The BioMaxEff proposal aims at the demonstration of ultra-low emission and highest efficiency performance small scale biomass boilers under real life operation. The demonstrated technologies will fulfil the requirements of three substantially different market sectors, namely boiler exchange, refurbishment, and new buildings.The boiler exchange and refurbishment markets are addressed with an outstanding natural draught log wood boiler and a product series of a 10 to 26 kW (and 60 kW) pellets boiler, and a 6 to 12 kW pellets boiler. The pellets boilers are demonstrated solely or in combination with modular built secondary components, such as a flue gas heat exchanger, an electrostatic precipitator and the combination of both.The investigated boilers are characterized by outstanding behaviour regarding load change. This allows the optimum integration with ventilation components for energy recovery to energetically optimize the energetic performance of buildings. Integrated solutions will be demonstrated in pre-fabricated houses to highlight the substantial potential for seasonal efficiency increase and emission reduction in this field.The chosen system approach of the BioMaxEff consortium rather than an isolated product optimization and demonstration approach consequently is:• Perform an analysis of framework conditions and market needs• Develop seasonal efficiency and emission factor determination methods for the test stand and field testing• Demonstrate and optimize considered technologies and components under test stand conditions• Demonstrate and optimize system solutions by integrating components into buildings• Demonstrate the performance of system by a wide spread field monitoring with sold installations (> 2.300)• Accompany the demonstration and optimization with R&D activities where necessary• Perform an overall environmental impact assessment• Dissemination of resultsThe consortium consists of 13 partners from 8 European countries.