Existing buildings account for the greatest share of energy used in buildings - worldwide but especially in industrialised countries. With an estimated 95% of the buildings standing today likely still in use in 2050, deep renovation must be a priority. A great number of these buildings require overall or partial refurbishment or modernisation immediately or in the upcoming decades. Each such occasion is a perfect opportunity to reduce the energy consumption of these buildings by applying appropriate methods. Using components and approaches developed for new Passive House buildings also leads for significant energy savings in existing buildings.

Context and introductory reading on the topic of refurbishment with Passive House components:

• Highly efficient building renovation as a societal no-regret measure
  
• Refurbishment with Passive House components - introduction
  
• Brochure: Renovation done right - Success stories with the EnerPHit Standard
  
• Brochure: EnerPHit - Renovating with Passive House components
  
• Research paper: Retrofit with Passive House components [Bastian et al. 2022]

Poor quality reburfishments can result in lock-in effects with suboptimal improvements typically left untouched for decades, if not generations. We simply cannot afford the resulting missed opportunities for energy savings and emissions reductions. Truly high performance refurbishment with a fabric first approach has the power to substanitally mitigate climate impacts while providing manifold other benefits (as outlined below). On a societal level, high-performance renovations will also dampen peak loads on our energy grids, boost our energy independence and facilitate out transition to a renewables-based energy supply, thus further contributing to our climate goals.

Comparison of a building's energy demand following either shallow retrofit (dark green) or deep retrofit measures at every reburbishment step. Choosing mediocre efficiency levels will lock in the long-term energy performance of the building, the so-called “lock-in effect”).

When the focus of refurbishment is expanded to prioritise energy efficiency, we not only reduce energy consumption but also enhance comfort and health benefits while combatting energy poverty - a triple win.

• Living comfort significantly improved due to warm walls, floors, and window surfaces
• No draughts, condensation, or mould
• Improved air quality due to constant supply of fresh air with a pleasant temperature
• Reduced operating costs due to lowered energy demand, thus protecting against fluctuating energy prices and alleviating fuel poverty
• Significant reduction of operational CO2 emissions due to a lower heating demand

1. Insulation - Passive House retrofits: Thermal envelope | Insulation

2. Thermal bridge free design - Passive House retrofits: Thermal envelope | Thermal bridges

3. Airtightness - Passive House retrofits: Thermal envelope | Airtightness

4. Passive House Windows - Passive House retrofit: Thermal envelope | Windows

5. Ventilation with heat recovery - Passive House retrofits: Mechanical systems | Ventilation

For the retrofit of existing buildings, the Passive House Standard cannot always be fully achieved with reasonable effort. This may be because of unavoidable thermal bridges due to existing basement walls, for example, or the building's fixed orientation. For such buildings, the Passive House Institute has developed the EnerPHit Standard. EnerPHit is to renovations what Passive House is to new builds. Both standards are based on the same, basic physical principles and both ensure that the energy savings over a building's lifecycle will more than make up for upfront investment.

The EnerPHit accreditation provides certainty and quality assurance that an optimal standard of thermal protection has been achieved for the existing building. There are two compliance methods: Based on component qualities or based on energy targets. This makes EnerPHit flexible and applicable for diverse building types and for different climate zones. It can be applied in one go or as phased refurbishment (step-by-step) and is founded on the principle of avoiding and preventing lock-in: If you do it, do it right

Read more about the EnerPHit Standard

The refurbishment of this multifamily building in Giessen, Germany achieved measured heating savings of more than 70 %. This success story confirms the potential of energyefficient refurbishment of existing buildings

For achieving cost efficiency, it is crucial to couple the energy-saving measures with renovation measures that would have been necessary in any case. For example, if the facade needs to be renovated anyway, then the additional expenditure for simultaneous thermal insulation to the Passive House Standard with remain manageable. Nowadays, it is possible to carry out better measures at low differential costs, later installation would require the same effort once again for scaffolding, installing, protection from weather, etc. That is why, from the very beginning, great attention must be paid to a high quality of the thermal and energy-relevant aspects of each procedure.

