The aim of this Bachelor’s thesis was to conduct field tests for a device that measures the actual U-value for a structure. This U-value meter is developed by the Arcada University of Applied Sciences, and there is no similar device on the market. The thesis was commissioned by Paloniitty Oy. The purpose of the testing was to study the need for and operability of the device in the field. The equivalence of the results obtained from the measurements to the calculated values were examined in the thesis. The amount of data achieved and the time spent on the measurements were also estimated. The results of field testing serve the commercialization of the device and the development of the service concept.

The theoretical background of the thesis consist of textbooks on building physics, tuition and lecture notes. To determine the U-values of the studied structure a DOF-Thermo –software was used. As there is no standard for the use of device, there are no official guidelines for measurements. The measurements were made in accordance with the instructions provided by the developer of the device.

As a result of the thesis, it was discovered that the calculated U-values may differ greatly from the actual values, to one direction or another. The device is definitely a good addition to examining properties of the buildings. The actual ability of thermal insulation of a structure can be quickly measured over a wide area by the device. Processing data obtained from the device needs to be improved. In order to utilize the device effectively software needs to be developed, so that the measured data can be obtained directly on computer for processing.