Make your city more liveable and sustainable: Ask, learn and share about energy, ICT and mobility!

Low energy retrofitting

On this page you will find lessons learnt that are distilled from various workshops that the SCIS team attended. The most important points are summarised, giving a quick overview of the challenges / barriers but also solutions with regard to each topic.
Low Energy Retrofitting
Lesson identified at: 


Low energy retrofitting is one of the main undertakings of smart city projects. Some of the challenges include: ensuring the desired end results with regard to increased comfort and realized energy savings; finding a good baseline energy consumption a priori; deploying a good monitoring system a posteriori.

Due to the duration and impact of renovation works, tenants might have to be reallocated. Of course this is not obvious, certainly not since from the tenants point of view retrofitting often is not a priority. This can be the result of the lack of environmental awareness or ignorance of the positive effects retrofitting could bring to their quality of life. Especially in private multi-owner residential buildings it is challenging to find an overall agreement on the building retrofitting, which is often caused by some owners lacking the financial capabilities to retrofit. In some cases with buildings in which not all flats are occupied, it is even harder to engage all the owners and to find suitable financial models. In case a retrofit does take place, to obtain tenants’ approval for individual metering and post-renovation monitoring after finishing the works turns out to be challenging, mainly due to privacy concerns. Yet, such monitoring would help to increase knowledge on the actual end-results of retrofitting and could therefore increase the credibility and reduce the risk of future business cases.

Finding a good finance mix between tenant, public and other private investments is not easy. Typically there is the discrepancy between the owner paying the retrofitting investment and the tenant paying the energy bills: when retrofitting results in lower energy bills, appropriate agreements have to be setup to make sure some of the energy cost savings can be recovered by the owner, for example through an increase in monthly rent. To lower the financial burden, retrofitting project teams try to identify those retrofitting measures that are eligible for subsidies. This is not always easy due to the many subsidy schemes that exist or due a lack of overview of all those schemes and measures.

Several small and medium sized cities have a hard time coming up with retrofitting solutions, mainly due to the fact that economy of scale is less applicable in their case (which makes it more challenging to find a working business model) and due to a lack of competences and time within these comparably smaller communities.

In general, the limited availability of skilled staff (craftsmen; people for coordination and supervision of subcontractors) is a barrier, since delivering qualitative work and good support towards building owners is key to ensure their engagement and support. Also towards future retrofitting projects, a convincing track record will definitely help to facilitate stakeholders engagement.

Concerning regulation, obtaining building permits as well as dealing with cultural heritage is challenging. Also the prohibition to transfer electricity between buildings (which in one workshop was identified to be the case in Finland, Spain and Sweden, but applies to many more European countries) and monitoring without breaking data protection laws are often encountered barriers towards more innovative retrofitting trajectories. Also the fact that in general cities cannot set more ambitious requirements for buildings’ energy efficiency than determined by national legislation (unless for example the city owns the land or makes use of an exploitation contract) is a barrier for ambitious cities. And finally, geographical differences might limit the easiness of replication of retrofitting solutions.


Policy makers could adjust regulations to facilitate permitting for energy retrofitting and to allow and promote energy exchange between buildings. The workshop participants suggested to apply regulations related to building properties on the building level and energy supply regulations on a community level.

To get support from buildings owners and user, is it recommended to measure the increase in comfort and to intensify the engagement with private owners, especially when working in a multi ownership context. On the other hand, it is known that buildings owned by a single entity (e.g. company) are easier to target. From a financial perspective, try to facilitate loans for the complete retrofitting operation in order to cover investment costs while at the same time avoiding tenants have to make the investment in one go themselves. Increasing stakeholders’ confidence could be realized through involving public services (in this case the roll out of a district heating grid infrastructure was given as an example). You can find more best practice on citizen engagement on the dedicated page.

Other best practices and suggestions are numerous. To include the energy performance in the procurement process and to have specified the expected energetic and comfort performance in tenders and contracts, could drastically increase the retrofitting quality. (Look at the Innovative Procurement of Smart City Solutions page to learn more about this topic.) This is also a solution for cities that want to apply more ambitious energy performance targets than those at national level. Using the already available monitoring data will help municipalities to create good business models. The same holds for identifying windows of opportunity, which in case of retrofitting often correspond with buildings’ end of lifetime, or new occupants or owners moving in.

It is recommended to increase the return on investment by incorporating PV installations or combining several forms of retrofitting (e.g. energy and structural retrofitting). One should also consider financing by ESCO’s, collective funding or a combination. It is to be avoided that tenants have to make the complete investment themselves.

During the workshops, many recommendations related to increasing the smartness of buildings and data monitoring were mentioned, such as: demand response and weather forecast to manage energy performance of the building, smart metering, individual thermal control and energy measurement for each flat, energy measurement at building level, IoT and real time data monitoring and real data collection (as opposed to data from simulations).

From a governance perspective, the setup of a so called Construction Consolidation Centre will result in time savings, less materials damaged during delivery and handling, and less waste.[1] To reduce the impact of a construction project even further, alternative fueled vehicles could be used.

To increase the project’s chances of success, the buildings to be retrofitted should be carefully chosen, taking into account several factors such as building ownership and legal context. A district thinking approach both for renovation and new construction could increase the applicability of the ESCO model. Targeting a mixed building portfolio (residential and tertiary) or big facilities could be beneficial for your business case due to higher flexibility and economy of scale. On the other hand, when focussing on similar buildings, tailor-made solutions can be applied to them[2]. Don’t forget to incorporate good communication from the early start of the project (see also Citizen Engagement). And finally, it is useful to organize workshops (e.g. for housing corporations) to show the benefits of retrofitting.

Plan for Implementation

To reach the national government, local authorities can combine efforts to have a stronger voice and as such reach change and affect policies. This is done for example in Denmark. Persons in charge can involve other partners in retrofitting projects and aim for a single holistic project instead of several smaller ones. They can also create a strategy campaign to promote the benefits of retrofitting (energy savings, better quality of living, etc.) to convince and gain trusts from tenants. It can also be considered as mandatory to provide clarification on the ownership of the data resulting from monitoring.

At a city level, more efforts can be put in advising private house/apartment owners and in spreading knowledge. Some of the workshops participants will look into scaling up the retrofitting in public office buildings, explore the possibilities of a revolving fund and take part in replication workshops with other cities. They will also set up workshops to discuss the district approach and share results with other housing associations.


[1] GrowSmarter, Factsheet Booklet Low Energy Districts, 9. Construction Consolidation Centre

[2] Examples of refurbishment of buildings with uniform shape can be found in the projects Energiesprong and Rennovates.