2.2.2. Method 2—Heat Flow Meter Method (HFM)

By measuring heat flux density, one can obtain a more accurate result as large fluctuations in air temperature readings can be partially eliminated in this way. In this case, the thermal resistance can be determined from the formula:

$$R = \frac{(T\_{si} - T\_{sc})}{q} \tag{5}$$

and then, total thermal resistance can be calculated from the formula:

$$R\_{tot} = R\_{si} + R + R\_{sc} \tag{6}$$

where:

*Tsi*, *Tse*—the temperature of respectively the internal and external surface of the tested building enclosure (K),

*q*—the measured heat flux flowing through the building enclosure (W/m2),

*Rsi*, *Rse*—the calculated surface thermal resistances on respectively the internal and external side of the building partition ((m2K)/W).
