How Can Passivhaus Principles Improve Your Renovation?

This was the design for an AECB Carbonlite retrofit of a semi-detached house. The proposal was to wrap the building in insulation, add a small ground floor infill extension and convert the roof space. We incorporated a little pergola for plants to scramble across to help with summer shading over the south facing patio doors.

The final result was a 70% reduction in space heating demand….

i.e. 70% less energy was needed to keep the house warm.

1. Enhanced Comfort All Year Round

One of the main goals of Passivhaus design is to create a comfortable indoor temperature all year round, regardless of external weather conditions. This is achieved through a number of key features:

Thermal Insulation: Thick insulation minimises heat loss in winter and keeps your home cooler in summer. This means consistent temperatures throughout your home, eliminating cold spots and draughts that are often found in older buildings.

Airtightness: By ensuring your home is airtight, you prevent unwanted drafts, which helps to maintain stable indoor temperatures. While some people worry that airtightness means lack of ventilation, it actually allows for greater control of fresh air through a mechanical ventilation system, rather than relying on gaps in the structure.

Shading: Windows are carefully designed to take advantage of the sun in winter and reduce overheating in summer. Size, orientation, shading and specification are all part of the consideration.

2. Drastically Lower Energy Bills

Passivhaus principles are designed to reduce the energy required to heat and cool your home—often achieving savings of up to 90% compared to conventional buildings. By focusing on maximising energy efficiency through:

High-Performance Windows: Triple-glazed windows with high quality frames minimise heat loss while still allowing natural light to flood in.

Mechanical Ventilation with Heat Recovery (MVHR): An MVHR system recovers heat from the air being extracted from your home and uses it to warm incoming fresh air. This provides a constant supply of clean, filtered air while significantly reducing heating demand.

These strategies together mean that your heating system will need to work much less, which translates into lower utility bills and less reliance on fossil fuels.

3. Improved Indoor Air Quality

Indoor air quality is crucial for both comfort and health, especially if you’re spending a lot of time at home. The MVHR system provides continuous pre-warmed (in winter) fresh air without losing valuable heat. This system also filters out dust, allergens and pollutants from the incoming air, ensuring that you and your family breathe cleaner, healthier air.

For renovation projects, adding an MVHR system can help contribute to tackling issues like condensation, dampness and mould. Better air quality can lead to fewer allergies and a more comfortable living environment, ultimately contributing to your overall well-being.

4. Long-Term Savings and Future-Proofing

While incorporating Passivhaus design elements into a renovation may require a higher upfront investment, the long-term benefits can outweigh these costs. Lower energy bills will add up over the years, meaning you’ll eventually recoup the cost of energy-efficient upgrades. Moreover, as energy prices continue to rise, having a home that requires minimal energy for heating and cooling makes it more resilient to future changes in the energy market.

Energy efficiency is also becoming an increasingly important factor for homebuyers, meaning that if you decide to sell your home in the future, the energy-efficient features could increase its value and marketability.

But, it’s not all about saving energy and reducing your energy bills. It’s also about living in a:

• home free of dust and drafts
• quieter home where outdoor noise is less invasive
• home where you don’t need to wear 6 layers of clothing to stay warm in winter or boil in mid-summer
• home where you can choose whether or not to open the windows…..and so much more!

5. Less Environmental Impact

Passivhaus renovations are not only good for your wallet—they’re good for the planet. By reducing the energy demand of your home, you contribute to lower greenhouse gas emissions, helping to mitigate climate change. While the Passivhaus principles are agnostic about what materials to use – using ecological materials will contribute further to shrinking the environmental footprint of your renovation.

Additionally, when your home requires less energy to maintain comfortable temperatures, you can explore renewable energy options, like solar panels, to further reduce your environmental impact.

6. Retrofitting Without Full Certification

You don’t have to go all-in on formal Passivhaus certification to benefit from its design principles. Many homeowners choose to cherry-pick key elements that fit within their renovation budget. Here are a few ways you can apply Passivhaus standards without a full certification:

Airtightness and Insulation: Start by improving the airtightness and adding high-quality insulation to walls, floors and the roof. This is one of the most effective steps you can take to reduce energy loss.

Better Windows and Doors: Replacing old windows and doors with high-performance alternatives can significantly reduce drafts and heat loss.

Ventilation System: Incorporate an MVHR system to maintain indoor air quality and recover heat. Even if the entire home isn’t airtight, improved ventilation can have substantial benefits.

By selectively incorporating appropriate Passivhaus design features into your renovation, you can achieve many of the benefits—such as improved comfort and lower energy bills—without committing to the full cost of a certified Passivhaus retrofit.

7. Design Integration with Character

When retrofitting a home, one concern many homeowners have is maintaining the character of the building while improving energy efficiency. Passivhaus design is highly flexible and can be adapted to work with older properties, whether it’s a traditional cottage or a Victorian terrace. The key is working with an architect who understands how to integrate these elements in a way that preserves or enhances the charm of the building while ensuring it performs well in terms of energy efficiency.

From drastically lower energy bills to enhanced comfort, better air quality and a reduced environmental impact – incorporating Passivhaus principles into your renovation brings a range of benefits.

You don’t have to fully certify your home as a Passivhaus to reap these rewards. Simply adopting a few core principles can lead to meaningful improvements in how your home feels and functions. However, these improvements must be considered and designed, to be sure to avoid unintended consequences. For example, adding lots of insulation but not considering ventilation may well cause increased humidity and the problems that causes. A step-by-step approach could be considered, which would allow for the improvements to be carried out as elements need to be renovated or replaced over a number of years.

If you want a renovation that’s future-proof, energy-efficient and comfortable, Passivhaus principles are well worth considering. They not only help you create a beautiful and functional space today but also ensure that your home is ready for the demands of tomorrow.

The approach to meeting the Passivhaus, EnerPHit or AECB standards on all buildings is essentially the same. The biggest difference between them is how much energy is allowed to be used for heating the building – as can be seen in the first row of this table.

On an AECB retrofitted property, for example, the maximum allowable energy to heat the building is 50kWh per square metre per year. So, a 144sqm house couldn’t use more than 7,200kWh/year for heating.

On a recent 144sqm semi-detached house the existing property was calculated to require 22,176kWh/year. Our proposed AECB retrofit improvements combined with extension works would take the new 189sqm property to demand 6,426kWh/year. In smaller numbers, this meant that the heating demand for the property would reduce from 154kWh/m2/year to 34kWh/m2/year.

A whopping 70% reduction in energy demand!