A low cost, accurate instrument to measure the moisture content of building envelopes in situ

Ye, Zhihui (2005). A low cost, accurate instrument to measure the moisture content of building envelopes in situ. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000d569

Abstract

Buildings must be designed and built to achieve a healthy environment, low energy consumption and a predictable service life. In order to achieve these goals the effects of combined heat, air and moisture (HAM) transfer must be understood. A suitable moisture measurement technique is thus required. There is a pressing need for a suitable instrument capable of in situ moisture measurements in building envelopes. Techniques do exist for such moisture measurement but all exhibit deficiencies in at least one critical area. A thermal dual-probe is investigated as a candidate for an appropriate instrument as such an approach offers significant potential benefits over existing methods.

It is demonstrated, via extensive finite-element (FE) modelling, that the thermal dual-probe technique is indeed applicable to in situ moisture measurements in typical building fabrics.

The thesis then moves on to deal with the optimisation of the design of such a probe. The results of relevant simulations using the proven two and three-dimensional FE models are detailed.

Finally, the extensive experimental work undertaken to support the modelling work is described. The measured data obtained from the thermal dual-probes is compared with the results of series of gravimetric analyses. Close agreement between the two methods is obtained.

The work, has successfully demonstrated that, depending upon the building fabric material,optimal probe lengths and spacing range from approximately 45-60mm and 12-20mm respectively. The experimental work clearly indicates that the thermal dual-probe is capable of accurate, in situ moisture measurements in building envelopes.