Erwin Mlecnik has over 30 years of experience in sustainable construction and innovation and leads multiple European projects. He is a member of several International Energy Agency working groups and a theme leader for accelerating housing renovation at TU Delft’s Urban Energy Institute.

He began his career at TU Delft’s OTB Research for the Built Environment, where he earned his PhD in 2013 with the thesis Innovation Development for Highly Energy-efficient Housing. Mlecnik now works in the Department of Management in the Built Environment, focusing on sustainable finance, real estate, and portfolio management, and advanced renovation concepts. Previously, he founded and served as a senior R&D expert at the Flemish Passiefhuis-Platform vzw (a non-profit organisation that specialised in disseminating knowledge for the realisation of highly energy-efficient buildings) and was R&D responsible at Energie Duurzaam vzw and Cenergie cvba, which specialised in developing energy services for construction professionals. He also worked at the universities of Palermo, Montpellier, and Brussels (VUB), where he obtained his degree in Civil Engineering and Architecture in 1992.

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BUILD UP (BUP): The One-Stop Shop (OSS) concept is increasingly promoted as a way to simplify energy renovation by offering homeowners a single point of contact for technical, financial and organisational support. From your perspective, what are the most significant challenges that still prevent OSS from becoming a mainstream solution across Europe?

Erwin Mlecnik (EM): About 15 years ago, the first OSS concepts emerged in Northern Europe as a supply-chain collaboration opportunity to unburden homeowners. The main idea was that a single contact point could support homeowners in their quest for reliable information and easy access to renovation solutions. We have seen evolutions in the local flavours and preferences regarding such a point of contact, and in the way stakeholders can interact and systematically refer to each other to manage an entire renovation journey. Nowadays, more than 100 OSS concepts are operational in Europe. However, their business model sometimes lacks viability in the long term. For example, publicly driven local-policy OSSs thrive because of available incentives but can become unstable owing to policy changes. Private, supply-driven OSSs risk failure because they cannot cover the costs of lengthy decision-making processes. A major challenge lies in combining the means and competencies of private and public OSS models. Overall, the renovation rate still needs to increase significantly, especially for collectively owned apartment buildings. Now the question arises: how can we realise a shift from publicly driven demand and privately driven supply to integrating collective, privately driven demand and collective, publicly driven supply? 
 

BUP: The recast Energy Performance of Buildings Directive (EPBD) (EU 2024/1275) introduces provisions in Article 18 that position OSS as central to the renovation process, tasked with delivering technical assistance and accessible services to building owners. From your experience, what are the principal operational and institutional challenges in setting up OSS that meet these new EU requirements?

EM: From our previous European projects, such as ERACOBUILD-ERANET One-stop-Shop, IEE COHERENO, and LIFE CondoReno, we see that delivering technical assistance is the easiest part of the job. Technologies, technical consultancy, and renovation services are readily available on the market. Making the assistance accessible to building owners requires a serious communication effort from both public and private actors. Companies also need to be accessible for renovation. Many companies still prefer working on new constructions because of all the risks that can occur during renovations and the uncertainties regarding timing. Ideally, local co-creation should lead to collaborative business-model development to establish local renovation hubs.  

Also, providing the service to homeowner associations is a whole new game compared to servicing individual homeowners. You often get only one chance per year to address a plenary homeowner association, so the procedure and milestones for each project must be clearly defined and followed up on. This requires social-process coaches alongside technical coaches, and a clear narrative based on expected monthly expenses and sustainable multi-year maintenance plans. A key operational challenge is therefore to introduce a human-centric adoption approach and to train OSS process coaches to deal with the social, financial, and legal barriers they can expect.

'Providing the service to homeowner associations is a whole new game compared to servicing individual homeowners’
 

At the same time, managing knowledge acquired during a renovation journey and customer relations in a digital resource centre, as well as supporting group decision-making among homeowners—including vulnerable households—becomes a key challenge.
 

BUP: The recast EPBD (EU 2024/1275) mandates a benchmark of one OSS per 80,000 inhabitants or at least one per region. What organisational and governance choices (for example, centralised versus decentralised or public versus private) tend to deliver the most effective OSS solutions, especially when addressing different national or regional contexts?  

EM: From our experience, the viability, desirability, and feasibility of an OSS service are determined by various factors related to local demand, available supply, and the way the local energy-efficiency governance is operationalised to address home renovation, housing shortages, SME innovation, and overall sustainability communication. The operational efficiency of an OSS is key, and this is strongly influenced by its management and by the direct link with financial incentives for homeowners or groups of citizens. In the end, we see that it is up to cities and communities to implement local action according to local needs in different districts.  

