In 2007 the Class 1 project commenced. Originally, 442 dwellings were to be designed and constructed as "low-energy class 1" houses according to requirements set by the Municipality of Egedal/Denmark. This means that the energy consumption is 50% below the existing energy regulations. Sixty five dwellings and about 30 single family houses have been constructed. The Concerto community also includes a kindergarten (completed) and an elderly centre. Currently, because of the financial crisis, only about 200 new dwellings will be constructed. Therefore, a contingency plan (plan B) has been developed replacing some of the new dwellings with renovation projects for public buildings. Simultaneously the originally planned district heating network supplied from a relatively small bio-gasification plant has been substantially enlarged to cover a large part of the existing Stenloese town as well and a large wood-chip heating plant has been added. The project demonstrates the benefits of ultra-low-energy buildings integrated with biomass- and solar heating energy supply. The Class 1 project involves four other countries: Estonia, France, Italy and Romania. These countries develop training activities based on the results and experiences gained from the Danish housing projects. This paper describes the comparisons between measured and calculated energy consumption in a social housing settlement and in a detached single-family house. Results show relatively large discrepancies between measured and calculated results, and discussions on possible explanations are given. (C) 2012 Elsevier Ltd. All rights reserved.