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 Design and technical improvement of heating concepts with renewable energy

The switch from fossil to renewable energy via individual heat pumps (HP), can drastically reduce CO₂-emissions of the Swiss building stock. This can be achieved with and without the combination of envelope retrofit, which could stretch over several decades. While the potential market is huge (up to 34 GW / 75 billion CHF investment), many challenges and obstacles need however to be solved, in particular for multi-family buildings and related large HPs.

This subproject will tackle these issues with following developments:

• Robust sizing, integration and control strategies for large HP systems (> 50 kW), to promote industrial developments for the switch from fossil to renewable solutions.
• Factsheets on heat pump concepts for the existing building stock, for better understanding of opportunities and issues based on actual cases, in diverse regional situations.
• Compact, scalable PCM storage units, for optimal integration in HP systems, enabling stable HP operation and increased HP performance with reduced storage volumes by a factor 3-5.
• Optimal / flexible strategies for the combination of renewable heating and envelope-retrofit, in terms of energy performance and CO₂ savings, cost, as well as architectural constraints and opportunities.

This will be sustained by various P&D projects, in particular within (but not limited to) an ambitious program for massive switch from fossil to renewable energies in Geneva. It will help foster a robust position along the entire supply chain.

2.2 Sustainable and resilient renovation of facade systems with insulating bricks

There is a recognized necessity to increase the refurbishment rate in the Swiss building stock, using new and durable renovation approaches. Hence, the present subproject intends to investigate the use of insulating bricks to increase the thermal performance of existing buildings. Insulating bricks are already employed in new constructions, but their use for the refurbishment of existing buildings has not yet been systematically and holistically investigated.

The use of insulating bricks for the refurbishment of facades also contributes to an increase of the heat storage capacity of the construction. Considering the present global warming trend, this aspect represents a competitive advantage towards conventional insulation materials.

This subproject is based on the KISmur facade system, which consists of a load-bearing brick wall and an insulation layer made of insulating bricks. It was developed in an Innosuisse project by HSLU in collaboration with Keller AG Ziegeleien. KISmur was first established for new buildings and shall now be further developed as a solution for refurbishment applications.

The aim is to develop an implementation guide with practical solutions for the renovation of common building typologies and targets a broad audience of market players.

2.3 Prefabricated active façade kits

In addition to the reduction of heating demand, in the future the building envelope is also expected to contribute to energy production.

In this subproject, a new modular façade element, prefabricated in the factory, called ProsumerSkin, is being developed. This development overcomes several renovation hurdles by improving technical and architectural aspects:

• Skilled labour shortage: It is expected that the needed renovation wave is hindered by a shortage of experts and skilled labour. A high degree of prefabrication can help to reduce this problem.
• Construction time and disturbance: Due to prefabrication, the construction time in the field is reduced and also the disturbance on the construction site.
• No vacancy for adding a floor heating system: The concept of an external wall heating can be applied for existing, occupied buildings, without the need to change the floor construction, unlike a floor heating system.
• Ventilation system: Existing buildings usually don't have a mechanical ventilation. This could lead to structural-physical problems (e.g. mold) as with a new insulation layer the building envelope becomes tight.
• Integrated energy production: The new façade module will include solar technologies for energy harvesting already assembled in the factory.

In a first phase several prototypes will be developed and tested in the lab. In a second phase the goal is to proof the concept on buildings in real conditions.

2.4 Decision support instruments combining geo and building data

Innovative tools are necessary to support planning and renovation and to boost the efficiency and efficacy of these processes. The approach needs to be systematic and, depending on the typology of the building, should take into consideration and build on the experiences gained in previous renovation projects. This improvement of the renovation process can only be achieved if the involved players have easy and fast access to the relevant body of knowledge.

This subproject aims at the building typologies that are common in Switzerland and building data that is available and needed to boost the renovation rate in future. The focus lies on the residential building stock with the following parallel tasks:

• Factsheets will be created for the most common Swiss building typologies. 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.
• An analysis will be performed on currently available and in future needed data on building and geo-information. A "White Paper" will be worked out and discussed with different stakeholders.
• A GIS map layer will be made available to the general public. It will present information about the typology of the building owners, enabling the stakeholders involved in the planning and construction process to understand which type of owner is behind a given construction project.