summer performance begins long before construction starts. Window orientation, glazing size and external shading all need to be considered together if overheating is to be avoided."

Effective shading strategies include:

• Architectural overhangs

• Vertical shading on east and west elevations

• Intelligent automated shading systems

Combined with night-time purge ventilation and careful control of internal heat gains, these passive cooling strategies significantly reduce the need for air conditioning.

Windows are unique because they perform two very different functions throughout the year. In winter they capture valuable solar energy while providing excellent insulation. In summer they must help prevent excessive solar gains without sacrificing daylight.

Choosing the correct glazing specification, window size and orientation is therefore essential. have been developed specifically to meet the demanding requirements of Passivhaus and EnerPHit projects, providing outstanding thermal performance, comfort and durability.

Absolutely. This remains one of the most common misconceptions.

You can open the windows whenever you wish. During winter, however, many occupants simply find there is little need because the MVHR continuously supplies fresh, filtered air without creating uncomfortable draughts or wasting valuable heat. During spring, summer and autumn, opening windows for cross ventilation and night cooling remains an important strategy for maintaining comfort.

While low energy bills often receive the most attention, many Passivhaus homeowners say the greatest benefit is how the house feels.

• Stable indoor temperatures.

• Excellent air quality.

• Quiet interiors.

• No cold spots.

• No draughts.

• No condensation.

Just consistent comfort throughout the year.

Designing a successful Passivhaus requires careful consideration of glazing, orientation, shading, airtightness and installation. Working with experienced specialists early in the design process helps ensure every element contributes to the overall performance of the building.

Internorm's Specifications Manager works closely with architects, Passivhaus Designers and contractors to develop high-performance glazing solutions for self-build, residential and commercial projects across the UK. We can also provide data for PHPP modelling software and Vasilis delivers in-depth CPDs on 'Windows & Doors for Passivhaus', which are endorsed by the Passivhaus Trust and the Passive House Institute in Germany. Passivhaus Designers receive 2 learning points for attending.

Whether you're designing your first Passivhaus, planning an EnerPHit deep retrofit or simply looking to improve the performance of your next project, our Specification Manager, as well as your local , can provide expert guidance on selecting the most appropriate window and door solutions.