Low cost method for measuring moisture in construction materials

Important results from the project

The purpose of the project was to identify an appropriate method for measuring moisture in building materials. We found out, that from several studied alternatives the best method is measuring relative humidity in a local air-filled cavity. This is a well-established method in the market today, but in general is only utilized in relatively expensive, complicated and wired systems. However, we believe that this method is very suitable to be adapted to a low cost, wireless and power efficient system.

Expected long term effects

Based on the project´s results, we believe that we are able to develop a measurement system for moisture in building materials with wireless connection to a cloud service, with a battery life time of 7-10 years, and a price of less than 250 kr. Low-cost capacitive sensors for relative humidity may be placed in a local cavity created by the mechanical design of the product. For both radio and battery technology there are many options. Therefore an evaluation of these technologies should be made. However, Sigma Connectivity´s has extensive experience in these areas.

Approach and implementation

We have studied four different methods for moisture measurement in building materials: complex relative permittivity, transmission line reflectometry, thermal conductivity, and relative humidity in a cavity. All four seem to work for the purpose. However, the first three have high power consumption and lack of compatibility with concrete. Measurement of relative humidity in a cavity was found to be the best choice. Its advantages are that the cavity can be defined by the product design, the sensors are well available, and they have low price and power consumption.