Also the heat flux entering from the laboratory influences the
results of the test: calibration curves are valid considering a dif-ference between the laboratory temperature and the hot side
temperature lower than 12–15
◦
C. But during summer this differ-ence could be higher than 12
◦
C, because of the high temperature in
the laboratory (28–30
◦
C). Therefore the test 1 is the most reliable,
due to the higher difference between input heat flux (58 W) and
the heat flux entering from the laboratory (about 17 W; consider-ing to a difference between the laboratory temperature and the hot
chamber temperature equal to 4.6
◦
C). Three different tests were
analysed also for S5 and S9 but, for the sake of brevity, only the
most reliable test was considered for each sample. The results of
the most significant tests are reported in Table 4. The global thermal transmittance measured with the Hot Box method was equal
to 1.54 W/m2
K for sample S5 and to 1.22 W/m2
K for S9. The thermal transmittance values calculated from the other tests are still
included in 6–10% range