New applications of recycled materials from defibering cellulose used for thermal insulation in several reference low-energy and passive houses were subject of one year monitoring with analysis of hygrothermal properties for different spatial density of cellulose and different hydrophobic treatment of fibres. Contemporary results from the monitoring and measurements of blowing and sprayed cellulose (tested in situ and in labs) used for thermal insulation in houses show that defibering and treated cellulose from waste selected paper originally produced in the Czech Republic is comparable with thermal properties to other thermal insulation materials produced from mineral or glass fibres.