REQUEST quality assurance instruments for housing renovation processes

Renovation of existing dwellings towards energy efficient levels is known to be a complex process. This is usually due to the fact that various trades firms are involved performing a rather large number of relatively small-scale interventions needed for improvement of thermal resistance, air tightness, indoor air quality, replacement of outdated services components, installation of renewable energy systems and of control and monitoring components. The quality and energy performance level reached during the housing renovation processes can be compromised by a lack of overall coordination, of cooperation between various trades, of clear agreements on responsibilities and of a start-to-finish process approach. In order to achieve competitiveness combined with a high quality level, small and medium-sized businesses in the construction industry indicate that there is a need for cooperation with reliable partners and for appropriate process guidance instruments.

During the REQUEST project, consultation workshops with trades people were organised in all REQUEST partner countries, leading to the development of quality assurance and process guidance instruments under coordination of the German Energy Agency (dena). A general process diagram and a set of quality checklists for housing energy renovations were developed. These items are intended as process guidance instruments facilitating quality control, cooperation and coordination between the various trades. The quality instruments are adaptable to the local context and building practice in various EU countries. During the REQUEST project, the quality checklists and process guidance diagram were tested in the German pilot project by tradesmen, energy experts and engineers in about 30 low carbon housing renovation projects. Finally, dena has also examined the feasibility for launching a REQUEST quality label linked to the above stated instruments through a partnership with CASA-bauen and consultation with key actors such as KfW Bank.

The general process diagram has been developed on the basis of the conclusions of the trades workshops, as well as market analysis of existing best practices of standards for the energy efficiency of buildings. The diagram is structured according to four defined stages within renovation processes, namely diagnosis, planning, construction, hand over. The diagram explicates tasks within the renovation process and related legal and recommended documentation requirements. The diagram then links to the quality checklists developed for the various process stages, intended for on-site use and stating minimum requirements and further recommended measures. 


The following minimum requirements form the backbone of the REQUEST quality assured renovation processes:


  • An energy performance certificate or an on-site energy audit should be available prior to the start of the planning process. On the basis of the energy audit or the Energy Performance Certificate the renovation measures are defined;
  • Thermography and a blower door test are recommended to get a clear picture of the initial condition of the building envelope. This information forms the basis to develop a thermal insulation concept, a concept for air tightness and a plan for minimising thermal bridges (for whole-house renovations).


  • The essential responsibilities, specification details have to be clarified and agreed upon in the planning phase. A QA controller should be assigned to follow up the entire renovation process (e.g. architect, construction manager, trades person involved). All trades people to be involved are informed and appointed by means of contracts;
  • The quality assurance instruments, tools and techniques (thermography, blower door test,...) that will be used on-site and their implementation date have to be determined for cost and time planning proposes;
  • Required design stage calculations in accordance with the relevant European standards have to be determined and planned in (hydraulic balancing, heating and/or ventilation system design).


  • An on-site kick off meeting is held at the start of the renovation process, wherein the trade people received the appropriate information on renovation objectives, quality assurance instruments, responsibilities, documentation requirements, schedule, etc..;
  • The assigned Quality Assurance controller performs site inspections and collects the required documents in accordance with the REQUEST quality checklists;
  • Thermography and a blower door test are recommended to ensure quality of the renovation work performed (for whole-house renovations);
  • A revised energy performance certificate is produced as a final performance review.

Hand over

  • At the hand over the home owner receives all documentation gathered, user guidance manuals and the updated energy performance certificate. The home owner is also given an introduction to the installed services systems, to commissioning recommendations for the equipment (heating, ventilation, control etc.) and on permanent user follow-up of the actual energy consumption.

Positive feedback on the REQUEST QA instruments has been received from a variety of German regional partners, as well as from trades and engineering companies that participated in the testing of the diagram and quality checklists in actual housing renovation projects within the German pilot project. The quality checklists could however be further adapted in order to improve their usability and to limit the amount of work. A differentiation between smaller refurbishments and large scale renovation projects, and between partial versus whole-house renovation is considered as a further step for improvement.