Annex 55: Reliability of energy efficient building retrofitting-probability assessment of performance and cost (RAP-RETRO)

This report could be used as a guideline for building owners on the possible risks and benefits of various energy retrofit options available to them. There are also best-practice examples provided which show projects of retrofitting and what should be considered and how the improvements can be implemented. Potential risks for retrofitting will be addressed in detail; most of them are related to: - Thermal bridges; - Moisture damages; - Uncertain cost calculation; - Improvement on ventilation (airflow, efficiency, thermal comfort). The advantages can be summarized as: - Increased living thermal comfort (indoor climate); - Use of existing building structure; - Cost savings for heating energy. These aspects are illustrated from different views of the Annex 55 participating countries. Most of the contributing countries are located in Europe: Austria, Belgium, Denmark, Estonia, Finland, Germany, Great Britain, The Netherlands, Portugal, Slovakia and Sweden; while three countries are from North-/ South- America: Brazil, Canada and the USA The energy consumption for the space conditioning of buildings can be reduced by the appropriate combination of several measures: - insulation of components: roof, wall and floor, - application of insulating glazing - airtightness of buildings, - orientation of buildings and rooms for the use of passive solar energy, (not a retrofit option) - use of an efficient and environment-friendly heating system, - installation of comfortable and efficient ventilation, - use of renewable energy as heating support, -use of heat pumps as heating support, - solar shading to avoid overheating in dwellings. Several studies have shown that the most efficient way to curb the energy consumption in the residential building sector (new & existing) remain the reduction of the heat loss by improving the insulation of the building envelope (roof, floor, wall & windows). Thermal insulation (combined with the application of high performance windows) holds a key position among these measures, which lay the foundation of low-energy building. The basic rules for low-energy building are - the reduction of energy demand and - production of the remaining demand more effectively and preferably - from renewable sources. The chapters of this report are organized by country to quickly guide the reader to find information which is relevant for to the reader or to inform about the statistics of other countries. In the end of each chapter, there is a compilation and overview of all countries, which summarizes the overall similarities and trends and points out major differences. Chapter 2 provides an overview of the energy consumption in residential buildings. This chapter should help to estimate the total effort and potential for each country in general. Chapter 3 covers the national regulation standards in order to provide the designer a scheme where to look for relevant standards and general references. The national regulations are birefly summarized and the most important information is highlighted. Chapter 4 highlights the most important data which should be considered when building new residential buildings or retrofit existing ones. Mainly thermal transmittances of the envelope, thermal bridges and ventilation regulations are addressed. Chapter 5 lists questions regarding testing of retrofitting. This might be relevant for building owners and architects or manufactures. Chapter 6 is divided into retrofitting certain building envelope parts. Contributing countries present typical examples of retrofitting including their risks and benefits from a national perspective. In addition, further local examples and references can be found in chapter 7. Finally, the last chapter summarizes this document, points out the most relevant information and provides a guideline on how to write guidelines for building owners, constructors and decision makers.