Overview of a Research Project of Novel and Rapid In-Situ U-Value Measurements

Abstract

A Finnish-German collaborative project was carried out in 2018–2020 with the objective to investigate the accuracy and reliability of a novel metering device for in-situ determination of U-values of envelope structures. A rapid and reliable in-situ measurement method would clearly be a desirable tool for surveying the actual energy performance of existing buildings. Series of experimental and computational studies around a novel measurement device were carried out in Rapid U project. Rapidness of the measurement is sought by scheduling the moment of measurement so that the outdoor temperature has been sufficiently stable and cold before the measurement. Several test building measurements were carried out for certain structures in real weather conditions. Numerical modelling was also used to estimate the total number of hours in a year when the conditions are theoretically possible for similar structures to be measured rapidly. Repeated test building measurements showed unfortunately significant variation in the results. However, on average the results were promising and according to the simulations there should be plenty of suitable hours per year for rapid U-value measurement in cold countries if certain error tolerance is allowed.