2. Technology and Architecture

A main challenge related to the building stock retrofit is the technical issues and high costs associated with the thermal renovation and fuel switch from fossil fuels to renewables. New components and approaches developed in close collaboration between research and industry will reduce related technical hurdles and costs. Innovative technological and architectural aspects will cover the improvement of the building envelope, successful implementation of renewable energy systems and the well-being of the inhabitants.

2.1.1 Sizing, integration and control strategies for HP system above 50 kW

Issue/Challenge
For existing multifamily buildings, there is a lack of standardized and proven heat pump (HP) sizing schemes, commonly leading to oversized, ill-integrated systems. 

Description
Development of robust, implementation-proven HP concepts, for non-retrofitted multifamily buildings:

• Standardized hydraulic schemes for integration in existing space heating (SH) and domestic hot water (DHW) distribution systems (with possible use of existing fossil fuel boiler for peak load).
• Integrated control strategies, related to multiple production units, modulating units, heat demands and sources, as well as heat storage strategies.
• Robust system sizing rules related to SH and DHW demands.
• Proper assessment of CO₂ savings, related to current and future hourly electricity mix.
• Optimal/flexible strategies for combined fuel-switch and envelope-retrofit, in terms of energy performance and CO₂ savings, cost, as well as architectural constraints and opportunities.

2.1.2 HP systems for Multifamily houses: Factsheets on case studies

Issue/Challenge
For large multifamily buildings, the energy refurbishment of the envelope and a switch from fossil heat supply to a HP-based supply can be challenging due to regulatory standards and reduced space to utilize the heat sources.

Description
Analysis of five typical real cases regarding costs, regulatory challenges, optimal sizing, and use of different heat sources for the heat pump. The cases cover urban, sub-urban and rural regions. The factsheets will inform building owners and planners about good examples for fuel-switch and building retrofit for similar-sized buildings, and to provide information to public authorities regarding current regulations and barriers for the realization of such operations. Results are summarized in compact, standardized factsheets.

2.1.3 Scalable PCM storage for renewable energy systems

Issue/Challenge
In retrofit projects, there are often pumps and other heat generators in the application. However, due to limited space, the installation of storage components — which are essential for the proper functioning of the heating system — becomes a challenge

Description
Development of phase change material (PCM) storage products and concepts to overcome space limitation with following features:

• Volume reduction of PCM storage in the range of 2-3 for the same storage capacity as water storage (see Figure above).
• More compact design due to avoidance of pressure requirements.
• Robust storage sizing rules related to SH and DHW demands.
• Optimal / flexible design of PCM characteristics for different retrofit application cases.
• Adapted control strategies for the application cases.

2.2 Sustainable and resilient renovation of facade systems with insulating bricks

Issue/Challenge
New and sustainable renovation concepts are needed for the many buildings that do not fulfill current energy standards. This SP investigates the use of insulating bricks to improve the thermal and energy efficiency of existing buildings. Insulating bricks are already used in new buildings, but their use in the refurbishment of existing buildings has not yet been systematically and holistically investigated.

Currently, between 80 and 90 percent of building facades are wrapped with synthetic insulation as ETICS (WDVS). Depending on the system, a large amount of technology (automated ventilation) and maintenance is required to compensate for the problems. Finally, a large amount of waste is generated when dismantling and disposing of standard systems

Description
We are developing new resilient uses for insulating bricks. In the current project status, possible façade typologies are being analyzed. Resilient exterior walls, including single-skin or double-skin brickwork and concrete constructions, are appropriate for refurbishment. Other criteria are for example the complexity of the façade, the development potential, or the given room around the building, as the Z7 brick itself has min. strength of 30 cm. Simulations show that current and future U-values can be met. This creates a low-tech system with a long lifespan and high thermal mass, which is equipped for climate change.

2.3 ProsumerSkin - Prefabricated active façade kits

Issue/Challenge
To achieve Switzerland's long-term climate goals, it is necessary to renovate a large number of buildings of the Swiss building stock to make them more energy efficient. New renovation concepts are needed for façade renovation, reducing the renovation time on-site, disruption of inhabitants, the need for skilled labor, and hence, costs.

Description
ProsumerSkin combines several functionalities within one façade element (the numbers below correspond to the numbers in the upper left picture):

1. Fully prefabricated façade element for serial refurbishment reducing installation time on-site, disturbance of inhabitants, and the amount of skilled labor needed.
2. Further thermal insulating reducing space heating demand.
3. Façade heating and/or cooling (optional), which eliminates the need for underfloor heating and allows occupants to remain in the apartments during refurbishment.
4. Building integrated photovoltaics (BIPV) and/or solar thermal collectors (optional) increasing renewable energy production and autarky.
5. Ventilation with heat recovery (optional) reducing energy consumption and increasing comfort.

2.4.1 Decision support instruments (sustainable refurbishment options for façade)  

Issue/Challenge
Innovative tools are needed to support planning and refurbishment and to increase the efficiency and effectiveness of these processes. The approach to new renovation interventions must be systematic and, depending on the typology of the building, consider and build on the experience gained from previous renovation projects. This improvement of the renovation process can only be achieved if the actors involved have easy and quick access to the relevant body of knowledge. The available data on the built environment is unsatisfactory and needs to be improved to overcome the hurdles of building renovation.

Description
We identify the main factors that influence decisions in the planning and construction of building façades. Based on the identified common residential building typologies, 2-3 prototypical standard façades are defined and presented with different refurbishment options. Based on these standard façades, an implementation guide with practical solutions for alternative refurbishment variants is presented. The focus is on buildings with single-skin brick walls from the 1950s onwards. The guide is intended to show possible options for sustainable, resource-saving, affordable and climate-resilient refurbishments and can be used as a planning tool in the future. These factsheets are targeted at market players and professionals involved in the development of refurbishment concepts and projects aimed at increasing the energy-efficiency of residential buildings, focusing on the envelope.

2.4.2 White paper on GIS - and data driven-tools for identifying and planning energy efficient building renovations in Swiz

Issue/Challenge
The Swiss building stock is responsible for 50 % of the country’s energy demand. Many buildings need to be renovated in the next years to reach the agreed-upon climate goals. To find affected buildings and to get optimal solutions for each renovation case, GIS-based planning tools can bring benefits. However, the data basis for such tools needs to include all relevant information and to be up to date, which is not necessarily the case today.

Description
The white paper being prepared within this task aims to give recommendations on GIS-based data management to aid the renovation of the Swiss building stock. We give an overview on the data needs, the missing information and their (potentially missing) representation in today's tools and how to get to their integration into the tools. We show examples of existing tools and their need for data through the result of a questionnaire among such tool developers and a case study of the municipality of Stäfa. The white paper will give a framework and recommendations for a data-driven building renovation process.