Introducing the new Viessmann Vitodens 100-W 26kW Combination boiler compact dimensions, low weight, and quiet operation. The Viessmann Vitodens 100-W range will intergrate into any living space. The new range of Viessmann vitodens 100-W and 111-W has the Inow-Radial stainless steel heat exchanger, which provides this boiler with an extremely high efficiency rate of 98% and exceptional relaible and efficient operation extending the life of your boiler