A laboratory technique simulating on-site conditions is used for hygrothermal performance assessment of two building envelopes. Interior thermal insulation system on the basis of hydrophilic mineral wool which is applied on two common load bearing structures is analyzed. Sufficiently large specimens of studied building envelopes are exposed to difference climate conditions very close to reality. Monitoring of moisture and temperature fields in the investigated structures is carried out using laboratory measuring technology. Experimental results give evidence that the hygrothermal performance of both tested building envelopes is satisfactory. (C) 2007 Elsevier B.V. All rights reserved.