• Economic feasibility of Passive House retrofits
• Economic analysis for the retrofit of a detached single family house to the EnerPHit standard
• Example of incentive programmes for retrofits: the KfW in Germany
• Study of energy efficiency for Sustainable Housing in Mexico

The best proof of concept is always in-use performance monitoring. Positives results of EnerPHit renovations have been demonstrated and documented. Here are some examples and relevant articles:

• Performance results of retrofit projects
• Nuremberg Case Study in detail
• Living Quality Monitoring

Example of a whole building retrofit: The Cartagena residential building is located in Madrid, Spain. A traditional approach without prefabrication was taken and tenants moved out the building before construction.
Read more about the project: ID 6898

Exisiting projects typically have quite individual challenges - both technically, as well as from practical, social or cost perspectives. It is important to assess and understand the specific project and context and then apply the most suitable retrofit approach without compromising on quality. The EnerPHit Standard deliberately does not prescribe a specific method or technology, which allows flexibility to chose an approach best suited to the individual context.

A whole building retrofit refers to renovating an entire building all at once to improve its performance from the original state to a high performance building. This approach requires highest immediate investment costs but can still be the most cost-effective from lifetime cost perspective.

Example residential building: A pilot project: modernising a block of flats in Nuremberg

Renovating in a step-by-step manner allows for incremental improvement to a building's energy performances, spreading costs and effort over time. This is also referrred to as phased or staged retrofit. The EnerPHit Retrofit Plan (ERP), based on PHPP, provides a valuable tool to plan and coordinate different retrofit steps. Read more about the ERP here. Such a phased approach is particulary useful when budget constraints or practical considerations make a full renovation executed all at once unfeasible. By planning each step to align with long-term energy efficiency goals such as those set by the EnerPHit standard, building owners can gradually reduce energy consumption, improve comfort, and avoid suboptimal interim solutions that would lead to energy lock-in.

Detailed brochure: Step by Step Retrofit with Passive House Component

Concept of step-by-step retrofit to EnerPHit

Articles on selected technical topis of step-by-step refurbishment:

• Practical implementations of step by-step-retrofit to EnerPHit standard
• Overview of inter-dependence of individual energy efficiency measures
• Windows in a step-by-step retrofit
• Building Integrated Photovoltaics (BIPV) in Step by Step Retrofitting Projects

Selected case studies:

• A road towards deep building renovation on a step-by-step basis in Bulgaria
• Step-by-step Retrofits towards EnerPHit Standard in social housing in Spain
• Step-by-step deep retrofit and building integrated façade/roof on a 'million program' house
• Wilmcote House: The EnerPHit Standard applied to large, complex existing buildings
  
• Step-by-step retrofit to achieve EnerPHit-Standard, the example of a single-family home

Renovating single units allows for targeted energy efficiency improvements within a multi-unit building, thereby addressing the specific needs and constrains of individual spaces. This approach is only recommended if the entire building cannot be considered for renovation due to financial or logistical reasons (e.g. shared ownership). By focusing on one unit at a time, owners and tennants can experience immediate benefits such as reduced energy bills and enhanced comfort. Learn more about pilot projects in the iPHA Webinar Two pilot EnerPHit Unit projects in Italy and Portugal.

Example of serial renovation: This apartment block in Cologne, Germany, was retrofitted to the Passive House Plus Standard uding prefabricated modules. The tenants stayed in the building during the works. Read more about the project ID 7540

Renovation using prefabricated Passive House modules, also called serial renovation, can offer a swift and effective way to upgrade building with minimal disruption. Prefabricated modules can be designed to meet specific energy efficiency criteria and pre-assembled offsite. They are then installed onsite, allowing for faster renovation, consistent quality control and a reduction of waste.

Even small retrofit measures can contribute to energy savings and home improvements. Implemented by professionals or as “Do-It-Yourself” DIY project, such small energy efficiency measures are an excellent way to speed up the energy transition. With the Efficiency NOW! campaign, the Passive House Institute are providing guidance and detailed instructions for people to make their homes more energy efficient. The information is intended for beginners, for experienced DIY-ers, as well as professionals.

[Bastian et al. 2022]: Bastian, Z., Schnieders, J., Conner, W., Kaufmann, B., Lepp, L., Norwood, Z., Simmonds, A., Theoboldt, I.: Retrofit with Passive House components. Energy Efficiency 15, 10 (2022). https://doi.org/10.1007/s12053-021-10008-7. The article can be read online here.

[PHTrust 2021] “Passivhaus Benefits” report issued by the Passivhaus Trust. Available for download here

EnerPHit: The Passive House Standard for retrofits

Built examples: Passive House and EnerPHit worldwide

Website of the EU funded outPHit project aims to make deep retrofits more cost-effective, faster and more reliable.

Website of the EU funded EuroPHit project with focus phased retrofit solutions, including case studies.

Website of the EU funded 3EnCult project bridges the gap between conservation of historic buildings and climate protection.

Passive House Research Group proceedings, including selected detailed topics related to refurbishment with Passive House components.