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Deep Energy Retrofit: how to reduce up to 60% of your home’s energy use

  • Writer: Karolline Dutra
    Karolline Dutra
  • Sep 18
  • 5 min read

Updated: Sep 30

Deep Energy Retrofit (DER), or deep energy renovation, is an essential approach for updating buildings with an emphasis on energy efficiency and sustainability. While this practice is already well-established in the UK and Ireland, it is still gaining traction in Portugal, where it presents considerable opportunities for cost reduction, enhanced comfort, and increased home value.


A brick house with solar panels on the roof. A patio with wooden furniture and a trimmed tree in the garden under a partly cloudy sky.

As technology advances and environmental regulations become stricter, one solution is gaining momentum in the construction sector: Deep Energy Retrofit (DER), also known as deep energy renovation. This approach goes far beyond a simple refurbishment. It is a sustainable and strategic method that modernizes existing buildings, making them more efficient, comfortable, and cost-effective. Already well established in the UK, Ireland, and other European countries, this practice is still emerging in Portugal, where it presents significant opportunities for growth.


With a well-planned retrofit, it is possible to significantly reduce energy and water consumption, extend the lifespan of a property, and ensure compliance with current environmental standards. More than just a renovation, DER is an investment in the future — capable of transforming older homes into modern, healthy, and highly valued spaces. Learn more about how to reduce your home's energy use.



What exactly is a Deep Energy Retrofit?


A Deep Energy Retrofit (DER) is a comprehensive modernization process for existing buildings. The main goal is to drastically reduce energy use and improve overall building performance.


Unlike traditional renovations, which often focus only on replacing windows or equipment, a deep retrofit takes an integrated, whole-building approach. It considers the building as a complete system — from its envelope to heating, cooling, and ventilation — ensuring consistent improvements in efficiency, comfort, and durability.


Close-up of blue solar panels arranged in rows, showing their grid-like pattern. The scene conveys a clean, sustainable energy focus.

When properly executed, this method can:


  • Substantially reduce energy bills, with immediate savings on electricity and gas.

  • Lower the building’s environmental footprint, aligning it with global sustainability goals.

  • Improve indoor comfort and air quality, creating healthier living environments.

  • Increase property value, making it more attractive and competitive in the real estate market.


These results are made possible by combining advanced technologies and engineering solutions, such as high-performance insulation, efficient heating systems, and smart energy monitoring.


Therefore, a Deep Energy Retrofit is an excellent way to reduce your home’s energy use. More than just a technical upgrade, it is a long-term strategy that benefits homeowners, occupants, and society as a whole.



The top three keys considerations of Deep Energy Retrofit for reducing your home's energy use


1. Building envelope


The envelope — walls, roofs, floors, and windows — is the first line of defense against energy loss. Adding high-performance insulation, combined with airtight windows and frames, dramatically improves efficiency. By eliminating air leaks and improving airtightness, the building maintains stable indoor temperatures, reducing the need for constant heating or cooling.



2. Heating and renewable energy systems


The second pillar focuses on replacing outdated heating systems with modern solutions. Heat pumps are the most efficient choice today, and they can work with underfloor heating or radiators. They consume less energy, rely on renewable resources, and can be connected to smart monitoring systems. This not only reduces costs but also ensures compliance with stricter environmental standards in the future.



3. Controlled mechanical ventilation


Ventilation is often overlooked in renovation projects, but it has a direct impact on occupants’ health. A mechanical ventilation system with heat recovery guarantees continuous fresh air, removes humidity, and prevents mold and mildew. At the same time, it recovers a large portion of the extracted heat, maintaining thermal balance and avoiding waste.


Person laying insulation in an attic, surrounded by wooden beams and a brick wall. Large rolls of insulation are being unrolled.



Benefits of Deep Energy Retrofit

A deep retrofit is not only a technical investment. It is also a direct improvement to daily quality of life. Among the main benefits are:

  • Lower energy costs: retrofitted homes can cut energy and water use by up to 70%, generating immediate savings.

  • Improved comfort: stable indoor temperatures, no drafts, and better acoustic insulation create a more pleasant living environment.