The current OSSs mainly emerged as socio-technical experiments that can contribute to locally or regionally increasing the renovation rate locally or regionally and to advancing the expected energy transition. Various types of OSS have emerged, and this now requires a coordinated effort. We see that in larger cities, public and private OSSs are sometimes competing for the same early adopters. In smaller cities and villages, there is sometimes no access to OSS services—or only a virtual desk. Meanwhile, specialised efforts to target vulnerable households are still added ad hoc to OSS services. Regional or provincial bodies need to ensure that everyone has the same level of access. They have to determine a single point of contact per 80,000 inhabitants or per region, taking into account the OSSs already active in a limited number of regions.  

Note that smaller municipalities in particular can suffer from limited resources while being asked to cover an ever-wider range of target groups and sustainability objectives. On the one hand, smaller municipalities are often physically incapable of providing even a limited number of OSS services. On the other hand, there is a risk that widening the scope may dilute goal specification and induce ecological fatigue as well as additional value conflicts among citizens and other stakeholders. In such cases, it is recommended that multiple municipalities engage in public-private collaboration to realise the required OSS services.

Additionally, there is a need to centralise the more specialised services, such as those providing legal advice, loans, and standard notary services, standardised energy-performance contracts, standardised procurement documents, urban-planning facilitation, certification of actors, the organisation of related training, and the identification of qualified technical master planners and social coaches for the renovation of large buildings.
 

BUP: Your research has shown that homeowners often face fragmented supply chains and must act as their own project managers. Are these structural issues effectively addressed through OSS, and what measures are needed to overcome them?

EM: Indeed, why—as homeowners—do we still have to make so much effort to answer a simple question such as ‘How can I make my home comfortable?’. We ask architects, energy experts, installers, suppliers, landlords, neighbours, and so on, and in many cases, they still come up with different answers, leaving us in doubt and not helping us to decide to carry out the necessary works. And suppose we decide to carry out an intervention costing several tens of thousands of euros. In that case, we are still expected to coordinate our plans with the municipality, a notary, a surveyor, a designer, a plumber, an electrician, a floor layer, a quality-assurance expert, and so on. We are expected to know everything about construction to carry out a once-in-a-lifetime intervention. It is obvious that conservatism still rules in planning and construction. As long as transaction costs remain so high, the renovation rate cannot increase.

Most OSSs still do not effectively address this structural need for full supply-chain collaboration. Public OSSs are often no longer involved after providing consultancy or once an actor decides to carry out a renovation measure. Private OSSs tend to wait for demand. The quality of the works is often not assessed by providers of incentives. I believe it is time to fully acknowledge that the current type of supply–demand interaction is outdated and that public–private collaboration needs to be legally facilitated.

‘Most OSSs still do not effectively address this structural need for full supply-chain collaboration’
 

We should also strengthen the full adoption of deep renovation at the natural moment of transaction—that is, when buying a home or when maintenance defects indicate the need to combine renovation measures. In essence, stakeholders such as real-estate brokers, notaries, and condominium managers should be able to act as key responsible change agents. These stakeholders are now barely involved in OSS initiatives, mainly because their legal context or business model is not adapted to support intensive supply-chain collaboration.
 

BUP: Ensuring quality and trust remain major issues in the renovation sector. How can OSS frameworks integrate stronger quality-assurance mechanisms, such as performance guarantees or certification schemes, to build confidence among homeowners?  

EM: The IEE COHERENO project examined this issue and concluded that quality assurance is key to customer confidence. Homeowners tend to trust independent actors (such as architects or intermediary agents) and public actors (such as municipalities) more than private actors (such as installers and contractors). Peer-to-peer communication is crucial for convincing homeowners to work with a private actor. That is one reason why many OSSs provide a public list of actors. For example, in Flanders, the Flemish Energy Agency provides a list of acknowledged master planners for condominium renovations. In the Netherlands, process coaches can obtain a certificate after completing a specialised training. In Paris, contractors who have contributed to subsidised condominium renovations are publicly visible in a digital resource centre for homeowner associations seeking experienced contractors. For advanced renovation concepts such as passive-house renovations, and for energy service companies, it is recommended to use professionals who are certified to assure energy quality. Today, quality-assurance schemes are scattered regionally and among different stakeholder types. On the one hand, customer confidence could be increased if OSSs systematically worked with certified or trained professionals. On the other hand, quality assurance of the final result needs to be recognised as an essential service of an OSS linked to the provision of renovation incentives or the issuance of a green certificate.  

Quality-assurance mechanisms should not only be stronger but also integrated. The quality-assurance landscape is now too fragmented and therefore too costly. There is a clear need for a single point of contact for quality assurance. In addition to regular commissioning at the delivery of a renovation, a homeowner undertaking renovation work might need a recognised surveyor to measure square metres, a financial check of the reserve fund or own capital to obtain a loan, an expert report on asbestos, a safety report from the fire department, a stability report from an engineer, a maintenance report from an installer, a safety report for the electrical system, a certificate of non-intrusion regarding biodiversity, an energy performance certificate, a smart-grid readiness certificate and so on. One might ask whether it is not time to compile all quality-assurance requirements into the task package of a single commissioning agent—providing all input to the building renovation passport, a full status report, and all necessary testing—preferably at a fixed cost.