HENS, H. Applied Building Physics – Boundary Conditions, Building Performance and Material Properties. Berlin: Wilhelm Ernst Sohn, 2011. 308 p. ISBN 978-3-433-02962-6.
HENS, H. Building Physics – Heat, Air and Moisture – Fundamentals and Engineering Methods with Examples And Exercises. 2nd Edition, Berlin: Wilhelm Ernst Sohn, 2012. 315 p. ISBN 978-3-433-03027-1.
EN ISO 6946:2007 Building components and building elements -- Thermal resistance and thermal transmittance -- Calculation method.
The Energy Performance of Buildings Directive (EPBD, Directive 2010/31/EU).