  • Increased property value: buildings with higher energy ratings are more attractive and sell at higher prices.

  • Regulatory compliance: energy performance standards are becoming stricter, and retrofitted buildings are prepared to meet them.

  • Environmental sustainability: reducing energy use directly cuts greenhouse gas emissions, supporting climate goals.



How to ensure a successful Retrofit?


Carrying out a deep retrofit requires careful planning and high-quality execution. Key factors include:


  • Integrated planning: fragmented or partial interventions may lead to waste and limited results. The best approach is a comprehensive upgrade.

  • Qualified professionals: poorly executed retrofits can cause serious problems, from leaks to health risks. Always work with certified experts.

  • Smart design and layout: the way spaces are designed influences overall efficiency. Careful design at this stage ensures better results.

  • Post-project monitoring: tracking energy performance after completion is essential to fine-tune and maximize benefits.


Tiled rooftop with antennas against a clear blue sky. The house features yellow and white walls with triangular gables, casting shadows.


How much does it cost and what is the return?


The cost of a Deep Energy Retrofit depends on the size, age, and condition of the building. In many cases, the investment ranges between 15% and 30% of the property value. It is crucial, however, to look at the medium- and long-term return: not only in energy savings, but also in increased property value and compliance with evolving legislation.


Example Estimates (Portugal, 2025)

Building type

Approximate investment

Average annual energy savings

Payback period

Apartment (80 m²)

€20,000 – €30,000

€900 – €1,200

15 – 20 years

Single-family home (150 m²)

€35,000 – €50,000

€1,800 – €2,400

12 – 18 years

Multifamily building (5 floors)

€200,000 – €300,000

€12,000 – €18,000

12 – 16 years

These values are indicative of average costs in Portugal and may vary depending on location, building condition, chosen technologies, and available incentives. Meanwhile, these are excellent indicators for reducing your home’s energy use by up to 60%.



Deep Retrofit as the future of construction


More than just a trend, deep energy retrofit represents a paradigm shift in the way we build and renovate. It is considered one of the most effective and cost-efficient methods to cut emissions, modernize existing building stock, and ensure healthier, more comfortable homes.


In the UK, Ireland, Germany, and the Nordic countries, this practice is already well established, supported by government programs and certification systems that demand high levels of energy efficiency. In these regions, Deep Energy Retrofit is seen not only as an opportunity but as a necessity to align the construction sector with medium- and long-term climate goals.


In Portugal, however, the topic is still relatively new and not widely discussed outside technical circles. Even so, progress has been made, largely driven by the demand for international certifications such as BREEAM and LEED, which have grown significantly in recent years in the mid- to high-end real estate market. This shows a clear upward trend, with more projects starting to integrate real concerns about energy efficiency and sustainability.


For construction professionals, it is also a rapidly expanding field of expertise. The demand for training, certifications, and sustainable retrofit practices is expected to grow, becoming a valued skill set and a competitive advantage for architects, engineers, and project managers.



Conclusion


A Deep Energy Retrofit is a comprehensive solution that combines technology, sustainability, and quality of life. For homeowners, it means living in a more comfortable, cost-effective, and healthy house. For society, it is an essential step in tackling climate change and using resources more responsibly.


If you are considering upgrading your home or building, count on a specialized team. Guedu Atelier supports every stage of the process — from planning to execution — ensuring your investment delivers lasting results.


Contact us and find out how we can help transform your project.




Karolline Dutra - Engenheira Civil e Ambiental | Interior Designer Especialista em Conservação e Reabilitação de Construções Cost Consultant e Project Manager Co-founder & CEO da Guedu Atelier

Written by Karolline Dutra

Civil e Environmental Engineer | Interior Designer

Building Conservation and Rehabilitation Specialist

Cost Consultant & Project Manager

Founder & CEO at Guedu Atelier



Do you have questions about your project?


Guedu Atelier is a consultancy company specialized in project management, cost consultancy, construction supervision, and interior design. We are ready to support strategic decisions and transform ideas into feasible projects, balancing quality, functionality, and investment.




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